[tsvwg] Re: WGLC for Convergence of Congestion Control from Retained State (draft-ietf-tsvwg-careful-resume)

[Kazuho Oku <[e-mail]>]

Hello,

I know it's really late but I finally had a chance to read -15 (the most
recent version). I see lots of improvements from -12, -15 looks really
great. Thank you for all the efforts.

When reading -15, I had the following questions floating inside my head. I
could very well be missing something, or it could be the case that the same
question has already been asked and answered. If so, please forgive me for
the noise.

Section 3.1:
> If the measured CWND is less than four times the Initial Window (IW) a
sender can choose to not save the CC parameters, because the additional
actions associated with performing Careful Resume for a small CWND would
not justify its use.

Isn't it two times, assuming that RTT is known during connection
establishment?

Section 3.6:

This section talks about RTO, but QUIC does not have RTO. QUIC uses Probe
Timeouts (PTOs) instead; see RFC 9002 Section 4.7.  Considering that the
I-D gives specific advices to QUIC implementers in other sections, it might
make sense to refer to PTO here.

Section 4.1:

> At the end of slow start, the CWND can be significantly larger than
needed to fully utilise the path (i.e., a CWND overshoot). It is
inappropriate to use an overshoot in the CWND as a basis for estimating the
capacity. In most cases, the CWND will converge to a stable value after
several more RTTs. One mitigation could be to set the saved_cwnd based on
the flight_size, or an averaged CWND.

I-D suggests the use of flight_size, but doesn’t flight_size share the same
problem? I think what we might want to suggest here is to use the confirmed
pipe size (i.e., CWND / 2) if the connection is closed during Slow Start.


2025年1月19日(日) 21:25 Marten Seemann <[e-mail]>:

> This email starts a 2 week WG Last Call call to determine if the
> following TSVWG ID is ready to publish:
>
> https://datatracker.ietf.org/doc/draft-ietf-tsvwg-careful-resume/
>
> This document targets Proposed Standard.
>
> The WGLC will conclude on February 2, 2025.
>
> Please do read the draft, and send any comments/concerns to the TSVWG
> mailing list, including notes on whether these are ready to publish (or
> send an email directly to the chairs).
>
> Best wishes,
> Gorry and Marten
> (tsvwg co-chairs)
>


-- 
Kazuho Oku