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Versions: 00 draft-ietf-trill-rbridge-vlan-mapping

TRILL Working Group                                        Radia Perlman
INTERNET-DRAFT                                          Sun Microsystems
Intended status: Proposed Standard                           Dinesh Dutt
                                                     Donald Eastlake 3rd
                                                    Eastlake Enterprises
Expires: April 2009                                         October 2008

                          RBridge VLAN Mapping
                          ------- ---- -------

Status of This Document

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   Some bridge products perform a feature known as "VLAN mapping", in
   which a bridge translates a data frame's VLAN ID from one VLAN to
   another when it forwards a frame from one port to another. This
   feature facilitates scenarios such as combining two bridged LANs with
   overlapping VLAN IDs into one bridged LAN without merging two
   communities just because they have been given the same VLAN ID in the
   original two clouds. This document describes how RBridges can achieve
   the same functionality.

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Table of Contents

      Status of This Document....................................1

      1. Introduction............................................3
      1.1 Terminology............................................4

      2. Internal RBridges and VLAN Mapping......................5
      3. Configuration of Cut Set VLAN Mapping RBridges..........5
      4. Advertisement of VLAN Mappings..........................5
      5. Translation of VLAN IDs by Cut Set RBridges.............6
      6. Reporting Attached VLANs by Cut Set RBridges in LSPs....6
      7. Advertising of Multicast Groups by Cut Set RBridges.....6
      8. Endnode Advertisements by cut set RBridges..............7

      9. IANA Considerations.....................................8
      10. Security Considerations................................8
      11. Normative References...................................9
      12. Informative References.................................9

      Copyright, Disclaimer, and Additional IPR Provisions......10
      Authors Addresses.........................................11

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1. Introduction

   Bridges perform a feature known as "VLAN mapping", in which two or
   more layer 2 clouds are connected together using a set of bridges,
   but in which the VLAN IDs are not consistent in the different clouds.

   The set of bridges interconnecting the clouds are known as the "cut
   set", meaning that if that set of bridges are removed, the clouds are

   Bridges in the cut set are configured to translate some set of VLAN
   IDs in one cloud to different VLAN IDs when forwarding from one cloud
   to the other.

   One reason to do this is to intentionally not merge VLAN-A endnodes
   in one layer 2 cloud with the community of VLAN-A endnodes in the
   other cloud.

   Another reason to do this is to intentionally merge two communities,
   marked with different VLAN IDs in the different clouds.

   This feature is accomplished with bridges solely by configuring
   bridges on the cut set.

   This document explains how to accomplish the same functionality with
   RBridges.  In this document we will assume there are two clouds
   "East" and "West", and RBridges RB1, RB2, and RB3 that interconnect
   the two clouds.

          .   .   .         +-----+            .   .   .
        .   .   . + - - - - + RB1 + - - - - +    .   .   .
      .   W   .             +-----+            .   . E .
        . e .   .                                .   a   .
      .   s   .             +-----+                . s .   .
        . t .   .+ - - - - -+ RB2 + - - - - - - +.   t   .
      .   .   .            -+-+---+                .   .   .
        . C .   .        /    |      _ _ _ _ _ _+.   C   .   .
          l   .  + - - -      |    /               . l .   .
        . o .   .           +-+---+              .   o   .   .
          u   .   .+ - - - -+ RB3 + - - - - - - - +. u .   .
        . d .   .           +-----+                  d   .   .
      .   .   .   .                                .   .   .

   We will refer to RBridges other than the cut set of RBridges as
   "internal RBridges".

   General familiarity with the base TRILL protocol [RFCtrill] is
   assumed in this document.

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1.1 Terminology

   The same terminology and acronyms are used in this document as in

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

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2. Internal RBridges and VLAN Mapping

   Internal RBridges will not be aware that VLAN mapping is going on.
   They will behave exactly as they would without VLAN mapping.  The
   only evidence they will have of VLAN mapping is the existence of an
   optional TLV field that a cut set RBridge, RB1, MAY include in its
   LSP, listing the VLAN mappings that RB1 is configured to be

   Internal RBridges will ignore this field. It is only there for
   detection of misconfiguration.

3. Configuration of Cut Set VLAN Mapping RBridges

   If VLAN A in cloud "East" is to be translated into VLAN B in cloud
   "West", a cut set RBridge RB1 must be configured, for each port, as
   to whether that port is in East or West, and configured with VLAN
   mappings, such as:

      "East/VLAN A <----> West/VLAN B"

   That mapping means that when RB1 forwards a frame on a port
   configured to be in East to a port configured to be in West, with the
   VLAN tag of A, it replaces the VLAN tag "A" with "B" in the inner
   encapsulated frame.

   Note that mappings are always symmetric, meaning that if RB1 is
   translating tag "VLAN A" to tag "VLAN B" when forwarding from East to
   West, it will translate tag "VLAN B" to tag "VLAN A" when forwarding
   from West to East.

4. Advertisement of VLAN Mappings

   To detect misconfiguration, a cut set RBridge RB1 MAY advertise its
   VLAN mappings. This would be done by assigning IDs to each of the
   clouds. All cut set RBridges SHOULD be configured with the same IDs
   for the clouds.  So, in our example, if "East" is "1" and "West" is
   "2", and VLAN A in East is mapped to VLAN B in West, the TLV would
   report a set of mappings, including:


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5. Translation of VLAN IDs by Cut Set RBridges

   If RB1 is configured to believe port a is in "East" and port b is in
   "West", and RB1 is configured such that "East/VLAN A <----> West/VLAN
   B", then when RB1 forwards a data frame from port a to port b, if the
   received frame from port a has (inner header VLAN ID) VLAN x , then
   RB1 changes the VLAN tag from VLAN A to VLAN B as it forwards onto
   port b.

   Note: This is true whether RB1 is the appointed forwarder on port a
   for VLAN x and the frame arrives unencapsulated, or whether the frame
   has arrived already encapsulated as a VLAN A frame.

   Likewise, RB1 performs the same VLAN translation whether the frame is
   unicast or multicast.

6. Reporting Attached VLANs by Cut Set RBridges in LSPs

   If RB1 is configured to translate VLAN A to VLAN B, then RB1 reports,
   in its LSP, that it is connected to both VLAN A and VLAN B, even if
   RB1 is not appointed forwarder for either or both VLAN A or VLAN B.

   The reason RB1 must claim to be attached to VLAN A and VLAN B is so
   that multicast data frames for VLAN A originating in West will not
   get filtered before reaching RB1, and multicast data frames for VLAN
   B originating in East will also not get prematurely filtered.

7. Advertising of Multicast Groups by Cut Set RBridges

   If RB1 is configured to translate VLAN A in East to VLAN B in West,
   then RB1 MUST do one of the following, in order to ensure that a
   multicast packet for group G in VLAN A will not be filtered inside
   the West cloud, if there are receivers for (VLAN A, group G) in East.
   If the cut set RBridges do nothing, then a multicast for VLAN B,
   group G would be filtered inside the West cloud, since RBridges
   inside the East cloud will only be requesting receipt of VLAN A,
   group G.

   Thus, RB1 MUST do one of the following for each mapped VLAN. It may
   use different strategies for different VLANs.

   a) for all IP-derived multicast addresses that have been requested by
      any RBridges in East for VLAN A, RB1 reports connectivity to those
      multicast addresses in VLAN B. Likewise, for all IP-derived
      multicast addresses that have been requested by any RBridges in
      West for VLAN B, RB1 reports connectivity to those multicast

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      addresses in VLAN A.

   b) RB1 reports connectivity to an IPv4 multicast router and an IPv6
      multicast router.

8. Endnode Advertisements by cut set RBridges

   TRILL allows RBridges to optionally advertise attached endnodes. This
   endnode advertisement protocol uses special instances of IS-IS known
   as ESADI (End System Address Distribution Instance).

   If cut set RBridge RB1 is translating VLAN A (in East) to VLAN B (in
   West), and RB1 is doing ESADI for its attached endnodes in VLAN A, it
   should transmit the ESADI advertisement tagged with VLAN A when
   forwarding onto ports labeled as "East", and transmit the same ESADI
   advertisement when forwarding onto ports labeled as "West". An East
   VLAN-A ESADI generated by any RBridge in East will automatically get
   translated into a VLAN B ESADI when forwarding into West, because
   ESADIs are handled just like ordinary encapsulated data frames, the
   VLAN tag to which the ESADI belongs is the VLAN tag on the inner data
   frame, and that VLAN tag will be translated by (properly configured)
   cut set RBridges when forwarding between East and West.

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9. IANA Considerations

   This document requires no IANA actions. This section should be
   deleted by the RFC Editor on publication.

10. Security Considerations

   See [RFCtrill] for general RBridge Security Considerations.

   If cut set RBridges have misconfigured VLAN mappings, VLANs may be
   inadvertently partitioned or inadvertently merged and frames may be
   delivered in the wrong VLAN. However, misconfiguration of VLAN
   mapping will not cause loops.

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11. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
      Requirement Levels", BCP 14, RFC 2119, March 1997

   [RFCtrill] R. Perlman, D. Eastlake, D. Dutt, S. Gai, and A. Ghanwani,
      draft-ietf-trill-rbridge-protocol-09.txt, work in progress.

12. Informative References


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Copyright, Disclaimer, and Additional IPR Provisions

   Copyright (C) The IETF Trust 2008.  This document is subject to the
   rights, licenses and restrictions contained in BCP 78, and except as
   set forth therein, the authors retain all their rights.

   This document and the information contained herein are provided on an

   The IETF takes no position regarding the validity or scope of any
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   The IETF invites any interested party to bring to its attention any
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Authors Addresses

   Radia Perlman
   Sun Microsystems
   16 Network Circle
   Menlo Park, CA 94025

   Phone: +1-650-960-1300
   Email: Radia.Perlman@sun.com

   Dinesh G. Dutt
   Cisco Systems
   170 Tasman Drive
   San Jose, CA 95134-1706 USA

   Phone: +1-408-527-0955
   EMail: ddutt@cisco.com

   Donald Eastlake 3rd
   Eastlake Enterprises
   155 Beaver Street
   Milford, MA 01757

   Tel:   +1-508-634-2066
   Email: d3e3e3@gmail.com

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