Janet,
On Thu, 16 Nov 2006, Janet P Gunn wrote:
In the circuit switched world, a circuit is either up or down, and
"preemption" means taking the circuit down.
Well, no. I think that I have mentioned here before in a previous
discussion on the topic of preemption that local telephone switches
often congest on the basis of line-side call attempts. This often
happens during natural disasters than invoke a collective behaviour
and result in mass calling attempts (often to 911). The result on
the switch is delayed dial tone (sometimes minutes depending on the
persistence of other callers). It has always been technically possible
in the design of telephone exchanges (based on principles applied to
military switching systems) to preempt or further degrade service to
some lines to allow other lines a higher probability of completing a
call is a shorter interval of time. Some local switches had a line
class option that would permit this. Most jurisdictions, (and carrier
lawyers), deemed that, in the public telephony, the importance of a
telephone call cannot be determined by the line that it originates on,
as it surely can in the case of military telephony. In public telephony
it is deemed only that the importance of a call can be determined by
its destination (e.g. 911) rather than its origin. I think that the
same principles apply to public telephone calls regardless of whether
they traverse the so antiquited circuit switched network, or the new
fangled Internet. I think most regulatory bodies responsible for
both agree with that too. I don't think that whether idle capacity
is incremental in unit circuits or continous bandwidth really has
much to do with it.
--brian
--
Brian F. G. Bidulock ¦ The reasonable man adapts himself to the ¦
bidulock(_at_)openss7(_dot_)org ¦ world; the unreasonable one persists in ¦
http://www.openss7.org/ ¦ trying to adapt the world to himself. ¦
¦ Therefore all progress depends on the ¦
¦ unreasonable man. -- George Bernard Shaw ¦
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