Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!labrea!decwrl!decvax!ucbvax!gateway.mitre.ORG!tsuchiya From: tsuchiya@gateway.mitre.ORG (Paul Tsuchiya) Newsgroups: comp.protocols.tcp-ip Subject: Re: ISO8473 vs. IP Message-ID: <8709081838.AA16085@gateway.mitre.org> Date: Tue, 8-Sep-87 14:38:21 EDT Article-I.D.: gateway.8709081838.AA16085 Posted: Tue Sep 8 14:38:21 1987 Date-Received: Wed, 9-Sep-87 06:28:58 EDT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 36 > From: "Marty Schoffstall" > Status: R > > > - 'congestion experienced'. Set by a router, when a router > experiences congestion. > > The infamous "DEC Bit", which reports to the recipient of the packet > that there is congestion. This bit has debatable merit, would the > two camps like to expound? > > Marty Ok, I'll bite. The DEC bit is used, at least in DECNET (phase 4 or 5, I don't know) to control the transport window such that the network doesn't get congested. It is a "congestion avoidance" mechanism. As far as I know, the algorithm assumes it knows the round trip time. I don't know if DEC measures this or assumes a value. (I understand the problems associated with trying to measure it.) The algorithm seems to be a good one, and works as long as all of the parts are there and everyone participates. (Please, someone from DEC correct me if I have this screwed up). DEC has released there algorithm for doing this (until recently, it was proprietary). In their IS-IS routing proposal, they have said when to set the bit. I am not sure how or if they intend to standardize the part that tells the transport machine what to do. I suppose this could be done right in ISO, or in one of the profile organizations like COS. Tsuchiya PS. We may be in two camps, but lets face it: if it rains, all of our campfires are going to go out.