[Asterisk-Users] QoS Help and survey

[Noah Miller]

Hi -

We've been using IAX forwards between sites for a little while now 
(with centralized VM).  For the most part, it is fine, but I have some 
very minor, yet persistent QoS issues on calls over the IAX forwards.  
For most normal calls, there are very occasional minor glitches, just 
an infrequent popping sound.  It is something most of my users don't 
really care about, although it is a minor annoyance for some of them.  
Strangely, the problem is significantly more noticeable on voicemail 
and directory calls, and it is not limited to just pops.  I also get 
large drops and strange metallic sounding echos and repeated sounds 
(voicema-ma-ma-ma-ma-mail   - a la Max Headroom, for those that 
remember that).  The issue isn't horrible, but it is a little weird and 
annoying.  It generally only happens when network traffic between the 
sites is heavy.

So, my survey question is - Is this normal?  Should I expect to be able 
to get PSTN quality calls over these IAX forwards, or are some audio 
glitches just part of the package?  I use a commercial VoIP service at 
home, and I don't have any of these issues, so I'm guessing it must be 
something in my network or setup.

Our setup:
- CVS HEAD from about a month ago on all machines (problem was also 
there with CVS HEAD as far back as 11/04)
- Late Model Dell Servers 1600SC and SC420's
- Cisco Routers - 1751 and 1721's (using Low Latency Queueing, matched 
to UDP 4569)
- T1's
- 10/100 Switches
- 10/100 hubs at one site (is this a problem for anyone?)
- SIP phones (Polycom IP300, IP500 and IP600, Snom 190)

Thanks,
Noah