From b7c497ab227828980837f176a9b6756b8adcdfb8 Mon Sep 17 00:00:00 2001 From: ianswett Date: Tue, 17 Sep 2019 19:14:04 -0400 Subject: [PATCH 1/2] Retransmitting ACK frames can inflate RTT Fixes #2748 --- draft-ietf-quic-recovery.md | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/draft-ietf-quic-recovery.md b/draft-ietf-quic-recovery.md index 8358c56ae8..b64e396914 100644 --- a/draft-ietf-quic-recovery.md +++ b/draft-ietf-quic-recovery.md @@ -291,6 +291,13 @@ are received within an RTT. As suggested in {{?RFC6298}}, doing so might result in inadequate history in smoothed_rtt and rttvar. Ensuring that RTT estimates retain sufficient history is an open research question. +### Retransmitted ACK frames + +Section 13.3 of {{QUIC-TRANSPORT}} recommends sending the most recent set of +acknowledgements in ACK frames, but if ACK frames are retransmitted, an inflated +RTT can be measured. Some incorrect RTT samples are prevented by only measuring +RTT when the largest acked increases. + ## Estimating min_rtt {#min-rtt} min_rtt is the minimum RTT observed over the lifetime of the connection. From 8ca6082686923931376d316a760573b1ce36d238 Mon Sep 17 00:00:00 2001 From: ianswett Date: Tue, 17 Sep 2019 21:47:45 -0400 Subject: [PATCH 2/2] Update draft-ietf-quic-recovery.md Co-Authored-By: Martin Thomson --- draft-ietf-quic-recovery.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/draft-ietf-quic-recovery.md b/draft-ietf-quic-recovery.md index b64e396914..8ee848b41d 100644 --- a/draft-ietf-quic-recovery.md +++ b/draft-ietf-quic-recovery.md @@ -296,7 +296,7 @@ retain sufficient history is an open research question. Section 13.3 of {{QUIC-TRANSPORT}} recommends sending the most recent set of acknowledgements in ACK frames, but if ACK frames are retransmitted, an inflated RTT can be measured. Some incorrect RTT samples are prevented by only measuring -RTT when the largest acked increases. +RTT when the largest acknowledged increases. ## Estimating min_rtt {#min-rtt}