Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!lll-crg!nike!ucbcad!ucbvax!andrew.cmu.edu!leong From: leong@andrew.cmu.edu (John Leong) Newsgroups: mod.protocols.tcp-ip Subject: Re: DELNI Strangeness Message-ID: Date: Thu, 11-Sep-86 19:58:36 EDT Article-I.D.: andrew.MS.leong.0.leong.249.0 Posted: Thu Sep 11 19:58:36 1986 Date-Received: Fri, 12-Sep-86 08:42:33 EDT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 26 Approved: tcp-ip@sri-nic.arpa Clive, I don't really know what specifically is your problem with the DELNI. However, one thing you may care to check is this : The DELNI (and for that matter, almost all multiport tranceiver in the market) does not handle "heart beat" correctly. For all practical purposes, heart beat is a kind of acknowledgment from the tranceiver to the station. Within a very short period of time after the tranceiver finished sending the packet into the coax cable, it issue a heart beat signal on the collision pairs of the tranceiver cable - essentially saying "all's well". In the case of the DELNI, this signal is (mistakenly) fanned out to ALL attached stations. The station doing the transmit will know it is a heart beat. However, the other attached stations will treat it as an asynchonous collision notification. Most station will ignore it but I don't know about the DEC-20. However, definitely, do not attached a repeater to a DELNI. Repeater will not toss away heart beat. It will act on it and generate collision reinforcement (jam) on the other side!!! The result is excessive collisions. Very bad news to the overall band width availability. John Leong .