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rfc:rfc7902

Internet Engineering Task Force (IETF) E. Rosen Request for Comments: 7902 Juniper Networks, Inc. Updates: 6514 T. Morin Category: Standards Track Orange ISSN: 2070-1721 June 2016

                    Registry and Extensions for
        P-Multicast Service Interface Tunnel Attribute Flags

Abstract

 The BGP-based control procedures for Multicast Virtual Private
 Networks (MVPNs) make use of a BGP attribute known as the
 "P-Multicast Service Interface (PMSI) Tunnel" attribute.  The
 attribute contains a one-octet "Flags" field.  The purpose of this
 document is to establish an IANA registry for the assignment of the
 bits in this field.  Since the "Flags" field contains only eight
 bits, this document also defines a new BGP Extended Community,
 "Additional PMSI Tunnel Attribute Flags", that can be used to carry
 additional flags for the "P-Multicast Service Interface (PMSI)
 Tunnel" attribute.  This document updates RFC 6514.

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
 http://www.rfc-editor.org/info/rfc7902.

Rosen & Morin Standards Track [Page 1] RFC 7902 PMSI Tunnel Attribute Flags June 2016

Copyright Notice

 Copyright (c) 2016 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
 (http://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  . . . . . . . . . . . . . . . . . . . . . . . .   2
 2.  Extending the "PMSI Tunnel" Attribute "Flags" Field . . . . .   3
 3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
 4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
 5.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1. Introduction

 A BGP attribute, "P-Multicast Service Interface (PMSI) Tunnel"
 attribute is defined in [RFC6514].  This attribute, referred to as
 the "PMSI Tunnel" attribute in this document, contains a one-octet
 "Flags" field.  Only one flag is defined in that RFC, but there is
 now a need to define additional flags.  However, that RFC did not
 create an IANA registry for the assignment of bits in the "Flags"
 field.  This document creates a registry for that purpose.  In
 addition, there may be a need to define more than eight flags.
 Therefore this document defines a new BGP Extended Community,
 "Additional PMSI Tunnel Attribute Flags", that can be used to carry
 additional flags for the "PMSI Tunnel" attribute.  A registry is also
 created for this Extended Community, allowing IANA to assign flag
 bits from the Extended Community's six-octet value field.
 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].

Rosen & Morin Standards Track [Page 2] RFC 7902 PMSI Tunnel Attribute Flags June 2016

2. Extending the "PMSI Tunnel" Attribute "Flags" Field

 In [RFC6514], only a single octet in the "PMSI Tunnel" attribute is
 defined to carry bit flags.  This allows eight flags, which is
 unlikely to be sufficient for all future applications.
 This document defines a new Transitive Opaque Extended Community
 ([RFC4360] [RFC7153]), "Additional PMSI Tunnel Attribute Flags".  It
 also defines a new bit flag in the "PMSI Tunnel" attribute "Flags"
 field, called the "Extension" flag.
 The "Additional PMSI Tunnel Attribute Flags" Extended Community MUST
 NOT be carried by a given BGP UPDATE message unless the following
 conditions both hold:
 o  the given BGP UPDATE message is also carrying a "PMSI Tunnel"
    attribute, and
 o  the "Extension" flag of that "PMSI Tunnel" attribute's "Flags"
    field is set.
 The six-octet value field of the "Additional PMSI Tunnel Attribute
 Flags" Extended Community is considered to be a string of 48 one-bit
 flags.  As shown in Figure 1, the leftmost bit (the most significant
 bit of the most significant octet) is bit 0, and the rightmost bit
 (the least significant bit of the least significant octet) is bit 47.
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               |               |               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    3               4
    2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               |               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             Figure 1: Value Field of the "Additional PMSI
              Tunnel Attribute Flags" Extended Community
 A BGP speaker MUST NOT attach more than one "Additional PMSI Tunnel
 Attribute Flags" Extended Community to a given BGP UPDATE.  If a
 given BGP UPDATE already contains an "Additional PMSI Tunnel
 Attribute Flags" Extended Community, a BGP speaker MUST NOT attach
 any additional such Extended Communities.

Rosen & Morin Standards Track [Page 3] RFC 7902 PMSI Tunnel Attribute Flags June 2016

 If a BGP speaker receives a BGP UPDATE with more than one "Additional
 PMSI Tunnel Attribute Flags" Extended Communities attached, only the
 flag settings in first occurrence of the Extended Community are
 significant.  Flag settings in subsequent occurrences of the Extended
 Community MUST be ignored.  When propagating the UPDATE, all
 instances of the Extended Community other than the first SHOULD be
 removed.
 Suppose a BGP speaker receives an UPDATE message that contains a
 "PMSI Tunnel" attribute, but does not contain an "Additional PMSI
 Tunnel Attribute Flags" Extended Community.  If the "Extension" flag
 of the "PMSI Tunnel" attribute is set, the UPDATE is considered to be
 malformed, and the "treat-as-withdraw" procedure of [RFC7606] MUST be
 applied.
 If a BGP speaker receives an UPDATE message that contains one or more
 "Additional PMSI Tunnel Attribute Flags" Extended Communities, but
 either (a) that UPDATE message does not contain a "PMSI Tunnel"
 attribute, or (b) the "Extension" flag of the "PMSI Tunnel" attribute
 is not set, then the Extended Community(ies) SHOULD be removed and
 SHOULD NOT be redistributed.  The BGP UPDATE message MUST be
 processed (and if necessary, redistributed) as if the Extended
 Community(ies) had not been present.
 A BGP speaker that supports the current document, but does not
 recognize a particular flag (either in the" PMSI Tunnel" attribute
 "Flags" field or in the "Additional PMSI Tunnel Attribute Flags"
 Extended Community) MUST simply ignore that flag.  If the BGP speaker
 propagates either the "PMSI Tunnel" attribute, the "Additional PMSI
 Tunnel Attribute Flags" Extended Community, or both along with the
 UPDATE message, it SHOULD leave the setting of the flag unchanged.
 It is possible that a particular application will require all members
 of a particular set of BGP speakers to support a particular flag.
 How it is determined whether all such BGP speakers support that flag
 is outside the scope of this document.
 In some situations, a BGP speaker may need to modify or replace the
 "PMSI Tunnel" attribute before propagating an UPDATE.  If the
 "Extension" flag of the "PMSI Tunnel" attribute was set before the
 attribute is modified or replaced, but that flag is no longer set
 after the attribute is modified or replaced, any "Additional PMSI
 Tunnel Attribute Flags" Extended Communities MUST be removed before
 the UPDATE is propagated.  If the "PMSI Tunnel" attribute is removed
 entirely before an UPDATE is propagated, the "Additional PMSI Tunnel
 Attribute Flags" Extended Communities (if any) MUST also be removed.

Rosen & Morin Standards Track [Page 4] RFC 7902 PMSI Tunnel Attribute Flags June 2016

3. IANA Considerations

 IANA has created a new registry called "P-Multicast Service Interface
 (PMSI) Tunnel Attribute Flags" in the "Border Gateway Protocol (BGP)
 Parameters" registry.
 Per Section 5 of [RFC6514], a "PMSI Tunnel" attribute contains a
 "Flags" octet.  The "Flags" field is a single octet, with bits
 numbered, left-to-right, from 0 to 7.  IANA has initialized the
 registry as follows:
     Bit Position      Description                      Reference
     (left to right)
          0            unassigned
          1            Extension                        This document
          2            unassigned
          3            unassigned
          4            unassigned
          5            unassigned
          6            unassigned
          7            Leaf Information Required (L)    RFC 6514
                     "PMSI Tunnel" Attribute Flags
 The registration procedure for this registry is Standards Action.
 IANA has also assigned the codepoint 0x07 from the "First Come, First
 Served" range of the "Transitive Opaque Extended Community Sub-Types"
 registry for "Additional PMSI Tunnel Attribute Flags".
 IANA has established a registry for the bit flags carried in the
 "Additional PMSI Tunnel Attribute Flags" Extended Community.  The
 bits are numbered 0-47, with 0 being the most significant bit and 47
 being the least significant bit.  The registration policy for this
 registry is "Standards Action".
 The initial registry should be as follows:
                 Bit Flag          Name          Reference
                  0-47            Unassigned
               Additional "PMSI Tunnel" Attribute Flags

Rosen & Morin Standards Track [Page 5] RFC 7902 PMSI Tunnel Attribute Flags June 2016

4. Security Considerations

 This document establishes an IANA registry, and defines a new
 Transitive Opaque Extended Community ([RFC4360], [RFC7153]).
 Establishment of an IANA registry does not raise any security
 considerations.
 While this document defines a new Extended Community for carrying bit
 flags, it does not define any of the bit flags in that Extended
 Community.  Therefore, no security considerations are raised.
 This document defines a new flag, the "Extension" flag, in the "PMSI
 Tunnel" attribute.  If a particular UPDATE contains a "PMSI Tunnel"
 attribute with this flag set, but the UPDATE does not contain an
 "Additional PMSI Tunnel Attribute Flags" Extended Community, then the
 UPDATE is considered to be malformed, and the "treat-as-withdraw"
 procedure of [RFC7606] is invoked.  Thus, one can cause an UPDATE to
 be treated as a withdrawal by incorrectly setting this bit.

5. 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,
            <http://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, <http://www.rfc-editor.org/info/rfc4360>.
 [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
            Encodings and Procedures for Multicast in MPLS/BGP IP
            VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
            <http://www.rfc-editor.org/info/rfc6514>.
 [RFC7153]  Rosen, E. and Y. Rekhter, "IANA Registries for BGP
            Extended Communities", RFC 7153, DOI 10.17487/RFC7153,
            March 2014, <http://www.rfc-editor.org/info/rfc7153>.
 [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,
            <http://www.rfc-editor.org/info/rfc7606>.

Rosen & Morin Standards Track [Page 6] RFC 7902 PMSI Tunnel Attribute Flags June 2016

Acknowledgments

 The authors wish to thank Martin Vigoureux for his review of this
 document.  We also thank Christian Huitema and Alexey Melnikov for
 their review and comments.

Authors' Addresses

 Eric C. Rosen
 Juniper Networks, Inc.
 10 Technology Park Drive
 Westford, Massachusetts  01886
 United States
 Email: erosen@juniper.net
 Thomas Morin
 Orange
 2, avenue Pierre-Marzin
 22307 Lannion Cedex
 France
 Email: thomas.morin@orange.com

Rosen & Morin Standards Track [Page 7]

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