[asterisk-users] Load balancing SIP trunks?

[Gordon Henderson]

On Wed, 15 Aug 2007, Nicholas Blasgen wrote:

> I have 10 SIP trunks that I'd really like to round-robin load balance.
> Currently I have a macro that switches between available lines, but there
> really must be a function in Asterisk to do this on its own.  So my question
> is just that, are there any easy ways for Asterisk to either balance between
> SIP trunks or even just a built in function to find the next available SIP
> trunk.  I think using a macro to test the state of each trunk is silly, but
> it's the only method I've found.

I wonder (and sometimes question!) the wisdom of putting everything into 
asterisk when it can be implemented in the dial-plan (or as I posted 
recently putting stuff out of the dialplan into AGI when it can be done in 
the dialplan) I'm sure there are cases where both are valid, but I'm a 
great believer in the KISS principle, and if we keep the "core" of 
asterisk clean and simple, then we can develop add-ons in the dialplan, or 
elsewhere...

(And after saying that, I have to say that the dial-plan programming 
language is one of the more esoteric programming languages I've used in 
the 26 years or so I've been programming!)


So, if we have sip-outX as out 10 sip trunks (0-9), then: (untested ;-)

[globals]
sipTrunk=9


  ...


[macro-dialSipTrunk]
exten => s,1,Noop(Dialling out via round-robin SIP trunk)
exten => s,n,Set(sipTrunk=$[${sipTrunk}+1])
exten => s,n,GotoIf($[${sipTrunk}=10],skip)
exten => s,n,Set(sipTrunk=0)
exten => s,n(skip)Noop(SIP dialling on trunk: ${sipTrunk})
exten => s,n,Dial(SIP/sip-out${sipTrunk},${ARG1},${ARG2})

... maybe stuff here to deal with result of the DIAL.
... eg. on congestion you might to jump back to step 2
... but if you did that then you might want to start a 2nd counter
... which when it reached 10, you're SOL and can return congestion
... to the caller.....

Maybe I've just been writing too much dialplan stuff lately!!!

Gordon