Advertising Layer 2 Bundle Member Link Attributes in IS-IS
RFC 8668

Document Type RFC - Proposed Standard (December 2019; No errata)
Authors Les Ginsberg  , Ahmed Bashandy  , Clarence Filsfils  , Mohan Nanduri  , Ebben Aries 
Last updated 2019-12-06
Replaces draft-ginsberg-isis-l2bundles
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Document shepherd Hannes Gredler
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IESG IESG state RFC 8668 (Proposed Standard)
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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
                                                                E. Aries
                                                             Arrcus Inc.
                                                           December 2019

       Advertising Layer 2 Bundle Member Link Attributes in IS-IS


   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

Copyright Notice

   Copyright (c) 2019 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
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  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
   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

   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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