[Asterisk-Users] Intermittent Silence

[Eric Wieling aka ManxPower]

If you have a Polycom make SURE the cable going into the handset is 
FULLY seated.

Andrew Kohlsmith wrote:

> First, I would like to commend you on your excellent list post.  Detailed 
> without burying people in details and to the point, and not running around 
> pointing fingers.
> 
> Now for the bad news.
> 
> On Wednesday 13 July 2005 15:40, Stuart Lester wrote:
> 
>>I am currently experiencing intermittent silences with my asterisk system.
>>The symptoms are as follows:
> 
> 
>> * Both for incoming and outgoing calls, I (and other users)
>>occasionally experience a brief period of silence.
>> * The silence lasts anywhere from 3 to 10 seconds.
>> * It is not due to silence suppression, because the silences
>>generally occur in the middle of sentences.
>> * Silences occur at various times of the day, for calls of various
>>lengths, and at different times during calls.
>> * Sliences have occured for incoming and outgoing calls, and
>>have affected both people on the VoIP side and the PSTN side.
> 
> 
> I had more or less identical symptoms.  I'd tried new motherboards, new cards, 
> experimental code, you name it.  We finally broke down and have made only one 
> change to our setup, which I'll explain below.
> 
> 
>> * Affected users are connecting to our asterisk system from
>>multiple geographic areas, using multiple ISPs, and all seem to have
>>reliable and acceptable network connections.
> 
> 
> This tells me it is on your side.
> 
> Our system looks like this:
> 
> Norstar MICS [ PRI ] Asterisk 1 [ SDSL ] Asterisk 2 [ PRI ] Telco
> 
> The SDSL loop is just a 4ish-km link between a downtown location and the 
> office.  It terminates into a regular old switch (Baystack 350) which also 
> carries the internet traffic for a half dozen businesses.  It is not VLANned 
> or anything, and the traffic between Asterisk 1 and 2 is over RFC1918 
> addresses.
> 
> Asterisk 2 can route calls through the telco PRI or through one of a half 
> dozen VOIP providers.
> 
> The change we made?  We stopped routing calls over the VOIP providers.
> 
> As soon as we did that our intermittent silent periods *disappeared*.  We've 
> been routing all calls through the telco for the last 45 days or so, and do 
> about 25-35000 minutes a month, if I'm not mistaken.
> 
> This ruled out:
> - Asterisk 1 & 2 (mobo, card, NIC, everything)
> - Asterisk jitter buffer code
> - the switch
> - the SDSL hardware (Megabit Modem 300S) and loop
> 
> Our culprit appears to be either the router, the ADSL uplink modem (Sangoma 
> S518) or the uplink itself.  I'd like to get another link and do some 
> testing.  I'm almost 100% certain it's not the hardware or the router 
> (linux).  In fact, we have the link, I just need to get the time to do the 
> testing.  My guess is that it's the upstream provider (Ikano), but I can't 
> rule out the others yet.
> 
> I am sorry I don't have better news for you.  I would suggest trying a couple 
> different upstream providers (even just regular ADSL should be good for 
> initial testing and it's not expensive to try a few...  I'm looking for a 
> more inexpensive T1 provider in my area.
> 
> -A.
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