[asterisk-users] QoS & VPN

[Brent Davidson]

David Backeberg wrote:
> On Thu, May 7, 2009 at 3:54 PM, Brent Davidson
> <brent at texascountrytitle.com> wrote:
>   
>> I've got multiple satellite office all linked back to the main office
>> via VPN.  Each office has their own asterisk server which registers back
>> to the main office's Asterisk server.  Each office also has a 1Mb
>> downstream / 384k - 768k upstream connection.  The branches are using
>> Speex for their connections back to the main office.  The issue I'm
>> having is that there are times that I need to VNC in to machines at the
>> various offices for tech support while the user is also on the phone.
>> Unfortunately the VNC connection apparently takes priority and makes it
>> impossible for me to understand anything the person on the phone is
>> saying, although they can still hear me fine.
>>     
>
> VNC is very asymmetric. It doesn't generate much traffic from the
> person viewing, and it generates lots of traffic FROM the system being
> viewed. This helps explain why the system being viewed side can hear
> incoming voice packets, and outbound voice packets that have to
> compete with the large amount of outgoing video signal data lose. QoS
> may or may not help you here.
>
>   
Well, the fact that our central office has a 10mb downstream / 5mb 
upstream connection (Two 5Mb down 2.5Mb up DSl connections load shared) 
helps with them hearing me clearly too, I'm sure.  I can get the packets 
to them faster than they can get packets to me.
> If voice quality is important, you should have a separate connection
> dedicated to just voice. The obvious workaround is grab your cell
> phone and call them with that. You DO have a way to dial directly to
> that office without going over the PIX, right, right? How do you call
> the remote office when the PIX goes down?
>
> What will help you is getting a bigger line or separating the voice
> traffic from the data traffic completely.
>
> If you are good with ssh, you can also do a compressed ssh tunnel to
> encrypt and on-the-fly compress the VNC session. But if this is
> Windows good luck with that.
>   
Yes, we can dial all satellite office through the PSTN if we really want 
to, but one of the reasons we went to a VOIP system was to cut down on 
the long-distance charges that result from office-to-office calls, and 
to be able to transfer calls from one office to another.  All in all the 
system works as designed, except for the rare occasions that I'm doing 
support with VNC and have a person on the remote extension as well.  But 
just because nobody else has complained yet doesn't mean there aren't 
other conditions that could trigger a poor-quality call.  If I can find 
a solution that works in my worst-case VNC situation then maybe I'll 
prevent a few future issues from ever becoming real problems.

Separating the voice off to it's own connection would defeat the 
cost-cutting reasoning behind the system.


Thanks,
Brent
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