The Babel Routing Protocol
RFC 6126

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Independent Submission                                     J. Chroboczek
Request for Comments: 6126                    PPS, University of Paris 7
Category: Experimental                                        April 2011
ISSN: 2070-1721

                       The Babel Routing Protocol

Abstract

   Babel is a loop-avoiding distance-vector routing protocol that is
   robust and efficient both in ordinary wired networks and in wireless
   mesh networks.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This is a contribution to the RFC Series, independently
   of any other RFC stream.  The RFC Editor has chosen to publish this
   document at its discretion and makes no statement about its value for
   implementation or deployment.  Documents approved for publication by
   the RFC Editor are not a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6126.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

Chroboczek                    Experimental                      [Page 1]
RFC 6126               The Babel Routing Protocol             April 2011

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Features . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.2.  Limitations  . . . . . . . . . . . . . . . . . . . . . . .  4
     1.3.  Specification of Requirements  . . . . . . . . . . . . . .  4
   2.  Conceptual Description of the Protocol . . . . . . . . . . . .  4
     2.1.  Costs, Metrics, and Neighbourship  . . . . . . . . . . . .  5
     2.2.  The Bellman-Ford Algorithm . . . . . . . . . . . . . . . .  5
     2.3.  Transient Loops in Bellman-Ford  . . . . . . . . . . . . .  6
     2.4.  Feasibility Conditions . . . . . . . . . . . . . . . . . .  6
     2.5.  Solving Starvation: Sequencing Routes  . . . . . . . . . .  8
     2.6.  Requests . . . . . . . . . . . . . . . . . . . . . . . . .  9
     2.7.  Multiple Routers . . . . . . . . . . . . . . . . . . . . . 10
     2.8.  Overlapping Prefixes . . . . . . . . . . . . . . . . . . . 11
   3.  Protocol Operation . . . . . . . . . . . . . . . . . . . . . . 11
     3.1.  Message Transmission and Reception . . . . . . . . . . . . 11
     3.2.  Data Structures  . . . . . . . . . . . . . . . . . . . . . 12
     3.3.  Acknowledged Packets . . . . . . . . . . . . . . . . . . . 15
     3.4.  Neighbour Acquisition  . . . . . . . . . . . . . . . . . . 15
     3.5.  Routing Table Maintenance  . . . . . . . . . . . . . . . . 17
     3.6.  Route Selection  . . . . . . . . . . . . . . . . . . . . . 21
     3.7.  Sending Updates  . . . . . . . . . . . . . . . . . . . . . 22
     3.8.  Explicit Route Requests  . . . . . . . . . . . . . . . . . 24
   4.  Protocol Encoding  . . . . . . . . . . . . . . . . . . . . . . 27
     4.1.  Data Types . . . . . . . . . . . . . . . . . . . . . . . . 28
     4.2.  Packet Format  . . . . . . . . . . . . . . . . . . . . . . 29
     4.3.  TLV Format . . . . . . . . . . . . . . . . . . . . . . . . 29
     4.4.  Details of Specific TLVs . . . . . . . . . . . . . . . . . 30
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 39
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 39
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 40
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 40
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 40
   Appendix A.  Cost and Metric Computation . . . . . . . . . . . . . 41
     A.1.  Maintaining Hello History  . . . . . . . . . . . . . . . . 41
     A.2.  Cost Computation . . . . . . . . . . . . . . . . . . . . . 42
     A.3.  Metric Computation . . . . . . . . . . . . . . . . . . . . 43
   Appendix B.  Constants . . . . . . . . . . . . . . . . . . . . . . 43
   Appendix C.  Simplified Implementations  . . . . . . . . . . . . . 44
   Appendix D.  Software Availability . . . . . . . . . . . . . . . . 45

Chroboczek                    Experimental                      [Page 2]
RFC 6126               The Babel Routing Protocol             April 2011

1.  Introduction

   Babel is a loop-avoiding distance-vector routing protocol that is
   designed to be robust and efficient both in networks using prefix-