Delay-based Metric Extension for the Babel Routing Protocol
draft-ietf-babel-rtt-extension-00

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Network Working Group                                         B. Jonglez
Internet-Draft                                                  ENS Lyon
Updates: 6126 (if approved)                                J. Chroboczek
Intended status: Experimental          IRIF, University of Paris-Diderot
Expires: October 28, 2019                                 April 26, 2019

      Delay-based Metric Extension for the Babel Routing Protocol
                   draft-ietf-babel-rtt-extension-00

Abstract

   This document defines an extension to the Babel routing protocol that
   uses symmetric delay in metric computation and therefore makes it
   possible to prefer lower latency links to higher latency ones.

Status of This Memo

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   This Internet-Draft will expire on October 28, 2019.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Protocol operation  . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Delay estimation  . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Metric computation  . . . . . . . . . . . . . . . . . . .   5
     2.3.  Stability issues  . . . . . . . . . . . . . . . . . . . .   6
     2.4.  Backwards and forwards compatibility  . . . . . . . . . .   6
   3.  Packet format . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Timestamp sub-TLV in Hello TLVs . . . . . . . . . . . . .   7
     3.2.  Timestamp sub-TLV in IHU TLVs . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   The Babel routing protocol [BABEL] does not mandate a specific
   algorithm for computing metrics; existing implementations use a
   packet-loss based metric on wireless links and a simple hop-count
   metric on all other types of links.  While this strategy works
   reasonably well in many networks, it fails to select reasonable
   routes in some topologies involving tunnels or VPNs.

   Consider for example the following topology, with three routers A, B
   and D located in Paris and a fourth router located in Tokyo,
   connected through tunnels in a diamond topology.

                      +------------+
                      | A (Paris)  +---------------+
                      +------------+                \
                     /                               \
                    /                                 \
                   /                                   \
     +------------+                                     +------------+
     | B  (Paris) |                                     | C  (Tokyo) |
     +------------+                                     +------------+
                   \                                   /
                    \                                 /
                     \                               /
                      +------------+                /
                      | D (Paris)  +---------------+
                      +------------+

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   When routing traffic from A to D, it is obviously preferable to use