[asterisk-users] SIP devices with packet loss tolerance

[Tim Panton]

On 24 Apr 2007, at 03:19, Chris Bagnall wrote:

> Thanks for all the replies. Answering the points raised in turn:
>
>> How did you perform the speed tests?
>
> Generally using thinkbroadband.com's speed test java applet.
>
>> On the matter of the BitTorrent factor: did you have the users  
>> connect
>> the phone, and only the phone, to the Internet connection?
>
> Yep, phone straight into the router, computers etc. all powered down.
>
>> I don't think it's the packet loss per se; it's more likely to be
>> jitter, and no, correcting for jitter in Asterisk isn't likely to  
>> make
>> much difference, because the jitter on upstream connections can be so
>> big that it overwhelms the jitter buffer.
>
> The strange thing here is that one some other sites with 2-3 users  
> (remote offices, etc.) where we've deployed "mini-asterisks" (Via  
> Epias in ITX boxes), call quality is much better even over equally  
> "consumer" internet connections. This makes me think that either  
> (or both): 1) IAX is much more tolerant than SIP; 2) Asterisk's  
> jitter buffering is far superior to that in any phones.

Or perhaps one of the ISP's is 'de-prioritizing' SIP and is ignorant  
of IAX.
You could test this theory by having a couple of test IAX devices  
(you can get them
in Tescos :-) ) or even an IAX softphone. When you get a problem user  
put the
IAX device there and see if the problem goes away.

>
>> The others responding on-list are certainly giving you good  
>> advice. I expect that
>> what you are suffering is unmanaged QoS at the roaming users end.  
>> This almost
>> certainly will be an issue
>> with 256k outbound on a network connection that is not dedicated  
>> to the voip
>> application alone.
>
> I'd hoped that by insisting the users test call quality with their  
> computers turned off that I'd been able to eliminate this factor.  
> You're right of course - if there's heavy net usage going on, call  
> quality will plummet, but it shouldn't be an issue without other  
> net usage, unless I'm mistaken?
>
>> but having a router
>> capable of QoS at each location is an absolute necessity. I prefer  
>> m0n0wall on a
>> Soekris Net4501.
>
> Generally we use a similar setup (though with pfSense) when we're  
> doing small-scale remote offices with 2-4 employees. The net4801/ 
> pfSense combo works very well in that environment.
>
> Unfortunately I can't really mandate a mini-asterisk server and  
> Soekris box for each remote user - it'd add many hundreds of pounds  
> to the cost :-)

Hardly - Talk to brianc at palaver.net , he has a build that runs on  
stock linksys routers, or
alternatively try an Nslu2.

The trick would be to keep doing what you are doing, but roll out  
special measures
for difficult installs.



Tim Panton

www.mexuar.net
www.westhawk.co.uk/