Network Working Group J. Xie
Internet-Draft Huawei Technologies
Intended status: Standards Track L. Geng
Expires: July 17, 2020 China Mobile
M. McBride
Futurewei
R. Asati
Cisco
S. Dhanaraj
Huawei
January 14, 2020
Encapsulation for BIER in Non-MPLS IPv6 Networks
draft-xie-bier-ipv6-encapsulation-05
Abstract
This document proposes a BIER IPv6 (BIERv6) encapsulation for Non-
MPLS IPv6 Networks using the IPv6 Destination Option extension
header. This document updates [RFC8296].
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] and
[RFC8174].
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 July 17, 2020.
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Copyright Notice
Copyright (c) 2020 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
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. BIER IPv6 Encapsulation . . . . . . . . . . . . . . . . . . . 3
3.1. BIER Option in IPv6 Destination Options Header . . . . . 3
3.2. Multicast and Unicast Destination Address . . . . . . . . 6
3.3. BIERv6 Packet Format . . . . . . . . . . . . . . . . . . 8
4. BIERv6 Packet Processing . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5.1. Intra Domain Deployment . . . . . . . . . . . . . . . . . 12
5.2. Inter Domain Deployment . . . . . . . . . . . . . . . . . 13
5.3. ICMP Error Processing . . . . . . . . . . . . . . . . . . 13
5.4. Security caused by BIER option . . . . . . . . . . . . . 14
5.5. Applicability of IPsec . . . . . . . . . . . . . . . . . 14
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. BIER Option Type . . . . . . . . . . . . . . . . . . . . 15
6.2. End.BIER Function . . . . . . . . . . . . . . . . . . . . 15
6.3. BIER Next Protocol Identifiers . . . . . . . . . . . . . 16
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
Bit Index Explicit Replication (BIER) [RFC8279] is an architecture
that provides optimal multicast forwarding without requiring
intermediate routers to maintain any per-flow state by using a
multicast-specific BIER header.
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[RFC8296] defines a common BIER Header format for MPLS and Non-MPLS
networks. It has defined two types of encapsulation methods using
the common BIER Header, (1) BIER encapsulation in MPLS networks,
here-in after referred as MPLS BIER Header in this document and (2)
BIER encapsulation in Non-MPLS networks, here-in after referred as
Non-MPLS BIER Header in this document. [RFC8296] also assigned
Ethertype=0xAB37 for Non-MPLS BIER Header packets to be directly
carried over the Ethernet links.
This document proposes a BIER IPv6 encapsulation for Non-MPLS IPv6
Networks, defining a method to carry the standard Non-MPLS BIER
header (as defined in [RFC8296]) in the native IPv6 header. A new
IPv6 Option type - BIER Option is defined to encode the standard Non-
MPLS BIER header and this newly defined BIER Option is carried under
the Destination Options header of the native IPv6 Header [RFC8200].
This document details one of the proposed solutions for transporting
BIER packets in an IPv6 network. To better understand the overall
BIER IPv6 problem space, use cases and proposed solutions, refer to
[I-D.ietf-bier-ipv6-requirements].
2. Terminology
Readers of this document are assumed to be familiar with the
terminology and concepts of the documents listed as Normative
References.
The following new terms are used throughout this document:
o BIERv6 - BIER IPv6.
o BIER Option - An Option type carried in IPv6 Destination Options
Header which includes the standard Non-MPLS BIER Header.
o BIERv6 Header - An IPv6 Header with BIER Option.
o BIERv6 Packet - An IPv6 packet with BIERv6 Header. Such an IPv6
packet typically carries the user multicast payload and is
forwarded by BFRs in the BIERv6 network towards the multicast
receivers.
3. BIER IPv6 Encapsulation
3.1. BIER Option in IPv6 Destination Options Header
Destination Options Header and the Options that can be carried under
this extension header is defined in [RFC8200]. This document defines
a new Option type - BIER Option, to encode the Non-MPLS BIER header.
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As specified in Section 4.2 [RFC8200], the BIER Option follows type-
length-value (TLV) encoding format and the standard Non-MPLS BIER
header [RFC8296] is encoded in the value portion of the BIER Option
TLV.
This BIER Option MUST be carried only inside the IPv6 Destination
Options header and MUST NOT be carried under the Hop-by-Hop Options
header.
Co-existence of Destination Options Header with BIER option TLV and
other IPv6 extension headers MUST confirm to the general requirements
defined in [RFC8200]. In addition to the requirements defined in
[RFC8200], this document requires that the Destination Options Header
with a BIER Option TLV MUST appear only after the Routing Header if
the Routing Header is present in the IPv6 Header.
The BIER Option is encoded in type-length-value (TLV) format as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | Option Type | Option Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Non-MPLS BIER Header (defined in RFC8296) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Next Header 8-bit selector. Identifies the type of header
immediately following the Destination Options header.
Hdr Ext Len 8-bit unsigned integer. Length of the Destination
Options header in 8-octet units, not including the first 8 octets.
Option Type To be allocated by IANA. See section 6.
Option Length 8-bit unsigned integer. Length of the option, in
octets, excluding the Option Type and Option Length fields.
Non-MPLS BIER Header The Non-MPLS BIER Header defined in RFC8296.
Fields in the Non-MPLS BIER Header MUST be encoded as below.
BIFT-id: The BIFT-id is a domain-wide unique value in Non-MPLS
IPv6 encapsulation. See Section 2.2 of RFC 8296.
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TC: SHOULD be set to binary value 000 upon transmission and MUST
be ignored upon. See Section 2.2 of RFC 8296.
S bit: SHOULD be set to 1 upon transmission, and MUST be ignored
upon reception. See Section 2.2 of RFC 8296.
TTL: MUST be set to a value larger than 0 upon encapsulation,
and SHOULD decrease by 1 by a BFR when forwarding a BIERv6
packet to a BFR adjacency. If the incoming TTL is 0, the packet
is considered to be "expired". See Section 2.1.1.2 of RFC 8296.
Nibble: SHOULD be set to 0000 upon transmission, and MUST be
ignored upon reception. See Section 2.2 of RFC 8296.
Ver: MUST be set to 0 upon transmission, and MUST be discarded
when it is not 0 upon reception. See Section 2.2 of RFC 8296.
BSL: See Section 2.1.2 of RFC 8296.
Entropy: See Section 2.1.2 of RFC 8296.
OAM: See Section 2.1.2 of RFC 8296.
Rsv: See Section 2.1.2 of RFC 8296.
DSCP: SHOULD be set to binary value 000000 upon transmission and
MUST be ignored upon reception. In IPv6 BIER encapsulation,
uses highest 6-bit of Traffic Class field of IPv6 header to hold
a Differentiated Services Codepoint [RFC2474].
Proto: This fileld is used for two functions. The first is to
identify the BIER Payload following the BIER header, and the
second is to deliver the packet to a proper overlay module by
BIER layer, with VRF lookup in case of BIER data process, or
without VRF lookup in case of BIER OAM process. In BIER IPv6
encapsulation, the first function of Proto is compromised by a
proper Next Header value combination, and the second function of
Proto should be kept with the semantic unique and consistent for
BIER demultiplexing. This updates section 2.1.2 of [RFC8296]
about Proto defination. This document support the following
combination of BIER Proto and Next Header:
Use Next Header value 4, 41 and TBD0 for IPv4 packet, IPv6
packet and Ethernet packet respectively, and use Proto value
TBD1 indicating "Delivering the data packet with VRF lookup
in IPv6 source address".
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Use Next Header value 59 for private packet format, and use
Proto value 5 indicating "Delivering the BIER OAM packet
without VRF lookup". The BIER-PING [I-D.ietf-bier-ping]
works equally in BIER IPv6 encapsulation as well as in BIER
MPLS or BIER Ethernet encapsulation.
Allocation of Next Header value TBD0 for Ethernet packet is
applying in [I-D.ietf-spring-srv6-network-programming] and
will not be listed in the IANA considerations section of this
document.
Allocation of BIER Proto value TBD1 is listed in the IANA
considerations section of this document.
BFIR-id: See Section 2.1.2 of RFC 8296.
BitString: See Section 2.1.2 of RFC 8296.
3.2. Multicast and Unicast Destination Address
BIER is generally a hop-by-hop and one-to-many architecture, and thus
the IPv6 Destination Address (DA) being a Multicast Address is a way
one may think of as an approach for both the two paradigms in BIERv6
encapsulation.
However using a unicast address has the following benefits:
1. Tunneling a BIERv6 packet over a non-BIER capable router.
2. Fast rerouting a BIERv6 packet using a unicast by-pass tunnel.
3. Forwarding a BIERv6 packet to one of the many BFR neighbors
connected on a LAN.
4. Connecting BIER domains, for example Data Center domains, in an
overlay manner.
Some of the above functions are assumed very basic requirements and
part of BIER architecture as described in [RFC8279]. This document
uses unicast address for both one-hop replication and multi-hop
replication.
The unicast address used in BIERv6 packet targeting a BFR SHOULD be
advertised as part of the BIER IPv6 Encapsulation. When a BFR
advertises the BIER information with BIERv6 encapsulation capability,
an IPv6 unicast address of this BFR MUST be selected specifically for
BIERv6 packet forwarding. Locally this "BIER Specific" IPv6 address
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is initialized in FIB with a flag of "BIER specific handling",
represented as End.BIER function.
If a BFR belongs to more than one sub-domain, it may (though it need
not) have a different End.BIER in each sub-domain. If different
End.BIER is used for each sub-domain, implementation SHOULD support
verifying the DA of a BIERv6 packet is the End.BIER address bound by
the sub-domain of the packet. See section 5.2 for such use case.
The following is an example of configuring a sub-domain using BIER
IPv6 encapsualation:
# Config an IPv6 block for End.BIER IPv6 address allocation
ipv6-block blk1 2001:DB8:A1:: 96 static 32
# Config BIER Sub-domain using End.BIER allocated from blk1
bier sub-domain 6 ipv6-underlay
bfr-prefix interface loopback0
end-bier ipv6-block blk1 opcode ::1
encapsulation ipv6 bsl 256 max-si 0
The co-existance of BIERv6 and SRv6 is allowed. The following is an
example of configuring a sub-domain using BIERv6 when SRv6 is already
deployed with a locator 'loc1' configured:
# Config BIER Sub-domain using End.BIER allocated from loc1
bier sub-domain 6 ipv6-underlay
bfr-prefix interface loopback0
end-bier locator loc1 opcode ::1
encapsulation ipv6 bsl 256 max-si 0
For the convenience of such co-existence of BIERv6 and SRv6, the
indication of End.BIER or "BIER specific handling" in FIB shares the
same space as SRv6 Endpoints Behaviors defined in
[I-D.ietf-spring-srv6-network-programming]. Apart from this sharing
of code space, there is nothing dependent on SRv6.
The following is an example pseudo-code of the End.BIER function:
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1. IF NH = 60 and HopLimit > 0 ;;Ref1
2. IF (OptType1 = BIER) and (OptLength1 = HdrExtLen*8 + 4) ;;Ref2
3. Lookup the BIER Header inside the BIER option TLV.
4. Forward via the matched entry.
5. ELSE ;;Ref3
6. Drop the packet and end the process.
7. ELSE IF NH=ICMPv6 or (NH=60 and Dest_NH=ICMPv6) ;;Ref4
8. Send to CPU.
9. ELSE ;;Ref5
10. Drop the packet.
Ref1: Destination options header follows the IPv6 header directly and
HopLimit is bigger than zero.
Ref2: The first TLV is BIER type and is the only TLV present in
Destination options header.
Ref3/Ref5: Undesired packet is droped because the destination address
is the BIER specific IPv6 address (End.BIER function).
Ref4: An ICMPv6 packet using End.BIER as destination address.
3.3. BIERv6 Packet Format
As a multicast packet enters the BIER domain in a Non-MPLS IPv6
network, the multicast packet will be encapsulated with BIERv6
Header.
Typically a BIERv6 header would contain the Destination Options
Header as the only Extensions Header besides IPv6 Header. However,
it is allowed and possible for other extension headers to appear
along with the Destination Options Header as long as the requirements
listed in section 3.1 of this document is met.
Format of the multicast packet with BIERv6 encapsulation carrying
only the Destination Options header is depicted in the below figure.
+---------------+--------------+------------
| IPv6 header | Dest Options | X type of
| | Header with | multicast
| | BIER Option | packet
| | |
| Next Hdr = 60 | Nxt Hdr = X |
+---------------+--------------+------------
Format of the multicast packet with BIERv6 encapsulation carrying
other extension headers along with Destination Options extension
header is required to follow general recommendations of [RFC8200] and
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examples in other RFCs. [RFC6275] introduces how the order should be
when other extension headers carries along with Home address option
in a destination options header. Similar to this example, this
document requires the Destination Options Header carrying the BIER
option MUST be placed as follows:
o After the routing header, if that header is present
o Before the Fragment Header, if that header is present
o Before the AH Header or ESP Header, if either one of those headers
is present
Source Address field in the IPv6 header MUST be a routable IPv6
unicast address of the BFIR in any case.
BFIR encodes the Non-MPLS BIER header in the above mentioned
encapsulation format and forwards the BIERv6 packet to the nexthop
BFR following the local BIFT table.
BFRs in the IPv6 network, processes and replicates the packets
towards the BFERs using the local BIFT table. The bit-string field
in the Non-MPLS BIER header may be changed by the BFRs as they
replicate the packet. BFRs MUST follow the procedures defined in
section 3.1 as they modify the other fields in the Non-MPLS BIER
header. The source address in the IPv6 header MUST NOT be modified
by the BFRs.
4. BIERv6 Packet Processing
There is no BIER-specific processing, and all the 8 steps in section
6.5 of RFC8279 apply to BIERv6 packet processing. However, there are
some IPv6-specific processing procedures due to the base and general
procedures of IPv6.
On the overlay layer, when a multicast packet enters the BIER domain
in a Non-MPLS IPv6 network, the Ingress BFR (BFIR) encapsulates the
multicast packet with a BIERv6 Header, transforming it to a BIERv6
packet. The BIERv6 header includes an IPv6 header and IPv6
Destination Options Header within a standard Non-MPLS BIER header.
Source Address field in the IPv6 header MUST be set to a routable
IPv6 unicast address of the BFIR. Destination Address field in the
IPv6 header is set to the End.BIER address of the next-hop BFR the
BIERv6 packet replicating to, no matter next-hop BFR is directly
connected (one-hop) or not directly connected (multi-hop).
On the BIER layer, upon receiving an BIERv6 packet, the BFR processes
the IPv6 header first. This is the general procedure of IPv6.
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If the IPv6 Destination address is an End.BIER IPv6 unicast address
of this BFR, a 'BIER Specific Handling' indication will be obtained
by the preceding Unicast DA lookup (FIB lookup). The BIER option, if
exists, will be checked to decide which neighbor(s) to replicate the
BIERv6 packet to.
It is a local behavior to handle the combination of extension
headers, options and the BIER option(s) in destination options header
when a 'BIER Specific Handling' indication is got by the preceding
FIB lookup. Early deployment of BIERv6 may require there is only one
BIER option TLV in the destination options header followed the IPv6
header. How other extension headers or more BIER option TLVs in a
BIERv6 packet is handled is outside the scope of this document.
A packet having a 'BIER Specific Handling' indication but not having
a BIER option is supposed to be a wrong packet or an ICMPv6 packet,
and the process can be refered to the example in section 3.2.
A packet not having a 'BIER Specific Handling' indication but having
a BIER option SHOULD be processed normally as unicast forwarding
procedures, which may be a behavior of drop, or send to CPU, or other
behaviors in existing implementations.
The Destination Address field in the IPv6 Header MUST change to the
nexthop BFR's End.BIER Unicast address in BIERv6.
The Hop Limit field of IPv6 header MUST decrease by 1 when sending
packets to a BFR neighbor, while the TTL in the BIER header MUST be
unchanged on a Non-BIER router, or decrease by 1 on a BFR.
The BitString in the BIER header in the Destination Options Header
may change when sending packets to a neighbor. Such change of
BitString MUST be aligned with the procedure defined in RFC8279.
Because of the requirement to change the content of the option when
forwarding BIERv6 packet, the BIER option type should have chg flag 1
per section 4.2 of RFC8200.
The procedures applies normally if a bit corresponding to the self
bfr-id is set in the bit-string field of the Non-MPLS BIER header of
the BIERv6 packet. The node is considered to be an Egress BFR (BFER)
in this case. The BFER removes the BIERv6 header, including the IPv6
header and the Destination Options header, and copies the packet to
the multicast flow overlay. The egress VRF of a packet may be
determined by a further lookup on the IPv6 source address instead of
the upstream-assigned MPLS Label as described in [RFC8556].
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The Fragment Header, AH Header or ESP Header, if exists after the
BIER options header, can be processed on BFER only as part of the
multicast flow overlay process.
5. Security Considerations
BIER IPv6 encapsulation provides a new encapsulation based on IPv6
and BIER to transport multicast data packet in a BIER domain. The
BIER domain can be a single IGP area, an anonymous system (AS) with
multiple IGP areas, or multiple anonymous systems (ASes) operated by
a network operator. This section reviews security considerations
related to the BIER IPv6 encapsulation, based on security
considerations of [RFC8279], [RFC8296], and other documents related
to IPv6 extension.
BIER-encapsulated packets should generally not be accepted from
untrusted interfaces or tunnels. For example, an operator may wish
to have a policy of accepting BIER-encapsulated packets only from
interfaces to trusted routers, and not from customer-facing
interfaces. See section 5.1 for normal Intra domain deployment.
There may be applications that require a BFR to accept a BIER-
encapsulated packet from an interface to a system that is not
controlled by the network operator. See section 5.2 for inter domain
deployment.
BIER IPv6 encapsulation may cause ICMP packet sent to BFIR and cause
security problems. See section 5.3 for ICMP related problems.
This document introduces a new option used in IPv6 Destination
Options Header, together with the special-use IPv6 address called
End.BIER in IPv6 destination address for BIER IPv6 forwarding.
However the option newly introduced may be wrongly used with normal
IPv6 destination address. See section 5.4 for problems introduced by
the new IPv6 option with normal IPv6 destination address.
If a BIER packet is altered, either the BIER header, or the multicast
data packet, by an intermediate router, packets may be lost, stolen,
or otherwise misdelivered. BIER IPv6 encapsulation provides the
ability of IPsec to ensure the confidentiality or integrity. See
section 5.5 for this security problem.
A BIER router accepts and uses the End.BIER IPv6 address to construct
BIFT only when the IPv6 address is configured explicitly, or received
from a router via control-plane protocols. The received information
is validated using existing authentication and security mechanisms of
the control-plane protocols. BIER IPv6 encapsulation does not define
any additional security mechanism in existing control-plane
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protocols, and it inherits any security considerations that apply to
the control-plane protocols.
5.1. Intra Domain Deployment
Generally nodes outside the BIER Domain are not trusted: they cannot
directly use the End.BIER of the domain. This is enforced by two
levels of access control lists:
1. Any packet entering the BIER Domain and destined to an End.BIER
IPv6 Address within the BIER Domain is dropped. This may be realized
with the following logic. Other methods with equivalent outcome are
considered compliant:
* allocate all the End.BIER IPv6 Address from a block S/s
* configure each external interface of each edge node of the domain
with an inbound infrastructure access list (IACL) which drops any
incoming packet with a destination address in S/s
* Failure to implement this method of ingress filtering exposes the
BIER Domain to BIER attacks as described and referenced in [RFC8296].
2. The distributed protection in #1 is complemented with per node
protection, dropping packets to End.BIER IPv6 Address from source
addresses outside the BIER Domain. This may be realized with the
following logic. Other methods with equivalent outcome are
considered compliant:
* assign all interface addresses from prefix A/a
* assign all the IPv6 addresses used as source address of BIER IPv6
packets from a block B/b
* at node k, all End.BIER IPv6 addresses local to k are assigned from
prefix Sk/sk
* configure each internal interface of each BIER node k in the BIER
Domain with an inbound IACL which drops any incoming packet with a
destination address in Sk/sk if the source address is not in A/a or
B/b.
For simplicity of deployment, a configuration of IACL effective for
all interfaces can be provided by a router. Such IACL can be
referred to as global IACL(GIACL) .Each BIER node k then simply
configs a GIACL which drops any incoming packet with a destination
address in Sk/sk if the source address is not in A/a or B/b for the
inter-domain deployment mode.
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5.2. Inter Domain Deployment
There may be applications that require a BFR to accept a BIER-
encapsulated packet from an interface to a system that is not
controlled by the network operator. For instance, there may be an
application in which a virtual machine in a data center submits BIER-
encapsulated packets to a router. In such a case, it is desirable to
verify that the packet is from a legitimate source and that its
BitString denotes only systems to which that source is allowed to
send. Using BIER IPv6 encapsulation, IACL can be configured on each
internal interface of each BIER node k to allow packet with a
destination address in Sk/sk and the source address is in an allowed
list of IPv6 address. However, the BIER IPv6 encapsulation itself
does not provide a way to verify that the source is legitimate or the
source is allowed to set any particular set of bits in the BitString.
The IACL allowing specific IPv6 address outside the domain of a
network operator can be more strict by the following method:
* configure one sub-domain using only one bit string length, and a
seperate End.BIER for this sub-domain as a service opened to agreed
source(s) outside the domain of the operator's network.
* configure on BIER node to check if the End.BIER address of a packet
is the correct one bound to the sub-domain of a packet.
* configure IACL on each interface of each BIER node k (or simply
configure GIACL on each BIER node k) to allow packet with an End.BIER
as destination address and the allowed source(s) as source address.
This provides a way to ensure that the inter-domain source is allowed
to access only the BIER IPv6 transport service bound to a sub-domain
with a specific bit string length.
5.3. ICMP Error Processing
ICMP error packets generated within the BIER Domain are sent to
source nodes within the BIER Domain.
A large number of ICMP may be elicited and sent to a BFIR router, in
case when a BIER IPv6 packet is filled with wrong TTL, either error
or malfeasance. A rate-limiting of ICMP packet should be implemented
on each BFR.
The ingress node can take note of the fact that it is getting, in
response to BIER IPv6 packet, one or more ICMP error packets. By
default, the reception of such a packets MUST be countered and
logged. However, it is possible for such log entries to be "false
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positives" that generate a lot of "noise" in the log; therefore,
implementations SHOULD have a knob to disable this logging.
OAM functions of PING and TRACE for BIER IPv6 encapsulation may also
need ICMP based on BIER IPv6 encapsulation and cause ICMP response
message containing BIER option. The ability of seperating such OAM
ICMP packets from error ICMP packets caused by error is necessary for
the availability of OAM, otherwise the OAM function may fail due to
the rate-limiting of ICMP error packets.
5.4. Security caused by BIER option
This document introduces a new option used in IPv6 Destination
Options Header. An IPv6 packet with a normal IPv6 address of a
router (e.g. loopback IPv6 address of the router) as destination
address will possibly carry a BIER option.
For a router incapable of BIERv6, such BIERv6 packet will not be
processed by the procedure described in this document, but be
processed as normal IPv6 packet with unknown option, and the existing
security considerations for handling IPv6 options apply. Possible
way of handling IPv6 packets with BIER option may be send to CPU for
slow path processing, with rate-limiting, or be discarded according
to the local policy.
For a router capable of BIERv6, such BIERv6 packet MUST NOT be
forwarded, but should be processed as a normal IPv6 packet with
unknown option, or additionally and optionally be countered and
logged if the router is capable of doing so.
5.5. Applicability of IPsec
IPsec [RFC4301] uses two protocols to provide traffic security
services -- Authentication Header (AH) [RFC4302] and Encapsulating
Security Payload (ESP) [RFC4303]. Each protocol supports two modes
of use: transport mode and tunnel mode. IPsec support both unicast
and multicast. IPsec implementations MUST support ESP and MAY
support AH.
This document assume IPsec working in tunnel mode with inner IPv4 or
IPv6 multicast packet encapsulated in outer BIERv6 header and IPsec
header(s).
IPsec used with BIER IPv6 encapsulation to ensure that a BIER payload
is not altered while in transit between BFIR and BFERs. If a BFR in
between BFIR and BFERs is compromised, there is no way to prevent the
compromised BFR from making illegitimate modifications to the BIER
payload or to prevent it from misforwarding or misdelivering the
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BIER-encapsulated packet, but the BFERs will detect the illegitimate
modifications to the BIER Payload (or the inner multicast data
packet). This could provide cryptographic integrity protection for
multicast data transport. This capability of IPsec comes from the
design that, the destination options header carrying the BIER header
is located before the AH or ESP and the BFR routers in between BFIR
and BFERs can process the BIER header without aware of AH or ESP.
For ESP, the Integrity Check Value (ICV) is computed over the ESP
header, Payload, and ESP trailer fields. It doesn't require the IP
or extension header for ICV calculating, and thus the change of DA
and BIER option data does not affect the function of ESP.
For AH, the Integrity Check Value (ICV) is computed over the IP or
extension header fields before the AH header, the AH header, and the
Payload. The IPv6 DA is immutable for unicast traffic in AH, and the
change of DA in BIER IPv6 forwarding for multicast traffic is
incompatible to this rule. How AH is extended to support multicast
traffic transporting through BIER IPv6 encapsulation is outside the
scope of this document.
The detailed control-plane for BIER IPv6 encapsulation IPsec function
is outside the scope of the document. Internet Key Exchange Protocol
Version 2 (IKEv2) [RFC5996] and Group Security Association (GSA)
[RFC5374] can be referred to for further studying.
6. IANA Considerations
6.1. BIER Option Type
Allocation is expected from IANA for a BIER Option Type codepoint
from the "Destination Options and Hop-by-Hop Options" sub-registry of
the "Internet Protocol Version 6 (IPv6) Parameters" registry. The
value 0x70 is suggested.
+-----------+-----+-----+-------+-------------+------------+
| Hex Value | act | chg | rest | Description | Reference |
+-----------+-----+-----+-------+-------------+------------+
| 0x70 | 01 | 1 | 10000 | BIER Option | This draft |
+-----------+-----+-----+-------+-------------+------------+
6.2. End.BIER Function
Allocation is expected from IANA for an End.BIER function codepoint
from the "SRv6 Endpoint Behaviors" sub-registry. The value 60 is
suggested.
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+-------+--------+--------------------------+------------+
| Value | Hex | Endpoint function | Reference |
+-------+--------+--------------------------+------------+
| TBD | TBD | End.BIER | This draft |
+-------+--------+--------------------------+------------+
6.3. BIER Next Protocol Identifiers
Allocation is expected from IANA for a BIER Proto codepoint from the
"BIER Next Protocol Identifiers" sub-registry.
TBD1: Delivering the packet with VRF lookup in IPv6 source address
7. Acknowledgements
The authors would like to thank Stig Venaas for his valuable
comments. Thanks IJsbrand Wijnands, Greg Shepherd, Tony Przygienda,
Toerless Eckert, Jeffrey Zhang for the helpful comments to improve
this document.
Thanks Aijun Wang for comments about BIER OAM function in BIER IPv6
encapsulation.
Thanks Mach Chen for review and suggestions about BIER-PING function
in BIER IPv6 encapsulation.
8. Contributors
Gang Yan
Huawei Technologies
China
Email: yangang@huawei.com
Yang(Yolanda) Xia
Huawei Technologies
China
Email: yolanda.xia@huawei.com
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9. References
9.1. Normative References
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, DOI 10.17487/RFC4301,
December 2005, <https://www.rfc-editor.org/info/rfc4301>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
RFC 4303, DOI 10.17487/RFC4303, December 2005,
<https://www.rfc-editor.org/info/rfc4303>.
[RFC5374] Weis, B., Gross, G., and D. Ignjatic, "Multicast
Extensions to the Security Architecture for the Internet
Protocol", RFC 5374, DOI 10.17487/RFC5374, November 2008,
<https://www.rfc-editor.org/info/rfc5374>.
[RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen,
"Internet Key Exchange Protocol Version 2 (IKEv2)",
RFC 5996, DOI 10.17487/RFC5996, September 2010,
<https://www.rfc-editor.org/info/rfc5996>.
[RFC6275] Perkins, C., Ed., Johnson, D., and J. Arkko, "Mobility
Support in IPv6", RFC 6275, DOI 10.17487/RFC6275, July
2011, <https://www.rfc-editor.org/info/rfc6275>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
for Bit Index Explicit Replication (BIER) in MPLS and Non-
MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
2018, <https://www.rfc-editor.org/info/rfc8296>.
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[RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S.,
and A. Dolganow, "Multicast VPN Using Bit Index Explicit
Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April
2019, <https://www.rfc-editor.org/info/rfc8556>.
9.2. Informative References
[I-D.ietf-bier-ipv6-requirements]
McBride, M., Xie, J., Dhanaraj, S., and R. Asati, "BIER
IPv6 Requirements", draft-ietf-bier-ipv6-requirements-03
(work in progress), November 2019.
[I-D.ietf-bier-ping]
Kumar, N., Pignataro, C., Akiya, N., Zheng, L., Chen, M.,
and G. Mirsky, "BIER Ping and Trace", draft-ietf-bier-
ping-06 (work in progress), October 2019.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-07 (work in
progress), December 2019.
[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>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Authors' Addresses
Jingrong Xie
Huawei Technologies
Email: xiejingrong@huawei.com
Liang Geng
China Mobile
Beijing 10053
Email: gengliang@chinamobile.com
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Mike McBride
Futurewei
Email: mmcbride7@gmail.com
Rajiv Asati
Cisco
Email: rajiva@cisco.com
Senthil Dhanaraj
Huawei
Email: senthil.dhanaraj@huawei.com
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