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From: kik@cernvax.UUCP (kik)
Newsgroups: comp.dcom.lans
Subject: Re: Tradeoff between LAN repeaters and routing gateways?
Message-ID: <425@cernvax.UUCP>
Date: Thu, 15-Jan-87 08:36:55 EST
Article-I.D.: cernvax.425
Posted: Thu Jan 15 08:36:55 1987
Date-Received: Sat, 17-Jan-87 00:38:11 EST
References: <476@savax.UUCP> <8238@topaz.RUTGERS.EDU>
Reply-To: kik@cernvax.UUCP ()
Organization: CERN European Laboratory for Particle Physics, CH-1211 Geneva, Switzerland
Lines: 34
Keywords: Bridge, routing

Sender:


In the "ROUTING" section of Charles  Hendrick's  article  on  gateways  and
bridges,  he  says  "It  is  very  hard to construct complex networks using
bridges".

This restriction comes from shortcomings in current products, not from  the
concept  of bridging.  Current offerings are nearer to stepping-stones than
bridges, in  that they rely on loop-free  point-to-point  links  for  their
interconnection.  Computers  also  used to do this before the advent of the
communications subnet: it is clear that the next step in bridge  technology
is for the bridges to use a separate, high-speed backbone network for their
interconnection.  In fact, we have developed such a system at CERN, and  it
works  very well:
  * ease of addition of new bridges into the full topology,
  * automatic reconfiguration in case of problems in the backbone,
  * optimal route automatically chosen,
  * monitoring included in the backbone management procedures,
  * no Ethernets forced to carry third-party traffic.

   Note that the last point underlines one other  disadvantage  of  current
offerings that Charles Hendrick missed: in the example

	   A -------- B --------- C

B will have to carry all of the A to C traffic.

So, in summary, the current topological shortcomings of bridges are due  to
the technology (and some manufacturer ignorance?); they are not inherent in
the concept.

		  Crispin Piney

CERN
1211, Geneva, 23
Switzerland