Subject: RE: [Ieprep] Understanding Congestion

From: "Dvorak, Charles A (Chuck), ALASO" <[email-masked]>
Date: Tue, 17 Dec 2002 02:36:28 -0500

FYI, systems for dealing with dynamic load (when fixed bandwidth is
getting congested) have been around since the 60s--TASI (time assignment
speech interpolation, I think) which was analog and then DCME (digital
circuit multiplication eqpt) in the early 1980s, followed by PCME
(packet circuit multiplication eqpt) in the late 1980s. Several US and
ITU standards were produced on these techniques, which were widely used
in international network segments.

Each of these systems produced certain speech impairments under severe
load, but even so they were capable of transporting up to 8 or 10 times
the traffic that the bandwidth would have otherwise supported. (Data
traffic was not compressed as much as voice, if at all).

In the 1990s carriers deployed real-time network routing, which was more
powerful than the non-RT dynamic routing techniques deployed in the
1980s. Both methods route calls to paths that are not congested.

The PSTN did *better* than having a "concept of congestion avoidance."
It actually *used it* decades ago, and probably everyone reading this
message has sometime in their life spoken over a phone call using one or
more of these techniques.

> -----Original Message-----
> From: RJ Atkinson [mailto:[email-masked]]
> Sent: Monday, December 16, 2002 2:01 PM
> To: ieprep
> Subject: Re: [Ieprep] Understanding Congestion
> 
> A key item to understand is that the PSTN does not really have the
> concept of congestion avoidance (e.g. slow down the bits/second rate
> of a session to help the network avoid being congested), whereas that
> is central to the Internet.
> 
> This is not a better/worse thing, just as call rejection capability
> isn't a better/worse thing.  The architectures are fundamentally
> different.  One needs to work with the architecture for the system
> in hand, not some other architecture.
> 
> Ran
> 
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---

From: RJ Atkinson <[email-masked]>
Date: Tue, 17 Dec 2002 09:41:41 -0500

On Tuesday, Dec 17, 2002, at 02:36 America/Montreal, Dvorak, Charles A 
> more of these techniques.

A POTS handset does not have a codec or any concept of congestion 
avoidance.
The PSTN has never had end-to-end congestion avoidance as one result.  
The Internet
has since [VJ88].  As discussion here has repeatedly noted, the 
potential congestion
point is on the access link, not in the core, so the existence of 
PSTN-unique
technology for congestion avoidance in the PSTN core is not 
tremendously relevant
to IEprep.  Fortunately for us, the Internet does not have significant 
congestion
in the core, even during natural disasters or man-made disasters.

The problem spaces are DIFFERENT.  The solution spaces will necessarily
also be DIFFERENT.

Ran