Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!yetti!geac!daveb From: daveb@geac.UUCP Newsgroups: comp.protocols.tcp-ip Subject: Re: host down (was ..."layering violations") Message-ID: <1801@geac.UUCP> Date: Tue, 10-Nov-87 14:56:52 EST Article-I.D.: geac.1801 Posted: Tue Nov 10 14:56:52 1987 Date-Received: Thu, 12-Nov-87 00:36:07 EST References: <12347435144.54.PADLIPSKY@A.ISI.EDU> <8711030915.AA00844@gumby.wisc.edu> Reply-To: daveb@geac.UUCP (Dave Collier-Brown) Organization: The little blue rock next to that twinkly star. Lines: 33 Summary: Two cases come to mind... In article <8711030915.AA00844@gumby.wisc.edu> Mitchell Tasman (g-tasman@GUMBY.WISC.EDU) writes: [discussion of the behavior on "host down"]... a daemon | should immediately close the associated TCP connection. | | With an 1822 Distant Host connection to DDN, this may be a fairly | reasonable approach. However, a typical DDN connection of late has been | X.25 or HDH. Here, "host down" may have a more transitory meaning: simply | that there was noise on the host access line. The remote host may well | reappear with all TCP connections intact. My experience with short-haul or secondary nets has been that there are two distinct kinds of events which TCP might regard as a "host down". One is a real host-down and the other is the aforementioned QRN (noise) on the line. The latter is particularly annoying on what is supposed to be a low-error medium... Methinks that TCP is being a bit pessimistic: IP is not supposed to be error-free, and I suggest that TCP may be misinterpreting the errors which a short-haul network seems to love to produce as a more serious and long-term event than it really should. Could map or someone comment? --dave (on the other hand, i could be biting my foot) c-b -- David Collier-Brown. {mnetor|yetti|utgpu}!geac!daveb Geac Computers International Inc., | Computer Science loses its 350 Steelcase Road,Markham, Ontario, | memory (if not its mind) CANADA, L3R 1B3 (416) 475-0525 x3279 | every 6 months.