Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!uunet!bu.edu!bu-it.bu.edu!kwe
From: kwe@bu-it.bu.edu (Kent England)
Newsgroups: comp.dcom.sys.cisco
Subject: Re: campus network configuration
Message-ID: <73000@bu.edu.bu.edu>
Date: 24 Jan 91 14:46:38 GMT
References: <31735@boulder.Colorado.EDU>
Sender: news@bu.edu.bu.edu
Reply-To: kwe@bu.edu
Organization: Boston University Information Technology
Lines: 37

In article <31735@boulder.Colorado.EDU>,
 ARCHERB@VAX1.UMKC.EDU (Barry Archer) writes:
> 
>   Backbone -- Big_Router -- ethernet_concentrator		! building A 
> 			      |
> 			     IGS -- ethernet_concentrator	! building B
> 					|
> 					IGS -- ether_concentrator ! building C
> 
	I would recommend avoiding the extra hops through the IGSs,
the extra expense, and the extra configuration management.  There are
many advantages to minimizing the diameter of the Internet and what
you do on your campus is very important to keeping that diameter
small.  If you plan on using IGRP or RIP, the smaller the diameter the
faster the routing convergence which I happen to think is important.

	If you have sufficient capacity in Big_Router or Big_Routers I
would suggest you consider extending an Ethernet interface out to each
of the concentrators with pairs of fiber optic transceivers.  You must
be cautious about violating the delay spec for whichever Ethernet
extension you use, because delay violations will result in undetected
collisions which are correctable, after considerable delay, only by
higher layer protocols.  If you wish Ethernet extensions of arbitrary
delay, you can talk to me or Kirk Lougheed at cisco about the
two-interface hack we did for NEARnet microwave Ethernet links, but it
requires a router on each end.

	I'm not a fan of putting all my eggs in one basket; at BU we
use a small set of routers on a high speed backbone with Ethernet f/o
extensions to buildings throughout largish service areas.  This seems
like a reasonable compromise among cost, reliability, ease and
performance.  If you think FDDI is too pricey or dicey as your
backbone, you could use a couple or three Ethernets as backbone among
the set of Big_Routers servicing your buildings; ethernet interfaces
are cheap on cisco routers; use them liberally.

	--Kent