I read the draft, and I neither understand the problem it's trying to solve, nor do I understand the way that it solves it.
According to RFC 9002, min_rtt is the minimum RTT observed on a path. While reducing the ACK frequency means that you'll get fewer RTT measurements over a given time frame, this seems probably the least relevant for min_rtt (as it's just the minimum of all measurements), and more relevant for smoothed_rtt (as it averages over the last couple of measurements). Even with the ACK frequency extension (and reasonable tuning of the parameters), you'll still get a couple of ACKs per RTT, so you'd still pick up on changes to min_rtt fairly quickly. In which situations is it relevant to pick up on min_rtt changes fractions of an RTT earlier? Regarding the proposed mechanism, it is unclear to me how measuring one-way delays would help in generating a better min_rtt estimate. A receiver already generates an immediate ACK for a packet that raced ahead (beyond the reordering threshold), thereby enabling the sender to accurately measure min_rtt. It is true that this doesn't capture RTT samples that could've been generated from reordered packets below the reordering threshold, but I'd like to see some data that this is a problem in practice, and if it is, why it can't be solved by lowering the reordering threshold. On Fri, 14 Nov 2025 at 10:32, tong.li <[email protected]> wrote: > Hi everyone, > > As we know, networks like WLAN, cellular, and satellite often perform > better with fewer ACKs to reduce overhead. Inspired by drafts such as > "draft-ietf-quic-ack-frequency" (Iyengar et al.), I've been working on a > draft that improves min RTT estimation for QUIC when ACK frequency is low. > > I'm keen to hear your perspectives if this is an area of interest. > > -Tong Li > > > Renmin University of China > [email protected] > Room 421, Information Building > 100872 > http://iir.ruc.edu.cn/~litong/index.html > ---- Forwarded Message ---- > From <[email protected]> <[email protected]> > Date 11/8/2025 22:11 > To Bo Wu<[email protected]>, > <[email protected]>Ke Xu<[email protected]>, > <[email protected]>Tong Li<[email protected]>, > <[email protected]>Youjian Zhao<[email protected]> > <[email protected]> > Subject New Version Notification for > draft-li-quic-minimum-rtt-estimation-00.txt > > A new version of Internet-Draft draft-li-quic-minimum-rtt-estimation-00.txt > has been successfully submitted by Tong Li and posted to the > IETF repository. > > Name: draft-li-quic-minimum-rtt-estimation > Revision: 00 > Title: Minimum RTT Estimation Under Low ACK Frequency > Date: 2025-11-08 > Group: Individual Submission > Pages: 10 > URL: > https://www.ietf.org/archive/id/draft-li-quic-minimum-rtt-estimation-00.txt > Status: > https://datatracker.ietf.org/doc/draft-li-quic-minimum-rtt-estimation/ > HTMLized: > https://datatracker.ietf.org/doc/html/draft-li-quic-minimum-rtt-estimation > > > Abstract: > > In traditional acknowledgment mechanisms, the sender frequently > "pulls" ACK packets, resulting in significant protocol control > overhead. This leads to wasted CPU and I/O resources, contention for > packet spectrum on half-duplex links (e.g., WLAN), and reverse-path > congestion in asymmetric links (e.g., satellite network). Reducing > the number of ACKs is essential in scenarios where ACK overhead is > non-negligible. However, a lower ACK frequency can introduce biases > in delay estimation, such as overestimating the minimum round-trip > time (minRTT). This document proposes how to calibrate the > estimation of the minRTT under low ACK frequency conditions. > > > > The IETF Secretariat > > > > >
