Yes its perfectly legal to set the ack flag in a payload carrying segment as the ack is acknowledging the segments coming in the opposite direction, they just hitch a ride on the outbound segment because its there. If there were no data the ack would go anyway but in its own packet with a zero segment length.
The rfc is the best place to go for the rules of tcp as it IS the rules of TCP - google for rfc793
Pete
-----Original Message-----
From: ethereal-users-bounces@xxxxxxxxxxxx
[mailto:ethereal-users-bounces@xxxxxxxxxxxx]On Behalf Of
andy@xxxxxxxxxxxxxxxxx
Sent: 09 January 2006 10:23
To: ethereal-users@xxxxxxxxxxxx
Subject: [Ethereal-users] Help with the Rules of TCP/IP
Hi Folks
Is it Legal to send a TCP segment with the ACK flag set and data in the payload.
I have a malfunctioning application and when it fails I see a continuos TCP
retransmission (5 attempts) of a packet that has an ACK flag only set and a
payload length of 1460 bytes.
Forgive me if I miss understand, but I though you had to have the PSH flag set
to send data? Is there a good document that would explain these rules?
Many Thanks for your help
Andy Harcup
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"If you discovered how one wheel in the 'clock' turns - you may speculate how
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