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Network Working Group                                            X. Geng
Internet-Draft                                                   M. Chen
Intended status: Experimental                                     Huawei
Expires: September 10, 2020                               March 09, 2020


                SRH Extension for Redundancy Protection
             draft-geng-spring-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 replicaiton, 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

   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
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   This Internet-Draft will expire on September 10, 2020.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
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   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
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions . . . . . . . . . . . . . . . . .   2
   3.  Redundancy Protection Requirement Analysis  . . . . . . . . .   3
   4.  SRH Extensions for Redundancy Protection  . . . . . . . . . .   3
     4.1.  Option 1: seperated TLVs for flow identification and
           sequence number . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Option 2 unified TLV for flow identification and sequence
           number  . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

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 replicaiton, 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 redudancy protection, which is a
   network device that could implement packet replication.

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

   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].




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3.  Redundancy Protection Requirement Analysis

   The figure shows how to provide redundancy protection over SRv6.

                |                                         |
    ----IPv6--->|<---------------SRv6 Domain------------->|<----IPv6---
                |                                         |
                |             +------+T2+----+            |
      +---+    +---+        +-+-+          +-+-+        +---+    +---+
      | E1+----| In|--+T1+--+Red|          |Mer|--+T4+--| Eg+----+ E2|
      +---+    +---+        +-+-+          +-+-+        +---+    +---+
                              +-----+T3+-----+

   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 header+SR of the 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 Rep(Redundancy Node); 2) Tow 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 the current
   draft[I-D.ietf-6man-segment-routing-header] 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 Extensions for Redundancy Protection

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









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4.1.  Option 1: seperated TLVs for flow identification and sequence
      number

     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            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |        RESERVED       |           Flow Identification         |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   o  Type: 8bits, to be assigned by IONA.

   o  Length: 8 octets.

   o  RESERVED: 28 bits, MUST be 0 on transmission and ignored on
      receipt.

   o  Flow Identification: 20 bits, which is used for identifying
      redundant protection flow.

     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            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |RESERVED|                    Sequence Number                   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   o  Type: 8 bits, to be assigned by IONA.

   o  Length: 8.

   o  RESERVED: 20 bits.  MUST be 0 on transmission and ignored on
      receipt.

   o  Sequence Number: 28 bits, which is used for indicating sequence
      number of the redundant protection flow.

4.2.  Option 2 unified TLV for flow identification and sequence number







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

   where:

   o  Type: 8bits, to be assigned by IANA.

   o  Length: 8 octets.

   o  Flow Identification: 20 bits, which is used for identifying the
      redundant protection flow.

   o  Sequence Number: 28 bits, which is used for indicating sequence
      number of the redundant protection flow.

   o  Reserved: 32 bits.  MUST be 0 on transmission and ignored on
      receipt.

5.  IANA Considerations

   TBD

6.  Security Considerations

   TBD

7.  Acknowledgements

   Thank you for valuable comments from James Guichard and Andrew Mail

8.  Normative References

   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
              Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-26 (work in
              progress), October 2019.







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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>.

   [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>.

Authors' Addresses

   Xuesong Geng
   Huawei

   Email: gengxuesong@huawei.com


   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com





























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