Domain-Wide Prefix Distribution with Two-Level IS-IS
RFC 5302
| Document | Type |
RFC - Proposed Standard
(October 2008; Errata)
Obsoletes RFC 2966
Updates RFC 1195
|
|
|---|---|---|---|
| Last updated | 2020-01-21 | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized with errata bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 5302 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Ross Callon | ||
| Send notices to | (None) | ||
Network Working Group T. Li
Request for Comments: 5302 Redback Networks, Inc.
Obsoletes: 2966 H. Smit
Updates: 1195
Category: Standards Track T. Przygienda
Z2 Sagl
October 2008
Domain-Wide Prefix Distribution with Two-Level IS-IS
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Abstract
This document describes extensions to the Intermediate System to
Intermediate System (IS-IS) protocol to support optimal routing
within a two-level domain. The IS-IS protocol is specified in ISO
10589, with extensions for supporting IPv4 (Internet Protocol)
specified in RFC 1195. This document replaces RFC 2966.
This document extends the semantics presented in RFC 1195 so that a
routing domain running with both level 1 and level 2 Intermediate
Systems (IS) (routers) can distribute IP prefixes between level 1 and
level 2, and vice versa. This distribution requires certain
restrictions to ensure that persistent forwarding loops do not form.
The goal of this domain-wide prefix distribution is to increase the
granularity of the routing information within the domain.
Li, et al. Standards Track [Page 1]
RFC 5302 Domain-wide Prefix Distribution October 2008
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Motivations for Domain-Wide Prefix Distribution . . . . . 3
1.2. Scalability . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 6
2. Proposed Syntax and Semantics for L2->L1 Inter-Area Routes . . 6
2.1. Clarification of External Route-Type and External
Metric-Type . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Definition of External IP Prefixes in Level 1 LSPs . . . . 8
3. Types of IP Routes in IS-IS and Their Order of Preference . . 8
3.1. Overview of All Types of IP Prefixes in IS-IS Link
State PDUs . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Order of Preference for all Types of IP Routes in IS-IS . 11
3.3. Additional Notes on What Prefixes to Accept or
Advertise . . . . . . . . . . . . . . . . . . . . . . . . 12
4. Inter-Operability with Older Implementations . . . . . . . . . 12
5. Comparisons with Other Proposals . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1. Normative References . . . . . . . . . . . . . . . . . . . 14
7.2. Informative References . . . . . . . . . . . . . . . . . . 14
Li, et al. Standards Track [Page 2]
RFC 5302 Domain-wide Prefix Distribution October 2008
1. Introduction
This document describes extensions to the Intermediate System to
Intermediate System (IS-IS) protocol to support optimal routing
within a two-level domain. The IS-IS protocol is specified in
[ISO-10589], with extensions for supporting IPv4 (Internet Protocol)
specified in [RFC1195].
This document replaces [RFC2966], which was an Informational
document. This document is on the standards track. No other
intentional substantive changes have been made.
This document extends the semantics presented in RFC 1195 so that a
routing domain running with both level 1 and level 2 Intermediate
Systems (IS) (routers) can distribute IP prefixes between level 1 and
level 2, and vice versa. This distribution requires certain
restrictions to ensure that persistent forwarding loops do not form.
The goal of this domain-wide prefix distribution is to increase the
granularity of the routing information within the domain.
An IS-IS routing domain (a.k.a. an autonomous system running IS-IS)
can be partitioned into multiple level 1 (L1) areas, and a level 2
(L2) connected subset of the topology that interconnects all of the
L1 areas. Within each L1 area, all routers exchange link state
information. L2 routers also exchange L2 link state information to
compute routes between areas.
RFC 1195 defines the Type, Length, and Value (TLV) tuples that are
used to transport IPv4 routing information in IS-IS. RFC 1195 also
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