Path: utzoo!attcan!uunet!cs.utexas.edu!samsung!zaphod.mps.ohio-state.edu!rpi!bu.edu!bu-it!kwe From: kwe@bu-it.bu.edu (Kent England) Newsgroups: comp.dcom.lans Subject: Re: "real-time" over a lan: token ring vs ethernet vs ? Keywords: real-time, token ring, 802.5, ethernet Message-ID: <61624@bu.edu.bu.edu> Date: 30 Jul 90 19:29:34 GMT References: <19300@well.sf.ca.us> Sender: news@bu.edu.bu.edu Reply-To: kwe@bu-it.bu.edu (Kent England) Distribution: comp Organization: Boston University Lines: 28 In article , hedrick@athos.rutgers.edu (Charles Hedrick) writes: > You've got to be real careful about this "guaranteed" stuff. How right. Even "guaranteed" begs the question on exactly what is guaranteed. I recall a discussion about FDDI that started with figuring out effective throughput and ended up talking about the effect on throughput of setting certain token rotation timers. I believe that discussion was right here on comp.dcom.lans two or three months ago. I can't recall exactly the other principals in the discussion or I would give credit for info. One thing I came away with from that discussion was that some of the worst case maximum token rotation times, for given congestion and timer settings, were positively geologic timeframes. 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. Seems to me that our profession is beyond making these sorts of arguments for one technology over another. It's out of fashion, like saying Ethernet can't sustain more than 3 Mbps throughput. --Kent