id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc	uname	nginx_version
2621	QUIC ACKs could be delayed by congestion controllers	yangfurong@…		"In NGINX QUIC, all QUIC ACK frames have to go through the congestion window limitation. This is problematic, as ACK frames could be delayed too much (even exceeding the max_ack_delay). As a consequence, the peer communicating with NGINX could see prolonged RTTs and may not be able to timely increase its congestion window.

Ideally, the ACK returning logic should be:
1. If there is free space in the congestion window and there are other frames going to be sent, ACK frames could be bundled with these frames and sent out together;
2. If the max_ack_delay has been reached, ACK frames must be sent immediately no matter whether there is available cwnd or not (pure ACK packets should be sent if there is no available cwnd)."	defect	closed	minor		other	1.23.x	fixed	quic, ack		4.19.91-013.xxxxx.xxxxx.x86_64	nginx/1.23.0