Date   : Sat, 11 Jul 2009 10:49:59 +0100
From   : pete@... (Pete Turnbull)
Subject: Master Ethernet upgrade

On 11/07/2009 10:07, Mark Usher wrote:
>> A bridge is specifically defined as a same-network to same-network
>> connection, 

Tanenbaum, page 40, for a start.  Or page 324 et seq.

> A bridge forwards packets based on the hardware address (Layer2) whereas a
> router forwards packets based on the network protocol address (Layer3).

Not quite.  A bridge forwards packets between systems that use the 
*same* network layer (but they may be different at the transport layer). 
  It acts as a selective repeater, which may or may not also change 
voltage levels or hardware technologies, but does no more.  The common 
example is Ethernet to/from Token Ring.  Econet and Ethernet do not use 
the same network layer, and things like addresses have to be translated. 
  In fact, more than that is different, there's data in the Ethernet 
layer that doesn't exist at all in Econet.  Also the handshaking is 
different, and the protocols have to be changed.

> So as this device process packets based on the Econet hardware address, it
> functions as a bridge.

No, it's a router, because it *must* do more than that.  Or a gateway, 
if you prefer.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York