Date: Wed, 25 Feb 1998 08:47:19 +0100 From: sthaug@nethelp.no To: cdillon@wolves.k12.mo.us Cc: hackers@FreeBSD.ORG Subject: Re: Token Ring for FreeBSD yet? Message-ID: <14181.888392839@verdi.nethelp.no> In-Reply-To: Your message of "Wed, 25 Feb 1998 00:12:33 -0600 (CST)" References: <Pine.BSF.3.96.980224224016.306A-100000@duey.hs.wolves.k12.mo.us>
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> For example, can you guarantee, > mathematically, that you can get a given mount of data across the network > in a given amount of time, worst-case? Can't do that with Ethernet, since > it works too chaotically. In token-passing and polling based networks, > you can say with certainty that even under maximum load, you can get a > packet from one machine to another in X milliseconds. Sorry, it's not that simple. On a token ring network, tokens can get lost. Yes, this happens in real life. So any "guarantee" that you give for token ring networks is based on statistics. Same with Ethernet. On a 10 Mbps Ethernet, the maximum accumulated waiting time for one station to send is 367 ms (corresponding to the 15th collision). You can give a statistical "guarantee" that the 15 collision case is extremely unlikely in a well constructed Ethernet. > The only reason I brought this up at all is > because an old professor of mine sparked a light about just WHY some of > these seemingly slower (judging by bit-rate) networks can actually be > faster than their higher-bitrate cousins under certain circumstances. > Same reason you shouldn't judge how fast a processor is just by its clock > rate. I was merely hoping to belay some of the common misconceptions. :-) Unfortunately, repeating the old slogan about how Token ring is deterministic and Ethernet is not, is *adding* to the misconceptions. Steinar Haug, Nethelp consulting, sthaug@nethelp.no To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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