Advertising Layer 2 Bundle Member Link Attributes in IS-IS
RFC 8668
Internet Engineering Task Force (IETF) L. Ginsberg, Ed.
Request for Comments: 8668 Cisco Systems, Inc.
Category: Standards Track A. Bashandy
ISSN: 2070-1721 Unaffiliated
C. Filsfils
Cisco Systems, Inc.
M. Nanduri
Oracle
E. Aries
Arrcus Inc.
December 2019
Advertising Layer 2 Bundle Member Link Attributes in IS-IS
Abstract
There are deployments where the Layer 3 interface on which IS-IS
operates is a Layer 2 interface bundle. Existing IS-IS
advertisements only support advertising link attributes of the Layer
3 interface. If entities external to IS-IS wish to control traffic
flows on the individual physical links that comprise the Layer 2
interface bundle, link attribute information about the bundle members
is required.
This document introduces the ability for IS-IS to advertise the link
attributes of Layer 2 (L2) Bundle Members.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8668.
Copyright Notice
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Table of Contents
1. Introduction
2. Requirements Language
3. L2 Bundle Member Attributes TLV
3.1. Parallel L3 Adjacencies
3.2. Shared Attribute Sub-TLVs
4. Advertising L2 Bundle Member Adj-SIDs
4.1. L2 Bundle Member Adjacency Segment Identifier Sub-TLV
4.2. L2 Bundle Member LAN Adjacency SID Sub-TLV
5. IANA Considerations
6. Security Considerations
7. References
7.1. Normative References
7.2. Informative References
Appendix A. Example Encoding
Acknowledgements
Contributors
Authors' Addresses
1. Introduction
There are deployments where the Layer 3 interface on which an IS-IS
adjacency is established is a Layer 2 interface bundle, for instance,
a Link Aggregation Group (LAG) [IEEE802.1AX]. This reduces the
number of adjacencies that need to be maintained by the routing
protocol in cases where there are parallel links between the
neighbors. Entities external to IS-IS such as Path Computation
Elements (PCEs) [RFC4655] may wish to control traffic flows on
individual members of the underlying Layer 2 bundle. In order to do
so, link attribute information about individual bundle members is
required. The protocol extensions defined in this document provide
the means to advertise this information.
This document introduces a new TLV to advertise link attribute
information for each of the L2 Bundle Members that comprise the Layer
3 interface on which IS-IS operates.
[RFC8667] introduces a new link attribute, adjacency segment
identifier (Adj-SID), which can be used as an instruction to
forwarding to send traffic over a specific link. This document
introduces additional sub-TLVs to advertise Adj-SIDs for L2 Bundle
Members.
Note that the new advertisements defined in this document are
intended to be provided to external (to IS-IS) entities. The
following items are intentionally not defined and/or are outside the
scope of this document:
* What link attributes will be advertised. This is determined by
the needs of the external entities.
* A minimum or default set of link attributes.
* How these attributes are configured.
* How the advertisements are used.
* What impact the use of these advertisements may have on traffic
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