[Asterisk-Users] call "load balancing"

[Jean-Michel Hiver]

Dave Redmore wrote:

> Hello All,
>
> Wondering what sort of real world mileage people are getting out of 
> different internet connecions - i.e. different DSL connection speeds, 
> cable modems, etc...  Is it reasonable to hope to carry 10 - 15 
> concurrent calls on a 768K DSL?  I'm not talking about theoretical BW 
> or looking for any difinitive absolute guarantee...  With DSL and 
> Cable - there is no guarantee, so I'm wondering what folks are getting 
> with real world usage...

I do up to 10 g.729 channels over 1024 / 256 DSL without noticeable 
difference in call statistics (i.e. avg length of calls). If you are 
using ADSL, the maximum bandwith you'll be able to use is your upload 
rate since VoIP calls send data bidirectionally.

Of course if you're using g.711 it's a different kettle of fish since it 
takes 80kbps (g.729 only uses about 24).

> Secondly, assuming I want to replace 8 - 10 POTS lines coming in with 
> someone like NuFone or TELIAX...  It would seem to be well worth 
> spending an extra $40/mnth for an extra DSL connection for redundancy 
> (probably with two different ISPs) - so, is there any way to get 
> asterisk to route calls based on the quality of a connection at any 
> given time?  If I had 2 DSL connections and Asterisk is registered to 
> 2-3 different service providers - can asterisk do some sort of "load 
> balancing" of calls?

I think you will have less headaches and get better results by 
dedicating 1 DSL connection to VoIP calls and having the 2nd for all 
your internet traffic.

An ever better way is get some kind of SLA with guaranteed uptime and 
bandwith, a symetrical link, and do some traffic shaping to ensure that 
VoIP has priority. Part of the point of VoIP is to save money by 
collapsing voice and data networks onto one (presumably robust) network, 
so having 2 shabby separate DSL connections kinds of defeats the purpose.

This being said, where symetrical, guaranteed links aren't available or 
affordable - I'm in this situation :( - ADSL remains a good choice. I 
have 6 links that are used every day and it works mostly fine.

Cheers,
Jean-Michel.