Jitter Considerations in Mobile Ad Hoc Networks (MANETs)
RFC 5148

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Network Working Group                                         T. Clausen
Request for Comments: 5148              LIX, Ecole Polytechnique, France
Category: Informational                                      C. Dearlove
                                  BAE Systems Advanced Technology Centre
                                                              B. Adamson
                                          U.S. Naval Research Laboratory
                                                           February 2008

        Jitter Considerations in Mobile Ad Hoc Networks (MANETs)

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Abstract

   This document provides recommendations for jittering (randomly
   modifying timing) of control traffic transmissions in Mobile Ad hoc
   NETwork (MANET) routing protocols to reduce the probability of
   transmission collisions.

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................3
   3. Applicability Statement .........................................4
   4. Protocol Overview and Functioning ...............................4
   5. Jitter ..........................................................5
      5.1. Periodic Message Generation ................................5
      5.2. Externally Triggered Message Generation ....................6
      5.3. Message Forwarding .........................................7
      5.4. Maximum Jitter Determination ...............................8
   6. Security Considerations .........................................9
   7. References .....................................................10
      7.1. Normative References ......................................10
      7.2. Informative References ....................................10
   Appendix A. Acknowledgements ......................................11

Clausen, et al.              Informational                      [Page 1]
RFC 5148                         Jitter                    February 2008

1.  Introduction

   In a wireless network, simultaneous packet transmission by nearby
   nodes is often undesirable.  This is because any resulting collision
   between these packets may cause a receiving node to fail to receive
   some or all of these packets.  This is a physical problem, which
   occurs before packets can be inserted into the receiver queue.
   Depending on the characteristics of the medium access control and
   other lower layer mechanisms, in particular whether retransmission of
   unacknowledged packets is supported, this may cause at best increased
   delay, and at worst complete packet loss.  In some instances, these
   problems can be solved in these lower layers, but in other instances,
   some help at the network and higher layers is necessary.

   This document considers the case when that help is required, and
   provides recommendations for using jitter (randomly varying timing)
   to provide it.  It is possible that the techniques described here
   could be implemented either by IP protocols designed for wireless
   networks or in conjunction with lower-layer mechanisms.

   The problems of simultaneous packet transmissions are amplified if
   any of the following features are present in a protocol:

   Regularly scheduled messages - If two nodes generate packets
      containing regularly scheduled messages of the same type at the
      same time, and if, as is typical, they are using the same message
      interval, all further transmissions of these messages will thus
      also be at the same time.  Note that the following mechanisms may
      make this a likely occurrence.

   Event-triggered messages - If nodes respond to changes in their
      circumstances, in particular changes in their neighborhood, with
      an immediate message generation and transmission, then two nearby
      nodes that respond to the same change will transmit messages
      simultaneously.

   Schedule reset - When a node sends an event-triggered message of a
      type that is usually regularly scheduled, then there is no
      apparent reason why it should not restart its corresponding
      message schedule.  This may result in nodes responding to the same
      change also sending future messages simultaneously.

   Forwarding - If nodes forward messages they receive from other nodes,
      then nearby nodes will commonly receive and forward the same
      message.  If forwarding is performed immediately, then the
      resulting packet transmissions may interfere with each other.

Clausen, et al.              Informational                      [Page 2]
RFC 5148                         Jitter                    February 2008

   A possible solution to these problems is to employ jitter, a
   deliberate random variation in timing.  Such jitter is employed in