TCPM Working Group Z. Du
Internet-Draft China Mobile
Intended status: Informational 3 March 2025
Expires: 4 September 2025
ACK Frequency Adjustment in Receiver
draft-du-tcpm-ack-rate-adjustment-in-receiver-00
Abstract
This document describes a mechanism for adjusting ACK frequency in
the receiver.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on 4 September 2025.
Copyright Notice
Copyright (c) 2025 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Procedure of ACK Frequency Modification . . . . . . . . . . . 2
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 3
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
In [I-D.ietf-tcpm-ack-rate-request], it is allowed that a sender to
request the ACK rate to be used by a receiver. It is a
straightforward way to modify the frequency of ACK.
However, in some scenario, it would be useful to enable the receiver
to modify the frequency of ACK directly without the need of the
signal from the sender. For example, for a long fat flow, the
receiver would receive packets of the flow continuingly. Thus, the
receiver can predict the arrivals of the packets of the flow, and
accordingly modify the frequency of ACK.
2. Procedure of ACK Frequency Modification
For a transport session with long duration and high bandwidth, the
receiver can predict the arrivals of the packet of the flow.
According to the statistic of the arrive time of the packets, the
receiver can speculate about the network status for the flow.
If every packet arrives in order, and at a relatively reasonable
interval, the receiver can adjust the ACK frequency. For example,
the receiver typically sends an ACK for at least every second segment
received in a stream of full-sized segments, and it can be changed to
send an ACK at least every third segment received in a stream of
full-sized segments. An even bigger value would also be possible
here, for example four segments.
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If all the packets of the stream have a large size, for example a
full-sized one is about 1500 bytes, the above descriptions would be
simpler. The receiver would typically return an ACK after receiving
every two packets, and it can be changed to return an ACK after
receiving every three or more packets.
As an option in this document, the receiver can predict the receiving
time of each packet. If the next packet is received within the
predicted time interval, we regards the prediction as verified.
According to the prediction result, we can change the policy of
responding ACK for the future packets. In a certain period, if all
the predictions are verified, the ACK rate could decrease, and if not
all the prediction are verified, the ACK rate would increase. Of
course, if an out-of-order packet is detected, an ACK will be
triggered immediately [RFC5681].
Hence, the policy of responding ACK in the receiver for a TCP stream
could be self-adjusted. A general procedure is described as follows:
1. As usual, the receiver would return an ACK every two packets.
2. If the predictions of successive N packets are all verified, the
receiver can change the policy of returning ACK to a less
frequent one, for example, returning an ACK after receiving every
three packets. N is an integer greater than 1.
3. If an out-of-order packet is detected, an ACK will be triggered
immediately, and the policy is changed back to the traditional
one. Normally, it will go back to step 1 after a few moment.
Alternatively, the receiver can also predict multiple packets would
be received within a certain period, and afterwards trigger the
modification of the policy of responding ACK for the packets of the
stream that would be received in future. The procedure is similar to
the above one.
3. IANA Considerations
TBD.
4. Security Considerations
TBD.
5. Acknowledgements
TBD.
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6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
6.2. Informative References
[I-D.ietf-tcpm-ack-rate-request]
Gomez, C. and J. Crowcroft, "TCP ACK Rate Request Option",
Work in Progress, Internet-Draft, draft-ietf-tcpm-ack-
rate-request-07, 17 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-
ack-rate-request-07>.
[RFC5681] Allman, M., Paxson, V., and E. Blanton, "TCP Congestion
Control", RFC 5681, DOI 10.17487/RFC5681, September 2009,
<https://www.rfc-editor.org/info/rfc5681>.
Author's Address
Zongpeng Du
China Mobile
No.32 XuanWuMen West Street
Beijing
100053
China
Email: duzongpeng@foxmail.com
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