Recommendation for a Routing Architecture
RFC 6115
| Document | Type | RFC - Informational (February 2011; No errata) | |
|---|---|---|---|
| Author | Tony Li | ||
| Last updated | 2015-10-14 | ||
| Stream | Internet Research Task Force (IRTF) | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Reviews | |||
| Stream | IRTF state | (None) | |
| Consensus Boilerplate | Unknown | ||
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 6115 (Informational) | |
| Action Holders |
(None)
|
||
| Telechat date | |||
| Responsible AD | Jari Arkko | ||
| Send notices to | jmh@joelhalpern.com | ||
Internet Research Task Force (IRTF) T. Li, Ed.
Request for Comments: 6115 Cisco Systems
Category: Informational February 2011
ISSN: 2070-1721
Recommendation for a Routing Architecture
Abstract
It is commonly recognized that the Internet routing and addressing
architecture is facing challenges in scalability, multihoming, and
inter-domain traffic engineering. This document presents, as a
recommendation of future directions for the IETF, solutions that
could aid the future scalability of the Internet. To this end, this
document surveys many of the proposals that were brought forward for
discussion in this activity, as well as some of the subsequent
analysis and the architectural recommendation of the chairs. This
document is a product of the Routing Research Group.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Research Task Force
(IRTF). The IRTF publishes the results of Internet-related research
and development activities. These results might not be suitable for
deployment. This RFC represents the individual opinion(s) of one or
more members of the Routing Research Group of the Internet Research
Task Force (IRTF). Documents approved for publication by the IRSG
are not a candidate for any level of Internet Standard; see Section 2
of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6115.
Li Informational [Page 1]
RFC 6115 RRG Recommendation February 2011
Copyright Notice
Copyright (c) 2011 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
(http://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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1. Background to This Document . . . . . . . . . . . . . . . 5
1.2. Areas of Group Consensus . . . . . . . . . . . . . . . . . 6
1.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 7
2. Locator/ID Separation Protocol (LISP) . . . . . . . . . . . . 8
2.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1.4. References . . . . . . . . . . . . . . . . . . . . . . 10
2.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 11
3. Routing Architecture for the Next Generation Internet
(RANGI) . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 12
3.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1.4. References . . . . . . . . . . . . . . . . . . . . . . 13
3.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 15
4. Internet Vastly Improved Plumbing (Ivip) . . . . . . . . . . . 16
4.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1.1. Key Ideas . . . . . . . . . . . . . . . . . . . . . . 16
4.1.2. Extensions . . . . . . . . . . . . . . . . . . . . . . 17
4.1.2.1. TTR Mobility . . . . . . . . . . . . . . . . . . . 17
4.1.2.2. Modified Header Forwarding . . . . . . . . . . . . 18
4.1.3. Gains . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1.4. Costs . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1.5. References . . . . . . . . . . . . . . . . . . . . . . 19
4.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 20
5. Hierarchical IPv4 Framework (hIPv4) . . . . . . . . . . . . . 21
5.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 21
Li Informational [Page 2]
RFC 6115 RRG Recommendation February 2011
5.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 21
5.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 22
5.1.3. Costs and Issues . . . . . . . . . . . . . . . . . . . 23
5.1.4. References . . . . . . . . . . . . . . . . . . . . . . 23
5.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 24
5.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 25
6. Name Overlay (NOL) Service for Scalable Internet Routing . . . 25
6.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 25
6.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 26
6.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 27
6.1.4. References . . . . . . . . . . . . . . . . . . . . . . 27
6.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 27
6.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 28
7. Compact Routing in a Locator Identifier Mapping System (CRM) . 29
7.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 29
7.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 29
7.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 30
7.1.4. References . . . . . . . . . . . . . . . . . . . . . . 30
7.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 30
7.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 31
8. Layered Mapping System (LMS) . . . . . . . . . . . . . . . . . 32
8.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 32
8.1.1. Key Ideas . . . . . . . . . . . . . . . . . . . . . . 32
8.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 32
8.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 33
8.1.4. References . . . . . . . . . . . . . . . . . . . . . . 33
8.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 33
8.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 34
9. Two-Phased Mapping . . . . . . . . . . . . . . . . . . . . . . 34
9.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.1.1. Considerations . . . . . . . . . . . . . . . . . . . . 34
9.1.2. Basics of a Two-Phased Mapping . . . . . . . . . . . . 35
9.1.3. Gains . . . . . . . . . . . . . . . . . . . . . . . . 35
9.1.4. Summary . . . . . . . . . . . . . . . . . . . . . . . 36
9.1.5. References . . . . . . . . . . . . . . . . . . . . . . 36
9.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 36
9.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 36
10. Global Locator, Local Locator, and Identifier Split
(GLI-Split) . . . . . . . . . . . . . . . . . . . . . . . . . 36
10.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 36
10.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 36
10.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 37
10.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 38
10.1.4. References . . . . . . . . . . . . . . . . . . . . . . 38
10.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 38
10.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 39
Li Informational [Page 3]
RFC 6115 RRG Recommendation February 2011
11. Tunneled Inter-Domain Routing (TIDR) . . . . . . . . . . . . . 40
11.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.1. Key Idea . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.2. Gains . . . . . . . . . . . . . . . . . . . . . . . . 40
11.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1.4. References . . . . . . . . . . . . . . . . . . . . . . 41
11.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 42
12. Identifier-Locator Network Protocol (ILNP) . . . . . . . . . . 42
12.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 42
12.1.1. Key Ideas . . . . . . . . . . . . . . . . . . . . . . 42
12.1.2. Benefits . . . . . . . . . . . . . . . . . . . . . . . 43
12.1.3. Costs . . . . . . . . . . . . . . . . . . . . . . . . 44
12.1.4. References . . . . . . . . . . . . . . . . . . . . . . 45
12.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 45
12.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 46
13. Enhanced Efficiency of Mapping Distribution Protocols in
Map-and-Encap Schemes (EEMDP) . . . . . . . . . . . . . . . . 48
13.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 48
13.1.1. Introduction . . . . . . . . . . . . . . . . . . . . . 48
13.1.2. Management of Mapping Distribution of Subprefixes
Spread across Multiple ETRs . . . . . . . . . . . . . 48
13.1.3. Management of Mapping Distribution for Scenarios
with Hierarchy of ETRs and Multihoming . . . . . . . . 49
13.1.4. References . . . . . . . . . . . . . . . . . . . . . . 50
13.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 50
13.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 51
14. Evolution . . . . . . . . . . . . . . . . . . . . . . . . . . 52
14.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 52
14.1.1. Need for Evolution . . . . . . . . . . . . . . . . . . 52
14.1.2. Relation to Other RRG Proposals . . . . . . . . . . . 53
14.1.3. Aggregation with Increasing Scopes . . . . . . . . . . 53
14.1.4. References . . . . . . . . . . . . . . . . . . . . . . 55
14.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 55
14.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 56
15. Name-Based Sockets . . . . . . . . . . . . . . . . . . . . . . 56
15.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 56
15.1.1. References . . . . . . . . . . . . . . . . . . . . . . 58
15.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 58
15.2.1. Deployment . . . . . . . . . . . . . . . . . . . . . . 59
15.2.2. Edge-networks . . . . . . . . . . . . . . . . . . . . 59
15.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 59
16. Routing and Addressing in Networks with Global Enterprise
Recursion (IRON-RANGER) . . . . . . . . . . . . . . . . . . . 59
16.1. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 59
16.1.1. Gains . . . . . . . . . . . . . . . . . . . . . . . . 60
16.1.2. Costs . . . . . . . . . . . . . . . . . . . . . . . . 61
16.1.3. References . . . . . . . . . . . . . . . . . . . . . . 61
Li Informational [Page 4]
RFC 6115 RRG Recommendation February 2011
16.2. Critique . . . . . . . . . . . . . . . . . . . . . . . . . 61
16.3. Rebuttal . . . . . . . . . . . . . . . . . . . . . . . . . 62
17. Recommendation . . . . . . . . . . . . . . . . . . . . . . . . 63
17.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 64
17.2. Recommendation to the IETF . . . . . . . . . . . . . . . . 65
17.3. Rationale . . . . . . . . . . . . . . . . . . . . . . . . 65
18. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 66
19. Security Considerations . . . . . . . . . . . . . . . . . . . 66
20. Informative References . . . . . . . . . . . . . . . . . . . . 66
1. Introduction
It is commonly recognized that the Internet routing and addressing
architecture is facing challenges in scalability, multihoming, and
inter-domain traffic engineering. The problem being addressed has
been documented in [Scalability_PS], and the design goals that we
have discussed can be found in [RRG_Design_Goals].
This document surveys many of the proposals that were brought forward
for discussion in this activity. For some of the proposals, this
document also includes additional analysis showing some of the
concerns with specific proposals, and how some of those concerns may
be addressed. Readers are cautioned not to draw any conclusions
about the degree of interest or endorsement by the Routing Research
Group (RRG) from the presence of any proposals in this document, or
the amount of analysis devoted to specific proposals.
1.1. Background to This Document
The RRG was chartered to research and recommend a new routing
architecture for the Internet. The goal was to explore many
alternatives and build consensus around a single proposal. The only
constraint on the group's process was that the process be open and
the group set forth with the usual discussion of proposals and trying
to build consensus around them. There were no explicit contingencies
in the group's process for the eventuality that the group did not
reach consensus.
The group met at every IETF meeting from March 2007 to March 2010 and
discussed many proposals, both in person and via its mailing list.
Unfortunately, the group did not reach consensus. Rather than lose
the contributions and progress that had been made, the chairs (Lixia
Zhang and Tony Li) elected to collect the proposals of the group and
some of the debate concerning the proposals and make a recommendation
from those proposals. Thus, the recommendation reflects the opinions
of the chairs and not necessarily the consensus of the group.
The group was able to reach consensus on a number of items that are
Li Informational [Page 5]
RFC 6115 RRG Recommendation February 2011
included below. The proposals included here were collected in an
open call amongst the group. Once the proposals were collected, the
group was solicited to submit critiques of each proposal. The group
was asked to self-organize to produce a single critique for each
proposal. In cases where there were several critiques submitted, the
editor selected one. The proponents of each proposal then were given
the opportunity to write a rebuttal of the critique. Finally, the
group again had the opportunity to write a counterpoint of the
rebuttal. No counterpoints were submitted. For pragmatic reasons,
each submission was severely constrained in length.
All of the proposals were given the opportunity to progress their
documents to RFC status; however, not all of them have chosen to
pursue this path. As a result, some of the references in this
document may become inaccessible. This is unfortunately unavoidable.
The group did reach consensus that the overall document should be
published. The document has been reviewed by many of the active
members of the Research Group.
1.2. Areas of Group Consensus
The group was also able to reach broad and clear consensus on some
terminology and several important technical points. For the sake of
posterity, these are recorded here:
1. A "node" is either a host or a router.
2. A "router" is any device that forwards packets at the network
layer (e.g., IPv4, IPv6) of the Internet architecture.
3. A "host" is a device that can send/receive packets to/from the
network, but does not forward packets.
4. A "bridge" is a device that forwards packets at the link layer
(e.g., Ethernet) of the Internet architecture. An Ethernet
switch or Ethernet hub are examples of bridges.
5. An "address" is an object that combines aspects of identity with
topological location. IPv4 and IPv6 addresses are current
examples.
6. A "locator" is a structured topology-dependent name that is not
used for node identification and is not a path. Two related
meanings are current, depending on the class of things being
named:
1. The topology-dependent name of a node's interface.
Li Informational [Page 6]
RFC 6115 RRG Recommendation February 2011
2. The topology-dependent name of a single subnetwork OR
topology-dependent name of a group of related subnetworks
that share a single aggregate. An IP routing prefix is a
current example of the latter.
7. An "identifier" is a topology-independent name for a logical
node. Depending upon instantiation, a "logical node" might be a
single physical device, a cluster of devices acting as a single
node, or a single virtual partition of a single physical device.
An OSI End System Identifier (ESID) is an example of an
identifier. A Fully Qualified Domain Name (FQDN) that precisely
names one logical node is another example. (Note well that not
all FQDNs meet this definition.)
8. Various other names (i.e., other than addresses, locators, or
identifiers), each of which has the sole purpose of identifying
a component of a logical system or physical device, might exist
at various protocol layers in the Internet architecture.
9. The Research Group has rough consensus that separating identity
from location is desirable and technically feasible. However,
the Research Group does NOT have consensus on the best
engineering approach to such an identity/location split.
10. The Research Group has consensus that the Internet needs to
support multihoming in a manner that scales well and does not
have prohibitive costs.
11. Any IETF solution to Internet scaling has to not only support
multihoming, but address the real-world constraints of the end
customers (large and small).
1.3. Abbreviations
This section lists some of the most common abbreviations used in the
remainder of this document.
DFZ Default-Free Zone
EID Endpoint IDentifier or Endpoint Interface iDentifier: The
precise definition varies depending on the proposal.
ETR Egress Tunnel Router: In a system that tunnels traffic across
the existing infrastructure by encapsulating it, the device
close to the actual ultimate destination that decapsulates the
traffic before forwarding it to the ultimate destination.
FIB Forwarding Information Base: The forwarding table, used in the
Li Informational [Page 7]
RFC 6115 RRG Recommendation February 2011
data plane of routers to select the next hop for each packet.
ITR Ingress Tunnel Router: In a system that tunnels traffic across
the existing infrastructure by encapsulating it, the device
close to the actual original source that encapsulates the
traffic before using the tunnel to send it to the appropriate
ETR.
PA Provider-Aggregatable: Address space that can be aggregated as
part of a service provider's routing advertisements.
PI Provider-Independent: Address space assigned by an Internet
registry independent of any service provider.
PMTUD Path Maximum Transmission Unit Discovery: The process or
mechanism that determines the largest packet that can be sent
between a given source and destination without being either i)
fragmented (IPv4 only), or ii) discarded (if not fragmentable)
because it is too large to be sent down one link in the path
from the source to the destination.
RIB Routing Information Base. The routing table, used in the
control plane of routers to exchange routing information and
construct the FIB.
RIR Regional Internet Registry.
RLOC Routing LOCator: The precise definition varies depending on
the proposal.
xTR Tunnel Router: In some systems, the term used to describe a
device which can function as both an ITR and an ETR.
2. Locator/ID Separation Protocol (LISP)
2.1. Summary
2.1.1. Key Idea
Implements a locator/identifier separation mechanism using
encapsulation between routers at the "edge" of the Internet. Such a
separation allows topological aggregation of the routable addresses
(locators) while providing stable and portable numbering of end
systems (identifiers).
Li Informational [Page 8]
RFC 6115 RRG Recommendation February 2011
2.1.2. Gains
o topological aggregation of locator space (RLOCs) used for routing,
which greatly reduces both the overall size and the "churn rate"
of the information needed to operate the Internet global routing
system
o separate identifier space (EIDs) for end systems, effectively
allowing "PI for all" (no renumbering cost for connectivity
changes) without adding state to the global routing system
o improved traffic engineering capabilities that explicitly do not
add state to the global routing system and whose deployment will
allow active removal of the more-specific state that is currently
used
o no changes required to end systems
o no changes to Internet "core" routers
o minimal and straightforward changes to "edge" routers
o day-one advantages for early adopters
o defined router-to-router protocol
o defined database mapping system
o defined deployment plan
o defined interoperability/interworking mechanisms
o defined scalable end-host mobility mechanisms
o prototype implementation already exists and is undergoing testing
o production implementations in progress
2.1.3. Costs
o mapping system infrastructure (map servers, map resolvers,
Alternative Logical Topology (ALT) routers). This is considered a
new potential business opportunity.
o interworking infrastructure (proxy ITRs). This is considered a
new potential business opportunity.
Li Informational [Page 9]
RFC 6115 RRG Recommendation February 2011
o overhead for determining/maintaining locator/path liveness. This
is a common issue for all identifier/locator separation proposals.
2.1.4. References
[LISP] [LISP+ALT] [LISP-MS] [LISP-Interworking] [LISP-MN] [LIG]
[LOC_ID_Implications]
2.2. Critique
LISP+ALT distributes mapping information to ITRs via (optional,
local, potentially caching) Map Resolvers and with globally
distributed query servers: ETRs and optional Map Servers (MSes).
A fundamental problem with any global query server network is that
the frequently long paths and greater risk of packet loss may cause
ITRs to drop or significantly delay the initial packets of many new
sessions. ITRs drop the packet(s) they have no mapping for. After
the mapping arrives, the ITR waits for a re-sent packet and will
tunnel that packet correctly. These "initial-packet delays" reduce
performance and so create a major barrier to voluntary adoption on a
wide enough basis to solve the routing scaling problem.
ALT's delays are compounded by its structure being "aggressively
aggregated", without regard to the geographic location of the
routers. Tunnels between ALT routers will often span
intercontinental distances and traverse many Internet routers.
The many levels to which a query typically ascends in the ALT
hierarchy before descending towards its destination will often
involve excessively long geographic paths and so worsen initial-
packet delays.
No solution has been proposed for these problems or for the
contradiction between the need for high aggregation while making the
ALT structure robust against single points of failure.
LISP's ITRs' multihoming service restoration depends on their
determining the reachability of end-user networks via two or more
ETRs. Large numbers of ITRs doing this is inefficient and may
overburden ETRs.
Testing reachability of the ETRs is complex and costly -- and
insufficient. ITRs cannot test network reachability via each ETR,
since the ITRs do not have the address of a device in each ETR's
network. So, ETRs must report network unreachability to ITRs.
Li Informational [Page 10]
RFC 6115 RRG Recommendation February 2011
LISP involves complex communication between ITRs and ETRs, with UDP
and 64-bit LISP headers in all traffic packets.
The advantage of LISP+ALT is that its ability to handle billions of
EIDs is not constrained by the need to transmit or store the mapping
to any one location. Such numbers, beyond a few tens of millions of
EIDs, will only result if the system is used for mobility. Yet the
concerns just mentioned about ALT's structure arise from the millions
of ETRs that would be needed just for non-mobile networks.
In LISP's mobility approach, each Mobile Node (MN) needs an RLOC
address to be its own ETR, meaning the MN cannot be behind a NAT.
Mapping changes must be sent instantly to all relevant ITRs every
time the MN gets a new address -- LISP cannot achieve this.
In order to enforce ISP filtering of incoming packets by source
address, LISP ITRs would have to implement the same filtering on each
decapsulated packet. This may be prohibitively expensive.
LISP monolithically integrates multihoming failure detection and
restoration decision-making processes into the Core-Edge Separation
(CES) scheme itself. End-user networks must rely on the necessarily
limited capabilities that are built into every ITR.
LISP+ALT may be able to solve the routing scaling problem, but
alternative approaches would be superior because they eliminate the
initial-packet delay problem and give end-user networks real-time
control over ITR tunneling.
2.3. Rebuttal
Initial-packet loss/delays turn out not to be a deep issue.
Mechanisms for interoperation with the legacy part of the network are
needed in any viably deployable design, and LISP has such mechanisms.
If needed, initial packets can be sent via those legacy mechanisms
until the ITR has a mapping. (Field experience has shown that the
caches on those interoperation devices are guaranteed to be
populated, as 'crackers' doing address-space sweeps periodically send
packets to every available mapping.)
On ALT issues, it is not at all mandatory that ALT be the mapping
system used in the long term. LISP has a standardized mapping system
interface, in part to allow reasonably smooth deployment of whatever
new mapping system(s) experience might show are required. At least
one other mapping system (LISP-TREE) [LISP-TREE], which avoids ALT's
problems (such as query load concentration at high-level nodes), has
already been laid out and extensively simulated. Exactly what
mixture of mapping system(s) is optimal is not really answerable
Li Informational [Page 11]
RFC 6115 RRG Recommendation February 2011
without more extensive experience, but LISP is designed to allow
evolutionary changes to other mapping system(s).
As far as ETR reachability goes, a potential problem to which there
is a solution with an adequate level of efficiency, complexity, and
robustness is not really a problem. LISP has a number of overlapping
mechanisms that it is believed will provide adequate reachability
detection (along the three axes above), and in field testing to date,
they have behaved as expected.
Operation of LISP devices behind a NAT has already been demonstrated.
A number of mechanisms to update correspondent nodes when a mapping
is updated have been designed (some are already in use).
3. Routing Architecture for the Next Generation Internet (RANGI)
3.1. Summary
3.1.1. Key Idea
Similar to Host Identity Protocol (HIP) [RFC4423], RANGI introduces a
host identifier layer between the network layer and the transport
layer, and the transport-layer associations (i.e., TCP connections)
are no longer bound to IP addresses, but to host identifiers. The
major difference from HIP is that the host identifier in RANGI is a
128-bit hierarchical and cryptographic identifier that has
organizational structure. As a result, the corresponding ID->locator
mapping system for such identifiers has a reasonable business model
and clear trust boundaries. In addition, RANGI uses IPv4-embedded
IPv6 addresses as locators. The Locator Domain Identifier (LD ID)
(i.e., the leftmost 96 bits) of this locator is a provider-assigned
/96 IPv6 prefix, while the last four octets of this locator are a
local IPv4 address (either public or private). This special locator
could be used to realize 6over4 automatic tunneling (borrowing ideas
from the Intra-Site Automatic Tunnel Addressing Protocol (ISATAP)
[RFC5214]), which will reduce the deployment cost of this new routing
architecture. Within RANGI, the mappings from FQDN to host
identifiers are stored in the DNS system, while the mappings from
host identifiers to locators are stored in a distributed ID/locator
mapping system (e.g., a hierarchical Distributed Hash Table (DHT)
system, or a reverse DNS system).
3.1.2. Gains
RANGI achieves almost all of the goals set forth by RRG as follows:
1. Routing Scalability: Scalability is achieved by decoupling
identifiers from locators.
Li Informational [Page 12]
RFC 6115 RRG Recommendation February 2011
2. Traffic Engineering: Hosts located in a multihomed site can
suggest the upstream ISP for outbound and inbound traffic, while
the first-hop Locator Domain Border Router (LDBR; i.e., site
border router) has the final decision on the upstream ISP
selection.
3. Mobility and Multihoming: Sessions will not be interrupted due to
locator change in cases of mobility or multihoming.
4. Simplified Renumbering: When changing providers, the local IPv4
addresses of the site do not need to change. Hence, the internal
routers within the site don't need renumbering.
5. Decoupling Location and Identifier: Obvious.
6. Routing Stability: Since the locators are topologically
aggregatable and the internal topology within the LD will not be
disclosed outside, routing stability could be improved greatly.
7. Routing Security: RANGI reuses the current routing system and
does not introduce any new security risks into the routing
system.
8. Incremental Deployability: RANGI allows an easy transition from
IPv4 networks to IPv6 networks. In addition, RANGI proxy allows
RANGI-aware hosts to communicate to legacy IPv4 or IPv6 hosts,
and vice versa.
3.1.3. Costs
1. A host change is required.
2. The first-hop LDBR change is required to support site-controlled
traffic-engineering capability.
3. The ID->locator mapping system is a new infrastructure to be
deployed.
4. RANGI proxy needs to be deployed for communication between RANGI-
aware hosts and legacy hosts.
3.1.4. References
[RFC3007] [RFC4423] [RANGI] [RANGI-PROXY] [RANGI-SLIDES]
Li Informational [Page 13]
RFC 6115 RRG Recommendation February 2011
3.2. Critique
RANGI is an ID/locator split protocol that, like HIP, places a
cryptographically signed ID between the network layer (IPv6) and
transport. Unlike the HIP ID, the RANGI ID has a hierarchical
structure that allows it to support ID->locator lookups. This
hierarchical structure addresses two weaknesses of the flat HIP ID:
the difficulty of doing the ID->locator lookup, and the
administrative scalability of doing firewall filtering on flat IDs.
The usage of this hierarchy is overloaded: it serves to make the ID
unique, to drive the lookup process, and possibly other things like
firewall filtering. More thought is needed as to what constitutes
these levels with respect to these various roles.
The RANGI document [RANGI] suggests FQDN->ID lookup through DNS, and
separately an ID->locator lookup that may be DNS or may be something
else (a hierarchy of DHTs). It would be more efficient if the FQDN
lookup produces both ID and locators (as does the Identifier-Locator
Network Protocol (ILNP)). Probably DNS alone is sufficient for the
ID->locator lookup since individual DNS servers can hold very large
numbers of mappings.
RANGI provides strong sender identification, but at the cost of
computing crypto. Many hosts (public web servers) may prefer to
forgo the crypto at the expense of losing some functionality
(receiver mobility or dynamic multihoming load balancing). While
RANGI doesn't require that the receiver validate the sender, it may
be good to have a mechanism whereby the receiver can signal to the
sender that it is not validating, so that the sender can avoid
locator changes.
Architecturally, there are many advantages to putting the mapping
function at the end host (versus at the edge). This simplifies the
problems of neighbor aliveness and delayed first packet, and avoids
stateful middleboxes. Unfortunately, the early-adopter incentive for
host upgrade may not be adequate (HIP's lack of uptake being an
example).
RANGI does not have an explicit solution for the mobility race
condition (there is no mention of a home-agent-like device).
However, host-to-host notification combined with fallback on the
ID->locators lookup (assuming adequate dynamic update of the lookup
system) may be good enough for the vast majority of mobility
situations.
Li Informational [Page 14]
RFC 6115 RRG Recommendation February 2011
RANGI uses proxies to deal with both legacy IPv6 and IPv4 sites.
RANGI proxies have no mechanisms to deal with the edge-to-edge
aliveness problem. The edge-to-edge proxy approach dirties up an
otherwise clean end-to-end model.
RANGI exploits existing IPv6 transition technologies (ISATAP and
softwire). These transition technologies are in any event being
pursued outside of RRG and do not need to be specified in RANGI
drafts per se. RANGI only needs to address how it interoperates with
IPv4 and legacy IPv6, which it appears to do adequately well through
proxies.
3.3. Rebuttal
The reason why the ID->locator lookup is separated from the FQDN->ID
lookup is: 1) not all applications are tied to FQDNs, and 2) it seems
unnecessary to require all devices to possess a FQDN of their own.
Basically, RANGI uses DNS to realize the ID->locator mapping system.
If there are too many entries to be maintained by the authoritative
servers of a given Administrative Domain (AD), Distributed Hash Table
(DHT) technology can be used to make these authoritative servers
scale better, e.g., the mappings maintained by a given AD will be
distributed among a group of authoritative servers in a DHT fashion.
As a result, the robustness feature of DHT is inherited naturally
into the ID->locator mapping system. Meanwhile, there is no trust
issue since each AD authority runs its own DHT ring, which maintains
only the mappings for those identifiers that are administrated by
that AD authority.
For host mobility, if communicating entities are RANGI nodes, the
mobile node will notify the correspondent node of its new locator
once its locator changes due to a mobility or re-homing event.
Meanwhile, it should also update its locator information in the
ID->locator mapping system in a timely fashion by using the Secure
DNS Dynamic Update mechanism defined in [RFC3007]. In case of
simultaneous mobility, at least one of the nodes has to resort to the
ID->locator mapping system for resolving the correspondent node's new
locator so as to continue their communication. If the correspondent
node is a legacy host, Transit Proxies, which fulfill a similar
function as the home agents in Mobile IP, will relay the packets
between the communicating parties.
RANGI uses proxies (e.g., Site Proxy and Transit Proxy) to deal with
both legacy IPv6 and IPv4 sites. Since proxies function as RANGI
hosts, they can handle Locator Update Notification messages sent from
remote RANGI hosts (or even from remote RANGI proxies) correctly.
Hence, there is no edge-to-edge aliveness problem. Details will be
specified in a later version of RANGI-PROXY.
Li Informational [Page 15]
RFC 6115 RRG Recommendation February 2011
The intention behind RANGI using IPv4-embedded IPv6 addresses as
locators is to reduce the total deployment cost of this new Internet
architecture and to avoid renumbering the site's internal routers
when such a site changes ISPs.
4. Internet Vastly Improved Plumbing (Ivip)
4.1. Summary
4.1.1. Key Ideas
Ivip (pronounced eye-vip, est. 2007-06-15) is a Core-Edge Separation
scheme for IPv4 and IPv6. It provides multihoming, portability of
address space, and inbound traffic engineering for end-user networks
of all sizes and types, including those of corporations, SOHO (Small
Office, Home Office), and mobile devices.
Ivip meets all the constraints imposed by the need for widespread
voluntary adoption [Ivip_Constraints].
Ivip's global fast-push mapping distribution network is structured
like a cross-linked multicast tree. This pushes all mapping changes
to full-database query servers (QSDs) within ISPs and end-user
networks that have ITRs. Each mapping change is sent to all QSDs
within a few seconds. (Note: "QSD" is from Query Server with full
Database.)
ITRs gain mapping information from these local QSDs within a few tens
of milliseconds. QSDs notify ITRs of changed mappings with similarly
low latency. ITRs tunnel all traffic packets to the correct ETR
without significant delay.
Ivip's mapping consists of a single ETR address for each range of
mapped address space. Ivip ITRs do not need to test reachability to
ETRs because the mapping is changed in real-time to that of the
desired ETR.
End-user networks control the mapping, typically by contracting a
specialized company to monitor the reachability of their ETRs, and
change the mapping to achieve multihoming and/or traffic engineering
(TE). So, the mechanisms that control ITR tunneling are controlled
by the end-user networks in real-time and are completely separate
from the Core-Edge Separation scheme itself.
ITRs can be implemented in dedicated servers or hardware-based
routers. The ITR function can also be integrated into sending hosts.
ETRs are relatively simple and only communicate with ITRs rarely --
for Path MTU management with longer packets.
Li Informational [Page 16]
RFC 6115 RRG Recommendation February 2011
Ivip-mapped ranges of end-user address space need not be subnets.
They can be of any length, in units of IPv4 addresses or IPv6 /64s.
Compared to conventional unscalable BGP techniques, and to the use of
Core-Edge Separation architectures with non-real-time mapping
systems, end-user networks will be able to achieve more flexible and
responsive inbound TE. If inbound traffic is split into several
streams, each to addresses in different mapped ranges, then real-time
mapping changes can be used to steer the streams between multiple
ETRs at multiple ISPs.
Default ITRs in the DFZ (DITRs; similar to LISP's Proxy Tunnel
Routers) tunnel packets sent by hosts in networks that lack ITRs. So
multihoming, portability, and TE benefits apply to all traffic.
ITRs request mappings either directly from a local QSD or via one or
more layers of caching query servers (QSCs), which in turn request it
from a local QSD. QSCs are optional but generally desirable since
they reduce the query load on QSDs. (Note: "QSC" is from Query
Server with Cache.)
ETRs may be in ISP or end-user networks. IP-in-IP encapsulation is
used, so there is no UDP or any other header. PMTUD (Path MTU
Discovery) management with minimal complexity and overhead will
handle the problems caused by encapsulation, and adapt smoothly to
jumbo frame paths becoming available in the DFZ. The outer header's
source address is that of the sending host -- this enables existing
ISP Border Router (BR) filtering of source addresses to be extended
to encapsulated traffic packets by the simple mechanism of the ETR
dropping packets whose inner and outer source address do not match.
4.1.2. Extensions
4.1.2.1. TTR Mobility
The Translating Tunnel Router (TTR) approach to mobility
[Ivip_Mobility] is applicable to all Core-Edge Separation techniques
and provides scalable IPv4 and IPv6 mobility in which the MN keeps
its own mapped IP address(es) no matter how or where it is physically
connected, including behind one or more layers of NAT.
Path lengths are typically optimal or close to optimal, and the MN
communicates normally with all other non-mobile hosts (no stack or
application changes), and of course other MNs. Mapping changes are
only needed when the MN uses a new TTR, which would typically occur
if the MN moved more than 1000 km. Mapping changes are not required
when the MN changes its physical address(es).
Li Informational [Page 17]
RFC 6115 RRG Recommendation February 2011
4.1.2.2. Modified Header Forwarding
Separate schemes for IPv4 and IPv6 enable tunneling from ITR to ETR
without encapsulation. This will remove the encapsulation overhead
and PMTUD problems. Both approaches involve modifying all routers
between the ITR and ETR to accept a modified form of the IP header.
These schemes require new FIB/RIB functionality in DFZ and some other
routers but do not alter the BGP functions of DFZ routers.
4.1.3. Gains
o Amenable to widespread voluntary adoption due to no need for host
changes, complete support for packets sent from non-upgraded
networks and no significant degradation in performance.
o Modular separation of the control of ITR tunneling behavior from
the ITRs and the Core-Edge Separation scheme itself: end-user
networks control mapping in any way they like, in real-time.
o A small fee per mapping change deters frivolous changes and helps
pay for pushing the mapping data to all QSDs. End-user networks
that make frequent mapping changes for inbound TE should find
these fees attractive considering how it improves their ability to
utilize the bandwidth of multiple ISP links.
o End-user networks will typically pay the cost of Open ITR in the
DFZ (OITRD) forwarding to their networks. This provides a
business model for OITRD deployment and avoids unfair distribution
of costs.
o Existing source address filtering arrangements at BRs of ISPs and
end-user networks are prohibitively expensive to implement
directly in ETRs, but with the outer header's source address being
the same as the sending host's address, Ivip ETRs inexpensively
enforce BR filtering on decapsulated packets.
4.1.4. Costs
QSDs receive all mapping changes and store a complete copy of the
mapping database. However, a worst-case scenario is 10 billion IPv6
mappings, each of 32 bytes, which fits on a consumer hard drive today
and should fit in server DRAM by the time such adoption is reached.
The maximum number of non-mobile networks requiring multihoming,
etc., is likely to be ~10 million, so most of the 10 billion mappings
would be for mobile devices. However, TTR mobility does not involve
frequent mapping changes since most MNs only rarely move more than
1000 km.
Li Informational [Page 18]
RFC 6115 RRG Recommendation February 2011
4.1.5. References
[Ivip_EAF] [Ivip_PMTUD] [Ivip_PLF] [Ivip_Constraints] [Ivip_Mobility]
[Ivip_DRTM] [Ivip_Glossary]
4.2. Critique
Looked at from the thousand-foot level, Ivip shares the basic design
approaches with LISP and a number of other map-and-encap designs
based on the Core-Edge Separation. However, the details differ
substantially. Ivip's design makes a bold assumption that, with
technology advances, one could afford to maintain a real-time
distributed global mapping database for all networks and hosts. Ivip
proposes that multiple parties collaborate to build a mapping
distribution system that pushes all mapping information and updates
to local, full-database query servers located in all ISPs within a
few seconds. The system has no single point of failure and uses end-
to-end authentication.
A "real time, globally synchronized mapping database" is a critical
assumption in Ivip. Using that as a foundation, Ivip design avoids
several challenging design issues that others have studied
extensively, that include
1. special considerations of mobility support that add additional
complexity to the overall system;
2. prompt detection of ETR failures and notification to all relevant
ITRs, which turns out to be a rather difficult problem; and
3. development of a partial-mapping lookup sub-system. Ivip assumes
the existence of local query servers with a full database with
the latest mapping information changes.
To be considered as a viable solution to the Internet routing
scalability problem, Ivip faces two fundamental questions. First,
whether a global-scale system can achieve real-time synchronized
operations as assumed by Ivip is an entirely open question. Past
experiences suggest otherwise.
The second question concerns incremental rollout. Ivip represents an
ambitious approach, with real-time mapping and local full-database
query servers -- which many people regard as impossible. Developing
and implementing Ivip may take a fair amount of resources, yet there
is an open question regarding how to quantify the gains by first
movers -- both those who will provide the Ivip infrastructure and
Li Informational [Page 19]
RFC 6115 RRG Recommendation February 2011
those that will use it. Significant global routing table reduction
only happens when a large enough number of parties have adopted Ivip.
The same question arises for most other proposals as well.
One belief is that Ivip's more ambitious mapping system makes a good
design tradeoff for the greater benefits for end-user networks and
for those that develop the infrastructure. Another belief is that
this ambitious design is not viable.
4.3. Rebuttal
Since the Summary and Critique were written, Ivip's mapping system
has been significantly redesigned: DRTM - Distributed Real Time
Mapping [Ivip_DRTM].
DRTM makes it easier for ISPs to install their own ITRs. It also
facilitates Mapped Address Block (MAB) operating companies -- which
need not be ISPs -- leasing Scalable Provider-Independent (SPI)
address space to end-user networks with almost no ISP involvement.
ISPs need not install ITRs or ETRs. For an ISP to support its
customers using SPI space, they need only allow the forwarding of
outgoing packets whose source addresses are from SPI space. End-user
networks can implement their own ETRs on their existing PA
address(es) -- and MAB operating companies make all the initial
investments.
Once SPI adoption becomes widespread, ISPs will be motivated to
install their own ITRs to locally tunnel packets that are sent from
customer networks and that must be tunneled to SPI-using customers of
the same ISP -- rather than letting these packets exit the ISP's
network and return in tunnels to ETRs in the network.
There is no need for full-database query servers in ISPs or for any
device that stores the full mapping information for all Mapped
Address Blocks (MABs). ISPs that want ITRs will install two or more
Map Resolver (MR) servers. These are caching query servers which
query multiple (typically nearby) query servers that are full-
database for the subset of MABs they serve. These "nearby" query
servers will be at DITR sites, which will be run by, or for, MAB
operating companies who lease MAB space to large numbers of end-user
networks. These DITR-site servers will usually be close enough to
the MRs to generate replies with sufficiently low delay and risk of
packet loss for ITRs to buffer initial packets for a few tens of
milliseconds while the mapping arrives.
DRTM will scale to billions of micronets, tens of thousands of MABs,
and potentially hundreds of MAB operating companies, without single
points of failure or central coordination.
Li Informational [Page 20]
RFC 6115 RRG Recommendation February 2011
The critique implies a threshold of adoption is required before
significant routing scaling benefits occur. This is untrue of any
Core-Edge Separation proposal, including LISP and Ivip. Both can
achieve scalable routing benefits in direct proportion to their level
of adoption by providing portability, multihoming, and inbound TE to
large numbers of end-user networks.
Core-Edge Elimination (CEE) architectures require all Internet
communications to change to IPv6 with a new locator/identifier
separation naming model. This would impose burdens of extra
management effort, packets, and session establishment delays on all
hosts -- which is a particularly unacceptable burden on battery-
operated mobile hosts that rely on wireless links.
Core-Edge Separation architectures retain the current, efficient,
naming model, require no changes to hosts, and support both IPv4 and
IPv6. Ivip is the most promising architecture for future development
because its scalable, distributed, real-time mapping system best
supports TTR mobility, enables ITRs to be simpler, and gives real-
time control of ITR tunneling to the end-user network or to
organizations they appoint to control the mapping of their micronets.
5. Hierarchical IPv4 Framework (hIPv4)
5.1. Summary
5.1.1. Key Idea
The Hierarchical IPv4 Framework (hIPv4) adds scalability to the
routing architecture by introducing additional hierarchy in the IPv4
address space. The IPv4 addressing scheme is divided into two parts,
the Area Locator (ALOC) address space, which is globally unique, and
the Endpoint Locator (ELOC) address space, which is only regionally
unique. The ALOC and ELOC prefixes are added as a shim header
between the IP header and transport protocol header; the shim header
is identified with a new protocol number in the IP header. Instead
of creating a tunneling (i.e., overlay) solution, a new routing
element is needed in the service provider's routing domain (called
ALOC realm) -- a Locator Swap Router. The current IPv4 forwarding
plane remains intact, and no new routing protocols, mapping systems,
or caching solutions are required. The control plane of the ALOC
realm routers needs some modification in order for ICMP to be
compatible with the hIPv4 framework. When an area (one or several
autonomous systems (ASes)) of an ISP has transformed into an ALOC
realm, only ALOC prefixes are exchanged with other ALOC realms.
Directly attached ELOC prefixes are only inserted to the RIB of the
local ALOC realm; ELOC prefixes are not distributed to the DFZ.
Multihoming can be achieved in two ways, either the enterprise
Li Informational [Page 21]
RFC 6115 RRG Recommendation February 2011
requests an ALOC prefix from the RIR (this is not recommended) or the
enterprise receives the ALOC prefixes from their upstream ISPs. ELOC
prefixes are PI addresses and remain intact when an upstream ISP is
changed; only the ALOC prefix is replaced. When the RIB of the DFZ
is compressed (containing only ALOC prefixes), ingress routers will
no longer know the availability of the destination prefix; thus, the
endpoints must take more responsibility for their sessions. This can
be achieved by using multipath enabled transport protocols, such as
SCTP [RFC4960] and Multipath TCP (MPTCP) [MPTCP_Arch], at the
endpoints. The multipath transport protocols also provide a session
identifier, i.e., verification tag or token; thus, the location and
identifier split is carried out -- site mobility, endpoint mobility,
and mobile site mobility are achieved. DNS needs to be upgraded: in
order to resolve the location of an endpoint, the endpoint must have
one ELOC value (current A-record) and at least one ALOC value in DNS
(in multihoming solutions there will be several ALOC values for an
endpoint).
5.1.2. Gains
1. Improved routing scalability: Adding additional hierarchy to the
address space enables more hierarchy in the routing architecture.
Early adapters of an ALOC realm will no longer carry the current
RIB of the DFZ -- only ELOC prefixes of their directly attached
networks and ALOC prefixes from other service providers that have
migrated are installed in the ALOC realm's RIB.
2. Scalable support for traffic engineering: Multipath enabled
transport protocols are recommended to achieve dynamic load-
balancing of a session. Support for Valiant Load-balancing (VLB)
[Valiant] schemes has been added to the framework; more research
work is required around VLB switching.
3. Scalable support for multihoming: Only attachment points of a
multihomed site are advertised (using the ALOC prefix) in the
DFZ. DNS will inform the requester on how many attachment points
the destination endpoint has. It is the initiating endpoint's
choice/responsibility to choose which attachment point is used
for the session; endpoints using multipath-enabled transport
protocols can make use of several attachment points for a
session.
4. Simplified Renumbering: When changing provider, the local ELOC
prefixes remains intact; only the ALOC prefix is changed at the
endpoints. The ALOC prefix is not used for routing or forwarding
decisions in the local network.
Li Informational [Page 22]
RFC 6115 RRG Recommendation February 2011
5. Decoupling Location and Identifier: The verification tag (SCTP)
and token (MPTCP) can be considered to have the characteristics
of a session identifier, and thus a session layer is created
between the transport and application layers in the TCP/IP model.
6. Routing quality: The hIPv4 framework introduces no tunneling or
caching mechanisms. Only a swap of the content in the IPv4
header and locator header at the destination ALOC realm is
required; thus, current routing and forwarding algorithms are
preserved as such. Valiant Load-balancing might be used as a new
forwarding mechanism.
7. Routing Security: Similar as with today's DFZ, except that ELOC
prefixes cannot be hijacked (by injecting a longest match prefix)
outside an ALOC realm.
8. Deployability: The hIPv4 framework is an evolution of the current
IPv4 framework and is backwards compatible with the current IPv4
framework. Sessions in a local network and inside an ALOC realm
might in the future still use the current IPv4 framework.
5.1.3. Costs and Issues
1. Upgrade of the stack at an endpoint that is establishing sessions
outside the local ALOC realm.
2. In a multihoming solution, the border routers should be able to
apply policy-based routing upon the ALOC value in the locator
header.
3. New IP allocation policies must be set by the RIRs.
4. There is a short timeframe before the expected depletion of the
IPv4 address space occurs.
5. Will enterprises give up their current globally unique IPv4
address block allocation they have gained?
6. Coordination with MPTCP is highly desirable.
5.1.4. References
[hIPv4] [Valiant]
Li Informational [Page 23]
RFC 6115 RRG Recommendation February 2011
5.2. Critique
hIPv4 is an innovative approach to expanding the IPv4 addressing
system in order to resolve the scalable routing problem. This
critique does not attempt a full assessment of hIPv4's architecture
and mechanisms. The only question addressed here is whether hIPv4
should be chosen for IETF development in preference to, or together
with, the only two proposals which appear to be practical solutions
for IPv4: Ivip and LISP.
Ivip and LISP appear to have a major advantage over hIPv4 in terms of
support for packets sent from non-upgraded hosts/networks. Ivip's
DITRs (Default ITRs in the DFZ) and LISP's PTRs (Proxy Tunnel
Routers) both accept packets sent by any non-upgraded host/network
and tunnel them to the correct ETR -- thus providing the full
benefits of portability, multihoming, and inbound TE for these
packets as well as those sent by hosts in networks with ITRs. hIPv4
appears to have no such mechanism, so these benefits are only
available for communications between two upgraded hosts in upgraded
networks.
This means that significant benefits for adopters -- the ability to
rely on the new system to provide the portability, multihoming, and
inbound TE benefits for all, or almost all, their communications --
will only arise after all, or almost all, networks upgrade their
networks, hosts, and addressing arrangements. hIPv4's relationship
between adoption levels and benefits to any adopter therefore are far
less favorable to widespread adoption than those of Core-Edge
Separation (CES) architectures such as Ivip and LISP.
This results in hIPv4 also being at a disadvantage regarding the
achievement of significant routing scaling benefits, which likewise
will only result once adoption is close to ubiquitous. Ivip and LISP
can provide routing scaling benefits in direct proportion to their
level of adoption, since all adopters gain full benefits for all
their communications, in a highly scalable manner.
hIPv4 requires stack upgrades, which are not required by any CES
architecture. Furthermore, a large number of existing IPv4
application protocols convey IP addresses between hosts in a manner
that will not work with hIPv4: "There are several applications that
are inserting IP address information in the payload of a packet.
Some applications use the IP address information to create new
sessions or for identification purposes. This section is trying to
list the applications that need to be enhanced; however, this is by
no means a comprehensive list" [hIPv4].
Li Informational [Page 24]
RFC 6115 RRG Recommendation February 2011
If even a few widely used applications would need to be rewritten to
operate successfully with hIPv4, then this would be such a
disincentive to adoption to rule out hIPv4 ever being adopted widely
enough to solve the routing scaling problem, especially since CES
architectures fully support all existing protocols, without the need
for altering host stacks.
It appears that hIPv4 involves major practical difficulties, which
mean that in its current form it is not suitable for IETF
development.
5.3. Rebuttal
No rebuttal was submitted for this proposal.
6. Name Overlay (NOL) Service for Scalable Internet Routing
6.1. Summary
6.1.1. Key Idea
The basic idea is to add a name overlay (NOL) onto the existing
TCP/IP stack.
Its functions include:
1. Managing host name configuration, registration, and
authentication;
2. Initiating and managing transport connection channels (i.e.,
TCP/IP connections) by name;
3. Keeping application data transport continuity for mobility.
At the edge network, we introduce a new type of gateway, a Name
Transfer Relay (NTR), which blocks the PI addresses of edge networks
into upstream transit networks. NTRs perform address and/or port
translation between blocked PI addresses and globally routable
addresses, which seem like today's widely used NAT / Network Address
Port Translation (NAPT) devices. Both legacy and NOL applications
behind a NTR can access the outside as usual. To access the hosts
behind a NTR from outside, we need to use NOL to traverse the NTR by
name and initiate connections to the hosts behind it.
Li Informational [Page 25]
RFC 6115 RRG Recommendation February 2011
Different from proposed host-based ID/locator split solutions, such
as HIP, Shim6, and name-oriented stack, NOL doesn't need to change
the existing TCP/IP stack, sockets, or their packet formats. NOL can
coexist with the legacy infrastructure, and the Core-Edge Separation
solutions (e.g., APT, LISP, Six/One, Ivip, etc.).
6.1.2. Gains
1. Reduce routing table size: Prevent edge network PI address from
leaking into the transit network by deploying gateway NTRs.
2. Traffic Engineering: For legacy and NOL application sessions,
the incoming traffic can be directed to a specific NTR by DNS.
In addition, for NOL applications, initial sessions can be
redirected from one NTR to other appropriate NTRs. These
mechanisms provide some support for traffic engineering.
3. Multihoming: When a PI addressed network connects to the
Internet by multihoming with several providers, it can deploy
NTRs to prevent the PI addresses from leaking into provider
networks.
4. Transparency: NTRs can be allocated PA addresses from the
upstream providers and store them in NTRs' address pool. By DNS
query or NOL session, any session that wants to access the hosts
behind the NTR can be delegated to a specific PA address in the
NTR address pool.
5. Mobility: The NOL layer manages the traditional TCP/IP transport
connections, and provides application data transport continuity
by checkpointing the transport connection at sequence number
boundaries.
6. No need to change TCP/IP stack, sockets, or DNS system.
7. No need for extra mapping system.
8. NTR can be deployed unilaterally, just like NATs.
9. NOL applications can communicate with legacy applications.
10. NOL can be compatible with existing solutions, such as APT,
LISP, Ivip, etc.
11. End-user-controlled multipath indirect routing based on
distributed NTRs. This will give benefits to the performance-
aware applications, such as video streaming, applications on
MSN.com, etc.
Li Informational [Page 26]
RFC 6115 RRG Recommendation February 2011
6.1.3. Costs
1. Legacy applications have trouble with initiating access to the
servers behind NTR. Such trouble can be resolved by deploying
the NOL proxy for legacy hosts, or delegating globally routable
PA addresses in the NTR address pool for these servers, or
deploying a proxy server outside the NTR.
2. NOL may increase the number of entries in DNS, but it is not
drastic because it only increases the number of DNS records at
domain granularity not the number of hosts. The name used in
NOL, for example, is similar to an email address
hostname@example.net. The needed DNS entries and query are just
for "example.net", and the NTR knows the "hostnames". Not only
will the number of DNS records be increased, but the dynamics of
DNS might be agitated as well. However, the scalability and
performance of DNS are guaranteed by its naming hierarchy and
caching mechanisms.
3. Address translating/rewriting costs on NTRs.
6.1.4. References
No references were submitted.
6.2. Critique
1. Applications on hosts need to be rebuilt based on a name overlay
library to be NOL-enabled. The legacy software that is not
maintained will not be able to benefit from NOL in the Core-Edge
Elimination situation. In the Core-Edge Separation scheme, a new
gateway NTR is deployed to prevent edge-specific PI prefixes from
leaking into the transit core. NOL doesn't impede the legacy
endpoints behind the NTR from accessing the outside Internet, but
the legacy endpoints cannot access or will have difficultly
accessing the endpoints behind a NTR without the help of NOL.
2. In the case of Core-Edge Elimination, the end site will be
assigned multiple PA address spaces, which leads to renumbering
troubles when switching to other upstream providers. Upgrading
endpoints to support NOL doesn't give any benefits to edge
networks. Endpoints have little incentive to use NOL in a Core-
Edge Elimination scenario, and the same is true with other host-
based ID/locator split proposals. Whether they are IPv4 or IPv6
networks, edge networks prefer PI address space to PA address
space.
Li Informational [Page 27]
RFC 6115 RRG Recommendation February 2011
3. In the Core-Edge Separation scenario, the additional gateway NTR
is to prevent the specific prefixes from the edge networks, just
like a NAT or the ITR/ETR of LISP. A NTR gateway can be seen as
an extension of NAT (Network Address Translation). Although NATs
are deployed widely, upgrading them to support NOL extension or
deploying additional new gateway NTRs at the edge networks is on
a voluntary basis and has few economic incentives.
4. The stateful or stateless translation for each packet traversing
a NTR will require the cost of the CPU and memory of NTRs, and
increase forwarding delay. Thus, it is not appropriate to deploy
NTRs at the high-level transit networks where aggregated traffic
may cause congestion at the NTRs.
5. In the Core-Edge Separation scenario, the requirement for
multihoming and inter-domain traffic engineering will make end
sites accessible via multiple different NTRs. For reliability,
all of the associations between multiple NTRs and the end site
name will be kept in DNS, which may increase the load on DNS.
6. To support mobility, it is necessary for DNS to update the
corresponding name-NTR mapping records when an end system moves
from behind one NTR to another NTR. The NOL-enabled end relies
on the NOL layer to preserve the continuity of the transport
layer, since the underlying TCP/UDP transport session would be
broken when the IP address changed.
6.3. Rebuttal
NOL resembles neither CEE nor CES as a solution. By supporting
application-level sessions through the name overlay layer, NOL can
support some solutions in the CEE style. However, NOL is in general
closer to CES solutions, i.e., preventing PI prefixes of edge
networks from entering into the upstream transit networks. This is
done by the NTR, like the ITRs/ETRs in CES solutions, but NOL has no
need to define the clear boundary between core and edge networks.
NOL is designed to try to provide end users or networks a service
that facilitates the adoption of multihoming, multipath routing, and
traffic engineering by the indirect routing through NTRs, and that,
in the mean time, doesn't accelerate or decelerate the growth of
global routing table size.
Some problems are described in the NOL critique. In the original NOL
proposal document, the DNS query for a host that is behind a NTR will
induce the return of the actual IP addresses of the host and the
address of the NTR. This arrangement might cause some difficulties
for legacy applications due to the non-standard response from DNS.
To resolve this problem, we instead have the NOL service use a new
Li Informational [Page 28]
RFC 6115 RRG Recommendation February 2011
namespace, and have DNS not return NTR IP addresses for the legacy
hosts. The names used for NOL are formatted like email addresses,
such as "des@example.net". The mapping between "example.net" and the
IP address of the corresponding NTR will be registered in DNS. The
NOL layer will understand the meaning of the name "des@example.net" ,
and it will send a query to DNS only for "example.net". DNS will
then return IP addresses of the corresponding NTRs. Legacy
applications will still use the traditional FQDN name, and DNS will
return the actual IP address of the host. However, if the host is
behind a NTR, the legacy applications may be unable to access the
host.
The stateless address translation or stateful address and port
translation may cause a scaling problem with the number of table
entries NTR must maintain, and legacy applications cannot initiate
sessions with hosts inside the NOL-adopting End User Network (EUN).
However, these problems may not be a big barrier for the deployment
of NOL or other similar approaches. Many NAT-like boxes, proxy, and
firewall devices are widely used at the ingress/egress points of
enterprise networks, campus networks, or other stub EUNs. The hosts
running as servers can be deployed outside NTRs or can be assigned PA
addresses in an NTR-adopting EUN.
7. Compact Routing in a Locator Identifier Mapping System (CRM)
7.1. Summary
7.1.1. Key Idea
This proposal (referred to here as "CRM") is to build a highly
scalable locator identity mapping system using compact routing
principles. This provides the means for dynamic topology adaption to
facilitate efficient aggregation [CRM]. Map servers are assigned as
cluster heads or landmarks based on their capability to aggregate EID
announcements.
7.1.2. Gains
o Minimizes the routing table sizes at the system level (i.e., map
servers). Provides clear upper bounds for routing stretch that
define the packet delivery delay of the map request / first
packet.
o Organizes the mapping system based on the EID numbering space,
minimizes the administrative overhead of managing the EID space.
No need for administratively planned hierarchical address
allocation as the system will find convergence into a set of EID
allocations.
Li Informational [Page 29]
RFC 6115 RRG Recommendation February 2011
o Availability and robustness of the overall routing system
(including xTRs and map servers) are improved because of the
potential to use multiple map servers and direct routes without
the involvement of map servers.
7.1.3. Costs
The scalability gains will materialize only in large deployments. If
the stretch is bounded to those of compact routing (worst-case
stretch less or equal to 3, on average, 1+epsilon), then each xTR
needs to have memory/cache for the mappings of its cluster.
7.1.4. References
[CRM]
7.2. Critique
The CRM proposal is not a complete proposal and therefore cannot be
considered for further development by the IETF as a scalable routing
solution.
While Compact Routing principles may be able to improve a mapping
overlay structure such as LISP+ALT, there are several objections to
this approach.
Firstly, a CRM-modified ALT structure would still be a global query
server system. No matter how ALT's path lengths and delays are
optimized, there is a problem with a querier -- which could be
anywhere in the world -- relying on mapping information from one or
ideally two or more authoritative query servers, which could also be
anywhere in the world. The delays and risks of packet loss that are
inherent in such a system constitute a fundamental problem. This is
especially true when multiple, potentially long, traffic streams are
received by ITRs and forwarded over the CRM networks for delivery to
the destination network. ITRs must use the CRM infrastructure while
they are awaiting a map reply. The traffic forwarded on the CRM
infrastructure functions as map requests and can present a
scalability and performance issue to the infrastructure.
Secondly, the alterations contemplated in this proposal involve the
roles of particular nodes in the network being dynamically assigned
as part of the network's self-organizing nature.
The discussion of clustering in the middle of page 4 of [CRM] also
indicates that particular nodes are responsible for registering EIDs
from typically far-distant ETRs, all of which are handling closely
related EIDs that this node can aggregate. Since MSes are apparently
Li Informational [Page 30]
RFC 6115 RRG Recommendation February 2011
nodes within the compact routing system, and the process of an MS
deciding whether to accept EID registrations is determined as part of
the self-organizing properties of the system, there are concerns
about how EID registration can be performed securely, when no
particular physical node is responsible for it.
Thirdly, there are concerns about individually owned nodes performing
work for other organizations. Such problems of trust and of
responsibilities and costs being placed on those who do not directly
benefit already exist in the inter-domain routing system and are a
challenge for any scalable routing solution.
There are simpler solutions to the mapping problem than having an
elaborate network of routers. If a global-scale query system is
still preferred, then it would be better to have ITRs use local MRs,
each of which is dynamically configured to know the IP address of the
million or so authoritative Map Server (MS) query servers -- or two
million or so assuming they exist in pairs for redundancy.
It appears that the inherently greater delays and risks of packet
loss of global query server systems make them unsuitable mapping
solutions for Core-Edge Elimination or Core-Edge Separation
architectures. The solution to these problems appears to involve a
greater number of widely distributed authoritative query servers, one
or more of which will therefore be close enough to each querier that
delays and risk of packet loss are reduced to acceptable levels.
Such a structure would be suitable for map requests, but perhaps not
for handling traffic packets to be delivered to the destination
networks.
7.3. Rebuttal
CRM is most easily understood as an alteration to the routing
structure of the LISP+ALT mapping overlay system, by altering or
adding to the network's BGP control plane.
CRM's aims include the delivery of initial traffic packets to their
destination networks where they also function as map requests. These
packet streams may be long and numerous in the fractions of a second
to perhaps several seconds that may elapse before the ITR receives
the map reply.
Compact Routing principles are used to optimize the path length taken
by these query or traffic packets through a significantly modified
version of the ALT (or similar) network, while also generally
reducing typical or maximum paths taken by the query packets.
Li Informational [Page 31]
RFC 6115 RRG Recommendation February 2011
An overlay network is a diversion from the shortest path. However,
CMR limits this diversion and provides an upper bound. Landmark
routers/servers could deliver more than just the first traffic
packet, subject to their CPU capabilities and their network
connectivity bandwidths.
The trust between the landmarks (mapping servers) can be built based
on the current BGP relationships. Registration to the landmark nodes
needs to be authenticated mutually between the MS and the system that
is registering. This part is not documented in the proposal text.
8. Layered Mapping System (LMS)
8.1. Summary
8.1.1. Key Ideas
The layered mapping system proposal builds a hierarchical mapping
system to support scalability, analyzes the design constraints,
presents an explicit system structure, designs a two-cache mechanism
on ingress tunneling router (ITR) to gain low request delay, and
facilitates data validation. Tunneling and mapping are done at the
core, and no change is needed on edge networks. The mapping system
is run by interest groups independent of any ISP, which conforms to
an economical model and can be voluntarily adopted by various
networks. Mapping systems can also be constructed stepwise,
especially in the IPv6 scenario.
8.1.2. Gains
1. Scalability
A. Distributed storage of mapping data avoids central storage of
massive amounts of data and restricts updates within local
areas.
B. The cache mechanism in an ITR reasonably reduces the request
loads on the mapping system.
2. Deployability
A. No change on edge systems, only tunneling in core routers,
and new devices in core networks.
B. The mapping system can be constructed stepwise: a mapping
node needn't be constructed if none of its responsible ELOCs
is allocated. This makes sense especially for IPv6.
Li Informational [Page 32]
RFC 6115 RRG Recommendation February 2011
C. Conforms to a viable economic model: the mapping system
operators can profit from their services; core routers and
edge networks are willing to join the circle either to avoid
router upgrades or realize traffic engineering. Benefits
from joining are independent of the scheme's implementation
scale.
3. Low request delay: The low number of layers in the mapping
structure and the two-stage cache help achieve low request delay.
4. Data consistency: The two-stage cache enables an ITR to update
data in the map cache conveniently.
5. Traffic engineering support: Edge networks inform the mapping
system of their prioritized mappings with all upstream routers,
thus giving the edge networks control over their ingress flows.
8.1.3. Costs
1. Deployment of LMS needs to be further discussed.
2. The structure of the mapping system needs to be refined according
to practical circumstances.
8.1.4. References
[LMS_Summary] [LMS]
8.2. Critique
LMS is a mapping mechanism based on Core-Edge Separation. In fact,
any proposal that needs a global mapping system with keys with
similar properties to that of an "edge address" in a Core-Edge
Separation scenario can use such a mechanism. This means that those
keys are globally unique (by authorization or just statistically), at
the disposal of edge users, and may have several satisfied mappings
(with possibly different weights). A proposal to address routing
scalability that needs mapping but doesn't specify the mapping
mechanism can use LMS to strengthen its infrastructure.
The key idea of LMS is similar to that of LISP+ALT: that the mapping
system should be hierarchically organized to gain scalability for
storage and updates and to achieve quick indexing for lookups.
However, LMS advocates an ISP-independent mapping system, and ETRs
are not the authorities of mapping data. ETRs or edge-sites report
their mapping data to related mapping servers.
Li Informational [Page 33]
RFC 6115 RRG Recommendation February 2011
LMS assumes that mapping servers can be incrementally deployed in
that a server may not be constructed if none of its administered edge
addresses are allocated, and that mapping servers can charge for
their services, which provides the economic incentive for their
existence. How this brand-new system can be constructed is still not
clear. Explicit layering is only an ideal state, and the proposal
analyzes the layering limits and feasibility, rather than provide a
practical way for deployment.
The drawbacks of LMS's feasibility analysis also include that it 1)
is based on current PC power and may not represent future
circumstances (especially for IPv6), and 2) does not consider the
variability of address utilization. Some IP address spaces may be
effectively allocated and used while some may not, causing some
mapping servers to be overloaded while others are poorly utilized.
More thoughts are needed as to the flexibility of the layer design.
LMS doesn't fit well for mobility. It does not solve the problem
when hosts move faster than the mapping updates and propagation
between relative mapping servers. On the other hand, mobile hosts'
moving across ASes and changing their attachment points (core
addresses) is less frequent than hosts' moving within an AS.
Separation needs two planes: Core-Edge Separation (which is to gain
routing table scalability) and identity/location separation (which is
to achieve mobility). The Global Locator, Local Locator, and
Identifier (GLI) scheme does a good clarification of this, and in
that case, LMS can be used to provide identity-to-core address
mapping. Of course, other schemes may be competent, and LMS can be
incorporated with them if the scheme has global keys and needs to map
them to other namespaces.
8.3. Rebuttal
No rebuttal was submitted for this proposal.
9. Two-Phased Mapping
9.1. Summary
9.1.1. Considerations
1. A mapping from prefixes to ETRs is an M:M mapping. Any change of
a (prefix, ETR) pair should be updated in a timely manner, which
can be a heavy burden to any mapping system if the relation
changes frequently.
Li Informational [Page 34]
RFC 6115 RRG Recommendation February 2011
2. A prefix<->ETR mapping system cannot be deployed efficiently if
it is overwhelmed by worldwide dynamics. Therefore, the mapping
itself is not scalable with this direct mapping scheme.
9.1.2. Basics of a Two-Phased Mapping
1. Introduce an AS number in the middle of the mapping, the phase I
mapping is prefix<->AS#, phase II mapping is AS#<->ETRs. This
creates a M:1:M mapping model.
2. It is fair to assume that all ASes know their local prefixes (in
the IGP) better than other ASes and that it is most likely that
local prefixes can be aggregated when they can be mapped to the
AS number, which will reduce the number of mapping entries.
Also, ASes also know clearly their ETRs on the border between
core and edge. So, all mapping information can be collected
locally.
3. A registry system will take care of the phase I mapping
information. Each AS should have a registration agent to notify
the registry of the local range of IP address space. This system
can be organized as a hierarchical infrastructure like DNS, or
alternatively, as a centralized registry like "whois" in each
RIR. Phase II mapping information can be distributed between
xTRs as a BGP extension.
4. The basic forwarding procedure is that the ITR first gets the
destination AS number from the phase I mapper (or from cache)
when the packet is entering the "core". Then, it will extract
the closest ETR for the destination AS number. This is local,
since phase II mapping information has been "pushed" to the ITR
through BGP updates. Finally, the ITR tunnels the packet to the
corresponding ETR.
9.1.3. Gains
1. Any prefix reconfiguration (aggregation/deaggregation) within an
AS will not be reflected in the mapping system.
2. Local prefixes can be aggregated with a high degree of
efficiency.
3. Both phase I and phase II mappings can be stable.
4. A stable mapping system will reduce the update overhead
introduced by topology changes and/or routing policy dynamics.
Li Informational [Page 35]
RFC 6115 RRG Recommendation February 2011
9.1.4. Summary
1. The two-phased mapping scheme introduces an AS number between the
mapping prefixes and ETRs.
2. The decoupling of direct mapping makes highly dynamic updates
stable; therefore, it can be more scalable than any direct
mapping designs.
3. The two-phased mapping scheme is adaptable to any proposals based
on the core/edge split.
9.1.5. References
No references were submitted.
9.2. Critique
This is a simple idea on how to scale mapping. However, this design
is too incomplete to be considered a serious input to RRG. Take the
following two issues as example:
First, in this two-phase scheme, an AS is essentially the unit of
destinations (i.e., sending ITRs find out destination AS D, then send
data to one of D's ETRs). This does not offer much choice for
traffic engineering.
Second, there is no consideration whatsoever on failure detection and
handling.
9.3. Rebuttal
No rebuttal was submitted for this proposal.
10. Global Locator, Local Locator, and Identifier Split (GLI-Split)
10.1. Summary
10.1.1. Key Idea
GLI-Split implements a separation between global routing (in the
global Internet outside edge networks) and local routing (inside edge
networks) using global and local locators (GLs and LLs). In
addition, a separate static identifier (ID) is used to identify
communication endpoints (e.g., nodes or services) independently of
any routing information. Locators and IDs are encoded in IPv6
addresses to enable backwards-compatibility with the IPv6 Internet.
The higher-order bits store either a GL or a LL, while the lower-
Li Informational [Page 36]
RFC 6115 RRG Recommendation February 2011
order bits contain the ID. A local mapping system maps IDs to LLs,
and a global mapping system maps IDs to GLs. The full GLI-mode
requires nodes with upgraded networking stacks and special GLI-
gateways. The GLI-gateways perform stateless locator rewriting in
IPv6 addresses with the help of the local and global mapping system.
Non-upgraded IPv6 nodes can also be accommodated in GLI-domains since
an enhanced DHCP service and GLI-gateways compensate for their
missing GLI-functionality. This is an important feature for
incremental deployability.
10.1.2. Gains
The benefits of GLI-Split are:
o Hierarchical aggregation of routing information in the global
Internet through separation of edge and core routing
o Provider changes not visible to nodes inside GLI-domains
(renumbering not needed)
o Rearrangement of subnetworks within edge networks not visible to
the outside world (better support of large edge networks)
o Transport connections survive both types of changes
o Multihoming
o Improved traffic engineering for incoming and outgoing traffic
o Multipath routing and load balancing for hosts
o Improved resilience
o Improved mobility support without home agents and triangle routing
o Interworking with the classic Internet
* without triangle routing over proxy routers
* without stateful NAT
These benefits are available for upgraded GLI-nodes, but non-upgraded
nodes in GLI-domains partially benefit from these advanced features,
too. This offers multiple incentives for early adopters, and they
have the option to migrate their nodes gradually from non-GLI-stacks
to GLI-stacks.
Li Informational [Page 37]
RFC 6115 RRG Recommendation February 2011
10.1.3. Costs
o Local and global mapping system
o Modified DHCP or similar mechanism
o GLI-gateways with stateless locator rewriting in IPv6 addresses
o Upgraded stacks (only for full GLI-mode)
10.1.4. References
[GLI]
10.2. Critique
GLI-Split makes a clear distinction between two separation planes:
the separation between identifier and locator (which is to meet end-
users' needs including mobility) and the separation between local and
global locator (which makes the global routing table scalable). The
distinction is needed since ISPs and hosts have different
requirements, with both needing to make the changes inside and
outside GLI-domains invisible to their opposites.
A main drawback of GLI-Split is that it puts a burden on hosts.
Before routing a packet received from upper layers, network stacks in
hosts first need to resolve the DNS name to an IP address; if the IP
address is GLI-formed, it may look up the map from the identifier
extracted from the IP address to the local locator. If the
communication is between different GLI-domains, hosts may further
look up the mapping from the identifier to the global locator.
Having the local mapping system forward requests to the global
mapping system for hosts is just an option. Though host lookup may
ease the burden of intermediate nodes, which would otherwise to
perform the mapping lookup, the three lookups by hosts in the worst
case may lead to large delays unless a very efficient mapping
mechanism is devised. The work may also become impractical for low-
powered hosts. On one hand, GLI-Split can provide backward
compatibility where classic and upgraded IPv6 hosts can communicate.
This is its big virtue. On the other hand, the need to upgrade may
work against hosts' enthusiasm to change. This is offset against the
benefits they would gain.
GLI-Split provides additional features to improve TE and to improve
resilience, e.g., exerting multipath routing. However, the cost is
that more burdens are placed on hosts, e.g., they may need more
lookup actions and route selections. However, these kinds of
tradeoffs between costs and gains exist in most proposals.
Li Informational [Page 38]
RFC 6115 RRG Recommendation February 2011
One improvement of GLI-Split is its support for mobility by updating
DNS data as GLI-hosts move across GLI-domains. Through this, the
GLI-corresponding-node can query DNS to get a valid global locator of
the GLI-mobile-node and need not query the global mapping system
(unless it wants to do multipath routing), giving more incentives for
nodes to become GLI-enabled. The merits of GLI-Split, including
simplified-mobility-handover provision, compensate for the costs of
this improvement.
GLI-Split claims to use rewriting instead of tunneling for
conversions between local and global locators when packets span GLI-
domains. The major advantage is that this kind of rewriting needs no
extra state, since local and global locators need not map to each
other. Many other rewriting mechanisms instead need to maintain
extra state. It also avoids the MTU problem faced by the tunneling
methods. However, GLI-Split achieves this only by compressing the
namespace size of each attribute (identifier and local/global
locator). GLI-Split encodes two namespaces (identifier and local/
global locator) into an IPv6 address (each has a size of 2^64 or
less), while map-and-encap proposals assume that identifier and
locator each occupy a 128-bit space.
10.3. Rebuttal
The arguments in the GLI-Split critique are correct. There are only
two points that should be clarified here. First, it is not a
drawback that hosts perform the mapping lookups. Second, the
critique proposed an improvement to the mobility mechanism, which is
of a general nature and not specific to GLI-Split.
1. The additional burden on the hosts is actually a benefit,
compared to having the same burden on the gateways. If the
gateway would perform the lookups and packets addressed to
uncached EIDs arrive, a lookup in the mapping system must be
initiated. Until the mapping reply returns, packets must be
either dropped, cached, or sent over the mapping system to the
destination. All these options are not optimal and have their
drawbacks. To avoid these problems in GLI-Split, the hosts
perform the lookup. The short additional delay is not a big
issue in the hosts because it happens before the first packets
are sent. So, no packets are lost or have to be cached. GLI-
Split could also easily be adapted to special GLI-hosts (e.g.,
low-power sensor nodes) that do not have to do any lookup and
simply let the gateway do all the work. This functionality is
included anyway for backward compatibility with regular IPv6
hosts inside the GLI-domain.
Li Informational [Page 39]
RFC 6115 RRG Recommendation February 2011
2. The critique proposes a DNS-based mobility mechanism as an
improvement to GLI-Split. However, this improvement is an
alternative mobility approach that can be applied to any routing
architecture (including GLI-Split) and also raises some concerns,
e.g., the update speed of DNS. Therefore, we prefer to keep this
issue out of the discussion.
11. Tunneled Inter-Domain Routing (TIDR)
11.1. Summary
11.1.1. Key Idea
Provides a method for locator/identifier separation using tunnels
between routers on the edge of the Internet transit infrastructure.
It enriches the BGP protocol for distributing the identifier-to-
locator mapping. Using new BGP attributes, "identifier prefixes" are
assigned inter-domain routing locators so that they will not be
installed in the RIB and will be moved to a new table called the
Tunnel Information Base (TIB). Afterwards, when routing a packet to
an "identifier prefix", first the TIB will be searched to perform
tunneling, and secondly the RIB will be searched for actual routing.
After the edge router performs tunneling, all routers in the middle
will route this packet until the packet reaches the router at the
tail-end of the tunnel.
11.1.2. Gains
o Smooth deployment
o Size reduction of the global RIB
o Deterministic customer traffic engineering for incoming traffic
o Numerous forwarding decisions for a particular address prefix
o Stops AS number space depletion
o Improved BGP convergence
o Protection of the inter-domain routing infrastructure
o Easy separation of control traffic and transit traffic
o Different layer-2 protocol IDs for transit and non-transit traffic
o Multihoming resilience
Li Informational [Page 40]
RFC 6115 RRG Recommendation February 2011
o New address families and tunneling techniques
o Support for IPv4 or IPv6, and migration to IPv6
o Scalability, stability, and reliability
o Faster inter-domain routing
11.1.3. Costs
o Routers on the edge of the inter-domain infrastructure will need
to be upgraded to hold the mapping database (i.e., the TIB).
o "Mapping updates" will need to be treated differently from usual
BGP "routing updates".
11.1.4. References
[TIDR] [TIDR_identifiers] [TIDR_and_LISP] [TIDR_AS_forwarding]
11.2. Critique
TIDR is a Core-Edge Separation architecture from late 2006 that
distributes its mapping information via BGP messages that are passed
between DFZ routers.
This means that TIDR cannot solve the most important goal of scalable
routing -- to accommodate much larger numbers of end-user network
prefixes (millions or billions) without each such prefix directly
burdening every DFZ router. Messages advertising routes for TIDR-
managed prefixes may be handled with lower priority, but this would
only marginally reduce the workload for each DFZ router compared to
handling an advertisement of a conventional PI prefix.
Therefore, TIDR cannot be considered for RRG recommendation as a
solution to the routing scaling problem.
For a TIDR-using network to receive packets sent from any host, every
BR of all ISPs must be upgraded to have the new ITR-like
functionality. Furthermore, all DFZ routers would need to be altered
so they accepted and correctly propagated the routes for end-user
network address space, with the new LOCATOR attribute, which contains
the ETR address and a REMOTE-PREFERENCE value. Firstly, if they
received two such advertisements with different LOCATORs, they would
advertise a single route to this prefix containing both. Secondly,
for end-user address space (for IPv4) to be more finely divided, the
DFZ routers must propagate LOCATOR-containing advertisements for
prefixes longer than /24.
Li Informational [Page 41]
RFC 6115 RRG Recommendation February 2011
TIDR's ITR-like routers store the full mapping database -- so there
would be no delay in obtaining mapping, and therefore no significant
delay in tunneling traffic packets.
[TIDR] is written as if traffic packets are classified by reference
to the RIB, but routers use the FIB for this purpose, and "FIB" does
not appear in [TIDR].
TIDR does not specify a tunneling technique, leaving this to be
chosen by the ETR-like function of BRs and specified as part of a
second kind of new BGP route advertised by that ETR-like BR. There
is no provision for solving the PMTUD problems inherent in
encapsulation-based tunneling.
ITR functions must be performed by already busy routers of ISPs,
rather than being distributed to other routers or to sending hosts.
There is no practical support for mobility. The mapping in each end-
user route advertisement includes a REMOTE-PREFERENCE for each ETR-
like BR, but this is used by the ITR-like functions of BRs to always
select the LOCATOR with the highest value. As currently described,
TIDR does not provide inbound load-splitting TE.
Multihoming service restoration is achieved initially by the ETR-like
function of the BR at the ISP (whose link to the end-user network has
just failed). It looks up the mapping to find the next preferred
ETR-like BR's address. The first ETR-like router tunnels the packets
to the second ETR-like router in the other ISP. However, if the
failure was caused by the first ISP itself being unreachable, then
connectivity would not be restored until a revised mapping (with
higher REMOTE-PREFERENCE) from the reachable ETR-like BR of the
second ISP propagated across the DFZ to all ITR-like routers, or the
withdrawn advertisement for the first one reaches the ITR-like
router.
11.3. Rebuttal
No rebuttal was submitted for this proposal.
12. Identifier-Locator Network Protocol (ILNP)
12.1. Summary
12.1.1. Key Ideas
o Provides crisp separation of Identifiers from Locators.
o Identifiers name nodes, not interfaces.
Li Informational [Page 42]
RFC 6115 RRG Recommendation February 2011
o Locators name subnetworks, rather than interfaces, so they are
equivalent to an IP routing prefix.
o Identifiers are never used for network-layer routing, whilst
Locators are never used for Node Identity.
o Transport-layer sessions (e.g., TCP session state) use only
Identifiers, never Locators, meaning that changes in location have
no adverse impact on an IP session.
12.1.2. Benefits
o The underlying protocol mechanisms support fully scalable site
multihoming, node multihoming, site mobility, and node mobility.
o ILNP enables topological aggregation of location information while
providing stable and topology-independent identities for nodes.
o In turn, this topological aggregation reduces both the routing
prefix "churn" rate and the overall size of the Internet's global
routing table, by eliminating the value and need for more-specific
routing state currently carried throughout the global (default-
free) zone of the routing system.
o ILNP enables improved traffic engineering capabilities without
adding any state to the global routing system. TE capabilities
include both provider-driven TE and also end-site-controlled TE.
o ILNP's mobility approach:
* eliminates the need for special-purpose routers (e.g., home
agent and/or foreign agent now required by Mobile IP and NEMO).
* eliminates "triangle routing" in all cases.
* supports both "make before break" and "break before make"
layer-3 handoffs.
o ILNP improves resilience and network availability while reducing
the global routing state (as compared with the currently deployed
Internet).
o ILNP is incrementally deployable:
* No changes are required to existing IPv6 (or IPv4) routers.
Li Informational [Page 43]
RFC 6115 RRG Recommendation February 2011
* Upgraded nodes gain benefits immediately ("day one"); those
benefits gain in value as more nodes are upgraded (this follows
Metcalfe's Law).
* The incremental deployment approach is documented.
o ILNP is backwards compatible:
* ILNPv6 is fully backwards compatible with IPv6 (ILNPv4 is fully
backwards compatible with IPv4).
* Reuses existing known-to-scale DNS mechanisms to provide
identifier/locator mapping.
* Existing DNS security mechanisms are reused without change.
* Existing IP Security mechanisms are reused with one minor
change (IPsec Security Associations replace the current use of
IP addresses with the use of Identifier values). NB: IPsec is
also backwards compatible.
* The backwards compatibility approach is documented.
o No new or additional overhead is required to determine or to
maintain locator/path liveness.
o ILNP does not require locator rewriting (NAT); ILNP permits and
tolerates NAT, should that be desirable in some deployment(s).
o Changes to upstream network providers do not require node or
subnetwork renumbering within end-sites.
o ILNP is compatible with and can facilitate the transition from
current single-path TCP to multipath TCP.
o ILNP can be implemented such that existing applications (e.g.,
applications using the BSD Sockets API) do NOT need any changes or
modifications to use ILNP.
12.1.3. Costs
o End systems need to be enhanced incrementally to support ILNP in
addition to IPv6 (or IPv4 or both).
o DNS servers supporting upgraded end systems also should be
upgraded to support new DNS resource records for ILNP. (The DNS
protocol and DNS security do not need any changes.)
Li Informational [Page 44]
RFC 6115 RRG Recommendation February 2011
12.1.4. References
[ILNP_Site] [MobiArch1] [MobiArch2] [MILCOM1] [MILCOM2] [DNSnBIND]
[Referral_Obj] [ILNP_Intro] [ILNP_Nonce] [ILNP_DNS] [ILNP_ICMP]
[JSAC_Arch] [RFC4033] [RFC4034] [RFC4035] [RFC5534] [RFC5902]
12.2. Critique
The primary issue for ILNP is how the deployment incentives and
benefits line up with the RRG goal of reducing the rate of growth of
entries and churn in the core routing table. If a site is currently
using PI space, it can only stop advertising that space when the
entire site is ILNP capable. This needs (at least) clear elucidation
of the incentives for ILNP which are not related to routing scaling,
in order for there to be a path for this to address the RRG needs.
Similarly, the incentives for upgrading hosts need to align with the
value for those hosts.
A closely related question is whether this mechanism actually
addresses the sites need for PI addresses. Assuming ILNP is
deployed, the site does achieve flexible, resilient, communication
using all of its Internet connections. While the proposal addresses
the host updates when the host learns of provider changes, there are
other aspects of provider change that are not addressed. This
includes renumbering routers, subnets, and certain servers. (It is
presumed that most servers, once the entire site has moved to ILNP,
will not be concerned if their locator changes. However, some
servers must have known locators, such as the DNS server.) The
issues described in [RFC5887] will be ameliorated, but not resolved.
To be able to adopt this proposal, and have sites use it, we need to
address these issues. When a site changes points of attachment, only
a small amount of DNS provisioning should be required. The LP
resource record type is apparently intended to help with this. It is
also likely that the use of dynamic DNS will help this.
The ILNP mechanism is described as being suitable for use in
conjunction with mobility. This raises the question of race
conditions. To the degree that mobility concerns are valid at this
time, it is worth asking how communication can be established if a
node is sufficiently mobile that it is moving faster than the DNS
update and DNS fetch cycle can effectively propagate changes.
This proposal does presume that all communication using this
mechanism is tied to DNS names. While it is true that most
communication does start from a DNS name, it is not the case that all
exchanges have this property. Some communication initiation and
referral can be done with an explicit identifier/locator pair. This
does appear to require some extensions to the existing mechanism (for
Li Informational [Page 45]
RFC 6115 RRG Recommendation February 2011
both sides to add locators). In general, some additional clarity on
the assumptions regarding DNS, particularly for low-end devices,
would seem appropriate.
One issue that this proposal shares with many others is the question
of how to determine which locator pairs (local and remote) are
actually functional. This is an issue both for initial
communications establishment and for robustly maintaining
communication. It is likely that a combination of monitoring of
traffic (in the host, where this is tractable), coupled with other
active measures, can address this. ICMP is clearly insufficient.
12.3. Rebuttal
ILNP eliminates the perceived need for PI addressing and encourages
increased DFZ aggregation. Many enterprise users view DFZ scaling
issues as too abstruse, so ILNP creates more user-visible incentives
to upgrade deployed systems.
ILNP mobility eliminates Duplicate Address Detection (DAD), reducing
the layer-3 handoff time significantly when compared to IETF standard
Mobile IP, as shown in [MobiArch1] and [MobiArch2]. ICMP location
updates separately reduce the layer-3 handoff latency.
Also, ILNP enables both host multihoming and site multihoming.
Current BGP approaches cannot support host multihoming. Host
multihoming is valuable in reducing the site's set of externally
visible nodes.
Improved mobility support is very important. This is shown by the
research literature and also appears in discussions with vendors of
mobile devices (smartphones, MP3 players). Several operating system
vendors push "updates" with major networking software changes in
maintenance releases today. Security concerns mean most hosts
receive vendor updates more quickly these days.
ILNP enables a site to hide exterior connectivity changes from
interior nodes, using various approaches. One approach deploys
unique local address (ULA) prefixes within the site, and has the site
border router(s) rewrite the Locator values. The usual NAT issues
don't arise because the Locator value is not used above the network-
layer. [MILCOM1] [MILCOM2]
[RFC5902] makes clear that many users desire IPv6 NAT, with site
interior obfuscation as a major driver. This makes global-scope PI
addressing much less desirable for end sites than formerly.
Li Informational [Page 46]
RFC 6115 RRG Recommendation February 2011
ILNP-capable nodes can talk existing IP with legacy IP-only nodes,
with no loss of current IP capability. So, ILNP-capable nodes will
never be worse off.
Secure Dynamic DNS Update is standard and widely supported in
deployed hosts and DNS servers. [DNSnBIND] says many sites have
deployed this technology without realizing it (e.g., by enabling both
the DHCP server and Active Directory of the MS-Windows Server).
If a node is as mobile as the critique says, then existing IETF
Mobile IP standards also will fail. They also use location updates
(e.g., MN -> home agent, MN -> foreign agent).
ILNP also enables new approaches to security that eliminate
dependence upon location-dependent Access Control Lists (ACLs)
without packet authentication. Instead, security appliances track
flows using Identifier values and validate the identifier/locator
relationship cryptographically [RFC4033] [RFC4034] [RFC4035] or non-
cryptographically by reading the nonce [ILNP_Nonce].
The DNS LP record has a more detailed explanation now. LP records
enable a site to change its upstream connectivity by changing the L
resource records of a single FQDN covering the whole site, thereby
providing scalability.
DNS-based server load balancing works well with ILNP by using DNS SRV
records. DNS SRV records are not new, are widely available in DNS
clients and servers, and are widely used today in the IPv4 Internet
for server load balancing.
Recent ILNP documents discuss referrals in more detail. A node with
a binary referral can find the FQDN using DNS PTR records, which can
be authenticated [RFC4033] [RFC4034] [RFC4035]. Approaches such as
[Referral_Obj] improve user experience and user capability, so are
likely to self-deploy.
Selection from multiple Locators is identical to an IPv4 system
selecting from multiple A records for its correspondent. Deployed IP
nodes can track reachability via existing host mechanisms or by using
the SHIM6 method. [RFC5534]
Li Informational [Page 47]
RFC 6115 RRG Recommendation February 2011
13. Enhanced Efficiency of Mapping Distribution Protocols in
Map-and-Encap Schemes (EEMDP)
13.1. Summary
13.1.1. Introduction
We present some architectural principles pertaining to the mapping
distribution protocols, especially applicable to the map-and-encap
(e.g., LISP) type of protocols. These principles enhance the
efficiency of the map-and-encap protocols in terms of (1) better
utilization of resources (e.g., processing and memory) at Ingress
Tunnel Routers (ITRs) and mapping servers, and consequently, (2)
reduction of response time (e.g., first-packet delay). We consider
how Egress Tunnel Routers (ETRs) can perform aggregation of endpoint
ID (EID) address space belonging to their downstream delivery
networks, in spite of migration/re-homing of some subprefixes to
other ETRs. This aggregation may be useful for reducing the
processing load and memory consumption associated with map messages,
especially at some resource-constrained ITRs and subsystems of the
mapping distribution system. We also consider another architectural
concept where the ETRs are organized in a hierarchical manner for the
potential benefit of aggregation of their EID address spaces. The
two key architectural ideas are discussed in some more detail below.
A more complete description can be found in [EEMDP_Considerations]
and [EEMDP_Presentation].
It will be helpful to refer to Figures 1, 2, and 3 in
[EEMDP_Considerations] for some of the discussions that follow here
below.
13.1.2. Management of Mapping Distribution of Subprefixes Spread across
Multiple ETRs
To assist in this discussion, we start with the high level
architecture of a map-and-encap approach (it would be helpful to see
Figure 1 in [EEMDP_Considerations]). In this architecture, we have
the usual ITRs, ETRs, delivery networks, etc. In addition, we have
the ID-Locator Mapping (ILM) servers, which are repositories for
complete mapping information, while the ILM-Regional (ILM-R) servers
can contain partial and/or regionally relevant mapping information.
While a large endpoint address space contained in a prefix may be
mostly associated with the delivery networks served by one ETR, some
fragments (subprefixes) of that address space may be located
elsewhere at other ETRs. Let a/20 denote a prefix that is
conceptually viewed as composed of 16 subnets of /24 size that are
denoted as a1/24, a2/24, ..., a16/24. For example, a/20 is mostly at
Li Informational [Page 48]
RFC 6115 RRG Recommendation February 2011
ETR1, while only two of its subprefixes a8/24 and a15/24 are
elsewhere at ETR3 and ETR2, respectively (see Figure 2
[EEMDP_Considerations]). From the point of view of efficiency of the
mapping distribution protocol, it may be beneficial for ETR1 to
announce a map for the entire space a/20 (rather than fragment it
into a multitude of more-specific prefixes), and provide the
necessary exceptions in the map information. Thus, the map message
could be in the form of Map:(a/20, ETR1; Exceptions: a8/24, a15/24).
In addition, ETR2 and ETR3 announce the maps for a15/24 and a8/24,
respectively, and so the ILMs know where the exception EID addresses
are located. Now consider a host associated with ITR1 initiating a
packet destined for an address a7(1), which is in a7/24 that is not
in the exception portion of a/20. Now a question arises as to which
of the following approaches would be the best choice:
1. ILM-R provides the complete mapping information for a/20 to ITR1
including all maps for relevant exception subprefixes.
2. ILM-R provides only the directly relevant map to ITR1, which in
this case is (a/20, ETR1).
In the first approach, the advantage is that ITR1 would have the
complete mapping for a/20 (including exception subnets), and it would
not have to generate queries for subsequent first packets that are
destined to any address in a/20, including a8/24 and a15/24.
However, the disadvantage is that if there is a significant number of
exception subprefixes, then the very first packet destined for a/20
will experience a long delay, and also the processors at ITR1 and
ILM-R can experience overload. In addition, the memory usage at ITR1
can be very inefficient. The advantage of the second approach above
is that the ILM-R does not overload resources at ITR1, neither in
terms of processing or memory usage, but it needs an enhanced map
response in of the form Map:(a/20, ETR1, MS=1), where the MS (More
Specific) indicator is set to 1 to indicate to ITR1 that not all
subnets in a/20 map to ETR1. The key idea is that aggregation is
beneficial, and subnet exceptions must be handled with additional
messages or indicators in the maps.
13.1.3. Management of Mapping Distribution for Scenarios with Hierarchy
of ETRs and Multihoming
Now we highlight another architectural concept related to mapping
management (please refer to Figure 3 in [EEMDP_Considerations]).
Here we consider the possibility that ETRs may be organized in a
hierarchical manner. For instance, ETR7 is higher in the hierarchy
relative to ETR1, ETR2, and ETR3, and like-wise ETR8 is higher
relative to ETR4, ETR5, and ETR6. For instance, ETRs 1 through 3 can
relegate the locator role to ETR7 for their EID address space. In
Li Informational [Page 49]
RFC 6115 RRG Recommendation February 2011
essence, they can allow ETR7 to act as the locator for the delivery
networks in their purview. ETR7 keeps a local mapping table for
mapping the appropriate EID address space to specific ETRs that are
hierarchically associated with it in the level below. In this
situation, ETR7 can perform EID address space aggregation across ETRs
1 through 3 and can also include its own immediate EID address space
for the purpose of that aggregation. The many details related to
this approach and special circumstances involving multihoming of
subnets are discussed in detail in [EEMDP_Considerations]. The
hierarchical organization of ETRs and delivery networks should help
in the future growth and scalability of ETRs and mapping distribution
networks. This is essentially recursive map-and-encap, and some of
the mapping distribution and management functionality will remain
local to topologically neighboring delivery networks that are
hierarchically underneath ETRs.
13.1.4. References
[EEMDP_Considerations] [EEMDP_Presentation] [FIBAggregatability]
13.2. Critique
The scheme described in [EEMDP_Considerations] represents one
approach to mapping overhead reduction, and it is a general idea that
is applicable to any proposal that includes prefix or EID
aggregation. A somewhat similar idea is also used in Level-3
aggregation in the FIB aggregation proposal [FIBAggregatability].
There can be cases where deaggregation of EID prefixes occur in such
a way that the bulk of an EID prefix P would be attached to one
locator (say, ETR1) while a few subprefixes under P would be attached
to other locators elsewhere (say, ETR2, ETR3, etc.). Ideally, such
cases should not happen; however, in reality it can happen as the
RIR's address allocations are imperfect. In addition, as new IP
address allocations become harder to get, an IPv4 prefix owner might
split previously unused subprefixes of that prefix and allocate them
to remote sites (homed to other ETRs). Assuming these situations
could arise in practice, the nature of the solution would be that the
response from the mapping server for the coarser site would include
information about the more specifics. The solution as presented
seems correct.
The proposal mentions that in Approach 1, the ID-Locator Mapping
(ILM) system provides the complete mapping information for an
aggregate EID prefix to a querying ITR, including all the maps for
the relevant exception subprefixes. The sheer number of such more-
specifics can be worrisome, for example, in LISP. What if a
company's mobile-node EIDs came out of their corporate EID prefix?
Approach 2 is far better but still there may be too many entries for
Li Informational [Page 50]
RFC 6115 RRG Recommendation February 2011
a regional ILM to store. In Approach 2, the ILM communicates that
there are more specifics but does not communicate their mask-length.
A suggested improvement would be that rather than saying that there
are more specifics, indicate what their mask-lengths are. There can
be multiple mask lengths. This number should be pretty small for
IPv4 but can be large for IPv6.
Later in the proposal, a different problem is addressed, involving a
hierarchy of ETRs and how aggregation of EID prefixes from lower-
level ETRs can be performed at a higher-level ETR. The various
scenarios here are well illustrated and described. This seems like a
good idea, and a solution like LISP can support this as specified.
As any optimization scheme would inevitably add some complexity; the
proposed scheme for enhancing mapping efficiency comes with some of
its own overhead. The gain depends on the details of specific EID
blocks, i.e., how frequently the situations (such as an ETR that has
a bigger EID block with a few holes) arise.
13.3. Rebuttal
There are two main points in the critique that are addressed here:
(1) The gain depends on the details of specific EID blocks, i.e., how
frequently the situations arise such as an ETR having a bigger EID
block with a few holes, and (2) Approach 2 is lacking an added
feature of conveying just the mask-length of the more specifics that
exist as part of the current map response.
Regarding comment (1) above, there are multiple possibilities
regarding how situations can arise, resulting in allocations having
holes in them. An example of one of these possibilities is as
follows. Org-A has historically received multiple /20s, /22s, and
/24s over the course of time that are adjacent to each other. At the
present time, these prefixes would all aggregate to a /16 but for the
fact that just a few of the underlying /24s have been allocated
elsewhere historically to other organizations by an RIR or ISPs. An
example of a second possibility is that Org-A has an allocation of a
/16. It has suballocated a /22 to one of its subsidiaries, and
subsequently sold the subsidiary to another Org-B. For ease of
keeping the /22 subnet up and running without service disruption, the
/22 subprefix is allowed to be transferred in the acquisition
process. Now the /22 subprefix originates from a different AS and is
serviced by a different ETR (as compared to the parent \16 prefix).
We are in the process of performing an analysis of RIR allocation
data and are aware of other studies (notably at UCLA) that are also
performing similar analysis to quantify the frequency of occurrence
of the holes. We feel that the problem that has been addressed is a
realistic one, and the proposed scheme would help reduce the
overheads associated with the mapping distribution system.
Li Informational [Page 51]
RFC 6115 RRG Recommendation February 2011
Regarding comment (2) above, the suggested modification to Approach 2
would be definitely beneficial. In fact, we feel that it would be
fairly straightforward to dynamically use Approach 1 or Approach 2
(with the suggested modification), depending on whether there are
only a few (e.g., <=5) or many (e.g., >5) more specifics,
respectively. The suggested modification of notifying the mask-
length of the more specifics in the map response is indeed very
helpful because then the ITR would not have to resend a map-query for
EID addresses that match the EID address in the previous query up to
at least mask-length bit positions. There can be a two-bit field in
the map response that would be interpreted as follows.
(a) value 00: there are no more specifics
(b) value 01: there are more specifics and their exact information
follows in additional map-responses
(c) value 10: there are more-specifics and the mask-length of the
next more-specific is indicated in the current map-response.
An additional field will be included that will be used to specify the
mask-length of the next more-specific in the case of value 10 (case
(c) above).
14. Evolution
14.1. Summary
As the Internet continues its rapid growth, router memory size and
CPU cycle requirements are outpacing feasible hardware upgrade
schedules. We propose to solve this problem by applying aggregation
with increasing scopes to gradually evolve the routing system towards
a scalable structure. At each evolutionary step, our solution is
able to interoperate with the existing system and provide immediate
benefits to adopters to enable deployment. This document summarizes
the need for an evolutionary design, the relationship between our
proposal and other revolutionary proposals, and the steps of
aggregation with increasing scopes. Our detailed proposal can be
found in [Evolution].
14.1.1. Need for Evolution
Multiple different views exist regarding the routing scalability
problem. Networks differ vastly in goals, behavior, and resources,
giving each a different view of the severity and imminence of the
scalability problem. Therefore, we believe that, for any solution to
be adopted, it will start with one or a few early adopters and may
not ever reach the entire Internet. The evolutionary approach
Li Informational [Page 52]
RFC 6115 RRG Recommendation February 2011
recognizes that changes to the Internet can only be a gradual process
with multiple stages. At each stage, adopters are driven by and
rewarded with solving an immediate problem. Each solution must be
deployable by individual networks who deem it necessary at a time
they deem it necessary, without requiring coordination from other
networks, and the solution has to bring immediate relief to a single
first-mover.
14.1.2. Relation to Other RRG Proposals
Most proposals take a revolutionary approach that expects the entire
Internet to eventually move to some new design whose main benefits
would not materialize until the vast majority of the system has been
upgraded; their incremental deployment plan simply ensures
interoperation between upgraded and legacy parts of the system. In
contrast, the evolutionary approach depicts a system where changes
may happen here and there as needed, but there is no dependency on
the system as a whole making a change. Whoever takes a step forward
gains the benefit by solving his own problem, without depending on
others to take actions. Thus, deployability includes not only
interoperability, but also the alignment of costs and gains.
The main differences between our approach and more revolutionary map-
and-encap proposals are: (a) we do not start with a pre-defined
boundary between edge and core; and (b) each step brings immediate
benefits to individual first-movers. Note that our proposal neither
interferes nor prevents any revolutionary host-based solutions such
as ILNP from being rolled out. However, host-based solutions do not
bring useful impact until a large portion of hosts have been
upgraded. Thus, even if a host-based solution is rolled out in the
long run, an evolutionary solution is still needed for the near term.
14.1.3. Aggregation with Increasing Scopes
Aggregating many routing entries to a fewer number is a basic
approach to improving routing scalability. Aggregation can take
different forms and be done within different scopes. In our design,
the aggregation scope starts from a single router, then expands to a
single network and neighbor networks. The order of the following
steps is not fixed but is merely a suggestion; it is under each
individual network's discretion which steps they choose to take based
on their evaluation of the severity of the problems and the
affordability of the solutions.
1. FIB Aggregation (FA) in a single router. A router
algorithmically aggregates its FIB entries without changing its
RIB or its routing announcements. No coordination among routers
Li Informational [Page 53]
RFC 6115 RRG Recommendation February 2011
is needed, nor any change to existing protocols. This brings
scalability relief to individual routers with only a software
upgrade.
2. Enabling 'best external' on Provider Edge routers (PEs),
Autonomous System Border Routers (ASBRs), and Route Reflectors
(RRs), and turning on next-hop-self on RRs. For hierarchical
networks, the RRs in each Point of Presence (PoP) can serve as a
default gateway for nodes in the PoP, thus allowing the non-RR
nodes in each PoP to maintain smaller routing tables that only
include paths that egress that PoP. This is known as 'topology-
based mode' Virtual Aggregation, and can be done with existing
hardware and configuration changes only. Please see
[Evolution_Grow_Presentation] for details.
3. Virtual Aggregation (VA) in a single network. Within an AS, some
fraction of existing routers are designated as Aggregation Point
Routers (APRs). These routers are either individually or
collectively maintain the full FIB table. Other routers may
suppress entries from their FIBs, instead forwarding packets to
APRs, which will then tunnel the packets to the correct egress
routers. VA can be viewed as an intra-domain map-and-encap
system to provide the operators with a control mechanism for the
FIB size in their routers.
4. VA across neighbor networks. When adjacent networks have VA
deployed, they can go one step further by piggybacking egress
router information on existing BGP announcements, so that packets
can be tunneled directly to a neighbor network's egress router.
This improves packet delivery performance by performing the
encapsulation/decapsulation only once across these neighbor
networks, as well as reducing the stretch of the path.
5. Reducing RIB Size by separating the control plane from the data
plane. Although a router's FIB can be reduced by FA or VA, it
usually still needs to maintain the full RIB to produce complete
routing announcements to its neighbors. To reduce the RIB size,
a network can set up special boxes, which we call controllers, to
take over the External BGP (eBGP) sessions from border routers.
The controllers receive eBGP announcements, make routing
decisions, and then inform other routers in the same network of
how to forward packets, while the regular routers just focus on
the job of forwarding packets. The controllers, not being part
of the data path, can be scaled using commodity hardware.
6. Insulating forwarding routers from routing churn. For routers
with a smaller RIB, the rate of routing churn is naturally
reduced. Further reduction can be achieved by not announcing
Li Informational [Page 54]
RFC 6115 RRG Recommendation February 2011
failures of customer prefixes into the core, but handling these
failures in a data-driven fashion, e.g., a link failure to an
edge network is not reported unless and until there are data
packets that are heading towards the failed link.
14.1.4. References
[Evolution] [Evolution_Grow_Presentation]
14.2. Critique
All of the RRG proposals that scale the routing architecture share
one fundamental approach, route aggregation, in different forms,
e.g., LISP removes "edge prefixes" using encapsulation at ITRs, and
ILNP achieves the goal by locator rewrite. In this evolutionary path
proposal, each stage of the evolution applies aggregation with
increasing scopes to solve a specific scalability problem, and
eventually the path leads towards global routing scalability. For
example, it uses FIB aggregation at the single router level, virtual
aggregation at the network level, and then between neighboring
networks at the inter-domain level.
Compared to other proposals, this proposal has the lowest hurdle to
deployment, because it does not require that all networks move to use
a global mapping system or upgrade all hosts, and it is designed for
each individual network to get immediate benefits after its own
deployment.
Criticisms of this proposal fall into two types. The first type
concerns several potential issues in the technical design as listed
below:
1. FIB aggregation, at level-3 and level-4, may introduce extra
routable space. Concerns have been raised about the potential
routing loops resulting from forwarding otherwise non-routable
packets, and the potential impact on Reverse Path Forwarding
(RPF) checking. These concerns can be addressed by choosing a
lower level of aggregation and by adding null routes to minimize
the extra space, at the cost of reduced aggregation gain.
2. Virtual Aggregation changes the traffic paths in an ISP network,
thereby introducing stretch. Changing the traffic path may also
impact the reverse path checking practice used to filter out
packets from spoofed sources. More analysis is need to identify
the potential side-effects of VA and to address these issues.
Li Informational [Page 55]
RFC 6115 RRG Recommendation February 2011
3. The current Virtual Aggregation description is difficult to
understand, due to its multiple options for encapsulation and
popular prefix configurations, which makes the mechanism look
overly complicated. More thought is needed to simplify the
design and description.
4. FIB Aggregation and Virtual Aggregation may require additional
operational cost. There may be new design trade-offs that the
operators need to understand in order to select the best option
for their networks. More analysis is needed to identify and
quantify all potential operational costs.
5. In contrast to a number of other proposals, this solution does
not provide mobility support. It remains an open question as to
whether the routing system should handle mobility.
The second criticism is whether deploying quick fixes like FIB
aggregation would alleviate scalability problems in the short term
and reduce the incentives for deploying a new architecture; and
whether an evolutionary approach would end up with adding more and
more patches to the old architecture, and not lead to a fundamentally
new architecture as the proposal had expected. Though this solution
may get rolled out more easily and quickly, a new architecture, if/
once deployed, could solve more problems with cleaner solutions.
14.3. Rebuttal
No rebuttal was submitted for this proposal.
15. Name-Based Sockets
15.1. Summary
Name-based sockets are an evolution of the existing address-based
sockets, enabling applications to initiate and receive communication
sessions based on the use of domain names in lieu of IP addresses.
Name-based sockets move the existing indirection from domain names to
IP addresses from its current position in applications down to the IP
layer. As a result, applications communicate exclusively based on
domain names, while the discovery, selection, and potentially in-
session re-selection of IP addresses is centrally performed by the IP
stack itself.
Name-based sockets help mitigate the Internet routing scalability
problem by separating naming and addressing more consistently than
what is possible with the existing address-based sockets. This
supports IP address aggregation because it simplifies the use of IP
Li Informational [Page 56]
RFC 6115 RRG Recommendation February 2011
addresses with high topological significance, as well as the dynamic
replacement of IP addresses during network-topological and host-
attachment changes.
A particularly positive effect of name-based sockets on Internet
routing scalability is the new incentives for edge network operators
to use provider-assigned IP addresses, which are more aggregatable
than the typically preferred provider-independent IP addresses. Even
though provider-independent IP addresses are harder to get and more
expensive than provider-assigned IP addresses, many operators desire
provider-independent addresses due to the high indirect cost of
provider-assigned IP addresses. This indirect cost is comprised of
both difficulties in multihoming, and tedious and largely manual
renumbering upon provider changes.
Name-based sockets reduce the indirect cost of provider-assigned IP
addresses in three ways, and hence make the use of provider-assigned
IP addresses more acceptable: (1) They enable fine-grained and
responsive multihoming. (2) They simplify renumbering by offering an
easy means to replace IP addresses in referrals with domain names.
This helps avoiding updates to application and operating system
configurations, scripts, and databases during renumbering. (3) They
facilitate low-cost solutions that eliminate renumbering altogether.
One such low-cost solution is IP address translation, which in
combination with name-based sockets loses its adverse impact on
applications.
The prerequisite for a positive effect of name-based sockets on
Internet routing scalability is their adoption in operating systems
and applications. Operating systems should be augmented to offer
name-based sockets as a new alternative to the existing address-based
sockets, and applications should use name-based sockets for their
communications. Neither an instantaneous, nor an eventually complete
transition to name-based sockets is required, yet the positive effect
on Internet routing scalability will grow with the extent of this
transition.
Name-based sockets were hence designed with a focus on deployment
incentives, comprising both immediate deployment benefits as well as
low deployment costs. Name-based sockets provide a benefit to
application developers because the alleviation of applications from
IP address management responsibilities simplifies and expedites
application development. This benefit is immediate owing to the
backwards compatibility of name-based sockets with legacy
applications and legacy peers. The appeal to application developers,
in turn, is an immediate benefit for operating system vendors who
adopt name-based sockets.
Li Informational [Page 57]
RFC 6115 RRG Recommendation February 2011
Name-based sockets furthermore minimize deployment costs: Alternative
techniques to separate naming and addressing provide applications
with "surrogate IP addresses" that dynamically map onto regular IP
addresses. A surrogate IP address is indistinguishable from a
regular IP address for applications, but does not have the
topological significance of a regular IP address. Mobile IP and the
Host Identity Protocol are examples of such separation techniques.
Mobile IP uses "home IP addresses" as surrogate IP addresses with
reduced topological significance. The Host Identity Protocol uses
"host identifiers" as surrogate IP addresses without topological
significance. A disadvantage of surrogate IP addresses is their
incurred cost in terms of extra administrative overhead and, for some
techniques, extra infrastructure. Since surrogate IP addresses must
be resolvable to the corresponding regular IP addresses, they must be
provisioned in the DNS or similar infrastructure. Mobile IP uses a
new infrastructure of home agents for this purpose, while the Host
Identity Protocol populates DNS servers with host identities. Name-
based sockets avoid this cost because they function without surrogate
IP addresses, and hence without the provisioning and infrastructure
requirements that accompany surrogate addresses.
Certainly, some edge networks will continue to use provider-
independent addresses despite name-based sockets, perhaps simply due
to inertia. But name-based sockets will help reduce the number of
those networks, and thus have a positive impact on Internet routing
scalability.
A more comprehensive description of name-based sockets can be found
in [Name_Based_Sockets].
15.1.1. References
[Name_Based_Sockets]
15.2. Critique
Name-based sockets contribution to the routing scalability problem is
to decrease the reliance on PI addresses, allowing a greater use of
PA addresses, and thus a less fragmented routing table. It provides
end hosts with an API which makes the applications address-agnostic.
The name abstraction allows the hosts to use any type of locator,
independent of format or provider. This increases the motivation and
usability of PA addresses. Some applications, in particular
bootstrapping applications, may still require hard coded IP
addresses, and as such will still motivate the use of PI addresses.
Li Informational [Page 58]
RFC 6115 RRG Recommendation February 2011
15.2.1. Deployment
The main incentives and drivers are geared towards the transition of
applications to the name-based sockets. Adoption by applications
will be driven by benefits in terms of reduced application
development cost. Legacy applications are expected to migrate to the
new API at a slower pace, as the name-based sockets are backwards
compatible, this can happen in a per-host fashion. Also, not all
applications can be ported to a FQDN dependent infrastructure, e.g.,
DNS functions. This hurdle is manageable, and may not be a definite
obstacle for the transition of a whole domain, but it needs to be
taken into account when striving for mobility/multihoming of an
entire site. The transition of functions on individual hosts may be
trivial, either through upgrades/changes to the OS or as linked
libraries. This can still happen incrementally and independently, as
compatibility is not affected by the use of name-based sockets.
15.2.2. Edge-networks
Name-based sockets rely on the transition of individual applications
and are backwards compatible, so they do not require bilateral
upgrades. This allows each host to migrate its applications
independently. Name-based sockets may make an individual client
agnostic to the networking medium, be it PA/PI IP-addresses or in a
the future an entirely different networking medium. However, an
entire edge-network, with internal and external services will not be
able to make a complete transition in the near future. Hence, even
if a substantial fraction of the hosts in an edge-network use name-
based sockets, PI addresses may still be required by the edge-
network. In short, new services may be implemented using name-based
sockets, old services may be ported. Name-based sockets provide an
increased motivation to move to PA-addresses as actual provider
independence relies less and less on PI-addressing.
15.3. Rebuttal
No rebuttal was submitted for this proposal.
16. Routing and Addressing in Networks with Global Enterprise Recursion
(IRON-RANGER)
16.1. Summary
RANGER is a locator/identifier separation approach that uses IP-in-IP
encapsulation to connect edge networks across transit networks such
as the global Internet. End systems use endpoint interface
identifier (EID) addresses that may be routable within edge networks
but do not appear in transit network routing tables. EID to Routing
Li Informational [Page 59]
RFC 6115 RRG Recommendation February 2011
Locator (RLOC) address bindings are instead maintained in mapping
tables and also cached in default router FIBs (i.e., very much the
same as for the global DNS and its associated caching resolvers).
RANGER enterprise networks are organized in a recursive hierarchy
with default mappers connecting lower layers to the next higher layer
in the hierarchy. Default mappers forward initial packets and push
mapping information to lower-tier routers and end systems through
secure redirection.
RANGER is an architectural framework derived from the Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP).
16.1.1. Gains
o provides a scalable routing system alternative in instances where
dynamic routing protocols are impractical
o naturally supports a recursively-nested "network-of-networks" (or,
"enterprise-within-enterprise") hierarchy
o uses asymmetric security mechanisms (i.e., secure neighbor
discovery) to secure router discovery and the redirection
mechanism
o can quickly detect path failures and pick alternate routes
o naturally supports provider-independent addressing
o support for site multihoming and traffic engineering
o ingress filtering for multihomed sites
o mobility-agile through explicit cache invalidation (much more
reactive than dynamic DNS)
o supports neighbor discovery and neighbor unreachability detection
over tunnels
o no changes to end systems
o no changes to most routers
o supports IPv6 transition
Li Informational [Page 60]
RFC 6115 RRG Recommendation February 2011
o compatible with true identity/locator split mechanisms such as HIP
(i.e., packets contain a HIP Host Identity Tag (HIT) as an end
system identifier, IPv6 address as endpoint interface identifier
(EID) in the inner IP header and IPv4 address as Routing LOCator
(RLOC) in the outer IP header)
o prototype code available
16.1.2. Costs
o new code needed in enterprise border routers
o locator/path liveness detection using RFC 4861 neighbor
unreachability detection (i.e., extra control messages, but data-
driven) [RFC4861]
16.1.3. References
[IRON] [RANGER_Scen] [VET] [SEAL] [RFC5201] [RFC5214] [RFC5720]
16.2. Critique
The RANGER architectural framework is intended to be applicable for a
Core-Edge Separation (CES) architecture for scalable routing, using
either IPv4 or IPv6 -- or using both in an integrated system which
may carry one protocol over the other.
However, despite [IRON] being readied for publication as an
experimental RFC, the framework falls well short of the level of
detail required to envisage how it could be used to implement a
practical scalable routing solution. For instance, the document
contains no specification for a mapping protocol, or how the mapping
lookup system would work on a global scale.
There is no provision for RANGER's ITR-like routers being able to
probe the reachability of end-user networks via multiple ETR-like
routers -- nor for any other approach to multihoming service
restoration.
Nor is there any provision for inbound TE or support of mobile
devices which frequently change their point of attachment.
Therefore, in its current form, RANGER cannot be contemplated as a
superior scalable routing solution to some other proposals which are
specified in sufficient detail and which appear to be feasible.
Li Informational [Page 61]
RFC 6115 RRG Recommendation February 2011
RANGER uses its own tunneling and PMTUD management protocol: SEAL.
Adoption of SEAL in its current form would prevent the proper
utilization of jumbo frame paths in the DFZ, which will become the
norm in the future. SEAL uses "Packet Too Big" [RFC4443] and
"Fragmentation Needed" [RFC0792] messages to the sending host only to
fix a preset maximum packet length. To avoid the need for the SEAL
layer to fragment packets of this length, this MTU value (for the
input of the tunnel) needs to be set significantly below 1500 bytes,
assuming the typically ~1500 byte MTU values for paths across the DFZ
today. In order to avoid this excessive fragmentation, this value
could only be raised to a ~9k byte value at some time in the future
where essentially all paths between ITRs and ETRs were jumbo frame
capable.
16.3. Rebuttal
The Internet Routing Overlay Network (IRON) [IRON] is a scalable
Internet routing architecture that builds on the RANGER recursive
enterprise network hierarchy [RFC5720]. IRON bonds together
participating RANGER networks using VET [VET] and SEAL [SEAL] to
enable secure and scalable routing through automatic tunneling within
the Internet core. The IRON-RANGER automatic tunneling abstraction
views the entire global Internet DFZ as a virtual Non-Broadcast
Multi-Access (NBMA) link similar to ISATAP [RFC5214].
IRON-RANGER is an example of a Core-Edge Separation (CES) system.
Instead of a classical mapping database, however, IRON-RANGER uses a
hybrid combination of a proactive dynamic routing protocol for
distributing highly aggregated Virtual Prefixes (VPs) and an on-
demand data driven protocol for distributing more-specific Provider-
Independent (PI) prefixes derived from the VPs.
The IRON-RANGER hierarchy consists of recursively-nested RANGER
enterprise networks joined together by IRON routers that participate
in a global BGP instance. The IRON BGP instance is maintained
separately from the current Internet BGP Routing LOCator (RLOC)
address space (i.e., the set of all public IPv4 prefixes in the
Internet). Instead, the IRON BGP instance maintains VPs taken from
Endpoint Interface iDentifier (EID) address space, e.g., the IPv6
global unicast address space. To accommodate scaling, only O(10k) --
O(100k) VPs are allocated e.g., using /20 or shorter IPv6 prefixes.
IRON routers lease portions of their VPs as Provider-Independent (PI)
prefixes for customer equipment (CEs), thereby creating a sustainable
business model. CEs that lease PI prefixes propagate address
mapping(s) throughout their attached RANGER networks and up to VP-
owning IRON router(s) through periodic transmission of "bubbles" with
authentication and PI prefix information. Routers in RANGER networks
Li Informational [Page 62]
RFC 6115 RRG Recommendation February 2011
and IRON routers that receive and forward the bubbles securely
install PI prefixes in their FIBs, but do not inject them into the
RIB. IRON routers therefore keep track of only their customer base
via the FIB entries and keep track of only the Internet-wide VP
database in the RIB.
IRON routers propagate more-specific prefixes using secure
redirection to update router FIBs. Prefix redirection is driven by
the data plane and does not affect the control plane. Redirected
prefixes are not injected into the RIB, but rather are maintained as
FIB soft state that is purged after expiration or route failure.
Neighbor unreachability detection is used to detect failure.
Secure prefix registrations and redirections are accommodated through
the mechanisms of SEAL. Tunnel endpoints using SEAL synchronize
sequence numbers, and can therefore discard any packets they receive
that are outside of the current sequence number window. Hence, off-
path attacks are defeated. These synchronized tunnel endpoints can
therefore exchange prefixes with signed certificates that prove
prefix ownership in such a way that DoS vectors that attack crypto
calculation overhead are eliminated due to the prevention of off-path
attacks.
CEs can move from old RANGER networks and re-inject their PI prefixes
into new RANGER networks. This would be accommodated by IRON-RANGER
as a site multihoming event while host mobility and true locator-ID
separation is accommodated via HIP [RFC5201].
17. Recommendation
As can be seen from the extensive list of proposals above, the group
explored a number of possible solutions. Unfortunately, the group
did not reach rough consensus on a single best approach.
Accordingly, the recommendation has been left to the co-chairs. The
remainder of this section describes the rationale and decision of the
co-chairs.
As a reminder, the goal of the research group was to develop a
recommendation for an approach to a routing and addressing
architecture for the Internet. The primary goal of the architecture
is to provide improved scalability for the routing subsystem.
Specifically, this implies that we should be able to continue to grow
the routing subsystem to meet the needs of the Internet without
requiring drastic and continuous increases in the amount of state or
processing requirements for routers.
Li Informational [Page 63]
RFC 6115 RRG Recommendation February 2011
17.1. Motivation
There is a general concern that the cost and structure of the routing
and addressing architecture as we know it today may become
prohibitively expensive with continued growth, with repercussions to
the health of the Internet. As such, there is an urgent need to
examine and evaluate potential scalability enhancements.
For the long term future of the Internet, it has become apparent that
IPv6 is going to play a significant role. It has taken more than a
decade, but IPv6 is starting to see some non-trivial amount of
deployment. This is in part due to the depletion of IPv4 addresses.
It therefore seems apparent that the new architecture must be
applicable to IPv6. It may or may not be applicable to IPv4, but not
addressing the IPv6 portion of the network would simply lead to
recreating the routing scalability problem in the IPv6 domain,
because the two share a common routing architecture.
Whatever change we make, we should expect that this is a very long-
lived change. The routing architecture of the entire Internet is a
loosely coordinated, complex, expensive subsystem, and permanent,
pervasive changes to it will require difficult choices during
deployment and integration. These cannot be undertaken lightly.
By extension, if we are going to the trouble, pain, and expense of
making major architectural changes, it follows that we want to make
the best changes possible. We should regard any such changes as
permanent and we should therefore aim for long term solutions that
place the network in the best possible position for ongoing growth.
These changes should be cleanly integrated, first-class citizens
within the architecture. That is to say that any new elements that
are integrated into the architecture should be fundamental
primitives, on par with the other existing legacy primitives in the
architecture, that interact naturally and logically when in
combination with other elements of the architecture.
Over the history of the Internet, we have been very good about
creating temporary, ad-hoc changes, both to the routing architecture
and other aspects of the network layer. However, many of these band-
aid solutions have come with a significant overhead in terms of long-
term maintenance and architectural complexity. This is to be avoided
and short-term improvements should eventually be replaced by long-
term, permanent solutions.
In the particular instance of the routing and addressing architecture
today, we feel that the situation requires that we pursue both short-
term improvements and long-term solutions. These are not
incompatible because we truly intend for the short-term improvements
Li Informational [Page 64]
RFC 6115 RRG Recommendation February 2011
to be completely localized and temporary. The short-term
improvements are necessary to give us the time necessary to develop,
test, and deploy the long-term solution. As the long-term solution
is rolled out and gains traction, the short-term improvements should
be of less benefit and can subsequently be withdrawn.
17.2. Recommendation to the IETF
The group explored a number of proposed solutions but did not reach
consensus on a single best approach. Therefore, in fulfillment of
the routing research group's charter, the co-chairs recommend that
the IETF pursue work in the following areas:
Evolution [Evolution]
Identifier-Locator Network Protocol (ILNP) [ILNP_Site]
Renumbering [RFC5887]
17.3. Rationale
We selected Evolution because it is a short-term improvement. It can
be applied on a per-domain basis, under local administration and has
immediate effect. While there is some complexity involved, we feel
that this option is constructive for service providers who find the
additional complexity to be less painful than upgrading hardware.
This improvement can be deployed by domains that feel it necessary,
for as long as they feel it is necessary. If this deployment lasts
longer than expected, then the implications of that decision are
wholly local to the domain.
We recommended ILNP because we find it to be a clean solution for the
architecture. It separates location from identity in a clear,
straightforward way that is consistent with the remainder of the
Internet architecture and makes both first-class citizens. Unlike
the many map-and-encap proposals, there are no complications due to
tunneling, indirection, or semantics that shift over the lifetime of
a packet's delivery.
We recommend further work on automating renumbering because even with
ILNP, the ability of a domain to change its locators at minimal cost
is fundamentally necessary. No routing architecture will be able to
scale without some form of abstraction, and domains that change their
point of attachment must fundamentally be prepared to change their
locators in line with this abstraction. We recognize that [RFC5887]
is not a solution so much as a problem statement, and we are simply
recommending that the IETF create effective and convenient mechanisms
for site renumbering.
Li Informational [Page 65]
RFC 6115 RRG Recommendation February 2011
18. Acknowledgments
This document presents a small portion of the overall work product of
the Routing Research Group, who have developed all of these
architectural approaches and many specific proposals within this
solution space.
19. Security Considerations
Space precludes a full treatment of security considerations for all
proposals summarized herein. [RFC3552] However, it was a requirement
of the research group to provide security that is at least as strong
as the existing Internet routing and addressing architecture. Each
technical proposal has slightly different security considerations,
the details of which are in many of the references cited.
20. Informative References
[CRM] Flinck, H., "Compact routing in locator identifier mapping
system", <http://www.tschofenig.priv.at/rrg/
CR_mapping_system_0.1.pdf>.
[DNSnBIND]
Liu, C. and P. Albitz, "DNS & BIND", 2006, 5th
Edition, O'Reilly & Associates, Sebastopol, CA, USA. ISBN
0-596-10057-4.
[EEMDP_Considerations]
Sriram, K., Kim, Y., and D. Montgomery, "Enhanced
Efficiency of Mapping Distribution Protocols in Scalable
Routing and Addressing Architectures", Proceedings of the
ICCCN, Zurich, Switzerland, August 2010,
<http://www.antd.nist.gov/~ksriram/EEMDP_ICCCN2010.pdf>.
[EEMDP_Presentation]
Sriram, K., Gleichmann, P., Kim, Y., and D. Montgomery,
"Enhanced Efficiency of Mapping Distribution Protocols in
Scalable Routing and Addressing Architectures", Presented
at the LISP WG meeting, IETF 78, July 2010. Originally
presented at the RRG meeting at IETF 72,
<http://www.ietf.org/proceedings/78/slides/lisp-6.pdf>.
[Evolution]
Zhang, B. and L. Zhang, "Evolution Towards Global Routing
Scalability", Work in Progress, October 2009.
Li Informational [Page 66]
RFC 6115 RRG Recommendation February 2011
[Evolution_Grow_Presentation]
Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R., and
L. Zhang, "Virtual Aggregation (VA)", November 2009,
<http://www.ietf.org/proceedings/76/slides/grow-5.pdf>.
[FIBAggregatability]
Zhang, B., Wang, L., Zhao, X., Liu, Y., and L. Zhang, "An
Evaluation Study of Router FIB Aggregatability",
November 2009,
<http://www.ietf.org/proceedings/76/slides/grow-2.pdf>.
[GLI] Menth, M., Hartmann, M., and D. Klein, "Global Locator,
Local Locator, and Identifier Split (GLI-Split)",
April 2010,
<http://www3.informatik.uni-wuerzburg.de/TR/tr470.pdf>.
[ILNP_DNS]
Atkinson, R. and S. Rose, "DNS Resource Records for ILNP",
Work in Progress, February 2011.
[ILNP_ICMP]
Atkinson, R., "ICMP Locator Update message", Work
in Progress, February 2011.
[ILNP_Intro]
Atkinson, R., "ILNP Concept of Operations", Work
in Progress, February 2011.
[ILNP_Nonce]
Atkinson, R., "ILNP Nonce Destination Option", Work
in Progress, February 2011.
[ILNP_Site]
Atkinson, R., Bhatti, S., Hailes, S., Rehunathan, D., and
M. Lad, "ILNP - Identifier-Locator Network Protocol",
updated 06 January 2011,
<http://ilnp.cs.st-andrews.ac.uk>.
[IRON] Templin, F., "The Internet Routing Overlay Network
(IRON)", Work in Progress, January 2011.
[Ivip_Constraints]
Whittle, R., "List of constraints on a successful scalable
routing solution which result from the need for widespread
voluntary adoption", April 2009,
<http://www.firstpr.com.au/ip/ivip/RRG-2009/constraints/>.
Li Informational [Page 67]
RFC 6115 RRG Recommendation February 2011
[Ivip_DRTM]
Whittle, R., "DRTM - Distributed Real Time Mapping for
Ivip and LISP", Work in Progress, March 2010.
[Ivip_EAF]
Whittle, R., "Ivip4 ETR Address Forwarding", Work
in Progress, January 2010.
[Ivip_Glossary]
Whittle, R., "Glossary of some Ivip and scalable routing
terms", Work in Progress, March 2010.
[Ivip_Mobility]
Whittle, R., "TTR Mobility Extensions for Core-Edge
Separation Solutions to the Internet's Routing Scaling
Problem", August 2008,
<http://www.firstpr.com.au/ip/ivip/TTR-Mobility.pdf>.
[Ivip_PLF]
Whittle, R., "Prefix Label Forwarding (PLF) - Modified
Header Forwarding for IPv6",
<http://www.firstpr.com.au/ip/ivip/PLF-for-IPv6/>.
[Ivip_PMTUD]
Whittle, R., "IPTM - Ivip's approach to solving the
problems with encapsulation overhead, MTU, fragmentation
and Path MTU Discovery", January 2010,
<http://www.firstpr.com.au/ip/ivip/pmtud-frag/>.
[JSAC_Arch]
Atkinson, R., Bhatti, S., and S. Hailes, "Evolving the
Internet Architecture Through Naming", IEEE Journal on
Selected Areas in Communication (JSAC) 28(8),
October 2010.
[LIG] Farinacci, D. and D. Meyer, "LISP Internet Groper (LIG)",
Work in Progress, February 2010.
[LISP] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis,
"Locator/ID Separation Protocol (LISP)", Work in Progress,
October 2010.
[LISP+ALT]
Fuller, V., Farinacci, D., Meyer, D., and D. Lewis, "LISP
Alternative Topology (LISP+ALT)", Work in Progress,
October 2010.
Li Informational [Page 68]
RFC 6115 RRG Recommendation February 2011
[LISP-Interworking]
Lewis, D., Meyer, D., Farinacci, D., and V. Fuller,
"Interworking LISP with IPv4 and IPv6", Work in Progress,
August 2010.
[LISP-MN] Meyer, D., Lewis, D., and D. Farinacci, "LISP Mobile
Node", Work in Progress, October 2010.
[LISP-MS] Fuller, V. and D. Farinacci, "LISP Map Server", Work
in Progress, October 2010.
[LISP-TREE]
Jakab, L., Cabellos-Aparicio, A., Coras, F., Saucez, D.,
and O. Bonaventure, "LISP-TREE: A DNS Hierarchy to Support
the LISP Mapping System", IEEE Journal on Selected Areas
in Communications, Volume 28, Issue 8, October 2010, <http
://ieeexplore.ieee.org/stamp/
stamp.jsp?tp=&arnumber=5586446>.
[LMS] Letong, S., Xia, Y., ZhiLiang, W., and W. Jianping, "A
Layered Mapping System For Scalable Routing", <http://
docs.google.com/
fileview?id=0BwsJc7A4NTgeOTYzMjFlOGEtYzA4OC00NTM0LTg5ZjktN
mFkYzBhNWJhMWEy&hl=en>.
[LMS_Summary]
Sun, C., "A Layered Mapping System (Summary)", <http://
docs.google.com/
Doc?docid=0AQsJc7A4NTgeZGM3Y3o1NzVfNmd3eGRzNGhi&hl=en>.
[LOC_ID_Implications]
Meyer, D. and D. Lewis, "Architectural Implications of
Locator/ID Separation", Work in Progress, January 2009.
[MILCOM1] Atkinson, R. and S. Bhatti, "Site-Controlled Secure Multi-
homing and Traffic Engineering for IP", IEEE Military
Communications Conference (MILCOM) 28, Boston, MA, USA,
October 2009.
[MILCOM2] Atkinson, R., Bhatti, S., and S. Hailes, "Harmonised
Resilience, Multi-homing and Mobility Capability for IP",
IEEE Military Communications Conference (MILCOM) 27, San
Diego, CA, USA, November 2008.
[MPTCP_Arch]
Ford, A., Raiciu, C., Barre, S., Iyengar, J., and B. Ford,
"Architectural Guidelines for Multipath TCP Development",
Work in Progress, February 2010.
Li Informational [Page 69]
RFC 6115 RRG Recommendation February 2011
[MobiArch1]
Atkinson, R., Bhatti, S., and S. Hailes, "Mobility as an
Integrated Service through the Use of Naming", ACM
International Workshop on Mobility in the Evolving
Internet (MobiArch) 2, Kyoto, Japan, August 2007.
[MobiArch2]
Atkinson, R., Bhatti, S., and S. Hailes, "Mobility Through
Naming: Impact on DNS", ACM International Workshop on
Mobility in the Evolving Internet (MobiArch) 3, Seattle,
USA, August 2008.
[Name_Based_Sockets]
Vogt, C., "Simplifying Internet Applications Development
With A Name-Based Sockets Interface", December 2009, <http
://christianvogt.mailup.net/pub/
vogt-2009-name-based-sockets.pdf>.
[RANGER_Scen]
Russert, S., Fleischman, E., and F. Templin, "RANGER
Scenarios", Work in Progress, July 2010.
[RANGI] Xu, X., "Routing Architecture for the Next Generation
Internet (RANGI)", Work in Progress, August 2010.
[RANGI-PROXY]
Xu, X., "Transition Mechanisms for Routing Architecture
for the Next Generation Internet (RANGI)", Work
in Progress, July 2009.
[RANGI-SLIDES]
Xu, X., "Routing Architecture for the Next-Generation
Internet (RANGI)", <http://www.ietf.org/proceedings/76/
slides/RRG-1/RRG-1.htm>.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, September 1981.
[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, November 2000.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
July 2003.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements",
RFC 4033, March 2005.
Li Informational [Page 70]
RFC 6115 RRG Recommendation February 2011
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
[RFC4423] Moskowitz, R. and P. Nikander, "Host Identity Protocol
(HIP) Architecture", RFC 4423, May 2006.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson,
"Host Identity Protocol", RFC 5201, April 2008.
[RFC5214] Templin, F., Gleeson, T., and D. Thaler, "Intra-Site
Automatic Tunnel Addressing Protocol (ISATAP)", RFC 5214,
March 2008.
[RFC5534] Arkko, J. and I. van Beijnum, "Failure Detection and
Locator Pair Exploration Protocol for IPv6 Multihoming",
RFC 5534, June 2009.
[RFC5720] Templin, F., "Routing and Addressing in Networks with
Global Enterprise Recursion (RANGER)", RFC 5720,
February 2010.
[RFC5887] Carpenter, B., Atkinson, R., and H. Flinck, "Renumbering
Still Needs Work", RFC 5887, May 2010.
[RFC5902] Thaler, D., Zhang, L., and G. Lebovitz, "IAB Thoughts on
IPv6 Network Address Translation", RFC 5902, July 2010.
[RRG_Design_Goals]
Li, T., "Design Goals for Scalable Internet Routing", Work
in Progress, January 2011.
Li Informational [Page 71]
RFC 6115 RRG Recommendation February 2011
[Referral_Obj]
Carpenter, B., Boucadair, M., Halpern, J., Jiang, S., and
K. Moore, "A Generic Referral Object for Internet
Entities", Work in Progress, October 2009.
[SEAL] Templin, F., "The Subnetwork Encapsulation and Adaptation
Layer (SEAL)", Work in Progress, January 2011.
[Scalability_PS]
Narten, T., "On the Scalability of Internet Routing", Work
in Progress, February 2010.
[TIDR] Adan, J., "Tunneled Inter-domain Routing (TIDR)", Work
in Progress, December 2006.
[TIDR_AS_forwarding]
Adan, J., "yetAnotherProposal: AS-number forwarding",
March 2008,
<http://www.ops.ietf.org/lists/rrg/2008/msg00716.html>.
[TIDR_and_LISP]
Adan, J., "LISP etc architecture", December 2007,
<http://www.ops.ietf.org/lists/rrg/2007/msg00902.html>.
[TIDR_identifiers]
Adan, J., "TIDR using the IDENTIFIERS attribute",
April 2007, <http://www.ietf.org/mail-archive/web/ram/
current/msg01308.html>.
[VET] Templin, F., "Virtual Enterprise Traversal (VET)", Work
in Progress, January 2011.
[Valiant] Zhang-Shen, R. and N. McKeown, "Designing a Predictable
Internet Backbone Network", November 2004, <http://
conferences.sigcomm.org/hotnets/2004/
HotNets-III%20Proceedings/zhang-shen.pdf>.
[hIPv4] Frejborg, P., "Hierarchical IPv4 Framework", Work
in Progress, October 2010.
Li Informational [Page 72]
RFC 6115 RRG Recommendation February 2011
Author's Address
Tony Li (editor)
Cisco Systems
170 West Tasman Dr.
San Jose, CA 95134
USA
Phone: +1 408 853 9317
EMail: tony.li@tony.li
Li Informational [Page 73]