Internet access and telco usage patterns
rmg at ranma.com
Tue Jul 2 16:07:53 UTC 1996
From: Michael Dillon <michael at memra.com>
> When we discussed some of these things last year on can.infohighway I
> pointed out that if they could divide the traffic by type that they could
> get better trunk utilization by running IP between the CO's. This is the
> modem in every switch location scenario.
Thinking about this, this is not such a bad idea (I'm from a telco
background). But doing it on the IP level, we would need to look into
compression for transporting packets back to the nearest "routing center."
There are a few ways to compress (from good old STAC and predictor to
hardware-level compression like Magnalinks). No doubt that as ports
are made available, people will fill them up to create more traffic.
Also, a direct switch-port interface needs to be utilized. Without a
design right in the central-office switch fabric, all you'll have is
just a shorter path to clog up switch ports. Yes, you'll alleviate
interswitch trunking, but you'll still end up with no dialtone if
you're using twice as many ports to process an "IP call" (one port
for the caller and one port for the terminal server).
> Additionally, if they segregate
> voice traffic they could use compression technology to get as much as 4
> times the conversations on a trunk. Gandalf makes boxes that will run 4
> voice lines down a digital DS0 circuit and the quality is very good. You
> can tell there is compression there but it's better than long distance
> line quality often is.
MCI played with voice compression in the late 80's (called ADPCM). and
they had pretty bad results. They had equipment which was supposed to
detect the initial sequence of modem tones (the first tone "clears" out
any echo cancellors on the circuit), but they got so many calls for bad
faxes and modems not connecting that they ripped out most of the ADPCM
equipment. Some of it is still there, but at more remote sites now.
Mfgrs claim to have better detection (and also trying for MPEG compression)
but some of the early adoptors (read: telcos) still have healing scars.
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