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