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BGP Extra Extended Community
draft-heitz-idr-extra-extended-community-00

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Jakob Heitz , Ali Sajassi , Ignas Bagdonas
Last updated 2018-03-05
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draft-heitz-idr-extra-extended-community-00
IDR                                                             J. Heitz
Internet-Draft                                                A. Sajassi
Updates: 4684 (if approved)                                        Cisco
Intended status: Standards Track                             I. Bagdonas
Expires: September 6, 2018                                       Equinix
                                                           March 5, 2018

                      BGP Extra Extended Community
              draft-heitz-idr-extra-extended-community-00

Abstract

   Auto-derived identifiers are used by applications to enable zero
   configuration features.  Such identifiers are often a combination of
   primitive identifiers and are thus longer.  In addition, existing
   identifiers have grown longer.  IP addresses have grown from 4 octets
   to 16.  AS numbers have grown from 2 octets to 4.  In order to
   accommodate such longer identifiers in BGP extended communities, this
   document defines a new BGP path attribute, the Extra Extended
   Communities attribute.  It is similar to the Extended Community, but
   is 24 octets long.  Communities are mostly used within ASes under a
   single administration or between neighboring ASes.  Limiting the
   spread of communities beyond their intended reach and polluting the
   internet at large is complex and error prone.  To simplify this,
   enhanced transitivity options are provided.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

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   This Internet-Draft will expire on September 6, 2018.

Copyright Notice

   Copyright (c) 2018 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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  BGP Extra Extended Community Attribute  . . . . . . . . . . .   3
   3.  Transitivity  . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Capability  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Constrained Route Distribution  . . . . . . . . . . . . . . .   5
   6.  IPv6-Address-Specific Extra Extended Community type . . . . .   5
   7.  IPv4-Address-Specific Extra Extended Community type . . . . .   6
   8.  AS-Specific Extra Extended Community type . . . . . . . . . .   7
   9.  EVPN Extra Extended Community type  . . . . . . . . . . . . .   8
   10. EVPN ES-Import Route Target Extra Extended Community sub-type   9
   11. EVPN ESI-EVI Route Target Extra Extended Community sub-type .  10
   12. EVPN Overlay Route Target Extra Extended Community sub-type .  10
   13. Auto-derivation of EVPN RT-XXC  . . . . . . . . . . . . . . .  12
   14. Error Handling  . . . . . . . . . . . . . . . . . . . . . . .  12
   15. Security Considerations . . . . . . . . . . . . . . . . . . .  13
   16. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     16.1.  Registry: BGP Extra Extended Community Types . . . . . .  13
     16.2.  Registry: IPv6-Address-Specific Extra Extended Community
            Sub-Types  . . . . . . . . . . . . . . . . . . . . . . .  14
     16.3.  Registry: IPv4-Address-Specific Extra Extended Community
            Sub-Types  . . . . . . . . . . . . . . . . . . . . . . .  14
     16.4.  Registry: AS-Specific Extra Extended Community Sub-Types  14
     16.5.  Registry: EVPN Extra Extended Community Sub-Types  . . .  14
   17. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     17.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     17.2.  Informative References . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

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1.  Introduction

   A BGP Extended Community attribute is defined that encodes 24 octet
   communities.  It is similar to the Extended Communities attribute
   defined in [RFC4360], but larger.  To simplify the IANA registries,
   the transitivity of a Extra Extended Community is not part of the
   IANA registered type.  Any type can be encoded with any transitivity.
   BGP autonomous system (AS) relationships have become more complex.
   Several contiguous ASes may be under a common administration.  A
   transitivity is defined that allows a XXC to be sent among these ASes
   only.  Some XXCs may be required to be transferred only between
   neighboring ASes, even though they are under a different
   administration.  A transitivity type to allow this is defined.  Up to
   now, the range of ASes among which a community is distributed is
   enforced by routing policies.  These policies are sometimes executed
   in the receiving AS, not under the control of the sending AS.  The
   enhanced transitivity options offerend in this document will simplify
   policies that are used to distribute communities.

2.  BGP Extra Extended Community Attribute

   The Extra Extended Communities Attribute is a transitive optional BGP
   attribute, with the Type Code [to be assigned by IANA].  The
   attribute consists of a set of "Extra Extended Communities" (XXC).

   Each XXC is encoded as a 24-octet quantity, as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |    Type   |    Sub-Type   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+          Value                +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The fields are as shown below:

        T -          Transitivity field (2 bits).  This is further
                     described below.

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        Type -       6 bits.  IANA will maintain a registry of types.
                     Four types are described in this document.

        Sub-type -   8 bits.  IANA will maintain a registry of sub-types
                     for each registered type.  All even numbered Sub-
                     Types are a route target.

        Value -      The actual information according to the type and
                     sub-type.

3.  Transitivity

   The transitivity field determines how BGP speakers transfer the XXC
   across real Autonomous System (AS) boundaries.  The XXC is always
   transitive between Member-ASes in an AS confederation [RFC5065].  The
   values are:

        0 -  The XXC is transitive across ASes.

        1 -  The XXC is not transitive across ASes.

        2 -  The XXC is transitive across ASes under the same
             administration only.

        3 -  The XXC is transitive across ASes under the same
             administration and into an AS under the neighboring
             administration, but not into an AS under a further
             administration.

   To be not transitive means that a receiving BGP speaker MUST silently
   discard the community by default and a sending speaker MUST not send
   the community by default.  A speaker MAY send or receive a non-
   transitive XXC if explicitly configured to do so..

   A single administration may own a multitude of contiguous ASes.  XXCs
   with transitivity types 2 and 3 are transitive between these ASes.
   If a BGP neighbor session is to a speaker in the same administration,
   it needs a booelan configuration to indicate that.  Without this
   configuration, an EBGP BGP neighbor is assumed to be under a
   different administration.

   A BGP speaker that receives a XXC with transitivity 3 from a neighbor
   in an AS under a different administration MUST change the
   transitivity field of the XXC to 2.  As an exception, a route server
   as defined in [RFC7947] SHOULD NOT change the transitivity field.

   The Transitivity field is not implicitly associated with the Type and
   Sub-Type fields the way they are in Extended Communities.  The

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   Transitivity field should be set by the originator based upon
   individual circumstances at the originator.  The transitivity is not
   assigned by IANA.

4.  Capability

   BGP speakers that do not implement Extra Extended Communities will
   transfer XXCs even though they may not be transitive across their AS
   boundaries.  To prevent this, a BGP capability as defined in
   [RFC5492] is required.  The length of the capability is 0.  A BGP
   speaker MUST NOT by default send a XXC, the transitivity of which is
   not 0, to a speaker that has not sent the Extra Extended Community
   Capability in its OPEN message.  A BGP speaker MUST withdraw a route
   from a neighbor if that neighbor does not advertise this capability
   and the route contanis an XXC unless it is known that announcing the
   route will cause no adverse effects.  An example of where no adverse
   effects occur is when the neighbor is a route reflector that does not
   forward traffic and all the route reflector clients support XXC.

5.  Constrained Route Distribution

   [RFC4684] defines Constrained Route Distribution.  That document is
   updated as follows:

   The maximum prefix size is modified from 96 bits to 224 bits.

   Route targets can be expressed as prefixes, where, for instance, a
   prefix would encompass all route target extended communities assigned
   by a given Global Administrator.  Route Target prefixes can be
   aggregated.  However if done so, then Route Target Type, Sub-Type and
   the Global Administrator Route Target fields MUST NOT be aggregated.

   The Extra Extended Community capability in combination with the
   capability of the Constrained Route Distribution Address Family
   indicates the ability to use the longer RT Constraint prefix
   described herein.

6.  IPv6-Address-Specific Extra Extended Community type

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     0     |    Sub-Type   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   +                                                               +
   |                      Global Administrator                     |
   +                                                               +
   |                                                               |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                      Local Administrator                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 0.  The Sub-Type is to be assigned by IANA for
   individual functions.

   The Value field consists of 2 sub-fields:

      Global Administrator sub-field: 16 octets

         This sub-field contains an IPv6 unicast address assigned by one
         of the Internet registries.

      Local Administrator sub-field: 6 octets

         The organization identified by the IP address in the Global
         Administrator sub-field can encode any information in this sub-
         field.  The format and meaning of the value encoded in this
         sub-field should be defined by the sub-type of the XXC.

7.  IPv4-Address-Specific Extra Extended Community type

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     1     |    Sub-Type   |    Global Administrator       :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :  Global Administrator (cont.) |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   +                                                               +
   |                      Local Administrator                      |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 1.  The Sub-Type is to be assigned by IANA for
   individual functions.

   The Value field consists of 2 sub-fields:

      Global Administrator sub-field: 4 octets

         This sub-field contains an IPv4 unicast address assigned by one
         of the Internet registries.

      Local Administrator sub-field: 18 octets

         The organization identified by the IP address in the Global
         Administrator sub-field can encode any information in this sub-
         field.  The format and meaning of the value encoded in this
         sub-field should be defined by the sub-type of the XXC.

8.  AS-Specific Extra Extended Community type

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     2     |    Sub-Type   |    Global Administrator       :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :  Global Administrator (cont.) |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                      Local Administrator                      |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 2.  The Sub-Type is to be assigned by IANA for
   individual functions.

   The Value field consists of 2 sub-fields:

      Global Administrator sub-field: 4 octets

         This sub-field contains a 4-octet Autonomous System number
         assigned by IANA.  Note that an ASN that is less than 65536 in
         value is represented in 4 octets by setting the higher two
         octets to 0.

      Local Administrator sub-field: 18 octets

         The organization identified by the Autonomous System number in
         the Global Administrator sub-field can encode any information
         in this sub-field.  The format and meaning of the value encoded
         in this sub-field should be defined by the sub-type of the XXC.

9.  EVPN Extra Extended Community type

   This is a Extra Extended Community type with a Value field comprising
   22 octets.

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     6     |    Sub-Type   |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+         Value                 +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 6.  The Sub-Type is to be assigned by IANA for
   individual functions.  Three functions are defined in this document.

10.  EVPN ES-Import Route Target Extra Extended Community sub-type

   The ES-Import Route Target as specified in [RFC7432] Sec. 7.6 limits
   the ESI to 6 octets.  Thus it cannot be automatically derived for all
   ESI types.  This ES-Import RT-XXC allows the use of the full 10
   octets of ESI.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     6     |       2       |              GA               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :            GA (Cont.)         |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                              Zero                             |
   +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   +                              ESI                              +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 6.  The Sub-Type is 2.  The fields are as follows:

      GA         - 4 octets.  Global Administrator.  This is the
                   Autonomous System Number of the AS where this RT is
                   assigned.

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      Zero       - 8 octets filled with 0.  Must be ignored by the
                   receiver.

      ESI        - 10 octets.  Ethernet Segment Identifier.

11.  EVPN ESI-EVI Route Target Extra Extended Community sub-type

   The ESI-EVI Route Target is used in EVPN route types 7 and 8 to
   filter routes by both ESI and Ethernet Tag ID.  More details are in
   [I-D.ietf-bess-evpn-igmp-mld-proxy].

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     6     |       4       |              GA               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :            GA (Cont.)         |             Zero              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Zero             |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
   |                                                               |
   +                              ESI                              +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                              EVI                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 6.  The Sub-Type is 4.  The fields are as follows:

      GA         - 4 octets.  Global Administrator.  This is the
                   Autonomous System Number of the AS where this RT is
                   assigned.

      Zero       - 4 octets filled with 0.  Must be ignored by the
                   receiver.

      ESI        - 10 octets.  Ethernet Segment Identifier.

      EVI        - 4 octets.  Ethernet Tag ID.

12.  EVPN Overlay Route Target Extra Extended Community sub-type

   This EVPN Overlay Route Target Extra Extended Community type is used
   to filter routes based upon the identifier used in the specified
   overlay protocol.  More details are in [I-D.ietf-bess-evpn-overlay].

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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | T |     6     |       6       |              GA               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :            GA (Cont.)         |A|   Space     |    Domain     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                                                               |
   +                                                               +
   |                           Service-ID                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The Type field is 6.  The Sub-Type is 6.  The fields are as follows:

      GA         - 4 octets.  Global Administrator.  This is the
                   Autonomous System Number of the AS where this RT is
                   assigned.

      A         -  A single bit indicating if this RT is auto-derived

                              0 : auto-derived

                              1 : manually derived

      Space      - 7 bits.  The identifier space appropriate to the
                   service.  The following spaces are defined:

                              0 : VID (802.1Q VLAN ID)

                              1 : VXLAN

                              2 : NVGRE

                              3 : I-SID

                              4 : EVI

                              5 : dual-VID (QinQ VLAN ID)

      Domain     - 1 octet.  The default value of domain-id is zero
                   indicating that only a single numbering space exists
                   for a given technology.  However, if there is more
                   than one number space for a given technology (e.g.,
                   overlapping VXLAN spaces), then each of the number

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                   spaces need to be identified by their corresponding
                   domain-id starting from 1.

      Service-ID - 16 octets.  VNI, VSID, I-SID, VID or other identifier
                   as appropriate for the service specified in the Space
                   field.  If the contained identifier is less than 16
                   octets long, then it is placed in the least
                   significant octets of the Service-ID field with the
                   higher octets being filled with 0.

13.  Auto-derivation of EVPN RT-XXC

   Auto-derivation of EVPN Route Targets is described in [RFC7432] Sec.
   7.10.1.  Because of the limited size of Route Targets using Extended
   Communities, the auto-derivation is limited to using the 12 bit VLAN
   ID.  With the larger size of the RT-XXC, the complete 32 bits of the
   Ethernet Tag ID can be used.

   The EVPN RT-XXC can use all the RT-XXC types: AS-Specific, IPv4-
   Address-Specific and IPv6-Address-Specific.  In each case, the
   Ethernet Tag ID is placed into the least significant octets of the
   Local Administrator field.  The remaining higher order bits of the
   Local Administrator field are used as a discriminator as follows.
   The numerical value of the Ethernet Tag ID may be the same as a value
   that a different protocol may be using to create RT-XXCs of the same
   Type and Sub-Type.  EVPN needs to use a value of the discriminator
   such as not to cause value collisions with other protocols that are
   auto-deriving route targets in the same Global Administrator.

14.  Error Handling

   A BGP Extra Extended Communities attribute SHALL be considered
   malformed if the length of the BGP Extra Extended Communities
   Attribute value, expressed in octets, is not a non-zero multiple of
   24.  The error SHALL be handled using the approach of "treat-as-
   withdraw" as described in Section 2 of [RFC7606].

   The order in which the XXCs appear in the XXC attribute is not
   significant.  It is not an error for a BGP speaker to propagate a set
   of XXCs in a different order than in which they were received.

   A BGP speaker SHOULD NOT send a duplicate XXC.  However, this is not
   an error, but merely suboptimal.  The duplication of a XXC has no
   meaning.  A receiver of a duplicate XXC SHOULD silently discard the
   duplicate.  The duplication of a XXC cannot be used to compound its
   effect.  For example if one XXC causes the local preference to be
   incremented by 5, the presence of two of the same XXC will not
   increment the LP by 10.  OTOH, if one XXC increments the LP by 5 and

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   a different XXC increments it by 10, then the combination will cause
   an increment of 15.

   A BGP speaker MAY send XXCs that are duplictes except for the
   transitivity field.  Receipt of such duplicates MUST be treated as
   receipt of distinct XXCs.  While it makes little sense for a BGP
   speaker to originate such duplicates, this duplication may occur when
   XXCs from different received routes are aggregated.  In any case, the
   same kind of duplication is allowed in legacy Extended Communities.

   If a field in a specific type of XXC is invalid in another setting,
   it is not by default to be considered invalid in a XXC.  For example,
   0 is an invalid AS number when used in an AS path attribute.  That
   does not make it invalid as an ASN in the AS-Specific XXC.  The
   behavior and validity of fields in XXCs are to be defined by a
   specification of the specific type and sub-type of the XXC.

15.  Security Considerations

   TBD

16.  IANA Considerations

   IANA is requested to assign a BGP path attribute value for the Extra
   Extended Community attribute.

   IANA is requested to create and maintain registries as detailed in
   the following sections.  For each registry, the allocation policies
   as per [RFC8126] are stated for the ranges of values and some values
   are allocated by this document.

16.1.  Registry: BGP Extra Extended Community Types

         Range      Allocation Policy
         ---------  ------------------------------
          0-31      First Come First Served
         32-47      Experimental
         48-63      Standards Action

         Value      Description                     Reference
         ---------  ------------------------------  ---------
         0          IPv6-Address-Specific           This RFC
         1          IPv4-Address-Specific           This RFC
         2          AS-Specific                     This RFC
         6          EVPN                            This RFC

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16.2.  Registry: IPv6-Address-Specific Extra Extended Community Sub-
       Types

         Range      Allocation Policy
         ---------  ------------------------------
           0-191    First Come First Served
         192-255    IETF Review

         Value      Description                     Reference
         ---------  ------------------------------  ---------
         2          Route Target                    RFC4360

16.3.  Registry: IPv4-Address-Specific Extra Extended Community Sub-
       Types

         Range      Allocation Policy
         ---------  ------------------------------
           0-191    First Come First Served
         192-255    IETF Review

         Value      Description                     Reference
         ---------  ------------------------------  ---------
         2          Route Target                    RFC4360

16.4.  Registry: AS-Specific Extra Extended Community Sub-Types

         Range      Allocation Policy
         ---------  ------------------------------
           0-191    First Come First Served
         192-255    IETF Review

         Value      Description                     Reference
         ---------  ------------------------------  ---------
         2          Route Target                    RFC4360

16.5.  Registry: EVPN Extra Extended Community Sub-Types

         Range      Allocation Policy
         ---------  ------------------------------
           0-191    First Come First Served
         192-255    IETF Review

         Value      Description                     Reference
         ---------  ------------------------------  ---------
         2          EVPN ES-Import Route Target     This RFC
         4          EVPN ESI-EVI Route Target       This RFC
         6          EVPN Overlay Route Target       This RFC

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17.  References

17.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <https://www.rfc-editor.org/info/rfc4360>.

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684,
              November 2006, <https://www.rfc-editor.org/info/rfc4684>.

   [RFC5065]  Traina, P., McPherson, D., and J. Scudder, "Autonomous
              System Confederations for BGP", RFC 5065,
              DOI 10.17487/RFC5065, August 2007,
              <https://www.rfc-editor.org/info/rfc5065>.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <https://www.rfc-editor.org/info/rfc5492>.

   [RFC7432]  Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
              Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
              Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
              2015, <https://www.rfc-editor.org/info/rfc7432>.

   [RFC7606]  Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
              Patel, "Revised Error Handling for BGP UPDATE Messages",
              RFC 7606, DOI 10.17487/RFC7606, August 2015,
              <https://www.rfc-editor.org/info/rfc7606>.

   [RFC7947]  Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
              "Internet Exchange BGP Route Server", RFC 7947,
              DOI 10.17487/RFC7947, September 2016,
              <https://www.rfc-editor.org/info/rfc7947>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

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17.2.  Informative References

   [I-D.ietf-bess-evpn-igmp-mld-proxy]
              Sajassi, A., Thoria, S., Patel, K., Yeung, D., Drake, J.,
              and W. Lin, "IGMP and MLD Proxy for EVPN", draft-ietf-
              bess-evpn-igmp-mld-proxy-00 (work in progress), March
              2017.

   [I-D.ietf-bess-evpn-overlay]
              Sajassi, A., Drake, J., Bitar, N., Shekhar, R., Uttaro,
              J., and W. Henderickx, "A Network Virtualization Overlay
              Solution using EVPN", draft-ietf-bess-evpn-overlay-12
              (work in progress), February 2018.

Authors' Addresses

   Jakob Heitz
   Cisco
   170 West Tasman Drive
   San Jose, CA, CA  95054
   USA

   Email: jheitz@cisco.com

   Ali Sajassi
   Cisco
   170 West Tasman Drive
   San Jose, CA, CA  95134
   USA

   Email: sajassi@cisco.com

   Ignas Bagdonas
   Equinix
   London
   UK

   Email: ibagdona.ietf@gmail.com

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