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Network Working Group                                       P. Mohapatra
Internet-Draft                                          Sproute Networks
Intended status: Standards Track                          A. Sreekantiah
Expires: April 6, 2017                                     Cisco Systems
                                                                K. Patel
                                                              Arrcus Inc
                                                            B. Pithawala
                                                           Cisco Systems
                                                                   A. Lo
                                                         Arista Networks
                                                         October 3, 2016


            Automatic Route Target Filtering for legacy PEs
                      draft-ietf-idr-legacy-rtc-07

Abstract

   This document describes a simple procedure that allows "legacy" BGP
   speakers to exchange route target membership information in BGP
   without using mechanisms specified in [RFC4684].  The intention of
   the proposed technique is to help in partial deployment scenarios and
   is not meant to replace [RFC4684].

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 http://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."

   This Internet-Draft will expire on April 6, 2017.

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



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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Basic Idea  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Detailed Operation  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Legacy PE Behavior  . . . . . . . . . . . . . . . . . . .   3
     3.2.  RR Behavior . . . . . . . . . . . . . . . . . . . . . . .   6
       3.2.1.  Generating Route Target Membership NLRIs for the
               legacy PE clients . . . . . . . . . . . . . . . . . .   6
   4.  ROUTE_FILTER Community  . . . . . . . . . . . . . . . . . . .   7
   5.  Deployment Considerations . . . . . . . . . . . . . . . . . .   7
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informational References . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   [RFC4684]  provides a powerful and general means for BGP speakers to
   exchange and propagate Route Target reachability information and
   constrain VPN route distribution to achieve high scale.  However, it
   requires that all the BGP speakers in the network are upgraded to
   support this functionality.  For example, in a network with route



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   reflectors (RR), if one PE client in the cluster doesn't support
   constrained distribution, the cluster degenerates into storing and
   processing all the VPN routes.  The route reflectors need to request
   and store all the network routes since they do not receive route
   target membership information from the legacy PEs.  The RR will also
   generate all those routes to the legacy PEs and the legacy PEs will
   end up filtering the routes and store the subset of VPN routes that
   are of interest.

   This document specifies a mechanism for such legacy PE devices using
   existing configuration and toolset to provide similar benefits as
   [RFC4684].  At the same time, it is backward-compatible with the
   procedures defined in [RFC4684].  It also allows graceful upgrade of
   the legacy router to be [RFC4684] capable.

1.1.  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 RFC 2119 [RFC2119].

2.  Basic Idea

   The basic idea is to make use of VPN unicast route exchange from the
   legacy PEs to a new BGP speaker (e.g.  an RR) to signal RT
   membership.  The legacy PEs announce a set of "special" routes with
   mapped RTs to the RR along with a standard community (defined in this
   document).  The presence of the community triggers the RR to extract
   the RTs and build RT membership information.

3.  Detailed Operation

3.1.  Legacy PE Behavior

   The following simple steps are performed on the legacy PE device:

   o  Collect the "import route targets" of all the configured customer
      VRFs.  Let's call this set 'IRTS'.

   o  Create a special "route-filter VRF" with a route distinguisher(RD)
      that's configured with the same value across the network for all
      legacy PE devices.  Note: the equivalence of the RD value is for
      optimization - the operator may choose to use different values.

   o  Originate one or more routes in this VRF and attach a subset of
      'IRTS' as "translated route-target extended communities" with each
      route so as to evenly distribute the RTs (and to make sure they
      can fit into one BGP UPDATE message).  Collectively, the union of



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      the "translated route-target extended communities" of all these
      routes is equal to the set 'IRTS'.  The translated RTs are
      attached as export route-targets for the routes originated in the
      route-filter VRF.

   o  The translation of the IRTs is necessary in order to refrain from
      importing "route-filter" VRF routes into VPN VRFs that would
      import the same route-targets.  The translation of the IRTS is
      done as follows.  For a given IRT, the equivalent translated RT
      (TRT) is constructed by means of swapping the value of the high-
      order octet of the Type field for the IRT (as defined in
      [RFC4360]).







































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    0                   1              0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      0x00     |     0x02      |   |      0x01     |     0x02      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |2B AS                          |   |2B AS => IP(high)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<=>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Local Admin(high)              |   |Local Admin(high) => IP(low)   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Local Admin(low)               |   |Local Admin(low) => Local Admin|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    0                   1              0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      0x01     |     0x02      |   |      0x02     |     0x02      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |IP(high)                       |   |IP(high) => 4B AS(high)        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<=>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |IP(low)                        |   |IP(low) => 4B AS(low)          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Local Admin                    |   |Local Admin => Local Admin     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    0                   1              0                   1
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      0x02     |     0x02      |   |      0x00     |     0x02      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |4B AS(high)                    |   |4B AS(high) => 2B AS           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+<=>+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |4B AS(low)                     |   |4B AS(low) => Local Admin(high)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Local Admin                    |   |Local Admin => Local Admin(low)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


      As an example, if IRT R= 65500:12244(hex: 0x0002ffdc00002fd4),
      equivalent route-filter TRT: 255.220.0.0:12244(hex:
      0x0102ffdc00002fd4).  One shortcoming of the translation mechanism
      is a possible collision between IRTs and TRTs if the network has
      been configured with RTs of multiple higher order octet types
      (2-byte AS, IP address, and 4-byte AS).  It is expected that such
      a configuration is rare in practice.

   o  As an alternative to the translation of the IRTS, the subset of
      the 'IRTS' can be attached as-is (without swapping the type field
      as described earlier) as "export route-target extended



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      communities" with each route so as to evenly distribute the RTs
      (and to make sure they can fit into one BGP UPDATE message).  In
      this case, the IRT subsets can be attached in outbound policy to
      avoid the route-filter VRFs from being imported into VPN VRFs.
      Also in this case, the route-filter VRF routes must be tagged with
      a different special community (from that associated with the
      translated RTs) as described in Section 4 so that the receiving
      BGP speaker can distinguish the two cases.

   o  The routes are marked with NO_ADVERTISE and NO_EXPORT well-known
      communities as well as the appropriate new community that's
      defined in this document Section 4.  Note that there is no
      specific provision made to disallow configuration of subsequent
      route policies that can potentially alter the set of communities
      attached to "route-filter" VRF routes.  The protocol behavior in
      such a case is undefined and the use of those policy statements is
      discouraged.

3.2.  RR Behavior

   Upon receiving the "route-filter" routes, the BGP speaker does its
   usual processing to store them in its local RIB.  It recognizes them
   as route-filter routes based on the association of the new standard
   community as defined in this document.  If required (as indicated by
   the community value), it translates the attached route-target
   extended communities (TRT) to equivalent import route-targets (IRT).
   Finally it creates the route-target filter list for each legacy
   client by collecting the entire set of route targets.  From this
   point onwards, the behavior is similar to that defined in [RFC4684].
   The RR does not propagate the routes further because of their
   association with NO_ADVERTISE community.  Also the VPN EoR that is
   sent by the legacy PE should also be used as an indication that the
   legacy PE is done sending the route-filter information as per the
   procedures defined in [RFC4684] for implementing a EoR mechanism to
   signal the completion of initial RT membership exchange.

3.2.1.  Generating Route Target Membership NLRIs for the legacy PE
        clients

   The RR MAY also translate the received extended communities from
   legacy clients into route target membership NLRIs as if it had
   received those NLRIs from the client itself.  This is useful for
   further propagation of the NLRIs to rest of the network to create RT
   membership flooding graph.  When the route_filter routes are received
   with same RD (from all legacy PE speakers), processing of the paths
   to generate equivalent NLRIs becomes fairly easy.





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4.  ROUTE_FILTER Community

   This memo defines four BGP communities that are attached to BGP
   UPDATE messages at the legacy PE devices and processed by the route
   reflectors as defined above.  They are as follows:


   +----------------------------+--------------------------------------+
   |          Community         | Meaning                              |
   +----------------------------+--------------------------------------+
   |       ROUTE_FILTER_v4      | RTs are attached as-is for VPNv4     |
   |                            | route filtering                      |
   |             ...            | ...                                  |
   |       ROUTE_FILTER_v6      | RTs are attached as-is for VPNv6     |
   |                            | route filtering                      |
   |             ...            | ...                                  |
   | ROUTE_FILTER_TRANSLATED_v4 | Translated RTs are attached for      |
   |                            | VPNv4 route filtering                |
   |             ...            | ...                                  |
   | ROUTE_FILTER_TRANSLATED_v6 | Translated RTs are attached for      |
   |                            | VPNv6 route filtering                |
   +----------------------------+--------------------------------------+


   In the absence of (or lack of support of) AF specific communities
   (ROUTE_FILTER_v6, ROUTE_FILTER_TRANSLATED_v6), the ROUTE_FILTER_v4 or
   ROUTE_FILTER_TRANSLATED_v4 MAY be treated by an implementation as a
   default VPN route-filter community to build a combination VPN filter
   for all VPN AFs (VPNv4, VPNv6) present on the RR.  This is in
   accordance with the procedures in [RFC4684]  to build combination
   route-filters for VPN AFs and AF specific route-filters defined in
   [I-D.keyur-bgp-af-specific-rt-constrain].  If this is the case, then
   subsequent receipt of any "route-filter" routes with AF specific
   communities (ROUTE_FILTER_v6, ROUTE_FILTER_TRANSLATED_v6) will
   override the default filters sent with ROUTE_FILTER_v4 or
   ROUTE_FILTER_TRANSLATED_v4 for the VPNv6 AFI when support for the AF
   specific communities exists.  Suggested values for ROUTE_FILTER_v4
   and ROUTE_FILTER_TRANSLATED_v4 are 0xFFFF0002 (65535:2) and
   0xFFFF0003 (65535:3) respectively

5.  Deployment Considerations

   When both the legacy PE and the RR support extended community based
   Outbound Route Filtering as in [I-D.chen-bgp-ext-community-orf] this
   may be used as a alternate solution for the legacy PE to signal RT
   membership information, in order to realize the same benefits as
   [RFC4684].  Also extended community ORF can be used amongst the RRs
   in lieu of [RFC4684] to realize similar benefits.



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6.  Contributors

   Significant contributions were made by Stephane Litkowski, Luis M
   Tomotaki and James Uttaro which the authors would like to
   acknowledge.

7.  Acknowledgments

   The authors would like to thank Rob Shakir for his review and
   comments.

8.  IANA Considerations

   IANA shall assign new code points from BGP first-come first-serve
   communities for the four communities as listed in Section 4.

9.  Security Considerations

   There are no additional security risks introduced by this design.

10.  References

10.1.  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,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [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>.

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

   [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, <http://www.rfc-editor.org/info/rfc4684>.



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10.2.  Informational References

   [I-D.chen-bgp-ext-community-orf]
              Chen, E., Lo, A., and K. Patel, "Extended Community Based
              Outbound Route Filter for BGP-4", draft-chen-bgp-ext-
              community-orf-02 (work in progress), December 2011.

   [I-D.keyur-bgp-af-specific-rt-constrain]
              Patel, K., Raszuk, R., Djernaes, M., Dong, J., and M.
              Chen, "IPv6 AF Extensions for Route Target Distribution",
              draft-keyur-bgp-af-specific-rt-constrain-01 (work in
              progress), March 2011.

Authors' Addresses

   Pradosh Mohapatra
   Sproute Networks

   Email: mpradosh@yahoo.com


   Arjun Sreekantiah
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: asreekan@cisco.com


   Keyur Patel
   Arrcus Inc

   Email: keyurpat@yahoo.com


   Burjiz Pithawala
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: bpithaw@cisco.com








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   Alton Lo
   Arista Networks
   5470 Great America Parkway
   Santa Clara, CA  95054
   USA

   Email: altonlo@aristanetworks.com












































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