Applicability of the Babel routing protocol
draft-ietf-babel-applicability-03

Document Type Active Internet-Draft (babel WG)
Last updated 2018-07-18 (latest revision 2018-04-07)
Replaces draft-chroboczek-babel-applicability
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Network Working Group                                      J. Chroboczek
Internet-Draft                         IRIF, University of Paris-Diderot
Intended status: Informational                             April 7, 2018
Expires: October 9, 2018

              Applicability of the Babel routing protocol
                   draft-ietf-babel-applicability-03

Abstract

   Where we argue that, although OSPF and IS-IS are fine protocols,
   there exists a space where the Babel routing protocol (RFC 6126bis)
   is useful.

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   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on October 9, 2018.

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Table of Contents

   1.  Introduction and background . . . . . . . . . . . . . . . . .   2
     1.1.  Technical overview of the Babel protocol  . . . . . . . .   2
   2.  Properties of the Babel protocol  . . . . . . . . . . . . . .   3
     2.1.  Simplicity and implementability . . . . . . . . . . . . .   3
     2.2.  Robustness  . . . . . . . . . . . . . . . . . . . . . . .   3
     2.3.  Extensibility . . . . . . . . . . . . . . . . . . . . . .   4
     2.4.  Limitations . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Successful deployments of Babel . . . . . . . . . . . . . . .   6
     3.1.  Hybrid networks . . . . . . . . . . . . . . . . . . . . .   6
     3.2.  Large scale overlay networks  . . . . . . . . . . . . . .   6
     3.3.  Pure mesh networks  . . . . . . . . . . . . . . . . . . .   7
     3.4.  Small unmanaged networks  . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  Informational References  . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction and background

   Babel [RFC6126bis] is a routing protocol based on the familiar
   distance-vector algorithm (sometimes known as distributed Bellman-
   Ford) augmented with mechanisms for loop avoidance (there is no
   "counting to infinity") and starvation avoidance.  In this document,
   we argue that there exist niches where Babel is useful and that are
   not adequately served by more mature protocols such as OSPF [RFC5340]
   and IS-IS [RFC1195].

1.1.  Technical overview of the Babel protocol

   At its core, Babel is a traditional distance-vector protocol based on
   the distributed Bellman-Ford algorithm, similar in principle to RIP
   [RFC2453], but with two obvious extensions: provisions for sensing of
   neighbour reachability, bidirectional reachability and link quality,
   and support for multiple address families (e.g., IPv6 and IPv4) in a
   single protocol instance.

   Algorithms of this class are simple to understand and simple to
   implement, but unfortunately they do not work very well -- they
   suffer from "counting to infinity", a case of pathologically slow
   convergence in some topologies after a link failure.  Babel uses a
   mechanism pioneered by EIGRP [DUAL] [RFC7868], known as
   "feasibility", which avoids routing loops and therefore makes
   counting to infinity impossible.

   Feasibility is a conservative mechanism, one that not only avoids all
   looping routes but also rejects some loop-free routes.  Thus, it can

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   lead to a situation known as "starvation", where a router rejects all
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