On Dec 1, 2025, at 11:51 AM, Matt Mathis <[email protected]> wrote:
Sorry, I missed reply-all.
Our adjustments to you edits are inline below.
On Fri, Nov 21, 2025 at 3:50 PM <[email protected]> wrote:
Authors,
While reviewing this document during AUTH48, please resolve (as necessary)
the following questions, which are also in the source file.
Add PRR as an official abbreviation in the title
OLD:
<title abbrev="Proportional Rate Reduction"> Proportional Rate Reduction</title>
NEW:
<title abbrev="PRR"> Proportional Rate Reduction (PRR)</title>
Update my email address
OLD:
<email>[email protected]</email>
NEW:
<email>[email protected]</email>
1) <!-- [rfced] Please insert any keywords (beyond those that appear in
the title) for use on https://www.rfc-editor.org/search. -->
We could use some advice on keywords. Can you tell us the keywords associated
with RFC 5681 and RFC 6675?
Tentatively:
OLD:
<keyword>example</keyword>
NEW:
<keyword>loss recovery, SACK, self clock, fast retransmit, fast
recovery</keyword>
2) <!-- [rfced] "Reno" is not used in RFC 5681, except in titles in the
References section. Please review and let us know if/how this citation
should be updated. Note that there are multiple occurrences of this
throughout the document.
Original:
Congestion control algorithms like Reno [RFC5681] and CUBIC [RFC9438]
are built on the conceptual foundation of this self clock process.
-->
No changes to the citation for Reno [RFC 5681] here or elsewhere. Many other
documents that use this citation.
Reno was the genesis of modern Internet congestion control, and as such it is
the foundation of RFC 5681 and nearly all work in ICCRG, CCWG, and much of
TCPM. However, Reno was never properly described in any documents, as a
proposed standard or otherwise. If it had been, RFC 5681 (and all of its
predecessors) would almost certainly be described as updating Reno.
3) <!--[rfced] To have the abbreviation directly match the expanded form,
may we update this text as follows?
Original:
As a baseline, to be cautious when there may be
considerable congestion, PRR uses its Conservative Reduction Bound
(PRR-CRB), which is strictly packet conserving. When recovery seems
to be progressing well, PRR uses its Slow Start Reduction Bound (PRR-
SSRB), which is more aggressive than PRR-CRB by at most one segment
per ACK.
Perhaps:
As a baseline, to be cautious when there may be
considerable congestion, PRR uses its Conservative Reduction Bound
(CRB), which is strictly packet conserving. When recovery seems
to be progressing well, PRR uses its Slow Start Reduction Bound (SSRB),
which is more aggressive than PRR-CRB by at most one segment
per ACK.
-->
Yes this is good, for this paragraph only. I'm confirming that the rest of the
document will continue to use PRR-SSRB and PRR-CRB. Correct?
(Changes as above)
OLD:
As a baseline, to be cautious when there may be
considerable congestion, PRR uses its Conservative Reduction Bound
(PRR-CRB), which is strictly packet conserving. When recovery seems
to be progressing well, PRR uses its Slow Start Reduction Bound (PRR-
SSRB), which is more aggressive than PRR-CRB by at most one segment
per ACK.
NEW:
As a baseline, to be cautious when there may be
considerable congestion, PRR uses its Conservative Reduction Bound
(CRB), which is strictly packet conserving. When recovery seems
to be progressing well, PRR uses its Slow Start Reduction Bound (SSRB),
which is more aggressive than PRR-CRB by at most one segment
per ACK.
4) <!--[rfced] To avoid awkward hyphenation of an RFC citation, may we
rephrase the latter part of this sentence as follows?
Original:
Since [RFC6937] was written, PRR has also been adapted to perform
multiplicative window reduction for non-loss based congestion control
algorithms, such as for [RFC3168] style Explicit Congestion
Notification (ECN).
Perhaps:
Since [RFC6937] was written, PRR has also been adapted to perform
multiplicative window reduction for non-loss-based congestion control
algorithms, such as for Explicit Congestion Notification (ECN) as
described in [RFC3168].
-->
Yes this is good. As above.
OLD:
Since [RFC6937] was written, PRR has also been adapted to perform
multiplicative window reduction for non-loss based congestion control
algorithms, such as for [RFC3168] style Explicit Congestion
Notification (ECN).
NEW:
Since [RFC6937] was written, PRR has also been adapted to perform
multiplicative window reduction for non-loss-based congestion control
algorithms, such as for Explicit Congestion Notification (ECN) as
described in [RFC3168].
5) <!--[rfced] To improve readability, may we add parentheses in this
sentence? Please review and let us know if thus suggested update
retains the intended meaning.
Original:
In recovery without SACK, DeliveredData is estimated to be
1 SMSS on receiving a duplicate ACK, and on a subsequent partial or
full ACK DeliveredData is the change in SND.UNA, minus 1 SMSS for
each preceding duplicate ACK.
NO we want a different change Perhaps:
In recovery without SACK, DeliveredData is estimated to be
1 SMSS on receiving a duplicate ACK (and the change is in SND.UNA on
a subsequent partial or full ACK DeliveredData), minus 1 SMSS for
each preceding duplicate ACK.
-->
OLD:
In recovery without SACK, DeliveredData is estimated to be
1 SMSS on receiving a duplicate ACK, and on a subsequent partial or
full ACK DeliveredData is the change in SND.UNA, minus 1 SMSS for
each preceding duplicate ACK.
NEW:
In recovery without SACK, DeliveredData is estimated to be
1 SMSS on each received duplicate ACK (i.e. SND.UNA did not change).
When SND.UNA advances (i.e a full or partial ACK)
DeliveredData is the change in SND.UNA, minus 1 SMSS for
each preceding duplicate ACKs.
New edit, XML line 331, second paragraph of section 6.2. (This is a revision
of an rfc-editor change.)
OLD:
(signed) change in SACK.
NEW:
signed change in quantity of data marked SACKed in the scoreboard.
6) <!-- [rfced] May we clarify "[RFC6675] 'half window of silence'" as
follows?
Original:
The [RFC6675] "half window of silence" may temporarily
reduce queue pressure when congestion control does not reduce the
congestion window entering recovery to avoid further losses.
Perhaps:
The "half window of silence" that a SACK-based Conservative Loss
Recovery Algorithm [RFC6675] experiences may temporarily
reduce queue pressure when congestion control does not reduce the
congestion window entering recovery to avoid further losses.
-->
We want to delete the last three sentences of this paragraph. They got garbled
and don't belong here anyhow. This restores the text as it was RFC 6937.
OLD:
The [RFC6675] "half window of silence" may temporarily reduce queue
pressure when congestion control does not reduce the congestion window entering recovery
to avoid further losses. The goal of PRR is to minimize the opportunities to lose the
self clock by smoothly controlling inflight toward the target set by the congestion
control. It is the congestion control's responsibility to avoid a full queue, not PRR.
NEW:
(DELETED)
7) <!--[rfced] FYI - We found free access versions of these references in
the ACM Digital Library and added DOIs and URLs to these references.
Current:
[Flach2016policing]
Flach, T., Papageorge, P., Terzis, A., Pedrosa, L., Cheng,
Y., Karim, T., Katz-Bassett, E., and R. Govindan, "An
Internet-Wide Analysis of Traffic Policing", SIGCOMM '16:
Proceedings of the 2016 ACM SIGCOMM Conference, pp.
468-482, DOI 10.1145/2934872.2934873, August 2016,
<https://doi.org/10.1145/2934872.2934873>.
[Hoe96Startup]
Hoe, J., "Improving the Start-up Behavior of a Congestion
Control Scheme for TCP", SIGCOMM '96: Conference
Proceedings on Applications, Technologies, Architectures,
and Protocols for Computer Communications, pp. 270-280,
DOI 10.1145/248157.248180, August 1996,
<https://doi.org/10.1145/248157.248180>.
[IMC11] Dukkipati, N., Mathis, M., Cheng, Y., and M. Ghobadi,
"Proportional Rate Reduction for TCP", IMC '11:
Proceedings of the 2011 ACM SIGCOMM Conference on Internet
Measurement Conference, pp. 155-170,
DOI 10.1145/2068816.2068832, November 2011,
<https://doi.org/10.1145/2068816.2068832>.
[Jacobson88]
Jacobson, V., "Congestion Avoidance and Control",
Symposium proceedings on Communications architectures and
protocols (SIGCOMM '88), pp. 314-329,
DOI 10.1145/52325.52356, August 1988,
<https://doi.org/10.1145/52325.52356>.
[Savage99] Savage, S., Cardwell, N., Wetherall, D., and T. Anderson,
"TCP Congestion Control with a Misbehaving Receiver", ACM
SIGCOMM Computer Communication Review, vol. 29, no. 5, pp.
71-78, DOI 10.1145/505696.505704, October 1999,
<https://doi.org/10.1145/505696.505704>.
[VCC] Cronkite-Ratcliff, B., Bergman, A., Vargaftik, S., Ravi,
M., McKeown, N., Abraham, I., and I. Keslassy,
"Virtualized Congestion Control (Extended Version)",
SIGCOMM '16: Proceedings of the 2016 ACM SIGCOMM
Conference pp. 230-243, DOI 10.1145/2934872.2934889,
August 2016, <http://www.ee.technion.ac.il/~isaac/p/
sigcomm16_vcc_extended.pdf>.
-->
Thank you, Free access is goot!
8) <!-- [rfced] Some author comments are present in the XML. Please confirm
that no updates related to these comments are outstanding. Note that the
comments will be deleted prior to publication.
-->
Yes, We got that.
9) <!-- [rfced] Abbreviations
a) FYI - We have added expansions for the following abbreviations
per Section 3.6 of RFC 7322 ("RFC Style Guide"). Please review each
expansion in the document carefully to ensure correctness.
Content Delivery Network (CDN)
Forward Acknowledgment (FACK)
Recent Acknowledgment Tail Loss Probe (RACK-TLP)
Consistent use of CDN, FACK and RACK-TLP are good.
b) Both the expansion and the acronym for the following term are used
throughout the document. Would you like to update to use the expansion upon
first usage and the acronym for the rest of the document?
round-trip time (RTT)
-->Note that "round-trip time" is only used for the very high level description
of PRR. A round trip, as marked by an event (the arrival of an ACK, rather than the passing
of time), is correct and not abbreviated RTT. No changes.
10) <!--[rfced] Throughout the text, the following terminology appears to
be used inconsistently. May we update each to the form on the right?
Fast Retransmit > fast retransmit
limited transmit > Limited Transmit
-->
No changes please: The capitalized terms are proper names and used to refer to
the algorithms themselves. Lower case is used in running prose to refer to
packets triggered by the algorithms. e.g. the fast retransmit is the packet
triggered by the Fast Retransmit algorithm.
11) <!-- [rfced] Please review the "Inclusive Language" portion of the
online Style Guide
<https://www.rfc-editor.org/styleguide/part2/#inclusive_language>
and let us know if any changes are needed. Updates of this nature
typically result in more precise language, which is helpful for readers.
Note that our script did not flag any words in particular, but this should
still be reviewed as a best practice.
-->
We concur. Inclusivity is important.
Thank you.
Alanna Paloma and Sandy Ginoza
RFC Production Center
End of markups, and Thank You!
On Nov 21, 2025, at 3:46 PM, [email protected] wrote:
*****IMPORTANT*****
Updated 2025/11/21
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--------------------------------------
RFC 9937 (draft-ietf-tcpm-prr-rfc6937bis-21)
Title : Proportional Rate Reduction
Author(s) : M. Mathis, N. Cardwell, Y. Cheng, N. Dukkipati
WG Chair(s) : Yoshifumi Nishida, Michael Tüxen
Area Director(s) : Gorry Fairhurst, Mike Bishop
Thanks,
--MM--
Evil is defined by mortals who think they know "The Truth" and use force to
apply it to others.
-------------------------------------------
Matt Mathis (Email is best)
Home & mobile: 412-654-7529 please leave a message if you must call.
