[Asterisk-Users] Current echo status?

[Scott Laird]

I've been following the list for months, and I have a working Asterisk 
setup, but it'd be *really* useful to me at this point if someone could 
summarize when Asterisk has echo problems and when it doesn't.  For 
instance, I usually hear a far-end echo when talking on my 7940, but 
not when using a POTS phone plugged into a TDM400 FXO port.  It doesn't 
seem to matter if the call goes out over a POTS line or via NuFone; 
either way there's a fair bit of echo on most (but not all) calls.

Do different SIP phones have better echo cancellation then the Cisco 
7940/60s?  How about the Polycom IP500/600s?

Does it matter if calls go out via POTS/T-1/PRI/VoIP?

The general impression that I've received is that "fast" channels 
(basically traditionally telephony interfaces) don't exhibit noticeable 
echo, but the slight delay associated with VoIP packetization unmasks 
existing echo.  Is that a reasonable summary?

We're starting to plan for a new office build-out at work, and I'd love 
to use Asterisk and SIP phones in the new office, but I'm not going to 
try to sell management on a phone system with a horrible echo problem, 
even if it will get fixed eventually.

Thanks.


Scott