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Network Working Group                                            X. Geng
Internet-Draft                                                   M. Chen
Intended status: Experimental                                     Huawei
Expires: September 24, 2020                               March 23, 2020

               Redundancy Policy for Redundant Protection


   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 redundancy policy as an extension to the current SR policy to
   support redundancy protection.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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.

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   This Internet-Draft will expire on September 24, 2020.

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   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

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   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions . . . . . . . . . . . . . . . . .   2
   3.  Redundancy Protection Introduction  . . . . . . . . . . . . .   3
   4.  Redudancy Policy  . . . . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   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 redundancy policy to support redundancy protection.

2.  Terminology and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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

   Redundancy Policy: an extended sr policy which includes more than one
   active segment lists to support redundancy protection.

   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 Introduction

   The figure shows how to provide redundancy protection in an Segment
   Routing Domain.

                |                                         |
                |<---------------SR Domain--------------->|
                |                                         |
                |             +------+T2+----+            |
      +---+    +---+        +-+-+          +-+-+        +---+    +---+
      | E1+----| In|--+T1+--+Red|          |Mer|--+T4+--| Eg+----+ E2|
      +---+    +---+        +-+-+          +-+-+        +---+    +---+

   The process of redundancy protection is as follows: 1) The flow is
   replicated in Reb(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.

   In this document, we introduces Redundancy Policy as a variation of
   Segment Routing Policy defined in
   [I-D.ietf-spring-segment-routing-policy] to support redundancy
   protection.  Redundancy policy applys equally to both SR-MPLS and

4.  Redudancy Policy

   Redundancy Policy is used to enable packet replication and
   instantiation more than one ordered lists of segments between
   replication node and merging node to steer the same flow through
   different paths in an SR domain.

   A Redundancy Policy is identified through the tuple <replication
   node, redundancy ID, merging node>.  Redundancy node is specified as
   IPv4/IPv6 address of the head end, which is able to do packet
   replication.  Merging node is specified as IPv4/IPv6 address of the
   end point, which is able to do packet elimination and
   ordering(optional).  Replication ID could be a specified value of
   "color" define in section 2.1 of
   [I-D.ietf-spring-segment-routing-policy], which indicates the sr
   policy as a redundancy policy.  Replication ID could also be used to
   distinguish redundancy policy sharing the same redundancy node and
   merging node.

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   The following elements are extended in Redundancy Policy:

   o  Redundancy ID: is used to distinguish different redundancy policy

   o  Redundancy SID: is variation of Binding SID for Redundancy policy.
      Redundancy SID will be instantiated as Redundancy Policy in
      redundancy node.  Redundancy SID is define in draft-geng-spring-

   o  Candidate path: more than one candidate paths are included in
      redundancy policy.  In each candidate path, the last segment
      SHOULD be merging SID.  Merging SID is defined in draft-geng-
      spring-redundancy-protection-sid-00.  The preference of the
      candidate path is used to select the best candidate path for an SR
      Policy.  The preference of candidate paths in redundancy policy
      SHOULD be the same .

   A packet is steered into a Redundancy policy at a redundancy node in
   similar ways of SR policy defined in section 8 of

   o  Incoming packets have an active SID matching the redundancy SID at
      the redundancy node;

   o  Incoming packets match a BGP/Service route which recurses on an SR
      policy (BGP should be extended to support matching to a redundancy
      policy, which is supposed to be covered in the following work);

   o  Per-flow Steering: incoming packets match or recurse on a
      forwarding array of where some of the entries are Replication

   o  Policy-based Steering: incoming packets match a routing policy
      which directs them on a redundancy policy.

5.  IANA Considerations


6.  Security Considerations


7.  Acknowledgements

   Thank you for valuable comments from James Guichard and Andrew Mail

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8.  Normative References

              Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", draft-
              ietf-spring-segment-routing-policy-06 (work in progress),
              December 2019.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC8655]  Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", RFC 8655,
              DOI 10.17487/RFC8655, October 2019,

Authors' Addresses

   Xuesong Geng

   Email: gengxuesong@huawei.com

   Mach(Guoyi) Chen

   Email: mach.chen@huawei.com

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