SRv6 SID Bypass Functions
draft-chen-bess-srv6-service-bypass-sid-00

Versions: 00                                                            
Network Working Group                                            H. Chen
Internet-Draft                                             China Telecom
Intended status: Standards Track                                   Y. Gu
Expires: January 14, 2021                                        H. Wang
                                                                  Huawei
                                                           July 13, 2020


                       SRv6 SID Bypass Functions
               draft-chen-bess-srv6-service-bypass-sid-00

Abstract

   This document introduces the SRv6 SID Bypass Functions to enhance
   reliability and prevent traffic loop in fast reroute(FRR) scenario.

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].

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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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   This Internet-Draft will expire on January 14, 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
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   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.  SRv6 SID Bypass Functions . . . . . . . . . . . . . . . . . .   3
     2.1.  End.DX2L  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Control Plane Processing  . . . . . . . . . . . . . . . . . .   4
   4.  Data Plane Processing . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In SRv6 EVPN VPWS all-active scenario, a router or switch (CE1) is
   dual-homed to enterprise site (PE1 and PE2).  SRv6 EVPN VPWS service
   is run between enterprise sites (PE1, PE2, and CPE).  When one PE
   fails, services can be rapidly switched to the other PE, minimizing
   the impact on services.

   As shown in Figure 1, deploy fast reroute(FRR) service on PE1 and
   PE2.  When the AC(attachment circuit) link on PE1 fails, PE1 receives
   downlink traffic and can bypass it to the PE2 device for forwarding.
   PE2 is also the same.  If the AC side links on PE1 and PE2 fail
   together, a brief traffic loop between PE1 and PE2 occurs.  The
   traffic loop will waste the forwarding resources of the equipment and
   cause performance pressure.  The length of the traffic loop depends
   on the convergence of the control plane.  That is, PE1 withdraws the
   per-EVI Ethernet A-D route advertised to PE2.  The FRR backup path on
   PE2 is destroyed.  PE2 does not send traffic to PE1.  In order to
   solve the above problem, this document defines the SRv6 SID Bypass
   Functions that will be contained in the SRv6 SID Information Sub-TLV
   [I-D.ietf-bess-srv6-services], and to be advertised with per-EVI
   Ethernet A-D routes.







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                                   +-----+
                                   | CE2 |
                                   +-----+
                                      |
                                   +-----+
                                   |EVPL1| Local/Remote
                -------------------| PE3 | Ethernet Tag ID->100/200
                   |               +-----+
                   |               /      \
                   |              /        \
              SRv6 EVPN ELINE    /          \
                   |            /            \
                   |           /              \
                   |      +-----+SRv6 Bypass  +-----+
                --------- | PE1 | Tunnel      | PE2 |
   L/R Ethernet           |EVPL1|-------------|EVPL1| L/R Ethernet
   Tag ID->200/100        +-----+             +-----+ Tag ID->200/100
                                \             /
                                 \           /
                                 ESI1      ESI1
                                   \ Trunk /
                                   +\-----/+
                                   | \   / |
                                   +---+---+
                                       |
                                    +-----+
                                    | CE1 |
                                    +-----+

   Figure 1: Basic Networking of the SRv6 EVPN VPWS All-Active Scenario

2.  SRv6 SID Bypass Functions

2.1.  End.DX2L

   The "Endpoint with decapsulation and Layer-2 cross-connect to an
   local outgoing L2 interface (OIF) only" (End.DX2L for short) is a
   variant of the endpoint behavior.  Allocation is expected from IANA
   for an End.DX2L function codepoint from the "SRv6 Endpoint Behaviors"
   sub-registry.

   One of the applications of the End.DX2L behavior is the L2VPN/EVPN
   VPWS [RFC7432][RFC8214] use-case.

   The End.DX2L SID MUST be the last segment in a SR Policy, and it is
   associated with one outgoing interface I.





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   When N receives a packet destined to S and S is a local End.DX2L SID,
   N does:

   S01. When an SRH is processed {
   S02.   If (Segments Left != 0) {
   S03.      Send an ICMP Parameter Problem to the Source Address,
                Code 0 (Erroneous header field encountered),
                Pointer set to the Segments Left field.
                Interrupt packet processing and discard the packet.
   S04.   }
   S05.   Proceed to process the next header in the packet
   S06. }


   When processing the Upper-layer header of a packet matching a FIB
   entry locally instantiated as an SRv6 End.DX2L SID, the following is
   done:

S01. If (Upper-Layer Header type != 143) {
S02.    Process as per Section 4.1.1 of [I-D.ietf-spring-srv6-network-programming]
S03. }
S04. Remove the outer IPv6 Header with all its extension headers and forward the Ethernet frame to the OIF I.
S05. If (OIF I is down) {
S06.    Interrupt packet processing and discard the packet.
S07. }


3.  Control Plane Processing

   As shown in Figure 1:

   o  1.  PE1 advertises per-EVI Ethernet A-D routes to PE2 and PE3.
      The route carries the SRv6 Service SID (SID Type=2, End.DX2) sid1
      and SRv6 Service Bypass SID sid11 allocated by the EVPL1 service
      on PE1.

   o  2.  The PE2 device receives the per-EVI Ethernet A-D route
      advertised by PE1 and finds that it is the same as the Local/
      Remote Ethernet Tag ID and ESI1 of its own EVPL1.  PE2 considers
      it to be a dual-homing relationship with PE1.  PE2 uses the SRv6
      Service Bypass SID to establish an SRv6 bypass path to PE1.  The
      tunnel is marked as sid11.  The SRv6 Service Bypass SID takes
      effect when its EVPL Local/Remote Ethernet Tag ID and ESI are the
      same as the per-EVI Ethernet A-D route received.

   o  3.  The EVPL1 Local/Remote Ethernet Tag ID of the PE3 device
      matches PE1.  PE3 uses the SRv6 Service SID to establish an EVPN
      VPWS service to PE1.  The service is marked as sid1.  PE3's EVPL1



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      Local/Remote Ethernet Tag ID and ESI are different from the per-
      EVI Ethernet A-D routes received.  PE3 should ignore this
      attribute.

   o  4.  In the same way, PE2 advertises per-EVI Ethernet A-D routes to
      PE1 and PE3.  The routes carry the SRv6 Service SID sid2 and SRv6
      Service Bypass SID sid22 allocated by EVPL1 services on PE2.

   o  5.  Finally, the primary path from PE1 to CE1 is the local AC port
      and the bypass path is the SRv6 tunnel labeled by sid22.  The
      primary path from PE2 to CE1 is the local AC port and the bypass
      path is the SRv6 tunnel labeled by sid11.  Paths from PE3 to PE1
      and PE2 are marked as sid1 and sid2.

4.  Data Plane Processing

   This section will describe the processes of the downlink Layer 2
   packet forwarding cases.

   As shown in Figure 1:

   o  1.  After receiving a Layer 2 packet sent by the CE2, PE3
      encapsulates the packet with the EVPL1 sid1 as the destination
      IPv6 of the SRH header, and forwards the packet to PE1.

   o  2.  After receiving a Layer 2 packet sent by the PE3, PE1 parses
      the EVPL1 sid1 of the SRH header and forwards it according to the
      function End.DX2 of sid1.  When the primary path from PE1 to CE1
      fails, PE1 encapsulates the packet with the EVPL1 bypass sid22 as
      the destination IPv6 of the SRH header, and forwards the packet to
      PE2.

   o  3.  After receiving a Layer 2 packet sent by the PE1, PE2 parses
      the EVPL1 bypass sid22 of the SRH header and forwards it according
      to the function End.DX2L of sid22.  When the primary path from PE2
      to CE1 fails, PE2 discards the packet and successfully breaks the
      loop.

   o  4.  As above, if PE2 receives a Layer 2 packet from PE3, EVPL1
      bypass sid11 can also been used to break the loop.

5.  IANA Considerations

   TBD







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6.  Security Considerations

   TBD

7.  Contributors

   The following individuals gave significant contributions to this
   document:

      Shunwan Zhuang
      Huawei Technologies

      Email: zhuangshunwan@huawei.com

      Chongyang Hu
      Huawei Technologies

      Email: huchongyang@huawei.com

      Bingshe Liu
      Huawei Technologies

      Email: liubingshe@huawei.com


8.  Acknowledgements

   The authors would like to thank xxx for the discussion and review of
   this document.

9.  References

9.1.  Normative References

   [I-D.ietf-bess-srv6-services]
              Dawra, G., Filsfils, C., Raszuk, R., Decraene, B., Zhuang,
              S., and J. Rabadan, "SRv6 BGP based Overlay services",
              draft-ietf-bess-srv6-services-03 (work in progress), July
              2020.

   [I-D.ietf-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
              Matsushima, S., and Z. Li, "SRv6 Network Programming",
              draft-ietf-spring-srv6-network-programming-16 (work in
              progress), June 2020.






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   [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>.

   [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>.

   [RFC8214]  Boutros, S., Sajassi, A., Salam, S., Drake, J., and J.
              Rabadan, "Virtual Private Wire Service Support in Ethernet
              VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017,
              <https://www.rfc-editor.org/info/rfc8214>.

9.2.  Informative References

   [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,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC8200]  Deering, S. and R. Hinden, "Internet Protocol, Version 6
              (IPv6) Specification", STD 86, RFC 8200,
              DOI 10.17487/RFC8200, July 2017,
              <https://www.rfc-editor.org/info/rfc8200>.

Authors' Addresses

   Huanan Chen
   China Telecom
   109, West Zhongshan Road, Tianhe District
   Guangzhou  510000
   China

   Email: chenhuan6@chinatelecom.cn


   Yunan Gu
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: guyunan@huawei.com






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   Haibo Wang
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: rainsword.wang@huawei.com












































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