[Asterisk-Users] Echo on a PRI

[Rich Adamson]

> On the subject of echo on a PRI, I too get this, but only when calling
> people in certain rate centers.  Calls within my LATA (primarily VZ) are
> completely free of echo.  Calls to a neighboring LATA (all Sprint) have echo
> on almost every rate center.
> 
> I wish I knew more about this so I could rip Sprint a new one and tell them
> to fix their trunking, but...

Troy,

Given the reseach that is currently going on, etc, I would not bet
any more then a cup of coffee that Sprint (or any other carrier) has
an echo problem right now. There _appears_ to be an issue with the
echo cancellation routines in asterisk that is impacting more then
a couple of implementations.

The research to date suggests the current echo canceler works well
in some cases, and not so well in other cases. In other words, there
are a certain set of undocumented/unknown conditions (and/or PC systems)
that fall within the thresholds of the current canceler that work,
and other conditions (and PC systems) that fall outside the limits
of the canceler that are less then acceptable. The limits and thresholds
are _not_ black & white and may end up being one of the more difficult
problems to solve within asterisk. (E.g, it's entirely possible that 
your calls via Sprint fall outside the limits of *'s canceler.)

As you've probably seen earlier on this list, there is a high
probability that internal system issues (eg, interrupt servicing
latency, possibly PCI bus issues, etc) that are impacting this in
_some_ specific cases. In some cases, swapping the motherboard did
in fact impact the cancellation quality. However, be very carefull 
not to read anything more into that at this time.

There is no one at this time that knows "factually" what those limits,
thresholds, etc, happen to be (not even Mark).

Rich