Path: utzoo!utgpu!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!blake!oregon!jqj
From: jqj@oregon.uoregon.edu (J Q Johnson)
Newsgroups: comp.dcom.lans
Subject: Re: Token Ring (was: Re: Info on LANs)
Message-ID: <144@oregon.uoregon.edu>
Date: 2 Jan 89 14:27:38 GMT
References: <12786@cup.portal.com> <920001@hposdl.HP.COM> <10777@s.ms.uky.edu> <18659@agate.BERKELEY.EDU> <13096@bellcore.bellcore.com> <18672@agate.BERKELEY.EDU>
Organization: University of Oregon
Lines: 15

In article <18672@agate.BERKELEY.EDU>, glass@tehran.berkeley.edu (Brett 
Glass) argues for the superiority of token rings over Ethernets because of
> ... the built-in
> acknowledgement provided by the trailer at the end of a returning frame.  On
> an Ethernet, one must send a packet to acknowledge receipt of a message --
> with all the delays inherent in setting up a buffer, waiting for the cable
> to clear, etc. This overhead can cut the net throughput of an Ethernet by
> more than 75% under any protocol requiring reliable data transport.

To belabor the obvious, this "feature" is only useful at the local link
level.  It does not guarantee that a packet won't be lost (or corrupted)
in the network interface or in a gateway.  Designers of protocols
designed for internetworking (e.g.  TCP/IP, XNS, etc.) argue strongly
for end-to-end ACKs and error detection, which largely vitiate the
benefit of a TR ack.