TTL Procedures for SR-TE Paths in Label Switched Path Traceroute Mechanisms
draft-arora-mpls-spring-ttl-procedures-srte-paths-00

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Routing area                                                    K. Arora
Internet-Draft                                                  S. Hegde
Intended status: Standards Track                   Juniper Networks Inc.
Expires: April 19, 2019                                 October 16, 2018

    TTL Procedures for SR-TE Paths in Label Switched Path Traceroute
                               Mechanisms
          draft-arora-mpls-spring-ttl-procedures-srte-paths-00

Abstract

   Segment routing supports the creation of explicit paths using
   adjacency-sids, node-sids, and anycast-sids.  The SR-TE paths are
   built by stacking the labels that represent the nodes and links in
   the explicit path.  A very useful Operations And Maintenance
   requirement is to be able to trace these paths as defined in
   [RFC8029].  This document specifies a uniform mechanism to support
   MPLS traceroute for the SR-TE paths when the nodes in the network are
   following uniform mode or short-pipe mode [RFC3443].

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 RFC 2119 [RFC2119].

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   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on April 19, 2019.

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Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Problem with SR-TE Paths  . . . . . . . . . . . . . . . . . .   3
     2.1.  Short Pipe model  . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Uniform Model . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Detailed Solution For TTL procedures for SR-TE paths  . . . .   5
     3.1.  P bit in DDMT TLV . . . . . . . . . . . . . . . . . . . .   5
     3.2.  Procedures for a PHP router of the tunnel being traced  .   5
     3.3.  Procedures for a egress  router of the tunnel being
           traced  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Procedures for a ingress router of the SR-TE path . . . .   5
     3.5.  Example describing the solution . . . . . . . . . . . . .   5
   4.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   The mechanisms to handle TTL procedures for SR-TE paths are described
   in ([RFC8287]).  Section 7.5 of ([RFC8287]) defines the TTL
   manipulation procedures for short pipe model as the LSR initiating
   the traceroute SHOULD start by setting the TTL to 1 for the tunnel in
   the LSP's label stack it wants to start the tracing from, the TTL of
   all outer labels in the stack to the max value, and the TTL of all
   the inner labels in the stack to zero.  However this mechanism has
   issues when the constituent tunnels are penultimate-hop-popping(PHP).
   c

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   Section 2 describes problems tracing SR-TE paths and the need for a
   specialized mechanism to trace SR-TE paths.  Section 3 describes the
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