Delayed acks in Linux 2.2.14

From: anpol (
Date: Wed Jul 18 2001 - 13:52:59 EST

Hi everyone,

I am studying delayed acks in linux 2.2.14 and i come to the following

In bulk data transfer between two linux boxes i never saw a delayed ack. The
server sends an ack every 2 full sized segments. This is fine but in
transactional data transfer (e.g. a telnet session) i also do not see a
delayed ack. What i see is this:

1. Client sends a character
2. Server echoes the character
3. Client sends an ack for the echo

The time between segment 2 and 3 is never above 20ms even when i have a large
RTT (say 560 ms). This is a small delay(??) but its not enough to say that
the ack is delayed. I also could never see the max delay of HZ/2 on an ACK.
So delaying an ack does not depend on the RTT of the connection. Is that
correct? And if yes where does it depend? Has anyone seen the HZ/2 delay on
an ACK?

Thank you in advance


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