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Network Working Group                                              C. Hu
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                           July 02, 2018
Expires: January 3, 2019


     Enhance IPv6-Segment-Routing-based EVPN VPWS All Active Usage
                  draft-hu-bess-srv6-vpn-bypass-sid-00

Abstract

   This document describes the extensions to enhance SRv6 EVPN VPWS all-
   active Reliability.

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://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 January 3, 2019.

Copyright Notice

   Copyright (c) 2018 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must



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   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 VPN Bypass SID Attribute . . . . . . . . . . . . . . . .   3
     2.1.  End.DX2L: Endpoint with decapsulation and Layer-2 cross-
           connect to local access . . . . . . . . . . . . . . . . .   4
     2.2.  End.DT2UL: Endpoint with decapsulation and unicast Local
           MAC L2 table lookup . . . . . . . . . . . . . . . . . . .   5
   3.  Control Plane Processing  . . . . . . . . . . . . . . . . . .   6
   4.  Data Packets Processing . . . . . . . . . . . . . . . . . . .   7
   5.  EVPN Multipoint to Multipoint (MP2MP) services  . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

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 a sub type of the SRv6
   VPN SID attribute [draft-dawra-idr-srv6-vpn], to be included with
   per-EVI Ethernet A-D routes.








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

Figure 1: Basic networking of the SRv6 EVPN VPWS all-active scenario

2.  SRv6 VPN Bypass SID Attribute

   The SRv6 VPN Bypass SID is a sub type of the SRv6 VPN SID.  The SRv6
   VPN SID has been defined in draft-dawra-idr-srv6-vpn as follows:
















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        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       Type    |             Length            |   RESERVED    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  SRv6 SID information(Variable)                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    SRv6 SID information is encoded as follows:

                   +---------------------------------------+
                   |  SID Type (1 Octet)                   |
                   +---------------------------------------+
                   |  SRv6 SID (16 octet)                  |
                   +---------------------------------------+
 Figure 2: SRv6 VPN Bypass SID Attribute

   Because the SID Type values 1 and 2 have already been defined, the
   SID Type of the SRv6 VPN Bypass SID is a value to be defined that is
   different from 1, 2.  Current Type of SID defined as:

   o Type-3(Type value is TBD) - corresponds to the equivalent
   functionality provided by a MPLS Label1 for EVPN Route-Types as
   defined in [RFC7432].  Some functions which MAY be encoded are
   End.DX2L, End.DT2UL etc.

   We define hereafter a set of new functions that can be associated
   with a SID.  As in draft-filsfils-spring-srv6-network-programming, a
   function is locally defined on the node where it is executed and may
   range from simply moving forward in the segment list to any complex
   user-defined behavior.

   End.DX2L Endpoint with decapsulation and Layer-2 cross-connect to
   local access

   End.DT2UL Endpoint with decapsulation and unicast Local MAC L2 table
   lookup

2.1.  End.DX2L: Endpoint with decapsulation and Layer-2 cross-connect to
      local access

   The "Endpoint with decapsulation and Layer-2 cross-connect to local
   access OIF" function (End.DX2L for short) is a variant of the
   endpoint function.

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




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   1.  IF NH=SRH and SL > 0

   2. drop the packet ;; Ref1

   3.  ELSE IF ENH = 59 ;; Ref2

   4. pop the (outer) IPv6 header and its extension headers

   5. forward the resulting frame via local access OIF associated to the
   SID

   6.  ELSE

   7. drop the packet

   Ref1: An End.DX2L SID must always be the last SID, or it can be the
   Destination Address of an IPv6 packet with no SRH header.

   Ref2: We conveniently reuse the next-header value 59 allocated to
   IPv6 No Next Header [RFC8200].  When the SID corresponds to function
   End.DX2L and the Next-Header value is 59, we know that an Ethernet
   frame is in the payload without any further header.

   An End.DX2L function could be customized to expect a specific VLAN
   format and rewrite the egress VLAN header before forwarding on the
   outgoing interface.

   One of the applications of the End.DX2L function is the L2VPN use-
   case.

2.2.  End.DT2UL: Endpoint with decapsulation and unicast Local MAC L2
      table lookup

   The " Endpoint with decapsulation and unicast Local MAC L2 table
   lookup " function (End.DT2UL for short) is a variant of the endpoint
   function.

   When N receives a packet destined to S and S is a local End.DT2UL
   SID, N does:

   1.  IF NH=SRH and SL > 0

   2. drop the packet ;; Ref1

   3.  ELSE IF ENH = 59 ;; Ref2

   4. pop the (outer) IPv6 header and its extension headers




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   5. learn the exposed inner MAC SA in L2 table T ;; Ref3

   6. lookup the exposed inner MAC DA in L2 table T(Local)

   7. forward via the matched T entry else to all L2OIF in T(Local)

   8.  ELSE

   9. drop the packet

   Ref1: An End.DT2UL SID must always be the last SID, or it can be the
   Destination Address of an IPv6 packet with no SRH header.

   End.DT2UL and the Next-Header value is 59, we know that an Ethernet
   frame is in the payload without any further header.

   Ref3: In EVPN, the learning of the exposed inner MAC SA is done via
   control plane.

   The End.DT2UL is used for EVPN Bridging unicast Local use cases.

3.  Control Plane Processing

   As shown in Figure 1:

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

   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 VPN Bypass SID to establish
   an SRv6 bypass path to PE1.  The tunnel is marked as sid11.  The SRv6
   VPN 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.

   3.  The EVPL1 Local/Remote Ethernet Tag ID of the PE3 device matches
   PE1.  PE3 uses the SRv6 VPN SID to establish an EVPN VPWS service to
   PE1.  The service is marked as sid1.  PE3's EVPL1 Local/Remote
   Ethernet Tag ID and ESI are different from the per-EVI Ethernet A-D
   routes received.  PE3 should ignore this attribute.

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





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   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 Packets Processing

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

   As shown in Figure 1:

   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.

   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.

   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.

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

5.  EVPN Multipoint to Multipoint (MP2MP) services

   In SRv6 EVPN Multipoint to Multipoint (MP2MP) all-active scenario,
   function End.DT2UL of SRv6 VPN Bypass SID Attribute also has a
   similar effect.  When the AC side links on PE1 and PE2 fail together,
   downlink Layer 2 unicast packet will not traffic loop.

6.  IANA Considerations

   TBD.

7.  Security Considerations

   TBD.






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8.  Acknowledgements

   The authors of this document would like to thank xxx for their
   comments and review of this document.

9.  Contributors

   The following individuals gave significant contributions to this
   document:

   Bingshe Liu

   Huawei Technologies

   liubingshe@huawei.com

   Haibo Wang

   Huawei Technologies

   rainsword.wang@huawei.com

10.  References

   [I-D.dawra-idr-srv6-vpn]
              Dawra, G., Filsfils, C., Dukes, D., Brissette, P.,
              Camarillo, P., Leddy, J., daniel.voyer@bell.ca, d.,
              daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
              Decraene, B., Matsushima, S., and S. Zhuang, "BGP
              Signaling of IPv6-Segment-Routing-based VPN Networks",
              draft-dawra-idr-srv6-vpn-04 (work in progress), June 2018.

   [I-D.filsfils-spring-srv6-network-programming]
              Filsfils, C., Li, Z., Leddy, J., daniel.voyer@bell.ca, d.,
              daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
              Matsushima, S., Lebrun, D., Decraene, B., Peirens, B.,
              Salsano, S., Naik, G., Elmalky, H., Jonnalagadda, P., and
              M. Sharif, "SRv6 Network Programming", draft-filsfils-
              spring-srv6-network-programming-04 (work in progress),
              March 2018.

   [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>.






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   [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>.

   [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>.

   [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>.

Author's Address

   Chongyang Hu
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: huchongyang@huawei.com



























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