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SubjectRe: URGENT HELP on LINUX
Date
> I need to know in Linux TCP.h, how, is possible to modify the delay time
> before to acknoledge packets, from the default value to five seconds.

You can't. TCP doesn't work like that.

> I've modified the TCP_ACK_TIME value from 3 to 30.000 but I havent
> obtained the right result, some times the client wait before to send ack
> some times no.

It must ack every other frame, it must not delay acks to a frame that
is not MTU sized.

> I need this modification to minimize the numbet of ack packets in my
> satellite network (round trip delay of 1.5 sec) letting the ack
> procedure be done by data packets that are generated from the client at
> 0,25 pack/sec (5 seconds should be ok).

TCP _must_ ack every other frame. Its in the spec and the protocol doesn't
work very well otherwise. A delayed ack is not permitted to exceed a
certain short value otherwise it makes the rtt estimator unstable and you
then get retransmits of data frames.

The time for an ack doesn't generally matter. TCP when its not dropping many
frames will grow the congestion window to cope with the network (up to about
32K on Linux). On a very fast link long delay link there are protocols
for large windows and also selective ack. The large window stuff is not that
new but is only implemented by a few systems (Linux adds it in 2.1), Sack
is very new (in workable form anyway).

Alan


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