[Asterisk-Users] VoIP experiences with Cable and DSL

[Steve Szmidt]

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On Wednesday 04 August 2004 04:28 pm, Geoff Nordli wrote:
>
> I am using Shaw for cable access and Primus as my VSP.  I find on a fairly
> regular basis calls will just drop after 10 minutes or so.  The call
> doesn't hangup but you can't hear each other talk.
>
> I am not using any QOS or bandwidth rate control.
>
> Any ideas why this might be happening?

One thing that happens with networks is they queue up data, at various points, 
because it comes in too fast to route straight through. While the data is 
sitting in that queue your VoIP equipment is not getting anything, or enough, 
so it goes silent. If that occurs for too long a time, or in both directions, 
it will terminate the call.

A way around this is to put in some quality of service solution that can 
squelsh your out bound connection to a rate that can flow through onto the 
Internet backbone with needing to be buffered. (I use altq in OpenBSD.)

Here's one way: Let's say you have 384k up. But your upline cannot handle all 
without buffering. So you drop back 50%, see if it works. If so you increase 
25% (or original 384), and see if that's good. If not you cut back 12%, else 
increase another 12%. (Binary search method.) Repeat until you don't get 
queued.

Of course it could be easier to just back off 10% at a time until it works 
too : ) 

Anyway, as soon as your volume is low enough not to be buffered you will have 
less dropped/silent connections.

This is kind of funny because you are lowering your speed, but getting better 
quality.

- -- 
Steve

"They that would give up essential liberty for temporary safety deserve
neither liberty nor safety."
                                Benjamin Franklin

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