RFC 3366 (rfc3366) - Page 2 of 27

Advice to link designers on link Automatic Repeat reQuest (ARQ)

Alternative Format: Original Text Document


RFC 3366          Advice to Link Designers on Link ARQ       August 2002


Table of Contents

   1.    Introduction. . . . . . . . . . . . . . . . . . . . . . . . .2
   1.1   Link ARQ. . . . . . . . . . . . . . . . . . . . . . . . . . .4
   1.2   Causes of Packet Loss on a Link . . . . . . . . . . . . . . .5
   1.3   Why Use ARQ?. . . . . . . . . . . . . . . . . . . . . . . . .6
   1.4   Commonly-used ARQ Techniques. . . . . . . . . . . . . . . . .7
   1.4.1 Stop-and-wait ARQ . . . . . . . . . . . . . . . . . . . . . .7
   1.4.2 Sliding-Window ARQ. . . . . . . . . . . . . . . . . . . . . .7
   1.5   Causes of Delay Across a Link . . . . . . . . . . . . . . . .8
   2.    ARQ Persistence . . . . . . . . . . . . . . . . . . . . . . 10
   2.1   Perfectly-Persistent (Reliable) ARQ Protocols . . . . . . . 10
   2.2   High-Persistence (Highly-Reliable) ARQ Protocols. . . . . . 12
   2.3   Low-Persistence (Partially-Reliable) ARQ Protocols. . . . . 13
   2.4   Choosing Your Persistency . . . . . . . . . . . . . . . . . 13
   2.5   Impact of Link Outages. . . . . . . . . . . . . . . . . . . 14
   3.    Treatment of Packets and Flows. . . . . . . . . . . . . . . 15
   3.1   Packet Ordering . . . . . . . . . . . . . . . . . . . . . . 15
   3.2   Using Link ARQ to Support Multiple Flows. . . . . . . . . . 16
   3.3   Differentiation of Link Service Classes . . . . . . . . . . 17
   4.    Conclusions . . . . . . . . . . . . . . . . . . . . . . . . 19
   5.    Security Considerations . . . . . . . . . . . . . . . . . . 21
   6.    IANA Considerations . . . . . . . . . . . . . . . . . . . . 21
   7.    Acknowledgements. . . . . . . . . . . . . . . . . . . . . . 22
   8.    References. . . . . . . . . . . . . . . . . . . . . . . . . 22
   8.1   Normative References. . . . . . . . . . . . . . . . . . . . 22
   8.2   Informative References. . . . . . . . . . . . . . . . . . . 23
   9.    Authors' Addresses. . . . . . . . . . . . . . . . . . . . . 26
   10.   Full Copyright Statement. . . . . . . . . . . . . . . . . . 27

1. Introduction

   IP, the Internet Protocol [RFC 791], forms the core protocol of the
   global Internet and defines a simple "connectionless" packet-switched
   network.  Over the years, Internet traffic using IP has been carried
   over a wide variety of links, of vastly different capacities, delays
   and loss characteristics.  In the future, IP traffic can be expected
   to continue to be carried over a very wide variety of new and
   existing link designs, again of varied characteristics.

   A companion document [DRAFTKARN02] describes the general issues
   associated with link design.  This document should be read in
   conjunction with that and with other documents produced by the
   Performance Implications of Link Characteristics (PILC) IETF
   workgroup [RFC 3135, RFC 3155].






Fairhurst & Wood         Best Current Practice

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