An MPLS SR OAM option reducing the number of end-to-end path validations
draft-geib-spring-oam-opt-00

Document Type Active Internet-Draft (individual)
Author Ruediger Geib 
Last updated 2020-10-29
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Internet Engineering Task Force                             R. Geib, Ed.
Internet-Draft                                          Deutsche Telekom
Intended status: Best Current Practice                   28 October 2020
Expires: 1 May 2021

An MPLS SR OAM option reducing the number of end-to-end path validations
                      draft-geib-spring-oam-opt-00

Abstract

   MPLS traceroute implementations validate dataplane connectivity and
   isolate faults by sending messages along every end-to-end Label
   Switched Path (LSP) combination between a source and a destination
   node.  This requires a growing number of path validations in networks
   with a high number of equal cost paths between origin and
   destination.  Segment Routing (SR) introduces MPLS topology awareness
   combined with Source Routing.  By this combination, SR can be used to
   implement an MPLS traceroute option lowering the total number of LSP
   validations as compared to commodity MPLS traceroute.

Status of This Memo

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   This Internet-Draft will expire on 1 May 2021.

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Internet-Draft      Reducing MPLS OAM messages by SR        October 2020

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   5
   2.  MPLS OAM adding MPLS SR mechanisms  . . . . . . . . . . . . .   5
     2.1.  Operation in an SR MPLS domain applying only IP-header
           based ECMP  . . . . . . . . . . . . . . . . . . . . . . .   6
     2.2.  Operation in an SR MPLS domain additionally using incoming
           interface information for ECMP  . . . . . . . . . . . . .   7
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Commodity MPLS isn't topology aware and it offers no standard source
   routing methods.  It is reasonable to validate connectivity and
   locate faults of MPLS LSPs by detecting and testing all existing LSP
   combinations between a source and a destination node.  The source
   node originates all MPLS echo requests and evaluates all MPLS echo
   replies.  Operational MPLS OAM implementations were present, when SR
   MPLS entered standardisation.  They continue to work reliably in many
   cases.  MPLS domains with a high number of equal cost paths between
   source and destination nodes push the detection capabilities of
   commodity MPLS OAM to the limit.  So far, modes of MPLS OAM operation
   adding Segment Routing functionality to deal with limitations of
   commodity MPLS OAM have not been published within IETF.

   This draft assumes readers to be aware of MPLS OAM functionality as
   specified by RFC 8029 [RFC8029] and RFC 8287 [RFC8287].  The function
   described in the following works for Shortest Path First Paths or
   Label stacks based on MPLS Node-SID and MPLS Adj-SIDs (if the latter
   are distributed by Interior Gateway Protocols).

   Networks supporting a high number of equivalent cost paths between
   source and destination nodes require a high number of completed MPLS
   path validations.  Consider a network with Multiple equal cost paths,
   as shown in figure 1.

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