Alternatives for Multilevel TRILL (Transparent Interconnection of Lots of Links)
draft-perlman-trill-rbridge-multilevel-10

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TRILL Working Group                                        Radia Perlman
INTERNET-DRAFT                                                       EMC
Intended status: Informational                           Donald Eastlake
                                                            Mingui Zhang
                                                                  Huawei
                                                          Anoop Ghanwani
                                                                    Dell
                                                            Hongjun Zhai
                                                                     JIT
Expires: January 4, 2016                                    July 5, 2015

                   Alternatives for Multilevel TRILL
             (Transparent Interconnection of Lots of Links)
            <draft-perlman-trill-rbridge-multilevel-10.txt>

Abstract

   Extending TRILL to multiple levels has challenges that are not
   addressed by the already-existing capability of IS-IS to have
   multiple levels.  One issue is with the handling of multi-destination
   packet distribution trees. Another issue is with TRILL switch
   nicknames.  There have been two proposed approaches.  One approach,
   which we refer to as the "unique nickname" approach, gives unique
   nicknames to all the TRILL switches in the multilevel campus, either
   by having the level-1/level-2 border TRILL switches advertise which
   nicknames are not available for assignment in the area, or by
   partitioning the 16-bit nickname into an "area" field and a "nickname
   inside the area" field.  The other approach, which we refer to as the
   "aggregated nickname" approach, involves hiding the nicknames within
   areas, allowing nicknames to be reused in different areas, by having
   the border TRILL switches rewrite the nickname fields when entering
   or leaving an area. Each of those approaches has advantages and
   disadvantages. This informational document suggests allowing a choice
   of approach in each area. This allows the simplicity of the unique
   nickname approach in installations in which there is no danger of
   running out of nicknames and allows the complexity of hiding the
   nicknames in an area to be phased into larger installations on a per-
   area basis.

Status of This Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  Distribution of this document is
   unlimited.  Comments should be sent to the TRILL working group
   mailing list <trill@ietf.org>.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

R. Perlman, et al                                               [Page 1]
INTERNET-DRAFT                                          Multilevel TRILL

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R. Perlman, et al                                               [Page 2]
INTERNET-DRAFT                                          Multilevel TRILL

Table of Contents

      1. Introduction............................................4
      1.1 TRILL Scalability Issues...............................4
      1.2 Improvements Due to Multilevel.........................5
      1.3 Unique and Aggregated Nicknames........................6
      1.3 More on Areas..........................................6
      1.4 Terminology and Acronyms...............................7

      2. Multilevel TRILL Issues.................................8
      2.1 Non-zero Area Addresses................................9
      2.2 Aggregated versus Unique Nicknames.....................9
      2.2.1 More Details on Unique Nicknames....................10
      2.2.2 More Details on Aggregated Nicknames................11
      2.2.2.1 Border Learning Aggregated Nicknames..............12
      2.2.2.2 Swap Nickname Field Aggregated Nicknames..........14
      2.2.2.3 Comparison........................................14
      2.3 Building Multi-Area Trees.............................15
      2.4 The RPF Check for Trees...............................15
      2.5 Area Nickname Acquisition.............................16
      2.6 Link State Representation of Areas....................16
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