Route Target Constrain Extension
draft-zzhang-idr-bgp-rt-constrains-extension-00

Versions: 00                                                            
idr                                                             Z. Zhang
Internet-Draft                                                   J. Haas
Updates: 4684 (if approved)                             Juniper Networks
Intended status: Standards Track                           July 12, 2020
Expires: January 13, 2021


                    Route Target Constrain Extension
            draft-zzhang-idr-bgp-rt-constrains-extension-00

Abstract

   This document specifies the extensions to Route Target Constrain
   mechanism so that it works with various types of Route Targets of
   arbitrary lengths.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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
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   This Internet-Draft will expire on January 13, 2021.

Copyright Notice

   Copyright (c) 2020 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



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   (https://trustee.ietf.org/license-info) in effect on the date of
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   carefully, as they describe your rights and restrictions with respect
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Specification . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   The importation and propagation of BGP routes can be controled using
   Route Targets [RFC4364] and Route Target Constrains [RFC4684].

   A Route Target (RT) could be an 8-octet BGP Extended Community (EC)
   or a 20-octet IPv6 Address Sepcfic EC, though the RT Constrain
   mechanism specified in [RFC4684] was designed for the 8-octet RTs
   only.

   [I-D.ietf-idr-bgp-ipv6-rt-constrain] extends the mechanism to handle
   IPv6 Address Specific RTs by allowing the NLRI prefix to be of 0 to
   24 octets (vs. 0 to 12 octets as in [RFC4684]):

                        +-------------------------------+
                        | origin as        (4 octets)   |
                        +-------------------------------+
                        | route target  (8 or 20 octets)|
                        ~                               ~
                        |                               |
                        +-------------------------------+

   There is a limitation with the approach in [I-D.ietf-idr-bgp-ipv6-rt-
   constrain] - when the prefix is not more than 12 octets, there is no
   way to determine if the route target part is a partial IPv6 Address
   Sepcific RT or a full/partial AS or IPv4 Address Specific RT.





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   Additional types of RTs of arbitrary lengths could also be defined,
   e.g.  [I-D.zzhang-idr-bitmask-route-target].  To extend the RT
   Constrain mechanisms in a generic way so that any forseeable types of
   RTs can be used, this document proposes the extensions specified in
   the following section.

   While the extended mechnism specified in this document can be used
   for existing RTs including IPv6 Address Specific RTs, it is not the
   intention of this document to replace or obsolete the mechansim
   defined in [I-D.ietf-idr-bgp-ipv6-rt-constrain], given its current
   status and potential existing implementations and deployments.  An
   operator may choose either way as long as there is no ambiguity.

2.  Specification

   To advertise Route Target Membership with various types of RTs, a new
   NLRI encoding with a new SAFI "Extended Route Target constrains" is
   used as following:


        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Origin AS                                            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Path Attr Type |   Route Target                              ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~  Route Target (continued, variable length )                   ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The one-octet "Path Attr Type" indicates the category of Route Target
   that follows it, using the type of BGP Path Attribute for the RT.
   For example, the "Path Attr Type" is 16 (Extended Community) for
   regular RTs, 25 (IPv6 Address Specific Extended Community) for IPv6
   Address Specific RTs, or 34 (BGP Community Container Attribute) for
   any RT defined as a BGP Community Container (e.g.  [I-D.zzhang-idr-
   bitmask-route-target]).

   Similar to [RFC4684], except for the default route target, which is
   encoded as a zero-length prefix, the minimum prefix length is 40 bits
   - the Origin AS field and the Path Attr Type field cannot be
   interpreted as a prefix.  Route targets MAY then be expressed as
   prefixes, where, for instance, a prefix would encompass all regular
   or IPv6 Address Specific RTs assigned by a given Global
   Administrator.  Semantics of adverising Route Target Membership for
   other types of RTs as prefixes MUST be defined with the specfication
   of those types of RTs.



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3.  Security Considerations

   This document does not change security aspects as discussed in
   [RFC4684].

4.  IANA Considerations

   This document requests IANA to assign a new SAFI "Extended Route
   Target constrains".

5.  Acknowledgements

   The authors thank John Scudder for his comments and suggestions.

6.  References

6.1.  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>.

   [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>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2.  Informative References

   [I-D.ietf-idr-wide-bgp-communities]
              Raszuk, R., Haas, J., Lange, A., Decraene, B., Amante, S.,
              and P. Jakma, "BGP Community Container Attribute", draft-
              ietf-idr-wide-bgp-communities-05 (work in progress), July
              2018.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <https://www.rfc-editor.org/info/rfc4364>.






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Authors' Addresses

   Zhaohui Zhang
   Juniper Networks

   EMail: zzhang@juniper.net


   Jeffrey Haas
   Juniper Networks

   EMail: jhaas@juniper.net







































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