[asterisk-users] Dealing with 2 SIP providers

[Remco Post]

Brad Templeton wrote:
> On Fri, May 11, 2007 at 11:06:35AM -0400, Mike wrote:
>> Hi,
>>  
>> I have a question of using 2 SIP providers.  Let's say I have provider A and
>> provider B, and I would like my calls to go to A, and then B if A wasn`t
>> available
> 

there is a macro floating around called safedial. Basically this does
what you want, if one provider is unresponsive, use the other. You could
possibly have 2 variations, so you can first try your preferred provider
for that extension and then fail-over to the other. My provider provides
2 uplinks, so I randomly select one of the two...

> 
> What would be really cool, but require special code in the chan_sip
> dialer, would be automatic support of multiple providers in a similar
> fashion to the way Asterisk can ring two channels and only talk to
> the first to answer.
> 
> You can't just do this with outgoing providers, because if you try to
> ring two at once, you may very well have the second one go to
> a voicemail and thus answer right away (because the first is
> ringing) and you would treat that as the success.
> 
> What I have in mind is something like this:
> 
>     a) Invite to main provider
>     b) Await some intermediate response, such as a RINGING code
>        or some early media
>     c) If you don't get that after a short timeout (more like 5 seconds)
>        then INVITE the second provider
>     d) Upon the receipt of a ringing or early media code from either,
>        CANCEL the other.
> 
> Now you would have to get your timings right because there could still
> be risk of doing something bad, such as a 2nd call going to voice mail
> or residual ringing making a call waiting on the recipient.  (I don't
> know what typical 5ess do with a 2nd call that comes in while still
> ringing, anybody known?)
> 
> Anyway, this could be a good course when a provider has known
> unreliability.   Long timeouts and restarts are very annoying to
> users.
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-- 

Remco Post

"I didn't write all this code, and I can't even pretend that all of it
makes sense." -- Glen Hattrup