IPv6 Maintenance Working Group                                   X. Geng
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                 F. Yang
Expires: August 24, 2021                             Huawei Technologies
                                                       February 20, 2021


                SRH Extension for Redundancy Protection
              draft-geng-6man-redundancy-protection-srh-00

Abstract

   Redundancy protection is a method of service protection by sending
   copies of the same packets of one flow over multiple paths, which
   includes packet replication, elimination and ordering.  This document
   defines SRv6 header (SRH) extensions to support redundancy
   protection.

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 .

Status of This Memo

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   This Internet-Draft will expire on August 24, 2021.

Copyright Notice

   Copyright (c) 2021 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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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions . . . . . . . . . . . . . . . . .   2
   3.  Redundancy Protection over SRv6 Scenario  . . . . . . . . . .   3
   4.  SRH Extension for Redundancy Protection . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Redundancy protection is a method of providing 1+1 protection by
   sending copies of the same packets of one flow over multiple paths,
   which includes packet replication, elimination and ordering.  This
   document defines SRv6 header (SRH) extensions to support redundancy
   protection.

2.  Terminology and Conventions

   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 [RFC2119].

   Redundancy Node: the start point of redundancy protection, which is a
   network device that could implement packet replication.

   Merging Node: the end point of redundancy protection, which is a
   network node that could implement packet elimination and ordering
   (optionally).

   Flow Identification: information in SR data service to indicate one
   flow.

   Sequence Number: information in SR data service to indicate the
   packet sequence of one flow.





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   Editor's Note: Similar mechanism is defined as "Service Protection"
   in the [RFC8655].  In this document, we define a new term "Redundancy
   Protection" to distinguish with other service protection method.
   Some of the terms are the similar as [RFC8655].

3.  Redundancy Protection over SRv6 Scenario

   The figure shows how to provide redundancy protection over SRv6.

                |                                        |
    ----IPv6--->|<---------------SRv6 Domain------------>|<----IPv6---
                |                                        |
                |            +------+R1+----+            |
      +---+    +---+       +-+-+          +-+-+        +---+    +---+
      |E1 +----+In +-------+Red|          |Mer+--------+Eg +----+E2 |
      +---+    +---+       +-+-+          +-+-+        +---+    +---+
                             +------+R2+----+

   As the figure shows, an IPv6 flow is sent out from the end station
   E1.  The packet of the flow is encapsulated in an outer IPv6+SRH
   header in the Ingress(In) and transported through an SRv6 domain.  In
   the Egress(Eg), the outer IPv6+SRH header of packet is popped, and
   the packet is sent to the destination E2.

   The process of redundancy protection is as follows: 1) The flow is
   replicated in Red (Redundancy Node); 2) Two replicated flows go
   through different paths till Mer (Merging Node); When there is any
   failures happened in one the path, the service continues to deliver
   through the other path without break; 3) The first received packet of
   the flow is transmitted from Mer (Merging Node) to Eg(Egress), and
   the redundant packets are eliminated; 4) Sometimes, the packet will
   arrive out of order because of redundancy protection, the function of
   reordering may be necessary in the Merging Node.

   This document defines Flow Identification and Sequence Number in
   Segment Routing Header(SRH) as an extension of [RFC8754] to support
   redundancy protection.

   Flow Identification is used to distinguish flows, and Sequence Number
   is used to distinguish packets in the same flow when doing packet
   merging and ordering.

4.  SRH Extension for Redundancy Protection

   Flow Identification and Sequence Number could be defined in SRH
   optional TLV.





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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             |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Flow Identification                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                     Sequence Number                           |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   o  Type: 8 bits, indicates the use of redundancy protection, to be
      assigned by IANA.

   o  Length: 8 bits.

   o  Reserved: 16 bits.  MUST be 0 on transmission and ignored on
      receipt.

   o  Flow Identification: 32 bits, which is used for identifying the
      redundant protection flow.

   o  Sequence Number: 32 bits, which is used for indicating sequence
      number of the redundant protection flow.

5.  IANA Considerations

   This document requires registration of a specific type of TLV used
   for redundancy protection in "Segment Routing Header TLVs" registry.

6.  Security Considerations

   TBD

7.  Acknowledgements

   Thanks for the valuable comments from James Guichard and Andrew
   Malis.

8.  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>.





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   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,
              <https://www.rfc-editor.org/info/rfc8655>.

   [RFC8754]  Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
              <https://www.rfc-editor.org/info/rfc8754>.

Authors' Addresses

   Xuesong Geng
   Huawei Technologies
   Beijing
   China

   Email: gengxuesong@huawei.com


   Mach(Guoyi) Chen
   Huawei Technologies
   Beijing
   China

   Email: mach.chen@huawei.com


   Fan Yang
   Huawei Technologies
   Beijing
   China

   Email: shirley.yangfan@huawei.com

















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