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From: chen@cunixc.UUCP
Newsgroups: comp.dcom.lans
Subject: Using T1 multiplexers for Ethernet WANs
Message-ID: <226@cunixc.columbia.edu>
Date: Thu, 5-Nov-87 15:49:00 EST
Article-I.D.: cunixc.226
Posted: Thu Nov  5 15:49:00 1987
Date-Received: Sun, 8-Nov-87 09:02:00 EST
Reply-To: chen@cunixc.columbia.edu (Bill Chen)
Distribution: na
Organization: Columbia University
Lines: 46
Keywords: Ethernet, T1 muxes


We at Columbia University are planning for a Wide Area Network.
This net will connect three CU campuses which are 12 to 15 miles apart
in a triangular topology. A fourth campus might eventually come into
the picture also.

Our plan is to extend our Ethernet using gateways via common carrier
T1 service to these campuses. Since we also want to have sync and
async traffic on the T1 link besides the Ethernet traffic, we want to
put a T1 mux between the gateway and the CSU.

We already have a 56Kbps Ethernet link through Datatel T1 muxes using
Vitalink's TransLan bridges. But the Datatel muxes can only handle a
single T1 interface and the Vitalink boxes are level 2.

My question is whether anyone has had experience with using part of
the bandwidth of T1 muxes for Ethernet extensions of this sort.

In particular, what kinds of clocking concerns are there from both the
point of view of the gateway and the mux.

Does anyone have their gateways running at speeds that are higher than
64Kbps? If so, what if there is a tail circuit from the mux to the
Ether? Are there line drivers that can handle more than 64Kbps, up to
a little less than 1.544Mbps?

We've spoken to Timeplex about their miniLink products and they say
there should be no problems with what we want to do using their
equipment. But we would feel a lot better if we heard that from people
that have actually done this kind of thing.

In addition, any information with the kind of muxes used, the kind of
problems experienced, CSU's, etc. will be greatly appreciated.  The
gateways that we are looking at are Cisco and Proteon.



Thanks in advance for any and all information.  If other people are
interested in the answers I get, I will post a summary.


  Bill Chen
  Data Communications
  Columbia University

  Internet: chen@cunixc.columbia.edu