Subject: Re: TCP connections
To: None <gyro@zeta-soft.com>
From: Niklas Hallqvist <niklas@appli.se>
List: current-users
Date: 02/12/1996 08:42:55
>>>>> "Scott" == Scott L Burson <gyro@zeta-soft.com> writes:

Scott> I am trying to set up a telecommuting system for my company.
Scott> One thing I have noticed is that if a remote user has
Scott> established a TCP connection (`rlogin', say) over PPP, and the
Scott> PPP connection goes down for a while -- I haven't taken the
Scott> time to figure out exactly how long -- the TCP connection will
Scott> be closed.

Well, one side of the coin is that TCP connections will be reset when
too many retransmits have gone unacknowledged (10?).  For this too
change you have to change the kernel.  I walked down this road a year
ago or so, I hope I remember things correctly.

The other side of the coin is that the server side of the rlogin
protocol issues keepalive messages, thus forcing the above retransmits
to happen if the line is down.  This is easy to turn off, just add the
"-n" option to the rlogind invocation in inetd.conf.  This should make
the problem less severe even though it's still there.

Another option for you to consider is to use "screen" with the
detach/reattach functionality.   Then lost rlogin/telnet connections
aren't all that fatal.  Just call in again, login, and do "screen -R"
to reattach to your session.

BTW, does the TCP/IP standard allow/require connection arbitrary TCP
connection resets after a certain amount of retransmits?  I always
thought they would/should stay forever...  Of course a user-level way
to reap such connections would be nice.

Niklas

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