Path: utzoo!attcan!utgpu!bnr-vpa!bnr-fos!tpc
From: tpc@bnr-fos.UUCP (Tom Chmara)
Newsgroups: comp.protocols.tcp-ip
Subject: Reliable datagram service available?
Keywords: datagram UDP IP
Message-ID: <526@bnr-fos.UUCP>
Date: 29 May 89 14:54:39 GMT
Reply-To: tpc@bnr-fos.UUCP (Tom Chmara)
Organization: Bell-Northern Research, Ottawa, Canada
Lines: 37

We've identified a requirement for a reliable communications mechanism within
the UNIX environment, but can't accept the timeout restrictions for TCP
(we did some cocktail-napkin math, and came up with something like 45s to
detect that your destination isn't responding, and 6m to detect that he's gone
away).  As well, we may need HUNDREDS of connections from one process, and
that sort of blows the old "32/64/80 connections per process" out of the water.

According to the manual pages, UDP can drop, duplicate, and/or resequence
packets without warning (sounds reasonable for datagram).  Datagram offers us
the opportunity to maintain our "HUNDREDS" of clients, but is particularly
unfriendly, as we now have to maintain our OWN resequencing/retransmission
mechanisms in the application.

Does anyone know of any
	a) free
	b) $$
software which implements reliable datagram service, something like the
	SOCK_SEQPACKET
(sequenced, reliable, two-way connection-based byte stream for fixed-length
 datagram)
described in the literature?  Something which isn't quite this reliable is
also, obviously, worth investigating, as it's pretty much got to be better
than this (we're looking at bloody stop-and-wait, right now...yes, we're
desperate...)

The software would ideally run in any HP/SUN/4.3 environment, but then, we
can't have everything...
	
Please email; I will post a summary in a few weeks' time...

	Thanks for your time...
		---tpc---
-- 
I am sole owner of the above opinions. Licensing inquiries welcome.
------------------------------------------------------------------------
Tom Chmara			UUCP:  ..utgpu!bnr-vpa!bnr-fos!tpc
BNR Ltd.  			BITNET: TPC@BNR.CA