SRv6 and MPLS interworking for VPN service
draft-pzm-bess-spring-interdomain-vpn-00

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SPRING WG                                                   Shaofu. Peng
Internet-Draft                                              Zheng. Zhang
Intended status: Standards Track                            Greg. Mirsky
Expires: April 26, 2020                                  ZTE Corporation
                                                        October 24, 2019

               SRv6 and MPLS interworking for VPN service
                draft-pzm-bess-spring-interdomain-vpn-00

Abstract

   This document describes a method to achieve an inter-domain
   connection for a VPN (Virtual Private Network) service.

Status of This Memo

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   This Internet-Draft will expire on April 26, 2020.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Specification . . . . . . . . . . . . . . . . . . . . . . . .   2
     2.1.  SRv6 to SR-MPLS domain signaling  . . . . . . . . . . . .   2
     2.2.  SR-MPLS to SRv6 domain signaling  . . . . . . . . . . . .   3
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   [I-D.agrawal-spring-srv6-mpls-interworking] describes SRv6 and MPLS/
   SR-MPLS interworking and co-existence procedures.  The document
   leverages the function defined in
   [I-D.ietf-spring-srv6-network-programming] to give guidance to the
   forwarding in routers.

   [RFC4364] describes a method by which a Service Provider may use an
   IP backbone to provide IP Virtual Private Networks (VPNs) for its
   customers.  When SRv6 and SR-MPLS are co-existed in the backbone,
   controller or a control plane, for example, using BGP, should be used
   to instantiate the VPN service as described in
   [I-D.agrawal-spring-srv6-mpls-interworking].

   In case of option B inter-domain interconnection [RFC4364], only ASBR
   needs to do the stitching work between two ASes.  Thus PEs in SRv6
   and SR-MPLS domains do not have to support both SRv6 and SR-MPLS
   functions.  This document discusses the use of BGP for achieving VPN
   service through option B defined in [RFC4364] across a backbone that
   includes SRv6 and SR-MPLS domains.

2.  Specification

2.1.  SRv6 to SR-MPLS domain signaling

   [I-D.ietf-bess-srv6-services] defines the new TLVs for the BGP
   Prefix-SID Attribute that can be used to signaling of SRv6 SID for L3
   and L2 services.  In this document, we use L3 case as the example,
   the procedures for L2 are the same as in L3 scenario.

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                   +-------------+         +-------------+
                   |    AS1      |         |     AS2     |
                   |             |         |             |
         CE1+----+PE1          ASBR1+---+ASBR2          PE2+----+CE2
                   |             |         |             |
                   |    SRV6     |         |   SR-MPLS   |
                   +-------------+         +-------------+
                          Figure 1

   For example, CE1 and CE2 are connected through a backbone that
   includes AS1 and AS2.  AS1 supports SRv6 only, and AS2 supports SR-
   MPLS only.  ASBR1 supports both SRv6 and SR-MPLS capabilities, but
   ASBR2 supports SR-MPLS capability only.

   For a prefix advertised by CE1 to PE1, PE1 assigns SID with End.DT4
   (or End.DT6) defined in [I-D.ietf-spring-srv6-network-programming]
   section 4 (e.g., End.DT4 is used while the prefix is IPv4 prefix,
   End.DT6 is used while the prefix is IPv6 prefix), and advertises it
   to ASBR1.  Because ASBR2 supports SR-MPLS function only, the SRv6 SID
   advertised by ASBR1 cannot be executed by ASBR2 because ASBR2 cannot
   recognize it.

   ASBR1 uses specific execution function that is different from the
   function used in a single SRv6 domain or a single SR-MPLS domain.  In
   this situation, ASBR1 assigns an MPLS label for the prefix received
   from PE1 and advertises it to ASBR2.  The MPLS label has local
   significance that indicates this packet is associated with an SRv6
   SID list which leads the packet from ASBR1 to PE1.  The advertisement
   is the same as the format in [I-D.ietf-idr-bgp-prefix-sid].

   When a data flow packet which has the destination to CE1 is received
   by ASBR1, ASBR1 recognizes the MPLS label, removes the label and adds
   an SRH to the packet, then forwards it to PE1.

2.2.  SR-MPLS to SRv6 domain signaling

   In the same example, PE2 advertises a prefix received from CE2 with
   assigned SID to ASBR2 according to [I-D.ietf-idr-bgp-prefix-sid],
   ASBR2 assigns SID for this prefix and advertises it to ASBR1.  When
   ASBR1 advertises this prefix to PE1, ASBR1 should assign an SRv6 SID
   for it.  The SID indicates the new execution function (e.g., END.RM,
   it indicates that MPLS should replace the SRH) for exchanging the
   packet header from SRH to MPLS list.  The new function format is like
   the defination in [I-D.ietf-spring-srv6-network-programming] section
   4.

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   When a data flow packet, which has the destination to CE2, is
   received by ASBR1, ASBR1 recognizes the SRv6 SID, removes the SRH and
   adds a or a list of MPLS label in the packet, and forwards it to PE2.

3.  IANA Considerations

   There is no IANA consideration.

4.  Security Considerations

   This document introduces no new security consideration beyond those
   already specified in [RFC4364], [I-D.ietf-idr-bgp-prefix-sid],
   [I-D.ietf-spring-srv6-network-programming],
   [I-D.ietf-bess-srv6-services] and
   [I-D.agrawal-spring-srv6-mpls-interworking].

5.  References

5.1.  Normative References

   [I-D.ietf-bess-srv6-services]
              Dawra, G., Filsfils, C., Brissette, P., Agrawal, S.,
              Leddy, J., daniel.voyer@bell.ca, d.,
              daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
              Decraene, B., Matsushima, S., Zhuang, S., and J. Rabadan,
              "SRv6 BGP based Overlay services", draft-ietf-bess-
              srv6-services-00 (work in progress), October 2019.

   [I-D.ietf-idr-bgp-prefix-sid]
              Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A.,
              and H. Gredler, "Segment Routing Prefix SID extensions for
              BGP", draft-ietf-idr-bgp-prefix-sid-27 (work in progress),
              June 2018.

   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J.,
              daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
              Network Programming", draft-ietf-spring-srv6-network-
              programming-04 (work in progress), October 2019.

   [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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5.2.  Informative References

   [I-D.agrawal-spring-srv6-mpls-interworking]
              Agrawal, S., Ali, Z., Filsfils, C., daniel.voyer@bell.ca,
              d., and Z. Li, "SRv6 and MPLS interworking", draft-
              agrawal-spring-srv6-mpls-interworking-01 (work in
              progress), July 2019.

Authors' Addresses

   Shaofu Peng
   ZTE Corporation

   Email: peng.shaofu@zte.com.cn

   Zheng Zhang
   ZTE Corporation

   Email: zzhang_ietf@hotmail.com

   Greg Mirsky
   ZTE Corporation

   Email: gregimirsky@gmail.com

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