From: barry@dgbt.doc.ca (Barry McLarnon)
Subject: Re: High Speed Backbones?
Organization: The Communications Research Centre
Date: Mon, 25 Jan 93 04:27:24 GMT

This is a repost... dang newsreader defaulted to local distribution again...

In <C15MoI.GMp@law7.DaytonOH.NCR.COM> jra@law7.DaytonOH.NCR.COM (John Ackermann) writes:

>brian@ucsd.edu (Brian Kantor) writes:

>>Were I to do the San Diego Metro net over again, I'd put a single packet
>>9600 bps repeater up on a central location, and have all the outlying nodes
>>and services connect through it.

>This is what we're in Dayton with the 19.2 repeater.  It provides the 
>"backplane" for the other services to connect to.  Rather than upgrade 
>speed (for right now) our plans are to add a second repeater when the 
>load is high enough to justify it -- we'll put users on one repeater 
>and servers on the other.

>>Later, when there are more than two 9600 bps USER stations on the air in
>>town, we'd upgrade the repeater to 56kb.

The same approach is used here in Ottawa, except that we went directly to
56kb.  Our full-duplex 56kb repeater has been on the air for more than 3
years now, and the 56kb network (currently with 7 nodes) has become the
backbonefor the area.  We plan to multicouple a second high-speed repeater
in parallel with the original, sharing the rf equipment... but right now
the repeater handles the local traffic with ease.  Some of the 56kb stations
provide network access on 2m to small "cells" around them, and some have
trunks to other areas (see my article in the '91 CNC for more details).

Using fdx repeaters for linking as well as user LANs should be given serious
consideration.  Take a hypothetical situation where you want to link 3
network nodes that can't hear each other.  You could a find a suitable site
with good paths to the 3 nodes and put up a 3-port packet switch, with
hdx or fdx point-to-point links to each node.  This is an expensive
proposition, with lots of equipment to maintain at a site that may not be
readily accessible.  If a 4th node comes along which is hidden from the
others and needs to be linked, things get very messy.  Now consider putting
a repeater on the site instead... now the equipment on the site is very
simple and easy to maintain.  The equipment needed to link through the
repeater is likewise simple, and it is the same for each node.  Adding
another node is a trivial proposition, and your expensive packet switch
hardware is mostly at home stations instead of up on the hill, so it is
easier to maintain.  You're also using up less spectrum... of course, the
repeater has to support a data rate which can handle the combined traffic.
This isn't the answer when we want get trunks going at T1 rates and beyond,
but it *will* solve a lot of today's networking problems.

Barry VE3JF

-- 
Barry McLarnon                  |  Internet: barry@dgbt.doc.ca
Communications Research Center  |  AMPRnet:  barry@bbs.ve3jf.ampr.org
Ottawa, Canada  K2H 8S2         |  PBBSnet:  ve3jf@ve3jf.#eon.on.can

-- 
Barry McLarnon                  |  Internet: barry@dgbt.doc.ca
Communications Research Center  |  AMPRnet:  barry@bbs.ve3jf.ampr.org
Ottawa, Canada  K2H 8S2         |  PBBSnet:  ve3jf@ve3jf.#eon.on.can
Newsgroups: rec.radio.amateur.packet