Path: utzoo!attcan!uunet!portal!cup.portal.com!David
From: David@cup.portal.com
Newsgroups: comp.dcom.lans
Subject: Re: Ethernet bridges above 56Kb
Message-ID: <7632@cup.portal.com>
Date: 24 Jul 88 13:21:32 GMT
References: <9392@dartvax.Dartmouth.EDU> <116@ernie.NECAM.COM>
Distribution: na
Organization: The Portal System (TM)
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XPortal-User-Id: 1.1001.3426

VitaLink makes MAC-layer bridge products capable of running at speeds between
56k and T1, for instance, 256k, 512k, 772k, etc.  The trick is to obtain the
512k circuit.  Once you have the appropriate speed circuit, the bridge runs
at that rate.
 
The easiest way to do this is to use a T1 CSU device such as the SCITEC
"Saturn" product.  This mates the 1.544MHz T1 circuit to a selectable lower
speed circuit while maintaining things like pulse density according to the
rules of T1.  The only drawback of this kind of device is that you can only
put one channel of data over the T1, so if you are using a 512k circuit for
your bridge, you waste the remaining bandwidth (a megabit or so).
 
If you want to derive more than one channel from the T1, look at the various
T1 mux vendors such as NET, DCA, GDC, etc.
 
David@cup.portal.com