Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!helps!uudell!upurbmw.dell.com!sblair
From: sblair@upurbmw.dell.com (Steve Blair)
Newsgroups: comp.unix.sysv386
Subject: Re: tcp/ip & fddi chips (was Re: binary Mach distribution for 386)
Keywords: speed = "no networking"
Message-ID: <14325@uudell.dell.com>
Date: 21 Jan 91 17:22:47 GMT
References: <13963@uswat.UUCP> <1991Jan4.140341.11874@granite.cr.bull.com> <1991Jan15.182524.14868@scuzzy.in-berlin.de> <104@calcite.UUCP>
Sender: news@uudell.dell.com
Reply-To: sblair@upurbmw.dell.com (Steve Blair)
Organization: Dell Computer Corp.
Lines: 36

[the following are *MY* opinions, and >not< DELL's]


Having recently left a networking company in Ca., I spent
about 4 months working with FDDI. A few observations that
I observed while working with several FDDI TCP/IP implementations:

1) the only way almost anyone will every get close to 100Mb's/sec
	is if nothing is running on the network, and TCP/IP doesn't
	exist.
2) TCP/IP over FDDI was only successful in gaining a B/W of about
	45->60Mb's/sec in "normal" operation mode, and in "burst"
	mode, mabye about 65->72Mb's/sec.
3) TCP/IP is notoriously ineffecient as a statefull protocol on
	"any wire". Therefore, that's one of the reasons that on
	a fairly quiet network, you'll only see about 4->6.2Mb's/sec
	*due to the statefull overhead* of TCP/IP.


FDDI does/will add significantly to the networked performance of many
systems, and applications that are written to take advantage of the
increased bandwidth. However, there are other mitigating issues that
can(*and do*) hamper effeciency on a network(FDDI). Some of these
issues are:


1) not all vendors are racing to adopt/implement FDDI  until the
	marketing/compatibality  issues are "wrung out".
2)  FDDI has certain information that in restructuring the "ring":
	after a failure takes sometime to occur. Also there are
	other packets, like scrubber packets, that consume some
	network overhead, just like routing information does.

Hopefull this will help. *YOUR MILEAGE WILL VARY*

steve blair	DELL	UNIX	DIVISION