Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!joyce!distek4!mckenney
From: mckenney@distek4.uucp (Paul E. McKenney)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Keep alives....
Message-ID: <21652@joyce.istc.sri.com>
Date: 5 Jun 89 22:28:25 GMT
References: <8906040508.AA20495@uunet.uu.net>
Sender: news@joyce.istc.sri.com
Reply-To: mckenney@sri.com (Paul E. McKenney)
Organization: SRI International, Menlo Park CA
Lines: 17

In article <8906040508.AA20495@uunet.uu.net> mo@prisma.UUCP (Mike O'Dell) writes:
>Ok, so we don't do keep-alives at the TCP level.  This is the best reason
>I've heard for a session protocol.

Correct me if I am wrong, but if the transport layer cannot determine a
good keepalive ``timeout'' from the RTT and window-size information available
to it, then a session layer hasn't a ghost of a chance of coming up with
anything reasonable.

Has anyone tried to derive keepalive timeouts from RTT and window information?
For a simple example, one might set the timeout to (3000*RTT).  This would
yield a timeout of about 25 minutes for typical NSFnet RTTs (about half a
second).  On low-baudrate lines, the longer packet transmission times would
force the RTT higher (a 1200-baud line requires two-thirds of a second
to turn a minimum-size TCP packet around).

					Thanx, Paul