Implementing non protected paths using SPRING
draft-litkowski-spring-non-protected-paths-02

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SPRING Working Group                                        S. Litkowski
Internet-Draft                                                    Orange
Intended status: Informational                               M. Aissaoui
Expires: February 10, 2018                                         Nokia
                                                          August 9, 2017

             Implementing non protected paths using SPRING
             draft-litkowski-spring-non-protected-paths-02

Abstract

   Segment Routing (SR) leverages the source routing paradigm.  A node
   can steer a packet on a specific path by prepending the packet with
   an SR header.  In the framework of traffic-engineering use cases, a
   customer may request its service provider to implement some non
   protected paths.  This means that in case of a failure within the
   network, fast-reroute (or similar) techniques should not be activated
   for those paths.  This document analyzes the different options to
   implement a non protected path with Segment Routing and in a future
   release will provide a recommandation on the best option.

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 [RFC2119].

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   This Internet-Draft will expire on February 10, 2018.

Litkowski & Aissaoui    Expires February 10, 2018               [Page 1]
Internet-Draft         spring-non-protected-paths            August 2017

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Table of Contents

   1.  Problem statement . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements for a non protected LSP  . . . . . . . . . . . .   6
     2.1.  ECMP considerations . . . . . . . . . . . . . . . . . . .   7
   3.  Options to create a non protected path with Segment Routing .   7
     3.1.  Using only non protected adjacency segments . . . . . . .   7
     3.2.  Using a combination of node segments and adjacency
           segments  . . . . . . . . . . . . . . . . . . . . . . . .   8
       3.2.1.  Adding a protection flag in the Node SID  . . . . . .   8
       3.2.2.  Using Strict SPF Node SID . . . . . . . . . . . . . .   9
       3.2.3.  Using two Node-SIDs with different local policies . .   9
       3.2.4.  Advantages and drawbacks  . . . . . . . . . . . . . .   9
     3.3.  Using a combination of adjacency segments and binding-SID  10
   4.  Comparison  . . . . . . . . . . . . . . . . . . . . . . . . .  11
   5.  Recommended option(s) . . . . . . . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .  14
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Problem statement

   In some cases, a customer may prefer to react on network failures
   using its own mechanism.  In such cases, the customer usually has two
   disjoint paths, so a path can take over the traffic in case of
   failure of the other.  The disjoint paths can be provided by a single
   provider or by multihoming to different providers as displayed in the
   figure below.
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