Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!sdd.hp.com!decwrl!nsc!voder!dtg.nsc.com!andrew From: andrew@dtg.nsc.com (Lord Snooty @ The Giant Poisoned Electric Head ) Newsgroups: comp.dcom.lans Subject: Re: "real-time" over a lan: token ring vs ethernet vs ? Summary: fddi vs token ring Keywords: real-time, token ring, 802.5, ethernet Message-ID: <1350@berlioz.nsc.com> Date: 30 Jul 90 21:55:17 GMT References: <19300@well.sf.ca.us> <61624@bu.edu.bu.edu> Distribution: comp Organization: National Semiconductor, Santa Clara Lines: 21 In article <61624@bu.edu.bu.edu>, kwe@bu-it.bu.edu (Kent England) writes: > [..]So, token ring may be "guaranteed", but how long are you going > to wait for a given target token rotation time? And what happens to the > guarantee when the token is lost, or other losses occur? It does not > hold. I more or less agree with all that's been said, except to point out that FDDI uses a "timed token" protocol whereas 802.5 Token Ring does not. A fellow called Werner Bux (IBM Zurich I believe) has published many papers analysing loading vs. offered traffic (and vs. many other parameters). Also, it was mentioned that "the token is believed to be lost" when a new station inserts and clicks in its MAU relay, thus causing longish delay. This is not what the protocol specifies; the Initialisation Phase merely causes the new station to exchange special MAC frames with designated Server nodes on the ring. At any rate, there should be no loss of token *theoretically*. -- ........................................................................... Andrew Palfreyman Incidentally, in English, the name of the planet andrew@dtg.nsc.com is "Earth". - Henry Spencer