Sender RTT Estimate Option for the Datagram Congestion Control Protocol (DCCP)
RFC 6323
Internet Engineering Task Force (IETF) G. Renker
Request for Comments: 6323 G. Fairhurst
Updates: 4342, 5622 University of Aberdeen
Category: Standards Track July 2011
ISSN: 2070-1721
Sender RTT Estimate Option
for the Datagram Congestion Control Protocol (DCCP)
Abstract
This document specifies an update to the round-trip time (RTT)
estimation algorithm used for TFRC (TCP-Friendly Rate Control)
congestion control by the Datagram Congestion Control Protocol
(DCCP). It updates specifications for the CCID-3 and CCID-4
Congestion Control IDs of DCCP.
The update addresses parameter-estimation problems occurring with
TFRC-based DCCP congestion control. It uses a recommendation made in
the original TFRC specification to avoid the inherent problems of
receiver-based RTT sampling, by utilising higher-accuracy RTT samples
already available at the sender.
It is integrated into the feature set of DCCP as an end-to-end
negotiable extension.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in 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/rfc6323.
Renker & Fairhurst Standards Track [Page 1]
RFC 6323 Sender RTT Estimate Option for DCCP July 2011
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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problems Caused by Sampling the RTT at the Receiver . . . . . 4
2.1. List of Problems Encountered with a Real Implementation . 4
2.2. Other Areas Affected by the RTT Sampling Problems . . . . 5
2.2.1. Measured Receive Rate X_recv . . . . . . . . . . . . . 6
2.2.2. Disambiguation and Accuracy of Loss Intervals . . . . 6
2.2.3. Determining Quiescence . . . . . . . . . . . . . . . . 6
2.2.4. Practical Considerations . . . . . . . . . . . . . . . 7
3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 7
3.2. Options and Features . . . . . . . . . . . . . . . . . . . 7
3.2.1. RTT Estimate Option . . . . . . . . . . . . . . . . . 7
3.2.2. Send RTT Estimate Feature . . . . . . . . . . . . . . 9
3.3. Basic Usage . . . . . . . . . . . . . . . . . . . . . . . 9
3.4. Receiver Robustness Measures . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
5.1. Option Types . . . . . . . . . . . . . . . . . . . . . . . 11
5.2. Feature Numbers . . . . . . . . . . . . . . . . . . . . . 12
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Normative References . . . . . . . . . . . . . . . . . . . 12
6.2. Informative References . . . . . . . . . . . . . . . . . . 12
Renker & Fairhurst Standards Track [Page 2]
RFC 6323 Sender RTT Estimate Option for DCCP July 2011
1. Introduction
The Datagram Congestion Control Protocol (DCCP) [RFC4340] is a
transport protocol for connection-oriented, unreliable, and
congestion-controlled datagram delivery. In DCCP, an application has
a choice of congestion control mechanisms, each specified by a
Congestion Control Identifier (CCID; [RFC4340], Section 10).
This document defines a Standards-Track update to the sender and
receiver sides of two rate-based DCCP congestion control IDs: CCID-3
[RFC4342] and the Experimental CCID-4 variant [RFC5622].
Both CCIDs are based on the principles of TCP-Friendly Rate Control
(TFRC) [RFC5348], which performs rate-based congestion control. Its
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