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From: franka@hpctdlb.HP.COM (Frank Actis)
Newsgroups: comp.dcom.lans
Subject: Re: Token Ring installation
Message-ID: <31710004@hpctdlb.HP.COM>
Date: 4 Mar 91 18:48:13 GMT
References: <787@hwsw.gedas.de>
Organization: Hewlett-Packard CTD, Colo. Spgs.
Lines: 39


> > we are doing a project with LMX on Token Ring. I would like
> > to know, if there`s any installation with some 30 Token Rings
> > connected via bridges.
> 
> I'm under the impression that attempting source routing with that many
> rings would exceed the size of the source routing field in the packet
> header.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

It depends on how you interconnect the LANs.  If you use a single
backbone ring, any node is only two bridges from any other system on 
the LAN.

	  Backbone Ring	 
 		 _			A
		| |			|
		| |-Bridge ----------------------
 		| |-Bridge ----------------------
		| | .
		| | .
		| | .
		| | .
		| | .
		| |-Bridge ---------------------
		|_|-Bridge ---------------------
					|
					B

As you can see, there are only two bridges between nodes A and B.

If you were to connect many LANs in a serial fashion, you would quickly
exceed the maximum number of hops that source routing can handle for 
any particular path (7).

Frank Actis
Hewlett-Packard
Colorado Telecommunications Division
franka@hpctdlb.col.hp.com