RFC 3714 (rfc3714) - Page 1 of 32


IAB Concerns Regarding Congestion Control for Voice Traffic in the Internet



Alternative Format: Original Text Document



Network Working Group                                      S. Floyd, Ed.
Request for Comments: 3714                                 J. Kempf, Ed.
Category: Informational                                      March 2004


             IAB Concerns Regarding Congestion Control for
                     Voice Traffic in the Internet

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.

Copyright Notice

   Copyright (C) The Internet Society (2004).  All Rights Reserved.

Abstract

   This document discusses IAB concerns about effective end-to-end
   congestion control for best-effort voice traffic in the Internet.
   These concerns have to do with fairness, user quality, and with the
   dangers of congestion collapse.  The concerns are particularly
   relevant in light of the absence of a widespread Quality of Service
   (QoS) deployment in the Internet, and the likelihood that this
   situation will not change much in the near term.  This document is
   not making any recommendations about deployment paths for Voice over
   Internet Protocol (VoIP) in terms of QoS support, and is not claiming
   that best-effort service can be relied upon to give acceptable
   performance for VoIP.  We are merely observing that voice traffic is
   occasionally deployed as best-effort traffic over some links in the
   Internet, that we expect this occasional deployment to continue, and
   that we have concerns about the lack of effective end-to-end
   congestion control for this best-effort voice traffic.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  An Example of the Potential for Trouble. . . . . . . . . . . .  4
   3.  Why are Persistent, High Drop Rates a Problem? . . . . . . . .  6
       3.1.  Congestion Collapse. . . . . . . . . . . . . . . . . . .  6
       3.2.  User Quality . . . . . . . . . . . . . . . . . . . . . .  7
       3.3.  The Amorphous Problem of Fairness. . . . . . . . . . . .  8
   4.  Current efforts in the IETF. . . . . . . . . . . . . . . . . . 10
       4.1.  RTP. . . . . . . . . . . . . . . . . . . . . . . . . . . 10
       4.2.  TFRC . . . . . . . . . . . . . . . . . . . . . . . . . . 11
       4.3.  DCCP . . . . . . . . . . . . . . . . . . . . . . . . . . 12



Floyd & Kempf                Informational