[asterisk-users] Dealing with 2 SIP providers

[Chris Bagnall]

> What I mean is I want a call to go out on ProviderA, UNLESS it's down and
> then go to ProviderB.
> I want it to ring 30 seconds and then Hangup if nobody has answers.

This one's actually a bit more complicated than it first seems, since you need to know how each provider reports status when it's unavailable. We run the following AEL macros to achieve something similar:

(apologies to the list for the big chunk of code below - I'm not sure how well/if the list handles attachments)

// DIAL NUMBER (with a range of routing options)
macro outbound (number, route1, route2, route3, route4, route5) {
	// set correct outbound caller id
	if (${LEN(${CALLERID(number)})} < 10 & ${LEN(${CALLERID(number)})} > 0) {
		if (${LEN(${DB(callerid/${CDR(accountcode)})})} > 9) {
			CALLERID(number)=${DB(callerid/${CDR(accountcode)})};
		} else
			Set(CALLERID(number)=);
	};
	dialstart:
	switch (${route1}) {
		case dundi:
			if (${number:0:2} = 00) {
				&dundi-e164 (${number:2});
			} else if (${number:0:1} = 0) {
				&dundi-e164 (44${number:1});
			} else
				&dundi-e164 (${number});
			break;
		case provider1:
			&dialout (IAX2/provider1/${number});
			break;
		case provider2:
			&dialout (IAX2/provider2/${number});
			break;
		case provider3:
			&dialout (IAX2/provider3/${number});
			break;
		case pstn:
			&dialout (Zap/g1/${number});
			break;
		default:
			NoOp (invalid route: ${route1});
	};
	if (${LEN(${route2})} > 0) {
		route1=${route2};
	} else {
		Playtones (congestion);
		Congestion ();
	};
	if (${LEN(${route3})} > 0)
		route2=${route3};
	if (${LEN(${route4})} > 0)
		route3=${route4};
	if (${LEN(${route5})} > 0)
		route4=${route5};
	goto dialstart;
};

// DIAL NUMBER (ignoring anything except busy)
macro dialout (dialstring) {
	Dial (${dialstring},,TW);
	switch (${DIALSTATUS}) {
		case BUSY:
			Playtones (busy);
			Busy ();
			break;
		case CONGESTION:
			Playtones (busy);
			Busy ();
			break;
	};
};

You can then dial from your "main" dialplan something like this for UK landlines:
exten => _0[12]XXXXXXXXX,1,Macro(outbound,${EXTEN},provider1,provider2,pstn)

The "dialout" macro ignores any responses from the SIP/IAX provider except Busy or Congestion (we have a provider which provides "congestion" when the dialled number is busy, that's why it's there). So, if the provider's server is unavailable (through qualify=yes or whatever), it'll fall through as channel status "unknown" and loop onto the next provider.

On an outbound call made from one of your users, why would you want a 30 second timeout? Surely you'd want to keep ringing the callee until the caller (i.e. your user) loses interest and hangs up their device? The length of time for a device to be rung before doing something else is usually determined by the recipient, not the initiator.

Hope that helps.

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
For full contact details visit http://www.minotaur.it/chris.html
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