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IAB Concerns Regarding Congestion Control for Voice Traffic in the Internet (RFC3714)

IP.com Disclosure Number: IPCOM000022702D
Original Publication Date: 2004-Mar-01
Included in the Prior Art Database: 2004-Mar-26
Document File: 33 page(s) / 81K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

S. Floyd: AUTHOR [+3]

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.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 5% of the total text.

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 [Page 1]

RFC 3714 IAB Concerns Regarding Congestion Control March 2004

4.4. Adaptive Rate Audio Codecs . . . . . . . . . . . . . . . 12

4.5. Differentiated Services and Related Topics . . . . . . . 13

5. Assessing Minimum Acceptable Sending Rates . . . . . . . . . . 13

5.1. Drop Rates at 4.75 kbps Minimum Sending Rate . . . . . . 17

5.2. Drop Rates at 64 kbps Minimum Sending Rate . . . . . . . 18

5.3. Open Issues. . . . . . . . . . . . . . . . . . . . . . . 18

5.4. A Simple Heuristic . . . . . . . . . . . . . . . . . . . 19

6. Constraints on VoIP Systems . . . . . . . . . . . . . . . . . . 20

7. Conclusions and Recommendations. . . . . . . . . . . . . . . . 20

8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21

9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21

9.1. Normative References . . . . . . . . . . . . ....