Path: utzoo!attcan!uunet!husc6!purdue!narten
From: narten@cs.purdue.EDU (Thomas Narten)
Newsgroups: comp.dcom.lans
Subject: Re: Token Ring (was: Re: Info on LANs)
Message-ID: <5758@medusa.cs.purdue.edu>
Date: 3 Jan 89 01:18:41 GMT
Sender: news@cs.purdue.EDU
Organization: Department of Computer Science, Purdue University
Lines: 25

In article  <13096@bellcore.bellcore.com> karn@ka9q.bellcore.com (Phil Karn) writes:
>>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.
>

Indeed, the paper gives *experimental* results (read real numbers
measured by real hardware) that show that even in a worst case
scenario (25 transmitters competing against each another by
continously attempting to transmit tiny 64 byte packets) 85% of the
bandwidth was utilized for data (only 15% lost to collisions, etc.).
With large packets (1500 bytes) utilization surpasses 95%.

However, just because he gets good performance doesn't mean that your
whiz-bang Ethernet card will.  One of the paper's observations is that
much of the comercially available Ethernet hardware is braindamaged in
design in such areas as memory management -- a problem just as
prevalent in ring networks.
-- 
Thomas Narten
narten@cs.purdue.edu or {ucbvax,decvax}!purdue!narten