Re: IP QoS issues

[Tim Salo <salo at networkcs.com>]

> From: "Louis A. Mamakos" <louie at UU.NET>
> Subject: Re: IP QoS issues 
> Date: Tue, 07 Jul 1998 15:46:54 -0400
> 	[...]
> However, the number of VC's isn't the problem.  This is the same misconception
> that people have regarding the size of the routing table causing
> the next Internet apocolypse; it not the SIZE but the CHURN RATE that will
> kill you first.  The thing to worry about is the call setup rate in
> the ATM switches, not the number of VCs it supports.
> 	[...]

On the other hand, it is more likely that someone will be charged for 
establishing an SVC than is the case for adding a routing table entry.

A long time ago, a number of vendors developed support for X.21 networks,
(circuit switched networks with fairly fast setup times).  The end devices
would drop the VC after it had been idle for a while, and then re-
establish the VC when the device had characters to send, (which it could
reasonably do because the setup time was so short).  Because the fixed
cost of establishing a VC had a different relationship to the cost of
maintaining a VC on different networks (and because the PTTs also played
with this ratio) the devices had configurable timers for VC clearing.

In a similar fashion, if the establishment and use of an ATM VC is priced,
it is easy to determine the number of active VCs or the rate at which VCs
are established and cleared by adjusting the price, (with a little lag time
for the out-of-band feedback mechanism to effect changes).

-tjs