A YANG Data Model for the Routing Information Protocol (RIP)
draft-ietf-rtgwg-yang-rip-11
The information below is for an old version of the document that is already published as an RFC.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8695.
|
|
|---|---|---|---|
| Authors | Xufeng Liu , Prateek Sarda , Vikram Choudhary | ||
| Last updated | 2020-02-21 (Latest revision 2019-08-28) | ||
| Replaces | draft-liu-rtgwg-yang-rip | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | |||
| Yang Validation | ☯ 5 errors, 0 warnings | ||
| Reviews |
GENART Last Call review
(of
-06)
by Roni Even
Ready w/nits
YANGDOCTORS Early review
(of
-02)
by Ladislav Lhotka
Ready w/issues
|
||
| Additional resources |
Yang catalog entry for ietf-rip@2018-02-03.yang
Yang impact analysis for draft-ietf-rtgwg-yang-rip Mailing list discussion |
||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Yingzhen Qu | ||
| Shepherd write-up | Show Last changed 2017-06-27 | ||
| IESG | IESG state | Became RFC 8695 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Martin Vigoureux | ||
| Send notices to | Yingzhen Qu <yingzhen.qu@huawei.com> | ||
| IANA | IANA review state | IANA OK - Actions Needed | |
| IANA action state | RFC-Ed-Ack |
draft-ietf-rtgwg-yang-rip-11
Network Working Group F. Templin, Ed.
Internet-Draft The Boeing Company
Intended status: Informational A. Whyman
Expires: October 18, 2021 MWA Ltd c/o Inmarsat Global Ltd
April 16, 2021
Transmission of IP Packets over Overlay Multilink Network (OMNI)
Interfaces
draft-templin-6man-omni-04
Abstract
Mobile nodes (e.g., aircraft of various configurations, terrestrial
vehicles, seagoing vessels, enterprise wireless devices, etc.)
communicate with networked correspondents over multiple access
network data links and configure mobile routers to connect end user
networks. A multilink interface specification is presented that
enables mobile nodes to coordinate with a network-based mobility
service and/or with other mobile node peers. This document specifies
the transmission of IP packets over Overlay Multilink Network (OMNI)
Interfaces.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 18, 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 11
4. Overlay Multilink Network (OMNI) Interface Model . . . . . . 11
5. OMNI Interface Maximum Transmission Unit (MTU) . . . . . . . 17
6. The OMNI Adaptation Layer (OAL) . . . . . . . . . . . . . . . 18
6.1. OAL Source Encapsulation and Fragmentation . . . . . . . 18
6.2. OAL *NET Encapsulation and Re-Encapsulation . . . . . . . 23
6.3. OAL Destination Decapsulation and Reassembly . . . . . . 25
6.4. OAL Header Compression . . . . . . . . . . . . . . . . . 25
6.5. OAL Fragment Identification Window Maintenance . . . . . 28
6.6. OAL Fragment Retransmission . . . . . . . . . . . . . . . 29
6.7. OAL MTU Feedback Messaging . . . . . . . . . . . . . . . 30
6.8. OAL Requirements . . . . . . . . . . . . . . . . . . . . 32
6.9. OAL Fragmentation Security Implications . . . . . . . . . 33
6.10. OAL Super-Packets . . . . . . . . . . . . . . . . . . . . 34
7. Frame Format . . . . . . . . . . . . . . . . . . . . . . . . 36
8. Link-Local Addresses (LLAs) . . . . . . . . . . . . . . . . . 36
9. Unique-Local Addresses (ULAs) . . . . . . . . . . . . . . . . 37
10. Global Unicast Addresses (GUAs) . . . . . . . . . . . . . . . 39
11. Node Identification . . . . . . . . . . . . . . . . . . . . . 40
12. Address Mapping - Unicast . . . . . . . . . . . . . . . . . . 40
12.1. Sub-Options . . . . . . . . . . . . . . . . . . . . . . 42
12.1.1. Pad1 . . . . . . . . . . . . . . . . . . . . . . . . 44
12.1.2. PadN . . . . . . . . . . . . . . . . . . . . . . . . 44
12.1.3. Interface Attributes (Type 1) . . . . . . . . . . . 45
12.1.4. Interface Attributes (Type 2) . . . . . . . . . . . 46
12.1.5. Traffic Selector . . . . . . . . . . . . . . . . . . 50
12.1.6. MS-Register . . . . . . . . . . . . . . . . . . . . 51
12.1.7. MS-Release . . . . . . . . . . . . . . . . . . . . . 52
12.1.8. Geo Coordinates . . . . . . . . . . . . . . . . . . 52
12.1.9. Dynamic Host Configuration Protocol for IPv6
(DHCPv6) Message . . . . . . . . . . . . . . . . . . 53
12.1.10. Host Identity Protocol (HIP) Message . . . . . . . . 54
12.1.11. PIM-SM Message . . . . . . . . . . . . . . . . . . . 55
12.1.12. Reassembly Limit . . . . . . . . . . . . . . . . . . 56
12.1.13. Fragmentation Report . . . . . . . . . . . . . . . . 58
12.1.14. Node Identification . . . . . . . . . . . . . . . . 59
12.1.15. Sub-Type Extension . . . . . . . . . . . . . . . . . 60
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13. Address Mapping - Multicast . . . . . . . . . . . . . . . . . 64
14. Multilink Conceptual Sending Algorithm . . . . . . . . . . . 64
14.1. Multiple OMNI Interfaces . . . . . . . . . . . . . . . . 65
14.2. MN<->AR Traffic Loop Prevention . . . . . . . . . . . . 65
15. Router Discovery and Prefix Registration . . . . . . . . . . 66
15.1. Router Discovery in IP Multihop and IPv4-Only Networks . 70
15.2. MS-Register and MS-Release List Processing . . . . . . . 72
15.3. DHCPv6-based Prefix Registration . . . . . . . . . . . . 74
16. Secure Redirection . . . . . . . . . . . . . . . . . . . . . 75
17. AR and MSE Resilience . . . . . . . . . . . . . . . . . . . . 75
18. Detecting and Responding to MSE Failures . . . . . . . . . . 76
19. Transition Considerations . . . . . . . . . . . . . . . . . . 76
20. OMNI Interfaces on Open Internetworks . . . . . . . . . . . . 77
21. Time-Varying MNPs . . . . . . . . . . . . . . . . . . . . . . 79
22. (H)HITs and Temporary ULAs . . . . . . . . . . . . . . . . . 80
23. Address Selection . . . . . . . . . . . . . . . . . . . . . . 81
24. Error Messages . . . . . . . . . . . . . . . . . . . . . . . 81
25. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 81
25.1. "IEEE 802 Numbers" Registry . . . . . . . . . . . . . . 81
25.2. "IPv6 Neighbor Discovery Option Formats" Registry . . . 82
25.3. "Ethernet Numbers" Registry . . . . . . . . . . . . . . 82
25.4. "ICMPv6 Code Fields: Type 2 - Packet Too Big" Registry . 82
25.5. "OMNI Option Sub-Type Values" (New Registry) . . . . . . 82
25.6. "OMNI Geo Coordinates Type Values" (New Registry) . . . 83
25.7. "OMNI Node Identification ID-Type Values" (New Registry) 83
25.8. "OMNI Option Sub-Type Extension Values" (New Registry) . 84
25.9. "OMNI RFC4380 UDP/IP Header Option" (New Registry) . . . 84
25.10. "OMNI RFC6081 UDP/IP Trailer Option" (New Registry) . . 85
25.11. Additional Considerations . . . . . . . . . . . . . . . 85
26. Security Considerations . . . . . . . . . . . . . . . . . . . 86
27. Implementation Status . . . . . . . . . . . . . . . . . . . . 87
28. Document Updates . . . . . . . . . . . . . . . . . . . . . . 87
29. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 87
30. References . . . . . . . . . . . . . . . . . . . . . . . . . 89
30.1. Normative References . . . . . . . . . . . . . . . . . . 89
30.2. Informative References . . . . . . . . . . . . . . . . . 91
Appendix A. Interface Attribute Preferences Bitmap Encoding . . 98
Appendix B. VDL Mode 2 Considerations . . . . . . . . . . . . . 100
Appendix C. MN / AR Isolation Through L2 Address Mapping . . . . 101
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 102
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 103
1. Introduction
Mobile Nodes (MNs) (e.g., aircraft of various configurations,
terrestrial vehicles, seagoing vessels, enterprise wireless devices,
pedestrians with cellphones, etc.) often have multiple interface
connections to wireless and/or wired-line data links used for
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communicating with networked correspondents. These data links may
have diverse performance, cost and availability properties that can
change dynamically according to mobility patterns, flight phases,
proximity to infrastructure, etc. MNs coordinate their data links in
a discipline known as "multilink", in which a single virtual
interface is configured over the node's underlying interface
connections to the data links.
The MN configures a virtual interface (termed the "Overlay Multilink
Network Interface (OMNI)") as a thin layer over the underlying
interfaces. The OMNI interface is therefore the only interface
abstraction exposed to the IP layer and behaves according to the Non-
Broadcast, Multiple Access (NBMA) interface principle, while
underlying interfaces appear as link layer communication channels in
the architecture. The OMNI interface internally employs the "OMNI
Adaptation Layer (OAL)" to ensure that original IP packets are
delivered without loss due to size restrictions. The OMNI interface
connects to a virtual overlay service known as the "OMNI link". The
OMNI link spans one or more Internetworks that may include private-
use infrastructures and/or the global public Internet itself.
Each MN receives a Mobile Network Prefix (MNP) for numbering
downstream-attached End User Networks (EUNs) independently of the
access network data links selected for data transport. The MN
performs router discovery over the OMNI interface (i.e., similar to
IPv6 customer edge routers [RFC7084]) and acts as a mobile router on
behalf of its EUNs. The router discovery process is iterated over
each of the OMNI interface's underlying interfaces in order to
register per-link parameters (see Section 15).
The OMNI interface provides a multilink nexus for exchanging inbound
and outbound traffic via the correct underlying interface(s). The IP
layer sees the OMNI interface as a point of connection to the OMNI
link. Each OMNI link has one or more associated Mobility Service
Prefixes (MSPs), which are typically IP Global Unicast Address (GUA)
prefixes from which MNPs are derived. If there are multiple OMNI
links, the IPv6 layer will see multiple OMNI interfaces.
MNs may connect to multiple distinct OMNI links within the same OMNI
domain by configuring multiple OMNI interfaces, e.g., omni0, omni1,
omni2, etc. Each OMNI interface is configured over a set of
underlying interfaces and provides a nexus for Safety-Based Multilink
(SBM) operation. Each OMNI interface within the same OMNI domain
configures a common ULA prefix [ULA]::/48, and configures a unique
16-bit Subnet ID '*' to construct the sub-prefix [ULA*]::/64 (see:
Section 9). The IP layer applies SBM routing to select an OMNI
interface, which then applies Performance-Based Multilink (PBM) to
select the correct underlying interface. Applications can apply
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Segment Routing [RFC8402] to select independent SBM topologies for
fault tolerance.
The OMNI interface interacts with a network-based Mobility Service
(MS) through IPv6 Neighbor Discovery (ND) control message exchanges
[RFC4861]. The MS provides Mobility Service Endpoints (MSEs) that
track MN movements and represent their MNPs in a global routing or
mapping system.
Many OMNI use cases have been proposed. In particular, the
International Civil Aviation Organization (ICAO) Working Group-I
Mobility Subgroup is developing a future Aeronautical
Telecommunications Network with Internet Protocol Services (ATN/IPS)
and has issued a liaison statement requesting IETF adoption [ATN] in
support of ICAO Document 9896 [ATN-IPS]. The IETF IP Wireless Access
in Vehicular Environments (ipwave) working group has further included
problem statement and use case analysis for OMNI in a document now in
AD evaluation for RFC publication
[I-D.ietf-ipwave-vehicular-networking]. Still other communities of
interest include AEEC, RTCA Special Committee 228 (SC-228) and NASA
programs that examine commercial aviation, Urban Air Mobility (UAM)
and Unmanned Air Systems (UAS). Pedestrians with handheld devices
represent another large class of potential OMNI users.
In addition to many other aspects, OMNI supports the "6M's" of modern
Internetworking including:
1. Multilink - a mobile node's ability to coordinate multiple
diverse underlying data links as a single logical unit (i.e., the
OMNI interface) to achieve the required communications
performance and reliability objectives.
2. Multinet - the ability to span the OMNI link across multiple
diverse network administrative segments while maintaining
seamless end-to-end communications between mobile nodes and
correspondents such as air traffic controllers, fleet
administrators, etc.
3. Mobility - a mobile node's ability to change network points of
attachment (e.g., moving between wireless base stations) which
may result in an underlying interface address change, but without
disruptions to ongoing communication sessions with peers over the
OMNI link.
4. Multicast - the ability to send a single network transmission
that reaches multiple nodes belonging to the same interest group,
but without disturbing other nodes not subscribed to the interest
group.
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5. Multihop - a mobile node vehicle-to-vehicle relaying capability
useful when multiple forwarding hops between vehicles may be
necessary to "reach back" to an infrastructure access point
connection to the OMNI link.
6. MTU assurance - the ability to deliver packets of various robust
sizes between peers without loss due to a link size restriction,
and to dynamically adjust packets sizes to achieve the optimal
performance for each independent traffic flow.
This document specifies the transmission of IP packets and MN/MS
control messages over OMNI interfaces. The OMNI interface supports
either IP protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200])
as the network layer in the data plane, while using IPv6 ND messaging
as the control plane independently of the data plane IP protocol(s).
The OAL operates as a sublayer between L3 and L2 based on IPv6
encapsulation [RFC2473] as discussed in the following sections.
2. Terminology
The terminology in the normative references applies; especially, the
terms "link" and "interface" are the same as defined in the IPv6
[RFC8200] and IPv6 Neighbor Discovery (ND) [RFC4861] specifications.
Additionally, this document assumes the following IPv6 ND message
types: Router Solicitation (RS), Router Advertisement (RA), Neighbor
Solicitation (NS), Neighbor Advertisement (NA) and Redirect.
The Protocol Constants defined in Section 10 of [RFC4861] are used in
their same format and meaning in this document. The terms "All-
Routers multicast", "All-Nodes multicast" and "Subnet-Router anycast"
are the same as defined in [RFC4291] (with Link-Local scope assumed).
The term "IP" is used to refer collectively to either Internet
Protocol version (i.e., IPv4 [RFC0791] or IPv6 [RFC8200]) when a
specification at the layer in question applies equally to either
version.
The following terms are defined within the scope of this document:
Mobile Node (MN)
an end system with a mobile router having multiple distinct
upstream data link connections that are grouped together in one or
more logical units. The MN's data link connection parameters can
change over time due to, e.g., node mobility, link quality, etc.
The MN further connects a downstream-attached End User Network
(EUN). The term MN used here is distinct from uses in other
documents, and does not imply a particular mobility protocol.
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quot;IPv4 route information.";
list route {
key "ipv4-prefix";
description
"A RIPv2 IPv4 route.";
leaf ipv4-prefix {
type inet:ipv4-prefix;
description
"IPv4 address and prefix length, in the format
specified in RFC6991.";
}
leaf next-hop {
type inet:ipv4-address;
description
"Next hop IPv4 address.";
}
leaf interface {
type if:interface-ref;
description
"The interface that the route uses.";
}
uses route-attributes;
} // route
} // routes
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} // ipv4
container ipv6 {
when "derived-from-or-self(../../rt:type, 'rip:ripng')" {
description
"IPv6 address family is supported by RIPng.";
}
config false;
description
"IPv6 address family information.";
container neighbors {
description
"IPv6 neighbor information.";
list neighbor {
key "ipv6-address";
description
"A RIPng neighbor.";
leaf ipv6-address {
type inet:ipv6-address;
description
"IP address that a RIP neighbor is using as its
source address.";
}
leaf last-update {
type yang:date-and-time;
description
"The time when the most recent RIP update was
received from this neighbor.";
}
leaf bad-packets-rcvd {
type yang:counter32;
description
"The number of RIP invalid packets received from
this neighbor which were subsequently discarded
for any reason (e.g. a version 0 packet, or an
unknown command type).";
}
leaf bad-routes-rcvd {
type yang:counter32;
description
"The number of routes received from this neighbor,
in valid RIP packets, which were ignored for any
reason (e.g. unknown address family, or invalid
metric).";
}
} // neighbor
} // neighbors
container routes {
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description
"IPv6 route information.";
list route {
key "ipv6-prefix";
description
"A RIPng IPv6 route.";
leaf ipv6-prefix {
type inet:ipv6-prefix;
description
"IPv6 address and prefix length, in the format
specified in RFC6991.";
}
leaf next-hop {
type inet:ipv6-address;
description
"Next hop IPv6 address.";
}
leaf interface {
type if:interface-ref;
description
"The interface that the route uses.";
}
uses route-attributes;
} // route
} // routes
} // ipv6
container statistics {
if-feature global-statistics;
config false;
description
"Global statistic counters.";
leaf discontinuity-time {
type yang:date-and-time;
description
"The time on the most recent occasion at which any one
or more of the statistic counters suffered a
discontinuity. If no such discontinuities have occurred
since the last re-initialization of the local
management subsystem, then this node contains the time
the local management subsystem re-initialized itself.";
}
leaf requests-rcvd {
type yang:counter32;
description
"The number of requests received by RIP.";
}
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leaf requests-sent {
type yang:counter32;
description
"The number of requests sent by RIP.";
}
leaf responses-rcvd {
type yang:counter32;
description
"The number of responses received by RIP.";
}
leaf responses-sent {
type yang:counter32;
description
"The number of responses sent by RIP.";
}
} // statistics
} // container rip
}
/*
* RPCs
*/
rpc clear-rip-route {
description
"Clears RIP routes from the IP routing table and routes
redistributed into the RIP protocol for the specified RIP
instance or for all RIP instances in the current context.";
input {
leaf rip-instance {
type leafref {
path "/rt:routing/rt:control-plane-protocols/"
+ "rt:control-plane-protocol/rt:name";
}
description
"Instance name identifying a specific RIP instance.
This leaf is optional for the rpc.
If it is specified, the rpc will clear all routes in the
specified RIP instance;
if it is not specified, the rpc will clear all routes in
all RIP instances.Internet-Draft IPv6 over OMNI Interfaces April 2021
End User Network (EUN)
a simple or complex downstream-attached mobile network that
travels with the MN as a single logical unit. The IP addresses
assigned to EUN devices remain stable even if the MN's upstream
data link connections change.
Mobility Service (MS)
a mobile routing service that tracks MN movements and ensures that
MNs remain continuously reachable even across mobility events.
Specific MS details are out of scope for this document.
Mobility Service Endpoint (MSE)
an entity in the MS (either singular or aggregate) that
coordinates the mobility events of one or more MN.
Mobility Service Prefix (MSP)
an aggregated IP Global Unicast Address (GUA) prefix (e.g.,
2001:db8::/32, 192.0.2.0/24, etc.) assigned to the OMNI link and
from which more-specific Mobile Network Prefixes (MNPs) are
delegated. OMNI link administrators typically obtain MSPs from an
Internet address registry, however private-use prefixes can
alternatively be used subject to certain limitations (see:
Section 10). OMNI links that connect to the global Internet
advertise their MSPs to their interdomain routing peers.
Mobile Network Prefix (MNP)
a longer IP prefix delegated from an MSP (e.g.,
2001:db8:1000:2000::/56, 192.0.2.8/30, etc.) and assigned to a MN.
MNs sub-delegate the MNP to devices located in EUNs. Note that
OMNI link Relay nodes may also service non-MNP routes (i.e., GUA
prefixes not covered by an MSP) but that these correspond to fixed
correspondent nodes and not MNs. Other than this distinction, MNP
and non-MNP routes are treated exactly the same by the OMNI
routing system.
Access Network (ANET)
a data link service network (e.g., an aviation radio access
network, satellite service provider network, cellular operator
network, WiFi network, etc.) that connects MNs. Physical and/or
data link level security is assumed, and sometimes referred to as
"protected spectrum". Private enterprise networks and ground
domain aviation service networks may provide multiple secured IP
hops between the MN's point of connection and the nearest Access
Router.
Access Router (AR)
a router in the ANET for connecting MNs to correspondents in
outside Internetworks. The AR may be located on the same physical
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link as the MN, or may be located multiple IP hops away. In the
latter case, the MN uses encapsulation to communicate with the AR
as though it were on the same physical link.
ANET interface
a MN's attachment to a link in an ANET.
Internetwork (INET)
a connected network region with a coherent IP addressing plan that
provides transit forwarding services between ANETs and nodes that
connect directly to the open INET via unprotected media. No
physical and/or data link level security is assumed, therefore
security must be applied by upper layers. The global public
Internet itself is an example.
INET interface
a node's attachment to a link in an INET.
*NET
a "wildcard" term used when a given specification applies equally
to both ANET and INET cases.
OMNI link
a Non-Broadcast, Multiple Access (NBMA) virtual overlay configured
over one or more INETs and their connected ANETs. An OMNI link
can comprise multiple INET segments joined by bridges the same as
for any link; the addressing plans in each segment may be mutually
exclusive and managed by different administrative entities.
OMNI interface
a node's attachment to an OMNI link, and configured over one or
more underlying *NET interfaces. If there are multiple OMNI links
in an OMNI domain, a separate OMNI interface is configured for
each link.
OMNI Adaptation Layer (OAL)
an OMNI interface sublayer service whereby original IP packets
admitted into the interface are wrapped in an IPv6 header and
subject to fragmentation and reassembly. The OAL is also
responsible for generating MTU-related control messages as
necessary, and for providing addressing context for spanning
multiple segments of a bridged OMNI link.
original IP packet
a whole IP packet or fragment admitted into the OMNI interface by
the network layer prior to OAL encapsulation and fragmentation, or
an IP packet delivered to the network layer by the OMNI interface
following OAL decapsulation and reassembly.
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OAL packet
an original IP packet encapsulated in OAL headers and trailers
before OAL fragmentation, or following OAL reassembly.
OAL fragment
a portion of an OAL packet following fragmentation but prior to
*NET encapsulation, or following *NET encapsulation but prior to
OAL reassembly.
(OAL) atomic fragment
an OAL packet that does not require fragmentation is always
encapsulated as an "atomic fragment" with a Fragment Header with
Fragment Offset and More Fragments both set to 0, but with a valid
Identification value.
(OAL) carrier packet
an encapsulated OAL fragment following *NET encapsulation or prior
to *NET decapsulation. OAL sources and destinations exchange
carrier packets over underlying interfaces, and may be separated
by one or more OAL intermediate nodes. OAL intermediate nodes may
perform re-encapsulation on carrier packets by removing the *NET
headers of the first hop network and replacing them with new *NET
headers for the next hop network.
OAL source
an OMNI interface acts as an OAL source when it encapsulates
original IP packets to form OAL packets, then performs OAL
fragmentation and *NET encapsulation to create carrier packets.
OAL destination
an OMNI interface acts as an OAL destination when it decapsulates
carrier packets, then performs OAL reassembly and decapsulation to
derive the original IP packet.
OAL intermediate node
an OMNI interface acts as an OAL intermediate node when it removes
the *NET headers of carrier packets received on a first segment,
then re-encapsulates the carrier packets in new *NET headers and
forwards them into the next segment.
OMNI Option
an IPv6 Neighbor Discovery option providing multilink parameters
for the OMNI interface as specified in Section 12.
Mobile Network Prefix Link Local Address (MNP-LLA)
an IPv6 Link Local Address that embeds the most significant 64
bits of an MNP in the lower 64 bits of fe80::/64, as specified in
Section 8.
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Mobile Network Prefix Unique Local Address (MNP-ULA)
an IPv6 Unique-Local Address derived from an MNP-LLA.
Administrative Link Local Address (ADM-LLA)
an IPv6 Link Local Address that embeds a 32-bit administratively-
assigned identification value in the lower 32 bits of fe80::/96,
as specified in Section 8.
Administrative Unique Local Address (ADM-ULA)
an IPv6 Unique-Local Address derived from an ADM-LLA.
Multilink
an OMNI interface's manner of managing diverse underlying
interface connections to data links as a single logical unit. The
OMNI interface provides a single unified interface to upper
layers, while underlying interface selections are performed on a
per-packet basis considering factors such as DSCP, flow label,
application policy, signal quality, cost, etc. Multilinking
decisions are coordinated in both the outbound (i.e. MN to
correspondent) and inbound (i.e., correspondent to MN) directions.
Multinet
an OAL intermediate node's manner of bridging multiple diverse IP
Internetworks and/or private enterprise networks at the OAL layer
below IP. Through intermediate node concatenation of bridged
network segments in this way, multiple diverse Internetworks (such
as the global public IPv4 and IPv6 Internets) can serve as transit
segments in a bridged path for forwarding IP packets end-to-end.
This bridging capability proivde benefits such as supporting IPv4/
IPv6 transition and coexsitence, joining multiple diverse operator
networks into a cooperative single service network, etc.
Multihop
an iterative relaying of IP packets between MNs over an OMNI
underlying interface technology (such as omnidirectional wireless)
without support of fixed infrastructure. Multihop services entail
node-to-node relaying within a Mobile/Vehicular Ad-hoc Network
(MANET/VANET) for MN-to-MN communications and/or for "range
extension" where MNs within range of communications infrastructure
elements provide forwarding services for other MNs.
L2
The second layer in the OSI network model. Also known as "layer-
2", "link-layer", "sub-IP layer", "data link layer", etc.
L3
The third layer in the OSI network model. Also known as "layer-
3", "network-layer", "IP layer", etc.
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underlying interface
a *NET interface over which an OMNI interface is configured. The
OMNI interface is seen as a L3 interface by the IP layer, and each
underlying interface is seen as a L2 interface by the OMNI
interface. The underlying interface either connects directly to
the physical communications media or coordinates with another node
where the physical media is hosted.
Mobility Service Identification (MSID)
Each MSE and AR is assigned a unique 32-bit Identification (MSID)
(see: Section 8). IDs are assigned according to MS-specific
guidelines (e.g., see: [I-D.templin-6man-aero]).
Safety-Based Multilink (SBM)
A means for ensuring fault tolerance through redundancy by
connecting multiple affiliated OMNI interfaces to independent
routing topologies (i.e., multiple independent OMNI links).
Performance Based Multilink (PBM)
A means for selecting underlying interface(s) for packet
transmission and reception within a single OMNI interface.
OMNI Domain
The set of all SBM/PBM OMNI links that collectively provides
services for a common set of MSPs. Each OMNI domain consists of a
set of affiliated OMNI links that all configure the same ::/48 ULA
prefix with a unique 16-bit Subnet ID as discussed in Section 9.
3. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
An implementation is not required to internally use the architectural
constructs described here so long as its external behavior is
consistent with that described in this document.
4. Overlay Multilink Network (OMNI) Interface Model
An OMNI interface is a virtual interface configured over one or more
underlying interfaces, which may be physical (e.g., an aeronautical
radio link, etc.) or virtual (e.g., an Internet or higher-layer
"tunnel"). The OMNI interface architectural layering model is the
same as in [RFC5558][RFC7847], and augmented as shown in Figure 1.
The IP layer therefore sees the OMNI interface as a single L3
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interface nexus for multiple underlying interfaces that appear as L2
communication channels in the architecture.
+----------------------------+
| Upper Layer Protocol |
Session-to-IP +---->| |
Address Binding | +----------------------------+
+---->| IP (L3) |
IP Address +---->| |
Binding | +----------------------------+
+---->| OMNI Interface |
Logical-to- +---->| (OMNI Adaptation Layer) |
Physical | +----------------------------+
Interface +---->| L2 | L2 | | L2 |
Binding |(IF#1)|(IF#2)| ..... |(IF#n)|
+------+------+ +------+
| L1 | L1 | | L1 |
| | | | |
+------+------+ +------+
Figure 1: OMNI Interface Architectural Layering Model
Each underlying interface provides an L2/L1 abstraction according to
one of the following models:
o INET interfaces connect to an INET either natively or through one
or several IPv4 Network Address Translators (NATs). Native INET
interfaces have global IP addresses that are reachable from any
INET correspondent. NATed INET interfaces typically have private
IP addresses and connect to a private network behind one or more
NATs that provide INET access.
o ANET interfaces connect to a protected ANET that is separated from
the open INET by an AR acting as a proxy. The ANET interface may
be either on the same L2 link segment as the AR, or separated from
the AR by multiple IP hops.
o VPNed interfaces use security encapsulation over a *NET to a
Virtual Private Network (VPN) gateway. Other than the link-layer
encapsulation format, VPNed interfaces behave the same as for
Direct interfaces.
o Direct (aka "point-to-point") interfaces connect directly to a
peer without crossing any *NET paths. An example is a line-of-
sight link between a remote pilot and an unmanned aircraft.
The OMNI interface forwards original IP packets from the network
layer (L3) using the OMNI Adaptation Layer (OAL) (see: Section 5) as
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an encapsulation and fragmentation sublayer service. This "OAL
source" then further encapsulates the resulting OAL packets/fragments
in *NET headers to create OAL carrier packets for transmission over
underlying interfaces (L2/L1). The target OMNI interface receives
the carrier packets from underlying interfaces (L1/L2) and discards
the *NET headers. If the resulting OAL packets/fragments are
addressed to itself, the OMNI interface acts as an "OAL destination"
and performs reassembly if necessary, discards the OAL encapsulation,
and delivers the original IP packet to the network layer (L3). If
the OAL fragments are addressed to another node, the OMNI interface
instead acts as an "OAL intermediate node" by re-encapsulating in new
*NET headers and forwarding the new carrier packets over an
underlying interface without reassembling or discarding the OAL
encapsulation. The OAL source and OAL destination are seen as
"neighbors" on the OMNI link, while OAL intermediate nodes are seen
as "bridges" capable of multinet concatenation.
The OMNI interface can send/receive original IP packets to/from
underlying interfaces while including/omitting various encapsulations
including OAL, UDP, IP and L2. The network layer can also access the
underlying interfaces directly while bypassing the OMNI interface
entirely when necessary. This architectural flexibility may be
beneficial for underlying interfaces (e.g., some aviation data links)
for which encapsulation overhead may be a primary consideration.
OMNI interfaces that send original IP packets directly over
underlying interfaces without invoking the OAL can only reach peers
located on the same OMNI link segment. However, an ANET proxy that
receives the original IP packet can forward it further by performing
OAL encapsulation with source set to its own address and destination
set to the OAL destination corresponding to the final destination
(i.e., even if the OAL destination is on a different OMNI link
segment).
Original IP packets sent directly over underlying interfaces are
subject to the same path MTU related issues as for any
Internetworking path, and do not include per-packet identifications
that can be used for data origin verification and/or link-layer
retransmissions. Original IP packets presented directly to an
underlying interface that exceed the underlying network path MTU are
dropped with an ordinary ICMPv6 Packet Too Big (PTB) message
returned. These PTB messages are subject to loss [RFC2923] the same
as for any non-OMNI IP interface.
The OMNI interface encapsulation/decapsulation layering possibilities
are shown in Figure 2 below. In the figure, imaginary vertical lines
drawn between the Network Layer and Underlying interfaces denote the
encapsulation/decapsulation layering combinations possible. Common
combinations include NULL (i.e., direct access to underlying
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interfaces with or without using the OMNI interface), OMNI/IP,
OMNI/UDP/IP, OMNI/UDP/IP/L2, OMNI/OAL/UDP/IP, OMNI/OAL/UDP/L2, etc.
+------------------------------------------------------------+
| Network Layer |
+--+---------------------------------------------------------+
| OMNI Interface |
+--------------------------+------------------------------+
| OAL Encaps/Decaps |
+------------------------------+
| OAL Frag/Reass |
+------------+---------------+--------------+
| UDP Encaps/Decaps/Compress |
+----+---+------------+--------+--+ +--------+
| IP E/D | | IP E/D | | IP E/D |
+---+------+-+----+ +--+---+----+ +----+---+--+
|L2 E/D| |L2 E/D| |L2 E/D| |L2 E/D|
+-------+------+---+------+----+------+---------------+------+
| Underlying Interfaces |
+------------------------------------------------------------+
Figure 2: OMNI Interface Layering
The OMNI/OAL model gives rise to a number of opportunities:
o MNs receive a MNP from the MS, and coordinate with the MS through
IPv6 ND message exchanges. The MN uses the MNP to construct a
unique Link-Local Address (MNP-LLA) through the algorithmic
derivation specified in Section 8 and assigns the LLA to the OMNI
interface. Since MNP-LLAs are uniquely derived from an MNP, no
Duplicate Address Detection (DAD) or Multicast Listener Discovery
(MLD) messaging is necessary.
o since Temporary ULAs are statistically unique, they can be used
without DAD, e.g. for MN-to-MN communications until an MNP-LLA is
obtained.
o underlying interfaces on the same L2 link segment as an AR do not
require any L3 addresses (i.e., not even link-local) in
environments where communications are coordinated entirely over
the OMNI interface.
o as underlying interface properties change (e.g., link quality,
cost, availability, etc.), any active interface can be used to
update the profiles of multiple additional interfaces in a single
message. This allows for timely adaptation and service continuity
under dynamically changing conditions.
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o coordinating underlying interfaces in this way allows them to be
represented in a unified MS profile with provisions for mobility
and multilink operations.
o exposing a single virtual interface abstraction to the IPv6 layer
allows for multilink operation (including QoS based link
selection, packet replication, load balancing, etc.) at L2 while
still permitting L3 traffic shaping based on, e.g., DSCP, flow
label, etc.
o the OMNI interface allows inter-INET traversal when nodes located
in different INETs need to communicate with one another. This
mode of operation would not be possible via direct communications
over the underlying interfaces themselves.
o the OAL supports lossless and adaptive path MTU mitigations not
available for communications directly over the underlying
interfaces themselves. The OAL supports "packing" of multiple IP
payload packets within a single OAL packet.
o the OAL applies per-packet identification values that allow for
link-layer reliability and data origin authentication.
o L3 sees the OMNI interface as a point of connection to the OMNI
link; if there are multiple OMNI links (i.e., multiple MS's), L3
will see multiple OMNI interfaces.
o Multiple independent OMNI interfaces can be used for increased
fault tolerance through Safety-Based Multilink (SBM), with
Performance-Based Multilink (PBM) applied within each interface.
Other opportunities are discussed in [RFC7847]. Note that even when
the OMNI virtual interface is present, applications can still access
underlying interfaces either through the network protocol stack using
an Internet socket or directly using a raw socket. This allows for
intra-network (or point-to-point) communications without invoking the
OMNI interface and/or OAL. For example, when an IPv6 OMNI interface
is configured over an underlying IPv4 interface, applications can
still invoke IPv4 intra-network communications as long as the
communicating endpoints are not subject to mobility dynamics.
However, the opportunities discussed above are not realized when the
architectural layering is bypassed in this way.
Figure 3 depicts the architectural model for a MN with an attached
EUN connecting to the MS via multiple independent *NETs. When an
underlying interface becomes active, the MN's OMNI interface sends
IPv6 ND messages without encapsulation if the first-hop Access Router
(AR) is on the same underlying link; otherwise, the interface uses
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IP-in-IP encapsulation. The IPv6 ND messages traverse the ground
domain *NETs until they reach an AR (AR#1, AR#2, ..., AR#n), which
then coordinates with an INET Mobility Service Endpoint (MSE#1,
MSE#2, ..., MSE#m) and returns an IPv6 ND message response to the MN.
The Hop Limit in IPv6 ND messages is not decremented due to
encapsulation; hence, the OMNI interface appears to be attached to an
ordinary link.
+--------------+ (:::)-.
| MN |<-->.-(::EUN:::)
+--------------+ `-(::::)-'
|OMNI interface|
+----+----+----+
+--------|IF#1|IF#2|IF#n|------ +
/ +----+----+----+ \
/ | \
/ | \
v v v
(:::)-. (:::)-. (:::)-.
.-(::*NET:::) .-(::*NET:::) .-(::*NET:::)
`-(::::)-' `-(::::)-' `-(::::)-'
+----+ +----+ +----+
... |AR#1| .......... |AR#2| ......... |AR#n| ...
. +-|--+ +-|--+ +-|--+ .
. | | |
. v v v .
. <----- INET Encapsulation -----> .
. .
. +-----+ (:::)-. .
. |MSE#2| .-(::::::::) +-----+ .
. +-----+ .-(::: INET :::)-. |MSE#m| .
. (::::: Routing ::::) +-----+ .
. `-(::: System :::)-' .
. +-----+ `-(:::::::-' .
. |MSE#1| +-----+ +-----+ .
. +-----+ |MSE#3| |MSE#4| .
. +-----+ +-----+ .
. .
. .
. <----- Worldwide Connected Internetwork ----> .
...........................................................
Figure 3: MN/MS Coordination via Multiple *NETs
After the initial IPv6 ND message exchange, the MN (and/or any nodes
on its attached EUNs) can send and receive original IP packets over
the OMNI interface. OMNI interface multilink services will forward
the packets via ARs in the correct underlying *NETs. The AR
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encapsulates the packets according to the capabilities provided by
the MS and forwards them to the next hop within the worldwide
connected Internetwork via optimal routes.
5. OMNI Interface Maximum Transmission Unit (MTU)
The OMNI interface observes the link nature of tunnels, including the
Maximum Transmission Unit (MTU), Maximum Reassembly Unit (MRU) and
the role of fragmentation and reassembly [I-D.ietf-intarea-tunnels].
The OMNI interface is configured over one or more underlying
interfaces as discussed in Section 4, where the interfaces (and their
associated *NET paths) may have diverse MTUs. OMNI interface
considerations for accommodating original IP packets of various sizes
are discussed in the following sections.
IPv6 underlying interfaces are REQUIRED to configure a minimum MTU of
1280 bytes and a minimum MRU of 1500 bytes [RFC8200]. Therefore, the
minimum IPv6 path MTU is 1280 bytes since routers on the path are not
permitted to perform network fragmentation even though the
destination is required to reassemble more. The network therefore
MUST forward original IP packets of at least 1280 bytes without
generating an IPv6 Path MTU Discovery (PMTUD) Packet Too Big (PTB)
message [RFC8201]. (While the source can apply "source
fragmentation" for locally-generated IPv6 packets up to 1500 bytes
and larger still if it knows the destination configures a larger MRU,
this does not affect the minimum IPv6 path MTU.)
IPv4 underlying interfaces are REQUIRED to configure a minimum MTU of
68 bytes [RFC0791] and a minimum MRU of 576 bytes [RFC0791][RFC1122].
Therefore, when the Don't Fragment (DF) bit in the IPv4 header is set
to 0 the minimum IPv4 path MTU is 576 bytes since routers on the path
support network fragmentation and the destination is required to
reassemble at least that much. The OMNI interface therefore MUST set
DF to 0 in the IPv4 encapsulation headers of carrier packets that are
no larger than 576 bytes, and SHOULD set DF to 1 in larger carrier
packets. (Note: even if the encapsulation source has a way to
determine that the encapsulation destination configures an MRU larger
than 576 bytes, it should not assume a larger minimum IPv4 path MTU
without careful consideration of the issues discussed in
Section 6.9.)
The OMNI interface configures an MTU and MRU of 9180 bytes [RFC2492];
the size is therefore not a reflection of the underlying interface or
*NET path MTUs, but rather determines the largest original IP packet
the OAL (and/or underlying interface) can forward or reassemble. For
each OAL destination (i.e., for each OMNI link neighbor), the OAL
source may discover "hard" or "soft" Reassembly Limit values smaller
than the MRU based on receipt of IPv6 ND messages with OMNI
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Reassembly Limit sub-options (see: Section 12.1.12). The OMNI
interface employs the OAL as an encapsulation sublayer service to
transform original IP packets into OAL packets/fragments, and the OAL
in turn uses *NET encapsulation to forward carrier packets over the
underlying interfaces (see: Section 6).
6. The OMNI Adaptation Layer (OAL)
When an OMNI interface forwards an original IP packet from the
network layer for transmission over one or more underlying
interfaces, the OMNI Adaptation Layer (OAL) acting as the OAL source
drops the packet and returns a PTB message if the packet exceeds the
MRU and/or the hard Reassembly Limit for the intended OAL
destination. Otherwise, the OAL source applies encapsulation to form
OAL packets and fragmentation to produce resulting OAL fragments
suitable for *NET encapsulation and transmission as carrier packets
over underlying interfaces as described in Section 6.1.
These carrier packets travel over one or more underlying networks
bridged by OAL intermediate nodes, which re-encapsulate by removing
the *NET headers of the first underlying network and appending *NET
headers appropriate for the next underlying network in succession.
(This process supports the multinet concatenation capability needed
for joining multiple diverse networks.) After re-encapsulation by
zero or more OAL intermediate nodes, the carrier packets arrive at
the OAL destination.
When the OAL destination receives the carrier packets, it discards
the *NET headers and reassembles the resulting OAL fragments into an
OAL packet as described in Section 6.3. The OAL destination then
decapsulates the OAL packet to obtain the original IP packet, which
it then delivers to the network layer.
The OAL presents an OMNI sublayer abstraction similar to ATM
Adaptation Layer 5 (AAL5). Unlike AAL5 which performs segmentation
and reassembly with fixed-length 53 octet cells over ATM networks,
however, the OAL uses IPv6 encapsulation, fragmentation and
reassembly with larger variable-length cells over heterogeneous
underlying networks. Detailed operations of the OAL are specified in
the following sections.
6.1. OAL Source Encapsulation and Fragmentation
When the network layer forwards an original IP packet into the OMNI
interface, the OAL source inserts an IPv6 encapsulation header but
does not decrement the Hop Limit/TTL of the original IP packet since
encapsulation occurs at a layer below IP forwarding [RFC2473]. The
OAL source copies the "Type of Service/Traffic Class" [RFC2983] and
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"Congestion Experienced" [RFC3168] values in the original packet's IP
header into the corresponding fields in the OAL header, then sets the
OAL header "Flow Label" as specified in [RFC6438]. The OAL source
finally sets the OAL header IPv6 Hop Limit to a conservative value
sufficient to enable loop-free forwarding over multiple concatenated
OMNI link segments and sets the Payload Length to the length of the
original IP packet.
The OAL next selects source and destination addresses for the IPv6
header of the resulting OAL packet. MN OMNI interfaces set the OAL
IPv6 header source address to a Unique Local Address (ULA) based on
the Mobile Network Prefix (MNP-ULA), while AR and MSE OMNI interfaces
set the source address to an Administrative ULA (ADM-ULA) (see:
Section 9). When a MN OMNI interface does not (yet) have an MNP-ULA,
it can use a Temporary ULA and/or Host Identity Tag (HIT) instead
(see: Section 22).
When the OAL source forwards an original IP packet toward a final
destination via an ANET underlying interface, it sets the OAL IPv6
header source address to its own ULA and sets the destination to
either the Administrative ULA (ADM-ULA) of the ANET peer or the
Mobile Network Prefix ULA (MNP-ULA) corresponding to the final
destination (see below). The OAL source then fragments the OAL
packet if necessary, encapsulates the OAL fragments in any ANET
headers and sends the resulting carrier packets to the ANET peer
which either reassembles before forwarding if the OAL destination is
its own ULA or forwards the fragments toward the true OAL destination
without first reassembling otherwise.
When the OAL source forwards an original IP packet toward a final
destination via an INET underlying interface, it sets the OAL IPv6
header source address to its own ULA and sets the destination to the
ULA of an OAL destination node on the final *NET segment. The OAL
source then fragments the OAL packet if necessary, encapsulates the
OAL fragments in any *NET headers and sends the resulting carrier
packets toward the OAL destination on the final segment OMNI node
which reassembles before forwarding the original IP packets toward
the final destination.
Following OAL IPv6 encapsulation and address selection, the OAL
source next appends a 2 octet trailing Checksum (initialized to 0) at
the end of the original IP packet while incrementing the OAL header
IPv6 Payload Length field to reflect the addition of the trailer.
The format of the resulting OAL packet following encapsulation is
shown in Figure 4:
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+----------+-----+-----+-----+-----+-----+-----+----+
| OAL Hdr | Original IP packet |Csum|
+----------+-----+-----+-----+-----+-----+-----+----+
Figure 4: OAL Packet Before Fragmentation
The OAL source next selects a 32-bit Identification value for the
packet, beginning with an unpredictable value for the initial OAL
packet per [RFC7739] and monotonically incrementing for each
successive OAL packet until a new initial value is chosen.
The OAL source then calculates the 2's complement (mod 256)
Fletcher's checksum [CKSUM][RFC2328][RFC0905] over the entire OAL
packet beginning with a pseudo-header of the IPv6 header similar to
that found in Section 8.1 of [RFC8200]. The OAL IPv6 pseudo-header
is formed as shown in Figure 5:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ OAL Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ OAL Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAL Payload Length | zero | Next Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: OAL IPv6 Pseudo-Header
The OAL source then inserts a single OMNI Routing Header (ORH) if
necessary (see: [I-D.templin-6man-aero]) while incrementing Payload
Length to reflect the addition of the ORH (note that the late
addition of the ORH is not covered by the trailing checksum).
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The OAL source next fragments the OAL packet if necessary while
assuming the IPv4 minimum path MTU (i.e., 576 bytes) as the worst
case for OAL fragmentation regardless of the underlying interface IP
protocol version since IPv6/IPv4 protocol translation and/or IPv6-in-
IPv4 encapsulation may occur in any *NET path. By always assuming
the IPv4 minimum even for IPv6 underlying interfaces, the OAL source
may produce smaller fragments with additional encapsulation overhead
but will always interoperate and never run the risk of loss due to an
MTU restriction or due to presenting an underlying interface with a
carrier packet that exceeds its MRU. Additionally, the OAL path
could traverse multiple *NET "segments" with intermediate OAL
forwarding nodes performing re-encapsulation where the *NET
encapsulation of the previous segment is replaced by the *NET
encapsulation of the next segment which may be based on a different
IP protocol version and/or encapsulation sizes.
The OAL source therefore assumes a default minimum path MTU of 576
bytes at each *NET segment for the purpose of generating OAL
fragments for *NET encapsulation and transmission as carrier packets.
In the worst case, each successive *NET segment may re-encapsulate
with either a 20 byte IPv4 or 40 byte IPv6 header, an 8 byte UDP
header and in some cases an IP security encapsulation (40 bytes
maximum assumed). Any *NET segment may also insert a maximum-length
(40 byte) ORH as an extension to the existing 40 byte OAL IPv6 header
plus 8 byte Fragment Header if an ORH was not already present.
Assuming therefore an absolute worst case of (40 + 40 + 8) = 88 bytes
for *NET encapsulation plus (40 + 40 + 8) = 88 bytes for OAL
encapsulation leaves (576 - 88 - 88) = 400 bytes to accommodate a
portion of the original IP packet/fragment. The OAL source therefore
sets a minimum Maximum Payload Size (MPS) of 400 bytes as the basis
for the minimum-sized OAL fragment that can be assured of traversing
all segments without loss due to an MTU/MRU restriction. The Maximum
Fragment Size (MFS) for OAL fragmentation is therefore determined by
the MPS plus the size of the OAL encapsulation headers. (Note that
the OAL source includes the 2 octet trailer as part of the payload
during fragmentation, and the OAL destination regards it as ordinary
payload until reassembly and checksum verification are complete.)
The OAL source SHOULD maintain "path MPS" values for individual OAL
destinations initialized to the minimum MPS and increased to larger
values (up to the OMNI interface MTU) if better information is known
or discovered. For example, when *NET peers share a common
underlying link or a fixed path with a known larger MTU, the OAL
source can base path MPS on this larger size (i.e., instead of 576
bytes) as long as the *NET peer reassembles before re-encapsulating
and forwarding (while re-fragmenting if necessary). Also, if the OAL
source has a way of knowing the maximum *NET encapsulation size for
all segments along the path it may be able to increase path MPS to
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reserve additional room for payload data. The OAL source must
include the uncompressed OAL header size in its path MPS calculation,
since a full header could be included at any time.
The OAL source can also actively probe individual OAL destinations to
discover larger path MPS values using packetization layer probes per
[RFC4821][RFC8899], but care must be taken to avoid setting static
values for dynamically changing paths leading to black holes. The
probe involves sending an OAL packet larger than the current path MPS
and receiving a small acknowledgement message in response (with the
possible receipt of link-layer error message in case the probe was
lost). For this purpose, the OAL source can send an NS message with
one or more OMNI options with large PadN sub-options (see:
Section 12) in order to receive a small NA response from the OAL
destination. While observing the minimum MPS will always result in
robust and secure behavior, the OAL source should optimize path MPS
values when more efficient utilization may result in better
performance (e.g. for wireless aviation data links).
When the OAL source performs fragmentation, it SHOULD produce the
minimum number of non-overlapping fragments under current MPS
constraints, where each non-final fragment MUST be of equal length at
least as large as the minimum MPS, while the final fragment MAY be of
different length. The OAL source also converts all original IP
packets no larger than the current MPS into "atomic fragments" by
including a Fragment Header with Fragment Offset and More Fragments
both set to 0. The OAL source finally encapsulates the fragments in
*NET headers to form carrier packets and forwards them over an
underlying interface, while retaining the fragments and their ordinal
positions (i.e., as Frag #0, Frag #1, Frag #2, etc.) for a timeout
period in case link-layer retransmission is requested. The formats
of OAL fragments and carrier packets are shown in Figure 6.
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+----------+--+-------------+
| OAL Hdr |FH| Frag #0 |
+----------+--+-------------+
+----------+--+-------------+
| OAL Hdr |FH| Frag #1 |
+----------+--+-------------+
+----------+--+-------------+
| OAL Hdr |FH| Frag #2 |
+----------+--+-------------+
....
+----------+--+-------------+----+
| OAL Hdr |FH| Frag #(N-1) |Csum|
+----------+--+-------------+----+
a) OAL fragments after fragmentation
(FH = Fragment Header; Csum appears only in final fragment)
+--------+--+-----+-----+-----+-----+-----+----+
|OAL Hdr |FH| Original IP packet |Csum|
+--------+--+-----+-----+-----+-----+-----+----+
b) An OAL atomic fragment with FH but no fragmentation.
+--------+----------+--+-------------+
|*NET Hdr| OAL Hdr |FH| Frag #i |
+--------+----------+--+-------------+
c) OAL carrier packet after *NET encapsulation
Figure 6: OAL Fragments and Carrier Packets
6.2. OAL *NET Encapsulation and Re-Encapsulation
During *NET encapsulation, OAL sources first encapsulate each OAL
fragment in a UDP header as the first *NET encapsulation sublayer if
NAT traversal, packet filtering middlebox traversal and/or OAL header
compression are necessary. The OAL then optionally appends
additional encapsulation sublayer headers, then presents the *NET
packet to an underlying interface. This layering can be seen in
Figure 2.
When a UDP header is included, the OAL source next sets the UDP
source port to a constant value that it will use in each successive
carrier packet it sends to the next OAL hop. For packets sent to an
MSE, the OAL source sets the UDP destination port to 8060, i.e., the
IANA-registered port number for AERO. For packets sent to a MN peer,
the source sets the UDP destination port to the cached port value for
this peer. The OAL source then sets the UDP length to the total
length of the OAL fragment in correspondence with the OAL header
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Payload Length (i.e., the UDP length and IPv6 Payload Length must
agree). The OAL source finally sets the UDP checksum to 0
[RFC6935][RFC6936] since the only fields not already covered by the
OAL checksum or underlying *NET CRCs are the Fragment Header fields,
and any corruption in those fields will be garbage collected by the
reassembly algorithm (however, see Section 20 for additional
considerations). The UDP encapsulation header is often used in
association with IP encapsulation, but may also be used between
neighbors on a shared physical link with a true L2 header format such
as for transmission over IEEE 802 Ethernet links. This document
therefore requests a new Ether Type code assignment TBD1 in the IANA
'ieee-802-numbers' registry for direct User Datagram Protocol (UDP)
encapsulation over IEEE 802 Ethernet links (see: Section 25).
For *NET encapsulations over IP, the OAL source next copies the "Type
of Service/Traffic Class" [RFC2983] and "Congestion Experienced"
[RFC3168] values in the OAL IPv6 header into the corresponding fields
in the *NET IP header, then (for IPv6) sets the *NET IPv6 header
"Flow Label" as specified in [RFC6438]. The OAL source then sets the
*NET IP TTL/Hop Limit the same as for any *NET host, i.e., it does
not copy the Hop Limit value from the OAL header. For carrier
packets undergoing re-encapsulation at an OAL intermediate node, the
node decrements the OAL IPv6 header Hop Limit and discards the
carrier packet if the value reaches 0. The node then copies the
"Type of Service/Traffic Class" and "Congestion Experienced" values
from the previous hop *NET encapsulation header into the OAL IPv6
header before setting the next hop *NET IP encapsulation header
values the same as specified for the OAL source above.
Following *NET encapsulation/re-encapsulation, the OAL source sends
the resulting carrier packets over one or more underlying interfaces.
The underlying interfaces often connect directly to physical media on
the local platform (e.g., a laptop computer with WiFi, etc.), but in
some configurations the physical media may be hosted on a separate
Local Area Network (LAN) node. In that case, the OMNI interface can
establish a Layer-2 VLAN or a point-to-point tunnel (at a layer below
the underlying interface) to the node hosting the physical media.
The OMNI interface may also apply encapsulation at the underlying
interface layer (e.g., as for a tunnel virtual interface) such that
carrier packets would appear "double-encapsulated" on the LAN; the
node hosting the physical media in turn removes the LAN encapsulation
prior to transmission or inserts it following reception. Finally,
the underlying interface must monitor the node hosting the physical
media (e.g., through periodic keepalives) so that it can convey
up/down/status information to the OMNI interface.
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6.3. OAL Destination Decapsulation and Reassembly
When an OMNI interface receives a carrier packet from an underlying
interface, the OAL destination discards the *NET encapsulation
headers and examines the OAL header of the enclosed OAL fragment. If
the OAL fragment is addressed to a different node, the OAL
destination re-encapsulates and forwards as discussed below. If the
OAL fragment is addressed to itself, the OAL destination creates or
updates a checklist for this (Source, Destination, Identification)-
tuple to track the fragments already received (i.e., by examining the
Payload Length, Fragment Offset, More Fragments and Identification
values supplied by the OAL source). The OAL destination verifies
that all non-final OAL fragments are of equal length no less than the
minimum MPS and that no fragments overlap or leave "holes", while
dropping any non-conforming fragments. The OAL destination records
each conforming OAL fragment's ordinal position based on the OAL
header Payload Length and Fragment Offset values (i.e., as Frag #0,
Frag #1, Frag #2, etc.) and admits each fragment into the reassembly
cache.
When reassembly is complete, the OAL destination removes the ORH if
present while decrementing Payload Length to reflect the removal of
the ORH. The OAL destination next verifies the resulting OAL
packet's checksum and discards the packet if the checksum is
incorrect. If the OAL packet was accepted, the OAL destination then
removes the OAL header/trailer, then delivers the original IP packet
to the network layer. Note that link layers include a CRC-32
integrity check which provides effective hop-by-hop error detection
in the underlying network for payload sizes up to the OMNI interface
MTU [CRC], but that some hops may traverse intermediate layers such
as tunnels over IPv4 that do not include integrity checks. The
trailing Fletcher checksum therefore allows the OAL destination to
detect OAL packet splicing errors due to reassembly misassociations
and/or to verify integrity for OAL packets whose fragments may have
traversed unprotected underlying network hops [CKSUM]. The Fletcher
algorithm also provides diversity with respect to both lower layer
CRCs and upper layer Internet checksums as part of a complimentary
multi-layer integrity assurance architecture.
6.4. OAL Header Compression
When the OAL source and destination are on the same *NET segment, no
ORH is needed and carrier packet header compression is possible.
When the OAL source and destination exchange initial IPv6 ND messages
as discussed in the following Sections, each caches the observed *NET
UDP source port and source IP (or L2) address associated with the OAL
IPv6 source address found in the full-length OAL IPv6 header. After
the initial IPv6 ND message exchange, the OAL source can begin
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applying OAL Header Compression to significantly reduce the
encapsulation overhead required in each carrier packet.
When the OAL source determines that header compression state has been
established (i.e., following the IPv6 ND message exchange), it can
begin sending OAL fragments with significant portions of the IPv6
header and Fragment Header omitted thereby reducing the amount of
encapsulation overhead. For OAL first-fragments (including atomic
fragments), the OMNI Compressed Header - Type 0 (OCH-0) is used and
formatted as shown in Figure 7:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ *
| Source port | Destination port | U
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ D
| Length | Checksum | P
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ *
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Reserved |M| Identification (0 -1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification (2-3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+/
Figure 7: OMNI Compressed Header - Type 0 (OCH-0)
In this format, the UDP header appears in its entirety in the first 8
octets, then followed by the first 4 octets of the IPv6 header with
the remainder omitted. (The IPv6 Version field is set to the value 0
to distinguish this header from a true IP protocol version number and
from OCH-1 - see below.) The compressed IPv6 header is then followed
by a compressed IPv6 Fragment Header with the Fragment Offset field
and two Reserved bits omitted (since these fields always encode the
value 0 in first-fragments), and with the More Fragments (M) bit
relocated to the least significant bit of the first Reserved field.
The OCH-0 header is then followed by the OAL fragment body, and the
UDP length field is reduced by 38 octets (i.e., the difference in
length between full-length IPv6 and Fragment Headers and the length
of the compressed headers).
For OAL non-first fragments (i.e., those with non-zero Fragment
Offsets), the OMNI Compressed Header - Type 1 (OCH-1) is used and
formatted as shown in Figure 8:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ *
| Source port | Destination port | U
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ D
| Length | Checksum | P
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ *
|V|R|M| Fragment Offset | Identification (0-1) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification (1-3) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: OMNI Compressed Header - Type 1 (OCH-1)
In this format, the UDP header appears in its entirety in the first 8
octets, but all IPv6 header fields except for the most significant
Version (V) bit are omitted. (The V bit is set to the value 1 to
distinguish this header from a true IP protocol version number and
from OCH-0.) The V bit is followed by a single Reserved (R) bit and
the More Fragments (M) bit in a compressed IPv6 Fragment Header with
the Next Header and first Reserved fields omitted. The OCH-1 header
is then followed by the OAL fragment body, and the UDP length field
is reduced by 42 octets (i.e., the difference in length between full-
length IPv6 and Fragment Headers and the length of the compressed
headers).
When the OAL destination receives a carrier packet with an OCH, it
first determines the OAL IPv6 source and destination addresses by
examining the UDP source port and L2 source address, then determines
the length by examining the UDP length. The OAL destination then
examines the (V)ersion field immediately following the UDP header.
If the (4-bit) Version field encodes the value 0, the OAL destination
processes the remainder of the header as an OCH-0, then reconstitutes
the full-sized IPv6 and Fragment Headers and adds this OAL fragment
to the reassembly buffer if necessary. If the (1-bit) V bit encodes
the value 1, the OAL destination instead processes the remainder of
the header as an OCH-1, then reconstitutes the full-sized IPv6 and
Fragment Headers and adds this OAL fragment to the reassembly buffer.
Note that, since the OCH-1 does not include Traffic Class, Flow Label
or Next Header information, the OAL destination writes the value 0
into these fields when it reconstitutes the full headers. These
values will be correctly populated during reassembly after an OAL
first fragment with an OCH-0 or uncompressed OAL header arrives.
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6.5. OAL Fragment Identification Window Maintenance
As noted above, the OAL source establishes a window of 32-bit
Identifications beginning with an unpredictable value for the initial
message [RFC7739] and monotonically incrementing for each successive
OAL packet until a new initial value is chosen. The OAL source
asserts the starting value by including it as the Identification in
an IPv6 ND NS/RS messages. When the OAL destination receives the
IPv6 ND message, it resets the Identification window for this OAL
source to the new value coded in the message's OAL header and expects
future OAL fragments received from this OAL source to include
sequential Identification values (subject to loss and reordering)
until the neighbor reachable time expires or the OAL source sends a
new IPv6 ND message.
For example, if the OAL destination receives an NS/RS message with
Identification 0x12345678, it resets the window for this OAL source
to begin with 0x12345678 and examines the Identification values in
subsequent OAL fragments received from this OAL source. If the
Identification values of subsequent OAL fragments fall within the
window of (0x12345678 + N) the OAL destination accepts the fragment;
otherwise, it silently drops the fragment (where "N" represents the
maximum number of fragments expected before the neighbor reachable
time expires).
While monitoring the current window, the OAL destination must accept
new NS/RS Identification values even if outside the current window.
The new Identification value resets the OAL destination's window
start, and the window processing continues from this new starting
point while allowing a period of overlap in case OAL fragments with
Identification values from a previous window are still in flight.
Note also that unsolicited NA messages must include Identification
values within the current window, and therefore do not reset the
current window.
This implies that an IPv6 ND message used to reset the Identification
window should fit within a single OAL fragment (i.e., within current
MPS constraints), since a fragmented IPv6 ND message with an out-of-
window Identification value could be part of a DoS attack. While
larger IPv6 ND messages (up to the OMNI interface MTU) can certainly
be subject to OAL fragmentation, their Identification should be
within the current window maintained by the OAL destination to
increase the likelihood that they will be accepted.
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6.6. OAL Fragment Retransmission
When the OAL source sends carrier packets with OAL fragments to an
OAL destination, the source caches them for a timeout period in case
retransmission may be necessary. (The timeout duration is an
implementation matter, and may be influenced by factors such as
packet arrival rates, OAL source/destination round trip times, etc.)
The OAL destination in turn maintains a checklist for the (Source,
Destination, Identification)-tuple of each new OAL fragment received
and notes the ordinal positions of fragments already received (i.e.,
as Frag #0, Frag #1, Frag #2, etc.).
If the OAL destination notices some OAL fragments missing after most
other fragments within the same Identification window have already
arrived, it may send an IPv6 ND unsolicited Neighbor Advertisement
(uNA) message to the OAL source that originated the fragments to
report loss. The OAL destination creates a uNA message with an OMNI
option containing an authentication sub-option to provide
authentication (if the OAL source is on an open Internetwork)
followed by a Fragmentation Report sub-option that includes a list of
(Identification, Bitmap)-tuples for OAL fragments received and
missing from this OAL source (see: Section 12). The OAL destination
signs the message if an authentication sub-option is included,
performs OAL encapsulation (with the its own address as the OAL
source and the source address of the message that prompted the uNA as
the OAL destination) and sends the message to the OAL source.
When the OAL source receives the uNA message, it authenticates the
message using authentication sub-option (if present) then examines
the Fragmentation Report. For each (Source, Destination,
Identification)-tuple, the OAL source determines whether it still
holds the original OAL fragments in its cache and retransmits any for
which the Bitmap indicated a loss event. For example, if the Bitmap
indicates that the ordinal OAL fragments Frag #3, Frag #7, Frag #10
and Frag #13 from the same OAL packet are missing the OAL source
retransmits these fragments only and no others.
Note that the goal of this service is to provide a light-weight link-
layer Automatic Repeat Request (ARQ) capability in the spirit of
Section 8.1 of [RFC3819]. Rather than provide true end-to-end
reliability, however, the service provides timely link-layer
retransmissions that may improve packet delivery ratios and avoid
some delays inherent in true end-to-end services.
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6.7. OAL MTU Feedback Messaging
When the OMNI interface forwards original IP packets from the network
layer, it invokes the OAL and returns internally-generated ICMPv4
Fragmentation Needed [RFC1191] or ICMPv6 Path MTU Discovery (PMTUD)
Packet Too Big (PTB) [RFC8201] messages as necessary. This document
refers to both of these ICMPv4/ICMPv6 message types simply as "PTBs",
and introduces a distinction between PTB "hard" and "soft" errors as
discussed below.
Ordinary PTB messages with ICMPv4 header "unused" field or ICMPv6
header Code field value 0 are hard errors that always indicate that a
packet has been dropped due to a real MTU restriction. In
particular, the OAL source drops the packet and returns a PTB hard
error if the packet exceeds the OAL destination MRU. However, the
OMNI interface can also forward large original IP packets via OAL
encapsulation and fragmentation while at the same time returning PTB
soft error messages (subject to rate limiting) if it deems the
original IP packet too large according to factors such as link
performance characteristics, reassembly congestion, etc. This
ensures that the path MTU is adaptive and reflects the current path
used for a given data flow. The OMNI interface can therefore
continuously forward packets without loss while returning PTB soft
error messages recommending a smaller size if necessary. Original
sources that receive the soft errors in turn reduce the size of the
packets they send (i.e., the same as for hard errors), but can soon
resume sending larger packets if the soft errors subside.
An OAL source sends PTB soft error messages by setting the ICMPv4
header "unused" field or ICMPv6 header Code field to the value 1 if a
original IP packet was deemed lost (e.g., due to reassembly timeout)
or to the value 2 otherwise. The OAL source sets the PTB destination
address to the original IP packet source, and sets the source address
to one of its OMNI interface unicast/anycast addresses that is
routable from the perspective of the original source. The OAL source
then sets the MTU field to a value smaller than the original packet
size but no smaller than 576 for ICMPv4 or 1280 for ICMPv6, writes
the leading portion of the original IP packet into the "packet in
error" field, and returns the PTB soft error to the original source.
When the original source receives the PTB soft error, it temporarily
reduces the size of the packets it sends the same as for hard errors
but may seek to increase future packet sizes dynamically while no
further soft errors are arriving. (If the original source does not
recognize the soft error code, it regards the PTB the same as a hard
error but should heed the retransmission advice given in [RFC8201]
suggesting retransmission based on normal packetization layer
retransmission timers.)
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An OAL destination may experience reassembly cache congestion, and
can return uNA messages to the OAL source that originated the
fragments (subject to rate limiting) to advertise reduced hard/soft
Reassembly Limits and/or to report individual reassembly failures.
The OAL destination creates a uNA message with an OMNI option
containing an authentication message sub-option (if the OAL source is
on an open Internetwork) followed optionally by at most one hard and
one soft Reassembly Limit sub-options with reduced hard/soft values,
and with one of them optionally including the leading portion an OAL
first fragment containing the header of an original IP packet whose
source must be notified (see: Section 12). The OAL destination
encapsulates as much of the OAL first fragment (beginning with the
OAL header) as will fit in the "OAL First Fragment" field of sub-
option without causing the entire uNA message to exceed the minimum
MPS, signs the message if an authentication sub-option is included,
performs OAL encapsulation (with the its own address as the OAL
source and the source address of the message that prompted the uNA as
the OAL destination) and sends the message to the OAL source.
When the OAL source receives the uNA message, it records the new
hard/soft Reassembly Limit values for this OAL destination if the
OMNI option includes Reassembly Limit sub-options. If a hard or soft
Reassembly Limit sub-option includes an OAL First Fragment, the OAL
source next sends a corresponding network layer PTB hard or soft
error to the original source to recommend a smaller size. For hard
errors, the OAL source sets the PTB Code field to 0. For soft
errors, the OAL source sets the PTB Code field to 1 if the L flag in
the Reassembly Limit sub-option is 1; otherwise, the OAL source sets
the Code field to 2. The OAL source crafts the PTB by extracting the
leading portion of the original IP packet from the OAL First Fragment
field (i.e., not including the OAL header) and writes it in the
"packet in error" field of a PTB with destination set to the original
IP packet source and source set to one of its OMNI interface unicast/
anycast addresses that is routable from the perspective of the
original source. For future transmissions, if the original IP packet
is larger than the hard Reassembly Limit for this OAL destination the
OAL source drops the packet and returns a PTB hard error with MTU set
to the hard Reassembly Limit. If the packet is no larger than the
current hard Reassembly Limit but larger than the current soft limit,
the OAL source can also return PTB soft errors (subject to rate
limiting) with Code set to 2 and MTU set to the current soft limit
while still forwarding the packet to the OMNI destination.
Original sources that receive PTB soft errors can dynamically tune
the size of the original IP packets they to send to produce the best
possible throughput and latency, with the understanding that these
parameters may change over time due to factors such as congestion,
mobility, network path changes, etc. The receipt or absence of soft
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";
}
}
} // rcp clear-rip-route
}
<CODE ENDS>
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5. IANA Considerations
RFC Ed.: In this section, replace all occurrences of 'XXXX' with the
actual RFC number (and remove this note).
This document registers the following namespace URIs in the IETF XML
registry [RFC3688]:
--------------------------------------------------------------------
URI: urn:ietf:params:xml:ns:yang:ietf-rip
Registrant Contact: The IESG.
XML: N/A, the requested URI is an XML namespace.
--------------------------------------------------------------------
This document registers the following YANG modules in the YANG Module
Names registry [RFC7950]:
--------------------------------------------------------------------
name: ietf-rip
namespace: urn:ietf:params:xml:ns:yang:ietf-rip
prefix: rip
reference: RFC XXXX
--------------------------------------------------------------------
6. Security Considerations
The YANG module specified in this document defines a schema for data
that is designed to be accessed via network management protocols such
as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
is the secure transport layer, and the mandatory-to-implement secure
transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
is HTTPS, and the mandatory-to-implement secure transport is TLS
[RFC8446].
The NETCONF access control model [RFC8341] provides the means to
restrict access for particular NETCONF or RESTCONF users to a
preconfigured subset of all available NETCONF or RESTCONF protocol
operations and content.
There are a number of data nodes defined in this YANG module that are
writable/creatable/deletable (i.e., config true, which is the
default). These data nodes may be considered sensitive or vulnerable
in some network environments. Write operations (e.g., edit-config)
to these data nodes without proper protection can have a negative
effect on network operations. These are the subtrees and data nodes
and their sensitivity/vulnerability:
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/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/
rip:rip
Unauthorized access to any data node of these subtrees can adversely
affect the routing subsystem of both the local device and the
network. This may lead to network malfunctions, delivery of packets
to inappropriate destinations, and other problems.
Some of the readable data nodes in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control read access (e.g., via get, get-config, or
notification) to these data nodes. These are the subtrees and data
nodes and their sensitivity/vulnerability:
/rt:routing/rt:control-plane-protocols/rt:control-plane-protocol/
rip:rip
Unauthorized access to any data node of these subtrees can disclose
the operational state information of RIP on this device.
Some of the RPC operations in this YANG module may be considered
sensitive or vulnerable in some network environments. It is thus
important to control access to these operations. These are the
operations and their sensitivity/vulnerability:
RPC clear-rip-route:
Unauthorized access to the RPC above can adversely affect the routing
subsystem of both the local device and the network. This may lead to
network malfunctions, delivery of packets to inappropriate
destinations, and other problems.
7. References
7.1. Normative References
[RFC1724] Malkin, G. and F. Baker, "RIP Version 2 MIB Extension",
RFC 1724, DOI 10.17487/RFC1724, November 1994,
<https://www.rfc-editor.org/info/rfc1724>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC2453] Malkin, G., "RIP Version 2", STD 56, RFC 2453,
DOI 10.17487/RFC2453, November 1998,
<https://www.rfc-editor.org/info/rfc2453>.
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[RFC2080] Malkin, G. and R. Minnear, "RIPng for IPv6", RFC 2080,
DOI 10.17487/RFC2080, January 1997,
<https://www.rfc-editor.org/info/rfc2080>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure
Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011,
<https://www.rfc-editor.org/info/rfc6242>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8177] Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
Zhang, "YANG Data Model for Key Chains", RFC 8177,
DOI 10.17487/RFC8177, June 2017,
<https://www.rfc-editor.org/info/rfc8177>.
[RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration
Access Control Model", STD 91, RFC 8341,
DOI 10.17487/RFC8341, March 2018,
<https://www.rfc-editor.org/info/rfc8341>.
[RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
and R. Wilton, "Network Management Datastore Architecture
(NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
<https://www.rfc-editor.org/info/rfc8342>.
[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
<https://www.rfc-editor.org/info/rfc8343>.
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[RFC8344] Bjorklund, M., "A YANG Data Model for IP Management",
RFC 8344, DOI 10.17487/RFC8344, March 2018,
<https://www.rfc-editor.org/info/rfc8344>.
[RFC8349] Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
Routing Management (NMDA Version)", RFC 8349,
DOI 10.17487/RFC8349, March 2018,
<https://www.rfc-editor.org/info/rfc8349>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
7.2. Informative References
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
Documents Containing YANG Data Models", BCP 216, RFC 8407,
DOI 10.17487/RFC8407, October 2018,
<https://www.rfc-editor.org/info/rfc8407>.
[I-D.ietf-netconf-subscribed-notifications]
Voit, E., Clemm, A., Prieto, A., Nilsen-Nygaard, E., and
A. Tripathy, "Subscription to YANG Event Notifications",
draft-ietf-netconf-subscribed-notifications-26 (work in
progress), May 2019.
[I-D.ietf-netconf-yang-push]
Clemm, A. and E. Voit, "Subscription to YANG Datastores",
draft-ietf-netconf-yang-push-25 (work in progress), May
2019.
[I-D.ietf-bfd-yang]
Rahman, R., Zheng, L., Jethanandani, M., Networks, J., and
G. Mirsky, "YANG Data Model for Bidirectional Forwarding
Detection (BFD)", draft-ietf-bfd-yang-17 (work in
progress), August 2018.
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[I-D.ietf-isis-yang-isis-cfg]
Litkowski, S., Yeung, D., Lindem, A., Zhang, Z., and L.
Lhotka, "YANG Data Model for IS-IS Protocol", draft-ietf-
isis-yang-isis-cfg-35 (work in progress), March 2019.
[I-D.ietf-ospf-yang]
Yeung, D., Qu, Y., Zhang, Z., Chen, I., and A. Lindem,
"YANG Data Model for OSPF Protocol", draft-ietf-ospf-
yang-28 (work in progress), August 2019.
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Appendix A. Data Tree Example
This section contains an example of an instance data tree in the JSON
encoding [RFC7951], containing both configuration and state data.
+---------------------+
| |
| Router 203.0.113.1 |
| |
+----------+----------+
|eth1
|2001:db8:0:1::1/64
|
|
|2001:db8:0:1::2/64
+----------+----------+
| | |
| Another Router +---------| 2001:db8:0:2::/64
| | |
+---------------------+
The configuration instance data tree for Router 203.0.113.1 in the
above figure could be as follows:
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{
"ietf-interfaces:interfaces": {
"interface": [
{
"name": "eth1",
"description": "An interface with RIPng enabled.",
"type": "iana-if-type:ethernetCsmacd",
"ietf-ip:ipv6": {
"address": [
{
"ip": "2001:db8:0:1::1",
"prefix-length": 64
}
],
"forwarding": true
}
}
]
},
"ietf-routing:routing": {
"router-id": "203.0.113.1",
"control-plane-protocols": {
"control-plane-protocol": [
{
"type": "ietf-rip:ripng",
"name": "ripng-1",
"description": "RIPng instance ripng-1.",
"ietf-rip:rip": {
"redistribute": {
"connected": {
}
}
"interfaces": {
"interface": [
{
"interface": "eth1",
"split-horizon": "poison-reverse"
}
]
}
}
}
]
}
}
}
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The cooresponding operational state data for Router 203.0.113.1 could
be as follows:
{
"ietf-interfaces:interfaces": {
"interface": [
{
"name": "eth1",
"description": "An interface with RIPng enabled.",
"type": "iana-if-type:ethernetCsmacd",
"phys-address": "00:00:5e:00:53:01",
"oper-status": "up",
"statistics": {
"discontinuity-time": "2016-10-24T17:11:27+02:00"
},
"ietf-ip:ipv6": {
"forwarding": true,
"mtu": 1500,
"address": [
{
"ip": "2001:db8:0:1::1",
"prefix-length": 64,
"origin": "static",
"status": "preferred"
},
{
"ip": "fe80::200:5eff:fe00:5301",
"prefix-length": 64,
"origin": "link-layer",
"status": "preferred"
}
],
"neighbor": [
{
"ip": "2001:db8:0:1::2",
"link-layer-address": "00:00:5e:00:53:02",
"origin": "dynamic",
"is-router": [null],
"state": "reachable"
},
{
"ip": "fe80::200:5eff:fe00:5302",
"link-layer-address": "00:00:5e:00:53:02",
"origin": "dynamic",
"is-router": [null],
"state": "reachable"
}
]
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}
}
]
},
"ietf-routing:routing": {
"router-id": "203.0.113.1",
&errors should be seen as hints of when increasing or decreasing
packet sizes may be beneficial. The OMNI interface supports
continuous transmission and reception of packets of various sizes in
the face of dynamically changing network conditions. Moreover, since
PTB soft errors do not indicate a hard limit, original sources that
receive soft errors can begin sending larger packets without waiting
for the recommended 10 minutes specified for PTB hard errors
[RFC1191][RFC8201]. The OMNI interface therefore provides an
adaptive service that accommodates MTU diversity especially well-
suited for dynamic multilink environments.
6.8. OAL Requirements
In light of the above, OAL sources, destinations and intermediate
nodes observe the following normative requirements:
o OAL sources MUST NOT send OAL fragments including original IP
packets larger than the OMNI interface MTU or the OAL destination
hard Reassembly Limit, i.e., whether or not fragmentation is
needed.
o OAL sources MUST NOT perform OAL fragmentation for original IP
packets smaller than the minimum MPS minus the trailer size, and
MUST produce non-final fragments that contain equal-length
payloads no smaller than the minimum MPS when performing
fragmentation.
o OAL sources MUST NOT send OAL fragments that include any extension
headers other than a single ORH and a single Fragment Header.
o OAL intermediate nodes SHOULD and OAL destinations MUST
unconditionally drop OAL packets/fragments including original IP
packets larger than the OMNI interface MRU and/or OAL destination
hard Reassembly Limit, i.e., whether or not reassembly was needed.
o OAL intermediate nodes SHOULD and OAL destinations MUST
unconditionally drop any non-final OAL fragments containing a
payload smaller than the minimum MPS.
o OAL intermediate nodes SHOULD and OAL destinations MUST
unconditionally drop OAL fragments that include any extension
headers other than a single ORH and a single Fragment Header.
o OAL destination nodes MUST drop any new OAL non-final fragments of
different length than other non-final fragments that have already
been received, and MUST drop any new OAL fragments with Offset and
Payload length that would overlap with other fragments and/or
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leave too-small holes between fragments that have already been
received.
Note: Under the minimum MPS, ordinary 1500 byte original IP packets
would require at most 4 OAL fragments, with each non-final fragment
containing 400 payload bytes and the final fragment containing 302
payload bytes (i.e., the final 300 bytes of the original IP packet
plus the 2 octet trailer). Likewise, maximum-length 9180 byte
original IP packets would require at most 23 fragments. For all
packet sizes, the likelihood of successful reassembly may improve
when the OMNI interface sends all fragments of the same fragmented
OAL packet consecutively over the same underlying interface.
Finally, an assured minimum/path MPS allows continuous operation over
all paths including those that traverse bridged L2 media with
dissimilar MTUs.
Note: Certain legacy network hardware of the past millennium was
unable to accept packet "bursts" resulting from an IP fragmentation
event - even to the point that the hardware would reset itself when
presented with a burst. This does not seem to be a common problem in
the modern era, where fragmentation and reassembly can be readily
demonstrated at line rate (e.g., using tools such as 'iperf3') even
over fast links on average hardware platforms. Even so, the OAL
source could impose an inter-fragment delay while the OAL destination
is reporting reassembly congestion (see: Section 6.7) and decrease
the delay when reassembly congestion subsides.
6.9. OAL Fragmentation Security Implications
As discussed in Section 3.7 of [RFC8900], there are four basic
threats concerning IPv6 fragmentation; each of which is addressed by
effective mitigations as follows:
1. Overlapping fragment attacks - reassembly of overlapping
fragments is forbidden by [RFC8200]; therefore, this threat does
not apply to the OAL.
2. Resource exhaustion attacks - this threat is mitigated by
providing a sufficiently large OAL reassembly cache and
instituting "fast discard" of incomplete reassemblies that may be
part of a buffer exhaustion attack. The reassembly cache should
be sufficiently large so that a sustained attack does not cause
excessive loss of good reassemblies but not so large that (timer-
based) data structure management becomes computationally
expensive. The cache should also be indexed based on the arrival
underlying interface such that congestion experienced over a
first underlying interface does not cause discard of incomplete
reassemblies for uncongested underlying interfaces.
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3. Attacks based on predictable fragment identification values -
this threat is mitigated by selecting an unpredictable
Identification value per [RFC7739]. Additionally, inclusion of
the OAL checksum would make it very difficult for an attacker who
could somehow predict a fragment identification value to inject
malicious fragments resulting in undetected reassemblies of bad
data.
4. Evasion of Network Intrusion Detection Systems (NIDS) - this
threat is mitigated by setting a minimum MPS for OAL
fragmentation, which defeats all "tiny fragment"-based attacks.
Additionally, IPv4 fragmentation includes a 16-bit Identification (IP
ID) field with only 65535 unique values such that at high data rates
the field could wrap and apply to new carrier packets while the
fragments of old packets using the same ID are still alive in the
network [RFC4963]. However, since the largest carrier packet that
will be sent via an IPv4 path with DF = 0 is 576 bytes any IPv4
fragmentation would occur only on links with an IPv4 MTU smaller than
this size, and [RFC3819] recommendations suggest that such links will
have low data rates. Since IPv6 provides a 32-bit Identification
value, IP ID wraparound at high data rates is not a concern for IPv6
fragmentation.
Finally, [RFC6980] documents fragmentation security concerns for
large IPv6 ND messages. These concerns are addressed when the OMNI
interface employs the OAL instead of directly fragmenting the IPv6 ND
message itself. For this reason, OMNI interfaces MUST NOT send IPv6
ND messages larger than the OMNI interface MTU, and MUST employ OAL
encapsulation and fragmentation for IPv6 ND messages larger than the
current MPS for this OAL destination.
6.10. OAL Super-Packets
By default, the OAL source includes a 40-byte IPv6 encapsulation
header for each original IP packet during OAL encapsulation. The OAL
source also calculates and appends a 2 octet trailing Fletcher
checksum then performs fragmentation such that a copy of the 40-byte
IPv6 header plus an 8-byte IPv6 Fragment Header is included in each
OAL fragment (when an ORH is added, the OAL encapsulation headers
become larger still). However, these encapsulations may represent
excessive overhead in some environments. OAL header compression can
dramatically reduce the amount of encapsulation overhead, however a
complimentary technique known as "packing" (see:
[I-D.ietf-intarea-tunnels]) is also supported so that multiple
original IP packets and/or control messages can be included within a
single OAL "super-packet".
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When the OAL source has multiple original IP packets to send to the
same OAL destination with total length no larger than the OAL
destination MRU, it can concatenate them into a super-packet
encapsulated in a single OAL header and trailing checksum. Within
the OAL super-packet, the IP header of the first original IP packet
(iHa) followed by its data (iDa) is concatenated immediately
following the OAL header, then the IP header of the next original
packet (iHb) followed by its data (iDb) is concatenated immediately
following the first original packet, etc. with the trailing checksum
included last. The OAL super-packet format is transposed from
[I-D.ietf-intarea-tunnels] and shown in Figure 9:
<------- Original IP packets ------->
+-----+-----+
| iHa | iDa |
+-----+-----+
|
| +-----+-----+
| | iHb | iDb |
| +-----+-----+
| |
| | +-----+-----+
| | | iHc | iDc |
| | +-----+-----+
| | |
v v v
+----------+-----+-----+-----+-----+-----+-----+----+
| OAL Hdr | iHa | iDa | iHb | iDb | iHc | iDc |Csum|
+----------+-----+-----+-----+-----+-----+-----+----+
<--- OAL "Super-Packet" with single OAL Hdr/Csum --->
Figure 9: OAL Super-Packet Format
When the OAL source prepares a super-packet, it applies OAL
fragmentation and *NET encapsulation then sends the carrier packets
to the OAL destination. When the OAL destination receives the super-
packet it reassembles if necessary, verifies and removes the trailing
checksum, then regards the remaining OAL header Payload Length as the
sum of the lengths of all payload packets. The OAL destination then
selectively extracts each original IP packet (e.g., by setting
pointers into the super-packet buffer and maintaining a reference
count, by copying each packet into a separate buffer, etc.) and
forwards each packet to the network layer. During extraction, the
OAL determines the IP protocol version of each successive original IP
packet 'j' by examining the four most-significant bits of iH(j), and
determines the length of the packet by examining the rest of iH(j)
according to the IP protocol version.
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Note that OMNI interfaces must take care to avoid processing super-
packet payload elements that would subvert security. Specifically,
if a super-packet contains a mix of data and control payload packets
(which could include critical security codes), the node MUST NOT
process the data packets before processing the control packets
7. Frame Format
The OMNI interface forwards original IP packets from the network
layer by first invoking the OAL to create OAL packets/fragments if
necessary, then including any *NET encapsulations and finally
engaging the native frame format of the underlying interface. For
example, for Ethernet-compatible interfaces the frame format is
specified in [RFC2464], for aeronautical radio interfaces the frame
format is specified in standards such as ICAO Doc 9776 (VDL Mode 2
Technical Manual), for various forms of tunnels the frame format is
found in the appropriate tunneling specification, etc.
See Figure 2 for a map of the various *NET layering combinations
possible. For any layering combination, the final layer (e.g., UDP,
IP, Ethernet, etc.) must have an assigned number and frame format
representation that is compatible with the selected underlying
interface.
8. Link-Local Addresses (LLAs)
OMNI nodes are assigned OMNI interface IPv6 Link-Local Addresses
(LLAs) through pre-service administrative actions. "MNP-LLAs" embed
the MNP assigned to the mobile node, while "ADM-LLAs" include an
administratively-unique ID that is guaranteed to be unique on the
link. LLAs are configured as follows:
o IPv6 MNP-LLAs encode the most-significant 64 bits of a MNP within
the least-significant 64 bits of the IPv6 link-local prefix
fe80::/64, i.e., in the LLA "interface identifier" portion. The
prefix length for the LLA is determined by adding 64 to the MNP
prefix length. For example, for the MNP 2001:db8:1000:2000::/56
the corresponding MNP-LLA is fe80::2001:db8:1000:2000/120. Non-
MNP routes are also represented the same as for MNP-LLAs, but
include a GUA prefix that is not properly covered by the MSP.
o IPv4-compatible MNP-LLAs are constructed as fe80::ffff:[IPv4],
i.e., the interface identifier consists of 16 '0' bits, followed
by 16 '1' bits, followed by a 32bit IPv4 address/prefix. The
prefix length for the LLA is determined by adding 96 to the MNP
prefix length. For example, the IPv4-Compatible MN OMNI LLA for
192.0.2.0/24 is fe80::ffff:192.0.2.0/120 (also written as
fe80::ffff:c000:0200/120).
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o ADM-LLAs are assigned to ARs and MSEs and MUST be managed for
uniqueness. The lower 32 bits of the LLA includes a unique
integer "MSID" value between 0x00000001 and 0xfeffffff, e.g., as
in fe80::1, fe80::2, fe80::3, etc., fe80::feffffff. The ADM-LLA
prefix length is determined by adding 96 to the MSID prefix
length. For example, if the prefix length for MSID 0x10012001 is
16 then the ADM-LLA prefix length is set to 112 and the LLA is
written as fe80::1001:2001/112. The "zero" address for each ADM-
LLA prefix is the Subnet-Router anycast address for that prefix
[RFC4291]; for example, the Subnet-Router anycast address for
fe80::1001:2001/112 is simply fe80::1001:2000. The MSID range
0xff000000 through 0xffffffff is reserved for future use.
Since the prefix 0000::/8 is "Reserved by the IETF" [RFC4291], no
MNPs can be allocated from that block ensuring that there is no
possibility for overlap between the different MNP- and ADM-LLA
constructs discussed above.
Since MNP-LLAs are based on the distribution of administratively
assured unique MNPs, and since ADM-LLAs are guaranteed unique through
administrative assignment, OMNI interfaces set the autoconfiguration
variable DupAddrDetectTransmits to 0 [RFC4862].
Note: If future protocol extensions relax the 64-bit boundary in IPv6
addressing, the additional prefix bits of an MNP could be encoded in
bits 16 through 63 of the MNP-LLA. (The most-significant 64 bits
would therefore still be in bits 64-127, and the remaining bits would
appear in bits 16 through 48.) However, the analysis provided in
[RFC7421] suggests that the 64-bit boundary will remain in the IPv6
architecture for the foreseeable future.
Note: Even though this document honors the 64-bit boundary in IPv6
addressing, it specifies prefix lengths longer than /64 for routing
purposes. This effectively extends IPv6 routing determination into
the interface identifier portion of the IPv6 address, but it does not
redefine the 64-bit boundary. Modern routing protocol
implementations honor IPv6 prefixes of all lengths, up to and
including /128.
9. Unique-Local Addresses (ULAs)
OMNI domains use IPv6 Unique-Local Addresses (ULAs) as the source and
destination addresses in OAL packet IPv6 encapsulation headers. ULAs
are only routable within the scope of a an OMNI domain, and are
derived from the IPv6 Unique Local Address prefix fc00::/7 followed
by the L bit set to 1 (i.e., as fd00::/8) followed by a 40-bit
pseudo-random Global ID to produce the prefix [ULA]::/48, which is
then followed by a 16-bit Subnet ID then finally followed by a 64 bit
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Interface ID as specified in Section 3 of [RFC4193]. All nodes in
the same OMNI domain configure the same 40-bit Global ID as the OMNI
domain identifier. The statistic uniqueness of the 40-bit pseudo-
random Global ID allows different OMNI domains to be joined together
in the future without requiring renumbering.
Each OMNI link instance is identified by a value between 0x0000 and
0xfeff in bits 48-63 of [ULA]::/48; the values 0xff00 through 0xfffe
are reserved for future use, and the value 0xffff denotes the
presence of a Temporary ULA (see below). For example, OMNI ULAs
associated with instance 0 are configured from the prefix
[ULA]:0000::/64, instance 1 from [ULA]:0001::/64, instance 2 from
[ULA]:0002::/64, etc. ULAs and their associated prefix lengths are
configured in correspondence with LLAs through stateless prefix
translation where "MNP-ULAs" are assigned in correspondence to MNP-
LLAs and "ADM-ULAs" are assigned in correspondence to ADM-LLAs. For
example, for OMNI link instance [ULA]:1010::/64:
o the MNP-ULA corresponding to the MNP-LLA fe80::2001:db8:1:2 with a
56-bit MNP length is derived by copying the lower 64 bits of the
LLA into the lower 64 bits of the ULA as
[ULA]:1010:2001:db8:1:2/120 (where, the ULA prefix length becomes
64 plus the IPv6 MNP length).
o the MNP-ULA corresponding to fe80::ffff:192.0.2.0 with a 28-bit
MNP length is derived by simply writing the LLA interface ID into
the lower 64 bits as [ULA]:1010:0:ffff:192.0.2.0/124 (where, the
ULA prefix length is 64 plus 32 plus the IPv4 MNP length).
o the ADM-ULA corresponding to fe80::1000/112 is simply
[ULA]:1010::1000/112.
o the ADM-ULA corresponding to fe80::/128 is simply
[ULA]:1010::/128.
o etc.
Each OMNI interface assigns the Anycast ADM-ULA specific to the OMNI
link instance. For example, the OMNI interface connected to instance
3 assigns the Anycast address [ULA]:0003::/128. Routers that
configure OMNI interfaces advertise the OMNI service prefix (e.g.,
[ULA]:0003::/64) into the local routing system so that applications
can direct traffic according to SBM requirements.
The ULA presents an IPv6 address format that is routable within the
OMNI routing system and can be used to convey link-scoped IPv6 ND
messages across multiple hops using IPv6 encapsulation [RFC2473].
The OMNI link extends across one or more underling Internetworks to
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include all ARs and MSEs. All MNs are also considered to be
connected to the OMNI link, however OAL encapsulation is omitted
whenever possible to conserve bandwidth (see: Section 14).
Each OMNI link can be subdivided into "segments" that often
correspond to different administrative domains or physical
partitions. OMNI nodes can use IPv6 Segment Routing [RFC8402] when
necessary to support efficient forwarding to destinations located in
other OMNI link segments. A full discussion of Segment Routing over
the OMNI link appears in [I-D.templin-6man-aero].
Temporary ULAs are constructed per [RFC8981] based on the prefix
[ULA]:ffff::/64 and used by MNs when they have no other addresses.
Temporary ULAs can be used for MN-to-MN communications outside the
context of any supporting OMNI link infrastructure, and can also be
used as an initial address while the MN is in the process of
procuring an MNP. Temporary ULAs are not routable within the OMNI
routing system, and are therefore useful only for OMNI link "edge"
communications. Temporary ULAs employ optimistic DAD principles
[RFC4429] since they are probabilistically unique.
Note: IPv6 ULAs taken from the prefix fc00::/7 followed by the L bit
set to 0 (i.e., as fc00::/8) are never used for OMNI OAL addressing,
however the range could be used for MSP and MNP addressing under
certain limiting conditions (see: Section 10).
10. Global Unicast Addresses (GUAs)
OMNI domains use IP Global Unicast Address (GUA) prefixes [RFC4291]
as Mobility Service Prefixes (MSPs) from which Mobile Network
Prefixes (MNP) are delegated to Mobile Nodes (MNs). Fixed
correspondent node networks reachable from the OMNI domain are
represented by non-MNP GUA prefixes that are not derived from the
MSP, but are treated in all other ways the same as for MNPs.
For IPv6, GUA prefixes are assigned by IANA [IPV6-GUA] and/or an
associated regional assigned numbers authority such that the OMNI
domain can be interconnected to the global IPv6 Internet without
causing inconsistencies in the routing system. An OMNI domain could
instead use ULAs with the 'L' bit set to 0 (i.e., from the prefix
fc00::/8)[RFC4193], however this would require IPv6 NAT if the domain
were ever connected to the global IPv6 Internet.
For IPv4, GUA prefixes are assigned by IANA [IPV4-GUA] and/or an
associated regional assigned numbers authority such that the OMNI
domain can be interconnected to the global IPv4 Internet without
causing routing inconsistencies. An OMNI domain could instead use
private IPv4 prefixes (e.g., 10.0.0.0/8, etc.) [RFC3330], however
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this would require IPv4 NAT if the domain were ever connected to the
global IPv4 Internet.
11. Node Identification
OMNI MNs and MSEs that connect over open Internetworks include a
unique node identification value for themselves in the OMNI options
of their IPv6 ND messages (see: Section 12.1.14). One useful
identification value alternative is the Host Identity Tag (HIT) as
specified in [RFC7401], while Hierarchical HITs (HHITs)
[I-D.ietf-drip-rid] may provide a better alternative in certain
domains such as the Unmanned (Air) Traffic Management (UTM) service
for Unmanned Air Systems (UAS). Another alternative is the
Universally Unique IDentifier (UUID) [RFC4122] which can be self-
generated by a node without supporting infrastructure with very low
probability of collision.
When a MN is truly outside the context of any infrastructure, it may
have no MNP information at all. In that case, the MN can use an IPv6
temporary ULA or (H)HIT as an IPv6 source/destination address for
sustained communications in Vehicle-to-Vehicle (V2V) and (multihop)
Vehicle-to-Infrastructure (V2I) scenarios. The MN can also propagate
the ULA/(H)HIT into the multihop routing tables of (collective)
Mobile/Vehicular Ad-hoc Networks (MANETs/VANETs) using only the
vehicles themselves as communications relays.
When a MN connects to ARs over (non-multihop) protected-spectrum
ANETs, an alternate form of node identification (e.g., MAC address,
serial number, airframe identification value, VIN, etc.) may be
sufficient. The MN can then include OMNI "Node Identification" sub-
options (see: Section 12.1.14) in IPv6 ND messages should the need to
transmit identification information over the network arise.
12. Address Mapping - Unicast
OMNI interfaces maintain a neighbor cache for tracking per-neighbor
state and use the link-local address format specified in Section 8.
OMNI interface IPv6 Neighbor Discovery (ND) [RFC4861] messages sent
over physical underlying interfaces without encapsulation observe the
native underlying interface Source/Target Link-Layer Address Option
(S/TLLAO) format (e.g., for Ethernet the S/TLLAO is specified in
[RFC2464]). OMNI interface IPv6 ND messages sent over underlying
interfaces via encapsulation do not include S/TLLAOs which were
intended for encoding physical L2 media address formats and not
encapsulation IP addresses. Furthermore, S/TLLAOs are not intended
for encoding additional interface attributes needed for multilink
coordination. Hence, this document does not define an S/TLLAO format
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but instead defines a new option type termed the "OMNI option"
designed for these purposes.
MNs such as aircraft typically have many wireless data link types
(e.g. satellite-based, cellular, terrestrial, air-to-air directional,
etc.) with diverse performance, cost and availability properties.
The OMNI interface would therefore appear to have multiple L2
connections, and may include information for multiple underlying
interfaces in a single IPv6 ND message exchange. OMNI interfaces use
an IPv6 ND option called the OMNI option formatted as shown in
Figure 10:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | Preflen | S/T-omIndex |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Sub-Options ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: OMNI Option Format
In this format:
o Type is set to TBD2.
o Length is set to the number of 8 octet blocks in the option. The
value 0 is invalid, while the values 1 through 255 (i.e., 8
through 2040 octets, respectively) indicate the total length of
the OMNI option.
o Preflen is an 8 bit field that determines the length of prefix
associated with an LLA. Values 0 through 128 specify a valid
prefix length (all other values are invalid). For IPv6 ND
messages sent from a MN to the MS, Preflen applies to the IPv6
source LLA and provides the length that the MN is requesting or
asserting to the MS. For IPv6 ND messages sent from the MS to the
MN, Preflen applies to the IPv6 destination LLA and indicates the
length that the MS is granting to the MN. For IPv6 ND messages
sent between MS endpoints, Preflen provides the length associated
with the source/target MN that is subject of the ND message.
o S/T-omIndex is an 8 bit field corresponds to the omIndex value for
source or target underlying interface used to convey this IPv6 ND
message. OMNI interfaces MUST number each distinct underlying
interface with an omIndex value between '1' and '255' that
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represents a MN-specific 8-bit mapping for the actual ifIndex
value assigned by network management [RFC2863] (the omIndex value
'0' is reserved for use by the MS). For RS and NS messages, S/
T-omIndex corresponds to the source underlying interface the
message originated from. For RA and NA messages, S/T-omIndex
corresponds to the target underlying interface that the message is
destined to. (For NS messages used for Neighbor Unreachability
Detection (NUD), S/T-omIndex instead identifies the neighbor's
underlying interface to be used as the target interface to return
the NA.)
o Sub-Options is a Variable-length field, of length such that the
complete OMNI Option is an integer multiple of 8 octets long.
Contains one or more Sub-Options, as described in Section 12.1.
The OMNI option may appear in any IPv6 ND message type; it is
processed by interfaces that recognize the option and ignored by all
other interfaces. If multiple OMNI option instances appear in the
same IPv6 ND message, the interface processes the Preflen and S/
T-omIndex fields in the first instance and ignores those fields in
all other instances. The interface processes the Sub-Options of all
OMNI option instances in the same IPv6 ND message in the consecutive
order in which they appear.
The OMNI option(s) in each IPv6 ND message may include full or
partial information for the neighbor. The union of the information
in the most recently received OMNI options is therefore retained, and
the information is aged/removed in conjunction with the corresponding
neighbor cache entry.
12.1. Sub-Options
Each OMNI option includes zero or more Sub-Options. Each consecutive
Sub-Option is concatenated immediately after its predecessor. All
Sub-Options except Pad1 (see below) are in type-length-value (TLV)
encoded in the following format:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Sub-Type| Sub-length | Sub-Option Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 11: Sub-Option Format
o Sub-Type is a 5-bit field that encodes the Sub-Option type. Sub-
Options defined in this document are:
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Sub-Option Name Sub-Type
Pad1 0
PadN 1
Interface Attributes (Type 1) 2
Interface Attributes (Type 2) 3
Traffic Selector 4
MS-Register 5
MS-Release 6
Geo Coordinates 7
DHCPv6 Message 8
HIP Message 9
PIM-SM Message 10
Reassembly Limit 11
Fragmentation Report 12
Node Identification 13
Sub-Type Extension 30
Figure 12
Sub-Types 14-29 are available for future assignment for major
protocol functions. Sub-Type 31 is reserved by IANA.
o Sub-Length is an 11-bit field that encodes the length of the Sub-
Option Data ranging from 0 to 2034 octets.
o Sub-Option Data is a block of data with format determined by Sub-
Type and length determined by Sub-Length.
During transmission, the OMNI interface codes Sub-Type and Sub-Length
together in network byte order in 2 consecutive octets, where Sub-
Option Data may be up to 2034 octets in length. This allows ample
space for coding large objects (e.g., ASCII strings, domain names,
protocol messages, security codes, etc.), while a single OMNI option
is limited to 2040 octets the same as for any IPv6 ND option. If the
Sub-Options to be coded would cause an OMNI option to exceed 2040
octets, the OMNI interface codes any remaining Sub-Options in
additional OMNI option instances in the intended order of processing
in the same IPv6 ND message. Implementations must therefore observe
size limitations, and must refrain from sending IPv6 ND messages
larger than the OMNI interface MTU. If the available OMNI
information would cause a single IPv6 ND message to exceed the OMNI
interface MTU, the OMNI interface codes as much as possible in a
first IPv6 ND message and codes the remainder in additional IPv6 ND
messages.
During reception, the OMNI interface processes each OMNI option Sub-
Option while skipping over and ignoring any unrecognized Sub-Options.
The OMNI interface processes the Sub-Options of all OMNI option
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instances in the consecutive order in which they appear in the IPv6
ND message, beginning with the first instance and continuing through
any additional instances to the end of the message. If a Sub-Option
length would cause processing to exceed the OMNI option total length,
the OMNI interface accepts any Sub-Options already processed and
ignores the final Sub-Option. The interface then processes any
remaining OMNI options in the same fashion to the end of the IPv6 ND
message.
Note: large objects that exceed the Sub-Option Data limit of 2034
octets are not supported under the current specification; if this
proves to be limiting in practice, future specifications may define
support for fragmenting large objects across multiple OMNI options
within the same IPv6 ND message.
The following Sub-Option types and formats are defined in this
document:
12.1.1. Pad1
0
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| S-Type=0|x|x|x|
+-+-+-+-+-+-+-+-+
Figure 13: Pad1
o Sub-Type is set to 0. If multiple instances appear in OMNI
options of the same message all are processed.
o Sub-Type is followed by 3 'x' bits, set to any value on
transmission (typically all-zeros) and ignored on receipt. Pad1
therefore consists of 1 octet with the most significant 5 bits set
to 0, and with no Sub-Length or Sub-Option Data fields following.
12.1.2. PadN
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| S-Type=1| Sub-length=N | N padding octets ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 14: PadN
o Sub-Type is set to 1. If multiple instances appear in OMNI
options of the same message all are processed.
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o Sub-Length is set to N (from 0 to 2034) that encodes the number of
padding octets that follow.
o Sub-Option Data consists of N octets, set to any value on
transmission (typically all-zeros) and ignored on receipt.
12.1.3. Interface Attributes (Type 1)
The Interface Attributes (Type 1) sub-option provides a basic set of
attributes for underlying interfaces. Interface Attributes (Type 1)
is deprecated throughout the rest of this specification, and
Interface Attributes (Type 2) (see: Section 12.1.4) are indicated
wherever the term "Interface Attributes" appears without an
associated Type designation.
Nodes SHOULD NOT include Interface Attributes (Type 1) sub-options in
IPv6 ND messages they send, and MUST ignore any in IPv6 ND messages
they receive. If an Interface Attributes (Type 1) is included, it
must have the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Type=2| Sub-length=N | omIndex | omType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link | Resvd |P00|P01|P02|P03|P04|P05|P06|P07|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P08|P09|P10|P11|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P24|P25|P26|P27|P28|P29|P30|P31|P32|P33|P34|P35|P36|P37|P38|P39|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P40|P41|P42|P43|P44|P45|P46|P47|P48|P49|P50|P51|P52|P53|P54|P55|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P56|P57|P58|P59|P60|P61|P62|P63|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Interface Attributes (Type 1)
o Sub-Type is set to 2. If multiple instances with different
omIndex values appear in OMNI option of the same message all are
processed; if multiple instances with the same omIndex value
appear, the first is processed and all others are ignored
o Sub-Length is set to N (from 4 to 2034) that encodes the number of
Sub-Option Data octets that follow.
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o omIndex is a 1-octet field containing a value from 0 to 255
identifying the underlying interface for which the attributes
apply.
o omType is a 1-octet field containing a value from 0 to 255
corresponding to the underlying interface identified by omIndex.
o Provider ID is a 1-octet field containing a value from 0 to 255
corresponding to the underlying interface identified by omIndex.
o Link encodes a 4-bit link metric. The value '0' means the link is
DOWN, and the remaining values mean the link is UP with metric
ranging from '1' ("lowest") to '15' ("highest").
o Resvd is reserved for future use. Set to 0 on transmission and
ignored on reception.
o A 16-octet ""Preferences" field immediately follows 'Resvd', with
values P[00] through P[63] corresponding to the 64 Differentiated
Service Code Point (DSCP) values [RFC2474]. Each 2-bit P[*] field
is set to the value '0' ("disabled"), '1' ("low"), '2' ("medium")
or '3' ("high") to indicate a QoS preference for underlying
interface selection purposes.
12.1.4. Interface Attributes (Type 2)
The Interface Attributes (Type 2) sub-option provides L2 forwarding
information for the multilink conceptual sending algorithm discussed
in Section 14. The L2 information is used for selecting among
potentially multiple candidate underlying interfaces that can be used
to forward carrier packets to the neighbor based on factors such as
DSCP preferences and link quality. Interface Attributes (Type 2)
further includes link-layer address information to be used for either
OAL encapsulation or direct UDP/IP encapsulation (when OAL
encapsulation can be avoided).
Interface Attributes (Type 2) are the sole Interface Attributes
format in this specification that all OMNI nodes must honor.
Wherever the term "Interface Attributes" occurs throughout this
specification without a "Type" designation, the format given below is
indicated:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=3| Sub-length=N | omIndex | omType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Provider ID | Link |R| API | SRT | FMT | LHS (0 - 7) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LHS (bits 8 - 31) | ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ ~
~ Link Layer Address (L2ADDR) ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap(0)=0xff|P00|P01|P02|P03|P04|P05|P06|P07|P08|P09|P10|P11|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P12|P13|P14|P15|P16|P17|P18|P19|P20|P21|P22|P23|P24|P25|P26|P27|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|P28|P29|P30|P31| Bitmap(1)=0xff|P32|P33|P34|P35|P36| ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 16: Interface Attributes (Type 2)
o Sub-Type is set to 3. If multiple instances with different
omIndex values appear in OMNI options of the same message all are
processed; if multiple instances with the same omIndex value
appear, the first is processed and all others are ignored.
o Sub-Length is set to N (from 4 to 2034) that encodes the number of
Sub-Option Data octets that follow. The 'omIndex', 'omType',
'Provider ID', 'Link', 'R' and 'API' fields are always present;
hence, the remainder of the Sub-Option Data is limited to 2030
octets.
o Sub-Option Data contains an "Interface Attributes (Type 2)" option
encoded as follows:
* omIndex is set to an 8-bit integer value corresponding to a
specific underlying interface the same as specified above for
the OMNI option S/T-omIndex field. The OMNI options of a same
message may include multiple Interface Attributes Sub-Options,
with each distinct omIndex value pertaining to a different
underlying interface. The OMNI option will often include an
Interface Attributes Sub-Option with the same omIndex value
that appears in the S/T-omIndex. In that case, the actual
encapsulation address of the received IPv6 ND message should be
compared with the L2ADDR encoded in the Sub-Option (see below);
if the addresses are different (or, if L2ADDR is absent) the
presence of a NAT is assumed.
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* omType is set to an 8-bit integer value corresponding to the
underlying interface identified by omIndex. The value
represents an OMNI interface-specific 8-bit mapping for the
actual IANA ifType value registered in the 'IANAifType-MIB'
registry [http://www.iana.org].
* Provider ID is set to an OMNI interface-specific 8-bit ID value
for the network service provider associated with this omIndex.
* Link encodes a 4-bit link metric. The value '0' means the link
is DOWN, and the remaining values mean the link is UP with
metric ranging from '1' ("lowest") to '15' ("highest").
* R is reserved for future use.
* API - a 3-bit "Address/Preferences/Indexed" code that
determines the contents of the remainder of the sub-option as
follows:
+ When the most significant bit (i.e., "Address") is set to 1,
the SRT, FMT, LHS and L2ADDR fields are included immediately
following the API code; else, they are omitted.
+ When the next most significant bit (i.e., "Preferences") is
set to 1, a preferences block is included next; else, it is
omitted. (Note that if "Address" is set the preferences
block immediately follows L2ADDR; else, it immediately
follows the API code.)
+ When a preferences block is present and the least
significant bit (i.e., "Indexed") is set to 0, the block is
encoded in "Simplex" form as shown in Figure 15; else it is
encoded in "Indexed" form as discussed below.
* When API indicates that an "Address" is included, the following
fields appear in consecutive order (else, they are omitted):
+ SRT - a 5-bit Segment Routing Topology prefix length value
that (when added to 96) determines the prefix length to
apply to the ULA formed from concatenating [ULA*]::/96 with
the 32 bit LHS MSID value that follows. For example, the
value 16 corresponds to the prefix length 112.
+ FMT - a 3-bit "Framework/Mode/Type" code corresponding to
the included Link Layer Address as follows:
- When the most significant bit (i.e., "Framework") is set
to 1, L2ADDR is the INET encapsulation address for the
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Source/Target Client itself; otherwise L2ADDR is the
address of the Proxy/Server named in the LHS.
- When the next most significant bit (i.e., "Mode") is set
to 1, the Framework node is (likely) located behind an
INET Network Address Translator (NAT); otherwise, it is
on the open INET.
- When the least significant bit (i.e., "Type") is set to
0, L2ADDR includes a UDP Port Number followed by an IPv4
address; otherwise, it includes a UDP Port Number
followed by an IPv6 address.
+ LHS - the 32 bit MSID of the Last Hop Proxy/Server on the
path to the target. When SRT and LHS are both set to 0, the
LHS is considered unspecified in this IPv6 ND message. When
SRT is set to 0 and LHS is non-zero, the prefix length is
set to 128. SRT and LHS together provide guidance to the
OMNI interface forwarding algorithm. Specifically, if SRT/
LHS is located in the local OMNI link segment then the OMNI
interface can encapsulate according to FMT/L2ADDR (following
any necessary NAT traversal messaging); else, it must
forward according to the OMNI link spanning tree. See
[I-D.templin-6man-aero] for further discussion.
+ Link Layer Address (L2ADDR) - Formatted according to FMT,
and identifies the link-layer address (i.e., the
encapsulation address) of the source/target. The UDP Port
Number appears in the first 2 octets and the IP address
appears in the next 4 octets for IPv4 or 16 octets for IPv6.
The Port Number and IP address are recorded in network byte
order, and in ones-compliment "obfuscated" form per
[RFC4380]. The OMNI interface forwarding algorithm uses
FMT/L2ADDR to determine the encapsulation address for
forwarding when SRT/LHS is located in the local OMNI link
segment. Note that if the target is behind a NAT, L2ADDR
will contain the mapped INET address stored in the NAT;
otherwise, L2ADDR will contain the native INET information
of the target itself.
* When API indicates that "Preferences" are included, a
preferences block appears as the remainder of the Sub-Option as
a series of Bitmaps and P[*] values. In "Simplex" form, the
index for each singleton Bitmap octet is inferred from its
sequential position (i.e., 0, 1, 2, ...) as shown in Figure 16.
In "Indexed" form, each Bitmap is preceded by an Index octet
that encodes a value "i" = (0 - 255) as the index for its
companion Bitmap as follows:
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Index=i | Bitmap(i) |P[*] values ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 17
* The preferences consist of a first (simplex/indexed) Bitmap
(i.e., "Bitmap(i)") followed by 0-8 single-octet blocks of
2-bit P[*] values, followed by a second Bitmap (i), followed by
0-8 blocks of P[*] values, etc. Reading from bit 0 to bit 7,
the bits of each Bitmap(i) that are set to '1'' indicate the
P[*] blocks from the range P[(i*32)] through P[(i*32) + 31]
that follow; if any Bitmap(i) bits are '0', then the
corresponding P[*] block is instead omitted. For example, if
Bitmap(0) contains 0xff then the block with P[00]-P[03],
followed by the block with P[04]-P[07], etc., and ending with
the block with P[28]-P[31] are included (as shown in
Figure 15). The next Bitmap(i) is then consulted with its bits
indicating which P[*] blocks follow, etc. out to the end of the
Sub-Option.
* Each 2-bit P[*] field is set to the value '0' ("disabled"), '1'
("low"), '2' ("medium") or '3' ("high") to indicate a QoS
preference for underlying interface selection purposes. Not
all P[*] values need to be included in the OMNI option of each
IPv6 ND message received. Any P[*] values represented in an
earlier OMNI option but omitted in the current OMNI option
remain unchanged. Any P[*] values not yet represented in any
OMNI option default to "medium".
* The first 16 P[*] blocks correspond to the 64 Differentiated
Service Code Point (DSCP) values P[00] - P[63] [RFC2474]. Any
additional P[*] blocks that follow correspond to "pseudo-DSCP"
traffic classifier values P[64], P[65], P[66], etc. See
Appendix A for further discussion and examples.
12.1.5. Traffic Selector
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=4| Sub-length=N | omIndex | ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ ~
~ RFC 6088 Format Traffic Selector ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: Traffic Selector
o Sub-Type is set to 4. If multiple instances appear in OMNI
options of the same message all are processed, i.e., even if the
same omIndex value appears multiple times.
o Sub-Length is set to N (from 1 to 2034) that encodes the number of
Sub-Option Data octets that follow.
o Sub-Option Data contains a 1 octet omIndex encoded exactly as
specified in Section 12.1.3, followed by an N-1 octet traffic
selector formatted per [RFC6088] beginning with the "TS Format"
field. The largest traffic selector for a given omIndex is
therefore 2033 octets.
12.1.6. MS-Register
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=5| Sub-length=4n | MSID[1] (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... ... ... ... ... ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID [n] (bits 16 - 32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 19: MS-Register Sub-option
o Sub-Type is set to 5. If multiple instances appear in OMNI
options of the same message all are processed. Only the first
MAX_MSID values processed (whether in a single instance or
multiple) are retained and all other MSIDs are ignored.
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o Sub-Length is set to 4n, with 508 as the maximum value for n. The
length of the Sub-Option Data section is therefore limited to 2032
octets.
o A list of n 4 octet MSIDs is included in the following 4n octets.
The Anycast MSID value '0' in an RS message MS-Register sub-option
requests the recipient to return the MSID of a nearby MSE in a
corresponding RA response.
12.1.7. MS-Release
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=6| Sub-length=4n | MSID[1] (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID [1] (bits 16 - 32) | MSID[2] (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID [2] (bits 16 - 32) | MSID[3] (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... ... ... ... ... ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSID [n] (bits 16 - 32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 20: MS-Release Sub-option
o Sub-Type is set to 6. If multiple instances appear in OMNI
options of the same message all are processed. Only the first
MAX_MSID values processed (whether in a single instance or
multiple) are retained and all other MSIDs are ignored.
o Sub-Length is set to 4n, with 508 as the maximum value for n. The
length of the Sub-Option Data section is therefore limited to 2032
octets.
o A list of n 4 octet MSIDs is included in the following 4n octets.
The Anycast MSID value '0' is ignored in MS-Release sub-options,
i.e., only non-zero values are processed.
12.1.8. Geo Coordinates
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=7| Sub-length=N | Geo Type |Geo Coordinates
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ...
Figure 21: Geo Coordinates Sub-option
o Sub-Type is set to 7. If multiple instances appear in OMNI
options of the same message the first is processed and all others
are ignored.
o Sub-Length is set to N (from 0 to 2034) that encodes the number of
Sub-Option Data octets that follow.
o Geo Type is a 1 octet field that encodes a type designator that
determines the format and contents of the Geo Coordinates field
that follows. The following types are currently defined:
* 0 - NULL, i.e., the Geo Coordinates field is zero-length.
o A set of Geo Coordinates of length 0 - 2033 octets. New formats
to be specified in future documents and may include attributes
such as latitude/longitude, altitude, heading, speed, etc.
12.1.9. Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Message
The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) sub-option
may be included in the OMNI options of RS messages sent by MNs and RA
messages returned by MSEs. ARs that act as proxys to forward RS/RA
messages between MNs and MSEs also forward DHCPv6 sub-options
unchanged and do not process DHCPv6 sub-options themselves. Note
that DHCPv6 message sub-option integrity is protected by the Checksum
included in the IPv6 ND message header.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=8| Sub-length=N | msg-type | id (octet 0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| transaction-id (octets 1-2) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
. DHCPv6 options .
. (variable number and length) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 22: DHCPv6 Message Sub-option
o Sub-Type is set to 8. If multiple instances appear in OMNI
options of the same message the first is processed and all others
are ignored.
o Sub-Length is set to N (from 4 to 2034) that encodes the number of
Sub-Option Data octets that follow. The 'msg-type' and
'transaction-id' fields are always present; hence, the length of
the DHCPv6 options is restricted to 2030 octets.
o 'msg-type' and 'transaction-id' are coded according to Section 8
of [RFC8415].
o A set of DHCPv6 options coded according to Section 21 of [RFC8415]
follows.
12.1.10. Host Identity Protocol (HIP) Message
The Host Identity Protocol (HIP) Message sub-option may be included
in the OMNI options of RS messages sent by MNs and RA messages
returned by ARs. ARs that act as proxys authenticate and remove HIP
messages in RS messages they forward from a MN to an MSE. ARs that
act as proxys insert and sign HIP messages in the RA messages they
forward from an MSE to a MN.
The HIP message sub-option may also be included in any IPv6 ND
message that may traverse an open Internetwork, i.e., where link-
layer authentication is not already assured by lower layers.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| S-Type=9| Sub-length=N |0| Packet Type |Version| RES.|1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | Controls |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's Host Identity Tag (HIT) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receiver's Host Identity Tag (HIT) |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ HIP Parameters /
/ /
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 23: HIP Message Sub-option
o Sub-Type is set to 9. If multiple instances appear in OMNI
options of the same message the first is processed and all others
are ignored.
o Sub-Length is set to N, i.e., the length of the option in octets
beginning immediately following the Sub-Length field and extending
to the end of the HIP parameters. The length of the entire HIP
message is therefore restricted to 2034 octets.
o The HIP message is coded exactly as specified in Section 5 of
[RFC7401], except that the OMNI "Sub-Type" and "Sub-Length" fields
replace the first 2 octets of the HIP message header (i.e., the
Next Header and Header Length fields). Note that, since the IPv6
ND message header already includes a Checksum, the HIP message
Checksum field is set to 0 on transmission and ignored on
reception. (The Checksum field is still included to retain the
[RFC7401] message format.)
12.1.11. PIM-SM Message
The Protocol Independent Multicast - Sparse Mode (PIM-SM) Message
sub-option may be included in the OMNI options of IPv6 ND messages
sent by MNs and MSEs. PIM-SM messages are formatted as specified in
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Section 4.9 of [RFC7761], with the exception that the Checksum field
is omitted since the IPv6 ND message is already protected by a
checksum (and possibly also an authentication signature). The PIM-SM
message sub-option format is shown in Figure 24:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=10| Sub-length=N |PIM Ver| Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ PIM-SM Message /
/ /
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 24: PIM-SM Message Option Format
o Sub-Type is set to 10. If multiple instances appear in OMNI
options of the same message all are processed.
o Sub-Length is set to N, i.e., the length of the option in octets
beginning immediately following the Sub-Length field and extending
to the end of the PIM-SM message. The length of the entire PIM-SM
message is therefore restricted to 2034 octets.
o The PIM-SM message is coded exactly as specified in Section 4.9 of
[RFC7761], except that the Checksum field is omitted. The "PIM
Ver" field MUST encode the value 2, and the "Type" field encodes
the PIM message type. (See Section 4.9 of [RFC7761] for a list of
PIM-SM message types and formats.)
12.1.12. Reassembly Limit
The Reassembly Limit sub-option may be included in the OMNI options
of IPv6 ND messages. The message consists of a 14-bit Reassembly
Limit value, followed by two flag bits (H, L) optionally followed by
an (N-2)-octet leading portion of an OAL First Fragment that
triggered the message.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=11| Sub-length=N | Reassembly Limit |H|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OAL First Fragment (As much of invoking packet |
+ as possible without the IPv6 ND message +
| exceeding the minimum IPv6 MTU) |
+ +
Figure 25: Reassembly Limit
o Sub-Type is set to 11. If multiple instances appear in OMNI
options of the same message the first occurring "hard" and "soft"
Reassembly Limit values are accepted, and any additional
Reassembly Limit values are ignored.
o Sub-Length is set to 2 if no OAL First Fragment is included, or to
a value N greater than 2 if an OAL First Fragment is included.
o A 14-bit Reassembly Limit follows, and includes a value between
1500 and 9180. If any other value is included, the sub-option is
ignored. The value indicates the hard or soft limit for original
IP packets that the source of the message is currently willing to
reassemble; the source may increase or decrease the hard or soft
limit at any time through the transmission of new IPv6 ND
messages. Until the first IPv6 ND message with a Reassembly Limit
sub-option arrives, OMNI nodes assume initial default hard/soft
limits of 9180 bytes (I.e., the OMNI interface MRU). After IPv6
ND messages with Reassembly Limit sub-options arrive, the OMNI
node retains the most recent hard/soft limit values until new IPv6
ND messages with different values arrive.
o The 'H' flag is set to 1 if the Reassembly Limit is a "Hard"
limit, and set to 0 if the Reassembly Limit is a "Soft" limit.
o The 'L' flag is set to 1 if an OAL First Fragment corresponding to
a reassembly loss event was included; otherwise set to 0.
o If N is greater than 2, the remainder of the Reassembly Limit sub-
option encodes the leading portion of an OAL First Fragment that
prompted this IPv6 ND message. The first fragment is included
beginning with the OAL IPv6 header, and continuing with as much of
the fragment payload as possible without causing the IPv6 ND
message to exceed the minimum IPv6 MTU. (Note that only the OAL
First Fragment is consulted regardless of its size, and without
waiting for additional fragments.)
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12.1.13. Fragmentation Report
The Fragmentation Report may be included in the OMNI options of uNA
messages sent from an OAL destination to an OAL source. The message
consists of (N / 8)-many (Identification, Bitmap)-tuples which
include the Identification values of OAL fragments received plus a
Bitmap marking the ordinal positions of individual fragments received
and fragments missing.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=12| Sub-Length = N | Identification #1 (bits 0 -15)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification #1 (bits 15-31)| Bitmap #1 (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap #1 (bits 16-31) | Identification #2 (bits 0 -15)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification #2 (bits 15-31)| Bitmap #2 (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap #2 (bits 16-31) | Identification #3 (bits 0 -15)|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification #3 (bits 15-31)| Bitmap #3 (bits 0 - 15) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bitmap #3 (bits 16-31) | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ... +
| ... |
+ ... +
Figure 26: Fragmentation Report
o Sub-Type is set to 12. If multiple instances appear in OMNI
options of the same message all are processed.
o Sub-Length is set to N, i.e., the length of the option in octets
beginning immediately following the Sub-Length field and extending
to the end of the ICMPv6 error message body. N must be an
integral multiple of 8 octets; otherwise, the sub-option is
ignored. The length of the entire sub-option should not cause the
entire IPv6 ND message to exceed the minimum MPS.
o Identification (i) includes the IPv6 Identification value found in
the Fragment Header of a received OAL fragment. (Only those
Identification values included represent fragments for which loss
was unambiguously observed; any Identification values not included
correspond to fragments that were either received in their
entirety or are still in transit.)
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o Bitmap (i) includes an ordinal checklist of fragments, with each
bit set to 1 for a fragment received or 0 for a fragment missing.
For example, for a 20-fragment fragmented OAL packet with ordinal
fragments #3, #10, #13 and #17 missing and all other fragments
received, the bitmap would encode:
0 1 2
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
|1|1|1|0|1|1|1|1|1|1|0|1|1|0|1|1|1|0|1|1|0|0|0|...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
Figure 27
(Note that loss of an OAL atomic fragment is indicated by a
Bitmap(i) with all bits set to 0.)
12.1.14. Node Identification
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=13| Sub-length=N | ID-Type | ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ Node Identification Value (N-1 octets) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 28: Node Identification
o Sub-Type is set to 13. If multiple instances appear in OMNI
options of the same IPv6 ND message the first instance of a
specific ID-Type is processed and all other instances of the same
ID-Type are ignored. (Note therefore that it is possible for a
single IPv6 ND message to convey multiple Node Identifications -
each having a different ID-Type.)
o Sub-Length is set to N (from 1 to 2034) that encodes the number of
Sub-Option Data octets that follow. The ID-Type field is always
present; hence, the maximum Node Identification Value length is
2033 octets.
o ID-Type is a 1 octet field that encodes the type of the Node
Identification Value. The following ID-Type values are currently
defined:
* 0 - Universally Unique IDentifier (UUID) [RFC4122]. Indicates
that Node Identification Value contains a 16 octet UUID.
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* 1 - Host Identity Tag (HIT) [RFC7401]. Indicates that Node
Identification Value contains a 16 octet HIT.
* 2 - Hierarchical HIT (HHIT) [I-D.ietf-drip-rid]. Indicates
that Node Identification Value contains a 16 octet HHIT.
* 3 - Network Access Identifier (NAI) [RFC7542]. Indicates that
Node Identification Value contains an N-1 octet NAI.
* 4 - Fully-Qualified Domain Name (FQDN) [RFC1035]. Indicates
that Node Identification Value contains an N-1 octet FQDN.
* 5 - 252 - Unassigned.
* 253-254 - Reserved for experimentation, as recommended in
[RFC3692].
* 255 - reserved by IANA.
o Node Identification Value is an (N - 1) octet field encoded
according to the appropriate the "ID-Type" reference above.
When a Node Identification Value is needed for DHCPv6 messaging
purposes, it is encoded as a DHCP Unique IDentifier (DUID) using the
"DUID-EN for OMNI" format with enterprise number 45282 (see:
Section 25) as shown in Figure 29:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DUID-Type (2) | EN (high bits == 0) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EN (low bits = 45282) | ID-Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. Node Identification Value .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 29: DUID-EN for OMNI Format
In this format, the ID-Type and Node Identification Value fields are
coded exactly as in Figure 28 following the 6 octet DUID-EN header,
and the entire "DUID-EN for OMNI" is included in a DHCPv6 message per
[RFC8415].
12.1.15. Sub-Type Extension
Since the Sub-Type field is only 5 bits in length, future
specifications of major protocol functions may exhaust the remaining
Sub-Type values available for assignment. This document therefore
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defines Sub-Type 30 as an "extension", meaning that the actual sub-
option type is determined by examining a 1 octet "Extension-Type"
field immediately following the Sub-Length field. The Sub-Type
Extension is formatted as shown in Figure 30:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=30| Sub-length=N | Extension-Type| ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~
~ ~
~ Extension-Type Body ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 30: Sub-Type Extension
o Sub-Type is set to 30. If multiple instances appear in OMNI
options of the same message all are processed, where each
individual extension defines its own policy for processing
multiple of that type.
o Sub-Length is set to N (from 1 to 2034) that encodes the number of
Sub-Option Data octets that follow. The Extension-Type field is
always present; hence, the maximum Extension-Type Body length is
2033 octets.
o Extension-Type contains a 1 octet Sub-Type Extension value between
0 and 255.
o Extension-Type Body contains an N-1 octet block with format
defined by the given extension specification.
Extension-Type values 2 through 252 are available for assignment by
future specifications, which must also define the format of the
Extension-Type Body and its processing rules. Extension-Type values
253 and 254 are reserved for experimentation, as recommended in
[RFC3692], and value 255 is reserved by IANA. Extension-Type values
0 and 1 are defined in the following subsections:
12.1.15.1. RFC4380 UDP/IP Header Option
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=30| Sub-length=N | Ext-Type=0 | Header Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Header Option Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 31: RFC4380 UDP/IP Header Option (Extension-Type 0)
o Sub-Type is set to 30.
o Sub-Length is set to N (from 2 to 2034) that encodes the number of
Sub-Option Data octets that follow. The Extension-Type and Header
Type fields are always present; hence, the maximum-length Header
Option Value is 2032 octets.
o Extension-Type is set to 0. Each instance encodes exactly one
header option per Section 5.1.1 of [RFC4380], with the leading '0'
octet omitted and the following octet coded as Header Type. If
multiple instances of the same Header Type appear in OMNI options
of the same message the first instance is processed and all others
are ignored.
o Header Type and Header Option Value are coded exactly as specified
in Section 5.1.1 of [RFC4380]; the following types are currently
defined:
* 0 - Origin Indication (IPv4) - value coded per Section 5.1.1 of
[RFC4380].
* 1 - Authentication Encapsulation - value coded per
Section 5.1.1 of [RFC4380].
* 2 - Origin Indication (IPv6) - value coded per Section 5.1.1 of
[RFC4380], except that the address is a 16-octet IPv6 address
instead of a 4-octet IPv4 address.
o Header Type values 3 through 252 are available for assignment by
future specifications, which must also define the format of the
Header Option Value and its processing rules. Header Type values
253 and 254 are reserved for experimentation, as recommended in
[RFC3692], and value 255 is Reserved by IANA.
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12.1.15.2. RFC6081 UDP/IP Trailer Option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|S-Type=30| Sub-length=N | Ext-Type=1 | Trailer Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Trailer Option Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 32: RFC6081 UDP/IP Trailer Option (Extension-Type 1)
o Sub-Type is set to 30.
o Sub-Length is set to N (from 2 to 2034) that encodes the number of
Sub-Option Data octets that follow. The Extension-Type and
Trailer Type fields are always present; hence, the maximum-length
Trailer Option Value is 2032 octets.
o Extension-Type is set to 1. Each instance encodes exactly one
trailer option per Section 4 of [RFC6081]. If multiple instances
of the same trailer type appear in OMNI options of the same
message the first instance is processed and all others ignored.
o Trailer Type and Trailer Option Value are coded exactly as
specified in Section 4 of [RFC6081]; the following Trailer Types
are currently defined:
* 0 - Unassigned
* 1 - Nonce Trailer - value coded per Section 4.2 of [RFC6081].
* 2 - Unassigned
* 3 - Alternate Address Trailer (IPv4) - value coded per
Section 4.3 of [RFC6081].
* 4 - Neighbor Discovery Option Trailer - value coded per
Section 4.4 of [RFC6081].
* 5 - Random Port Trailer - value coded per Section 4.5 of
[RFC6081].
* 6 - Alternate Address Trailer (IPv6) - value coded per
Section 4.3 of [RFC6081], except that each address is a
16-octet IPv6 address instead of a 4-octet IPv4 address.
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o Trailer Type values 7 through 252 are available for assignment by
future specifications, which must also define the format of the
Trailer Option Value and its processing rules. Trailer Type
values 253 and 254 are reserved for experimentation, as
recommended in [RFC3692], and value 255 is Reserved by IANA.
13. Address Mapping - Multicast
The multicast address mapping of the native underlying interface
applies. The mobile router on board the MN also serves as an IGMP/
MLD Proxy for its EUNs and/or hosted applications per [RFC4605] while
using the L2 address of the AR as the L2 address for all multicast
packets.
The MN uses Multicast Listener Discovery (MLDv2) [RFC3810] to
coordinate with the AR, and *NET L2 elements use MLD snooping
[RFC4541].
14. Multilink Conceptual Sending Algorithm
The MN's IPv6 layer selects the outbound OMNI interface according to
SBM considerations when forwarding original IP packets from local or
EUN applications to external correspondents. Each OMNI interface
maintains a neighbor cache the same as for any IPv6 interface, but
with additional state for multilink coordination. Each OMNI
interface maintains default routes via ARs discovered as discussed in
Section 15, and may configure more-specific routes discovered through
means outside the scope of this specification.
After an original IP packet enters the OMNI interface, one or more
outbound underlying interfaces are selected based on PBM traffic
attributes, and one or more neighbor underlying interfaces are
selected based on the receipt of Interface Attributes sub-options in
IPv6 ND messages (see: Figure 15). Underlying interface selection
for the nodes own local interfaces are based on attributes such as
DSCP, application port number, cost, performance, message size, etc.
OMNI interface multilink selections could also be configured to
perform replication across multiple underlying interfaces for
increased reliability at the expense of packet duplication. The set
of all Interface Attributes received in IPv6 ND messages determines
the multilink forwarding profile for selecting the neighbor's
underlying interfaces.
When the OMNI interface sends an original IP packet over a selected
outbound underlying interface, the OAL employs encapsulation and
fragmentation as discussed in Section 5, then performs *NET
encapsulation as determined by the L2 address information received in
Interface Attributes. The OAL also performs encapsulation when the
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nearest AR is located multiple hops away as discussed in
Section 15.1. (Note that the OAL MAY employ packing when multiple
original IP packets and/or control messages are available for
forwarding to the same OAL destination.)
OMNI interface multilink service designers MUST observe the BCP
guidance in Section 15 [RFC3819] in terms of implications for
reordering when original IP packets from the same flow may be spread
across multiple underlying interfaces having diverse properties.
14.1. Multiple OMNI Interfaces
MNs may connect to multiple independent OMNI links concurrently in
support of SBM. Each OMNI interface is distinguished by its Anycast
ULA (e.g., [ULA]:0002::, [ULA]:1000::, [ULA]:7345::, etc.). The MN
configures a separate OMNI interface for each link so that multiple
interfaces (e.g., omni0, omni1, omni2, etc.) are exposed to the IPv6
layer. A different Anycast ULA is assigned to each interface, and
the MN injects the service prefixes for the OMNI link instances into
the EUN routing system.
Applications in EUNs can use Segment Routing to select the desired
OMNI interface based on SBM considerations. The Anycast ULA is
written into an original IP packet's IPv6 destination address, and
the actual destination (along with any additional intermediate hops)
is written into the Segment Routing Header. Standard IP routing
directs the packet to the MN's mobile router entity, and the Anycast
ULA identifies the OMNI interface to be used for transmission to the
next hop. When the MN receives the packet, it replaces the IPv6
destination address with the next hop found in the routing header and
transmits the message over the OMNI interface identified by the
Anycast ULA.
Multiple distinct OMNI links can therefore be used to support fault
tolerance, load balancing, reliability, etc. The architectural model
is similar to Layer 2 Virtual Local Area Networks (VLANs).
14.2. MN<->AR Traffic Loop Prevention
After an AR has registered an MNP for a MN (see: Section 15), the AR
will forward packets destined to an address within the MNP to the MN.
The MN will under normal circumstances then forward the packet to the
correct destination within its internal networks.
If at some later time the MN loses state (e.g., after a reboot), it
may begin returning packets destined to an MNP address to the AR as
its default router. The AR therefore must drop any packets
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originating from the MN and destined to an address within the MN's
registered MNP. To do so, the AR institutes the following check:
o if the IP destination address belongs to a neighbor on the same
OMNI interface, and if the link-layer source address is the same
as one of the neighbor's link-layer addresses, drop the packet.
15. Router Discovery and Prefix Registration
MNs interface with the MS by sending RS messages with OMNI options
under the assumption that one or more AR on the *NET will process the
message and respond. The MN then configures default routes for the
OMNI interface via the discovered ARs as the next hop. The manner in
which the *NET ensures AR coordination is link-specific and outside
the scope of this document (however, considerations for *NETs that do
not provide ARs that recognize the OMNI option are discussed in
Section 20).
For each underlying interface, the MN sends an RS message with an
OMNI option to coordinate with MSEs identified by MSID values.
Example MSID discovery methods are given in [RFC5214] and include
data link login parameters, name service lookups, static
configuration, a static "hosts" file, etc. When the AR receives an
RS', it selects a nearby MSE (which may be itself) and returns an RA
with the selected MSID in an MS-Register sub-option. The AR selects
only a single nearby MSE while also soliciting the MSEs corresponding
to any non-zero MSIDs.
MNs configure OMNI interfaces that observe the properties discussed
in the previous section. The OMNI interface and its underlying
interfaces are said to be in either the "UP" or "DOWN" state
according to administrative actions in conjunction with the interface
connectivity status. An OMNI interface transitions to UP or DOWN
through administrative action and/or through state transitions of the
underlying interfaces. When a first underlying interface transitions
to UP, the OMNI interface also transitions to UP. When all
underlying interfaces transition to DOWN, the OMNI interface also
transitions to DOWN.
When an OMNI interface transitions to UP, the MN sends RS messages to
register its MNP and an initial set of underlying interfaces that are
also UP. The MN sends additional RS messages to refresh lifetimes
and to register/deregister underlying interfaces as they transition
to UP or DOWN. The MN's OMNI interface sends initial RS messages
over an UP underlying interface with its MNP-LLA as the source (or
with the unspecified address (::) as the source if it does not yet
have an MNP-LLA) and with destination set to link-scoped All-Routers
multicast (ff02::2) [RFC4291]. The OMNI interface includes an OMNI
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option per Section 12 with a Preflen assertion, Interface Attributes
appropriate for underlying interfaces, MS-Register/Release sub-
options containing MSID values, Reassembly Limits, an authentication
sub-option and with any other necessary OMNI sub-options (e.g., a
Node Identification sub-option as an identity for the MN). The OMNI
interface then sets the S/T-omIndex field to the index of the
underlying interface over which the RS message is sent.
The OMNI interface then sends the RS over the underlying interface
using OAL encapsulation and fragmentation if necessary. If OAL
encapsulation is used for RS messages sent over an INET interface,
the entire RS message must appear within a single carrier packet so
that it can be authenticated without requiring reassembly. The OMNI
interface selects an unpredictable initial Identification value per
Section 6.5, sets the OAL source address to the ULA corresponding to
the RS source (Or a Temporary ULA if the RS source is the unspecified
address (::)) and sets the OAL destination to site-scoped All-Routers
multicast (ff05::2) then sends the message.
ARs process IPv6 ND messages with OMNI options and act as an MSE
themselves and/or as a proxy for other MSEs. ARs receive RS messages
and create a neighbor cache entry for the MN, then prepare to act as
an MSE themselves and/or coordinate with any MSEs named in the
Register/Release lists in a manner outside the scope of this
document. When an MSE processes the OMNI information, it first
validates the prefix registration information then injects/withdraws
the MNP in the routing/mapping system and caches/discards the new
Preflen, MNP and Interface Attributes. The MSE then informs the AR
of registration success/failure, and the AR returns an RA message to
the MN with an OMNI option per Section 12.
The AR's OMNI interface returns the RA message via the same
underlying interface of the MN over which the RS was received, and
with destination address set to the MNP-LLA (i.e., unicast), with
source address set to its own LLA, and with an OMNI option with S/
T-omIndex set to the value included in the RS. The OMNI option also
includes a Preflen confirmation, Interface Attributes, MS-Register/
Release and any other necessary OMNI sub-options (e.g., a Node
Identification sub-option as an identity for the AR). The RA also
includes any information for the link, including RA Cur Hop Limit, M
and O flags, Router Lifetime, Reachable Time and Retrans Timer
values, and includes any necessary options such as:
o PIOs with (A; L=0) that include MSPs for the link [RFC8028].
o RIOs [RFC4191] with more-specific routes.
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o an MTU option that specifies the maximum acceptable packet size
for this underlying interface.
If the RS message arrived as an OAL atomic fragment, the AR prepares
the RA using OAL encapsulation/fragmentation with the same
Identification value that appeared in the RS message, with source set
to the ULA corresponding to the RA source and with destination set to
the ULA corresponding to the RA destination. The AR then sends the
initial RA message to the MN and MAY later send additional periodic
and/or event-driven unsolicited RA messages per [RFC4861]. In that
case, the S/T-omIndex field in the OMNI option of the unsolicited RA
message identifies the target underlying interface of the destination
MN.
The AR can combine the information from multiple MSEs into one or
more "aggregate" RAs sent to the MN in order conserve *NET bandwidth.
Each aggregate RA includes an OMNI option with MS-Register/Release
sub-options with the MSEs represented by the aggregate. If an
aggregate is sent, the RA message contents must consistently
represent the combined information advertised by all represented
MSEs. Note that since the AR uses its own ADM-LLA as the RA source
address, the MN determines the addresses of the represented MSEs by
examining the MS-Register/Release OMNI sub-options.
When the MN receives the RA message, it creates an OMNI interface
neighbor cache entry for each MSID that has confirmed MNP
registration via the L2 address of this AR. If the MN connects to
multiple *NETs, it records the additional L2 AR addresses in each
MSID neighbor cache entry (i.e., as multilink neighbors). The MN
then configures a default route via the MSE that returned the RA
message, and assigns the Subnet Router Anycast address corresponding
to the MNP (e.g., 2001:db8:1:2::) to the OMNI interface. The MN then
manages its underlying interfaces according to their states as
follows:
o When an underlying interface transitions to UP, the MN sends an RS
over the underlying interface with an OMNI option. The OMNI
option contains at least one Interface Attribute sub-option with
values specific to this underlying interface, and may contain
additional Interface Attributes specific to other underlying
interfaces. The option also includes any MS-Register/Release sub-
options.
o When an underlying interface transitions to DOWN, the MN sends an
RS or unsolicited NA message over any UP underlying interface with
an OMNI option containing an Interface Attribute sub-option for
the DOWN underlying interface with Link set to '0'. The MN sends
an RS when an acknowledgement is required, or an unsolicited NA
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"interface": [
"eth1"
]
},
"control-plane-protocols": {
"control-plane-protocol": [
{
"type": "ietf-rip:ripng",
"name": "ripng-1",
"description": "RIPng instance ripng-1.",
"ietf-rip:rip": {
"default-metric": 1,
"next-triggered-update": 5
"interfaces": {
"interface": [
{
"interface": "eth1",
"oper-status": "up",
"cost": 1,
"split-horizon": "poison-reverse",
"valid-address": true
}
]
},
"ipv6" {
"neighbors": {
"neighbor": [
{
"address": "fe80::200:5eff:fe00:5302",
"last-update": "2017-01-02T10:34:55+02:00"
}
]
}
"routes": {
"route": [
{
"ipv6-prefix": "2001:db8:0:1::/64",
"interface": "eth1",
"redistributed": true,
"route-type": "connected",
"metric": 1,
Liu, et al. Expires February 29, 2020 [Page 42]
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"expire-time": 22
},
{
"ipv6-prefix": "2001:db8:0:2::/64",
"next-hop": "fe80::200:5eff:fe00:5302",
"interface": "eth1",
"redistributed": false,
"route-type": "rip",
"metric": 2,
"expire-time": 82
}
]
}
},
"statistics": {
"discontinuity-time": "2016-10-24T17:11:27+02:00",
"requests-rcvd": 523,
"requests-sent": 262,
"responses-rcvd": 261,
"responses-sent": 523
}
}
}
]
}
}
}
Authors' Addresses
Xufeng Liu
Volta Networks
EMail: xufeng.liu.ietf@gmail.com
Prateek Sarda
Ericsson
Fern Icon, Survey No 28 and 36/5, Doddanakundi Village
Bangalore Karnataka 560037
India
EMail: prateek.sarda@ericsson.com
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Vikram Choudhary
Individual
Bangalore 560066
India
EMail: vikschw@gmail.com
Liu, et al. Expires February 29, 2020 [Page 44]