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Path: utzoo!mnetor!seismo!brl-adm!brl-sem!ron
From: ron@brl-sem.ARPA (Ron Natalie )
Newsgroups: comp.dcom.lans
Subject: Re: Tradeoff between LAN repeaters and routing gateways?
Message-ID: <567@brl-sem.ARPA>
Date: Wed, 7-Jan-87 21:07:48 EST
Article-I.D.: brl-sem.567
Posted: Wed Jan  7 21:07:48 1987
Date-Received: Thu, 8-Jan-87 00:46:34 EST
References: <476@savax.UUCP>
Organization: Electronic Brain Research Lab
Lines: 62

In article <476@savax.UUCP>, dove@savax.UUCP (webster dove) writes:
> 
> We are just beginning to setup a TCP/IP network here.  We have several
> facilities separated by 5-20 miles, and most facilities have several
> distinct ethernet cables.
> 
> I am looking for explanations of the tradeoffs between using filtering
> repeaters to convey traffic between wires and between facilities (e.g.
> VITALINK) and using TCP routers for the same purpose (e.g. PROTEON).
> 
First, your terminology is off.  The VITALINK TRANSLAN is not a repeater.
A repeater passes through the ethernet signal between two points.  The
translan actually receives the packet into it's memory and then retransmits
it on the other cable.  The community is not overly sure what to call this
but the word "bridge" in lower case seems to be gaining popularity.

The Proteon is not a TCP router, it is an IP router.

BRIDGE:
	VitaLink TransLan, DEC LANBridge

ADVANTAGES-
	- Will pass data without regard to protocol.
	- Maintains your ethernet address space so every host
	  is direcly accessable to every other host.
	- Broadcast messages are received everywhere.

DISADVANTAGES-
	- Problems on one ethernet cable such as transceiver jabbering
	  will be propagated to other segments.
	- Broadcast messages are receieved everywhere.
	- All segments of the cable will receieve a large percentage
	  of the total traffic, hence you will run into the maximum
	  throughput limits faster.

ROUTER:
	Proteon, CISCO, Bridge, among others

ADVANTAGES:
	- Isolates the cable segments from each other for better
	  performance and fault tolerance.
	- Multiple routes can be provided in the system to provide
	  for increased performance and redundancy.
	- Can interface to things other than Ethernet.

DISADVANTAGES:
	- Some level of IP routing must be done (generally handled
		automatically though).
	- Must be designed to handle each protocol that they will
	  route (multi-protocol routers have been built, or just
	  use a different router for each protocol).


==================================

Frankly, the performance and fault tolerance problems are enough
to scare anyone into routers.  There is an ethernet spread through
eight states by satellite and TRANSLAN boxes and while it is amusing,
I'm sure that any of the parties can tell you it is no way to run a
network.

-Ron