Very Computer

Hello

We're having a problem on a few of our networks:
each network has a number of PCs connected to a SCO 3.4 Unix server
that,
in turn, is connected to an X.25 network.
Frequently, for no apparent reason, a random PC fails to connect.
The server-side of the connection is stuck in SYN_RCVD so it would seem
that the ACK from the PC to server is getting lost somewhere!

During our search for a solution we were informed that some variants of
the SVR4 TCP/IP kernel would occasionally ignore TCP ACKs.
Is this correct?

If so, would someone please give me more information?

Please respond via email; thanks in advance.

-- Marty

Casper
--
Casper Dik - Sun Microsystems - via my guest account at the University

Statements on Sun products included here are not gospel.
Unsolicited e-mail adverti*ts will be proofread for $250.

    >> We're having a problem on a few of our networks: each network
    >> has a number of PCs connected to a SCO 3.4 Unix server that, in
    >> turn, is connected to an X.25 network.  Frequently, for no
    >> apparent reason, a random PC fails to connect.  The server-side
    >> of the connection is stuck in SYN_RCVD so it would seem that
    >> the ACK from the PC to server is getting lost somewhere!

    Casper> Or the ack from the server to the PC.  Are you sure that
    Casper> there's a route from the server to the PC and vice versa?
    Casper> Can you ping the PC from the server?

The original poster can check that if it's PC has anything similiar to
netstat (I believe windows does have). If the state in the PC is SYN-SENT
the server reply never arrived, if it is ESTABLISHED then the server's
SYN,ACK packet got through.

The more probable explanation is in fact the server not being able to reach the
client.

./Pedro.

It could be the SYN/ACK from server to PC that is being lost but, as I
mentioned,
we have been told that some variants of the SVR4 TCP/IP kernel
occasionally
ignore ACKs.  We were not told under what circumstances this occurs;
this is
what I'd really like to know.

Another bit of info that I'd omitted: this usually happens in the
morning while
all the PCs are rebooting; network traffic at this time would be very
heavy with
all PCs using bootp and then a proprietry file transfer protocol on TCP.

Any more help appreciated.

Thanks.

-- Marty