Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!bellcore!ka9q.bellcore.com!karn
From: karn@ka9q.bellcore.com (Phil Karn)
Newsgroups: comp.dcom.lans
Subject: Re: Token Ring (was: Re: Info on LANs)
Message-ID: <13096@bellcore.bellcore.com>
Date: 31 Dec 88 23:59:13 GMT
References: <12786@cup.portal.com> <920001@hposdl.HP.COM> <10777@s.ms.uky.edu> <18659@agate.BERKELEY.EDU>
Sender: news@bellcore.bellcore.com
Reply-To: karn@ka9q.bellcore.com (Phil Karn)
Organization: Home for Burned-out Hackers
Lines: 20

>A 4-Mbps Token Ring will outperform a 10-Mbps Ethernet under
>heavy loads because of the absence of collisions.

This is news to me. Dave Boggs, one of the inventers of Ethernet, recently
published a series of tests of Ethernet performance under heavy load.  The
results were presented at ACM SIGCOMM last summer at Stanford, and in
abbreviated form during the Interop '88 conference at Santa Clara.

His results show that a properly constructed Ethernet is quite capable of
carrying a sustained load at a level considerably greater than 40% of its
capacity.  Therefore it is impossible for a 4 Mbps Token Ring to outperform
a 10 Mbps Ethernet, regardless of the Token Ring's efficiency.

He also observed that with the progress being made in "porting" Ethernet to
media other than coaxial cable, "it is now possible to run Ethernet on
wiring plants originally installed for IBM Token Ring". Needless to say,
this got quite a reaction out of the audience. So did the comment, "Ethernet
works in practice, but not in theory".

Phil