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Technology Stocks : Cisco Systems, Inc. (CSCO)

CSCO 78.03

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Nov 14 9:30 AM EST

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To: polarisnh who wrote (5286)	4/10/1997 11:18:00 AM
From: aladin	of 77399

Steven, Define the word 'switch' and define the word 'router'. These are thrown like weapons in your posts with the adage that switching is good and routing is bad. A device making a forwarding decision at layer 3 is a router - plane and simple. The definition of a router is a device that makes a forwarding decision based on a layer 3 address. A bridge is a device that makes this decision at layer 2. At layer one the term is repeater. Now enter the strange new world of marketure. The original lan 'switches' are essentially multiport bridges and gain speed from the advantages of isolating traffic. This is then extended into hardware by creating matrix backplanes rather than traditional bus designs. The word 'switch' is born. However all devices on a lan see all the broadcast and multicats traffic. A traditional router uses a processor to deal with routing updates from other routers. From this it builds a layer 3 forwarding table and when packets are received decisions are made and forwarding occurs. The overhead of the routing protocols precludes early deployment in switches (no one did it until very recently so this is self-evident). A layer 3 switch claims to 'switch' layer 3 protocols. This is a router all marketing aside. We have two solutions at the lan level, one involves a router attached to the campus switch backbone. This edge router does the routing protocol work, but downloads its table to the switch as sessions are started. Thus the router is only involved at session startup and the switch can forward at wire speed. The second solution is putting the router on a card and inserting it in the switch. Both of these involve routing. Now the 'switch' only companies seem to think that layer 3 either doesn't exist - or that they can write it from scratch. Routing protocols are not simple. We have world class switches - both the 5000 and the BPX win their respective marketspaces. We also have world class routers. I think we have an edge in getting the two together. John

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