Alternatives for Multilevel Transparent Interconnection of Lots of Links (TRILL)
RFC 8243

Document Type RFC - Informational (September 2017; No errata)
Last updated 2017-09-10
Replaces draft-perlman-trill-rbridge-multilevel
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Document shepherd Susan Hares
Shepherd write-up Show (last changed 2016-08-28)
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Internet Engineering Task Force (IETF)                        R. Perlman
Request for Comments: 8243                                           EMC
Category: Informational                                  D. Eastlake 3rd
ISSN: 2070-1721                                                 M. Zhang
                                                                  Huawei
                                                             A. Ghanwani
                                                                    Dell
                                                                 H. Zhai
                                                                     JIT
                                                          September 2017

                      Alternatives for Multilevel
          Transparent Interconnection of Lots of Links (TRILL)

Abstract

   Although TRILL is based on IS-IS, which supports multilevel unicast
   routing, extending TRILL to multiple levels has challenges that are
   not addressed by the already-existing capabilities of IS-IS.  One
   issue is with the handling of multi-destination packet distribution
   trees.  Other issues are with TRILL switch nicknames.  How are such
   nicknames allocated across a multilevel TRILL network?  Do nicknames
   need to be unique across an entire multilevel TRILL network?  Or can
   they merely be unique within each multilevel area?

   This informational document enumerates and examines alternatives
   based on a number of factors including backward compatibility,
   simplicity, and scalability; it makes recommendations in some cases.

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 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).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see 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/rfc8243.

Perlman, et al.               Informational                     [Page 1]
RFC 8243              Multilevel TRILL Alternatives       September 2017

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Perlman, et al.               Informational                     [Page 2]
RFC 8243              Multilevel TRILL Alternatives       September 2017

Table of Contents

   1. Introduction ....................................................4
      1.1. The Motivation for Multilevel ..............................4
      1.2. Improvements Due to Multilevel .............................5
           1.2.1. The Routing Computation Load ........................5
           1.2.2. LSDB Volatility Creating Too Much Control Traffic ...5
           1.2.3. LSDB Volatility Causing Too Much Time Unconverged ...6
           1.2.4. The Size of the LSDB ................................6
           1.2.5. Nickname Limit ......................................6
           1.2.6. Multi-Destination Traffic ...........................7
      1.3. Unique and Aggregated Nicknames ............................7
      1.4. More on Areas ..............................................8
      1.5. Terminology and Abbreviations ..............................9
   2. Multilevel TRILL Issues ........................................10
      2.1. Non-Zero Area Addresses ...................................11
      2.2. Aggregated versus Unique Nicknames ........................12
           2.2.1. More Details on Unique Nicknames ...................12
           2.2.2. More Details on Aggregated Nicknames ...............13
      2.3. Building Multi-Area Trees .................................18
      2.4. The RPF Check for Trees ...................................18
      2.5. Area Nickname Acquisition .................................19
      2.6. Link State Representation of Areas ........................19
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