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Trunk failover setup


koolandrew
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We have tried using trunk failover for 4.2.0.3981 and never got it to work. We have tried it on 5.0 and it works; however,

 

1. Rollover doesnt work without a timeout value, which i set at 10 seconds

2. The caller doesnt hear a ring when it rolls over

3. The caller hears a busy signal when the receiver hangs up.

 

Is there a solution for this or it is best efforts.

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The typical cases for the rollover are (1) that the lines on the primary PSTN gateway are busy and the PBX needs to access another SIP trunk to make an outbound call and (2) that the first SIP trunk is unavailable because the Internet connection is down and the call needs to be terminated with a local backup PSTN gateway.

 

In the first case the timeout should not matter because the gateway will send an error code back; this code should trigger the fail-over immediately. In the second case you need to explicitly tell the PBX how long the user should wait before the fail-over happens. 5-15 seconds seem realistic.

 

Ringback tone generally means that the called party is alerting its user. There is a lot of confusion out there about the meaning of ringback tone. IMHO it is wrong to play a ringback tone when the other phone has not even been reached yet. This is the case when the trunk is down; in that case it is better to play some "comfort noise", so that the line does not sound dead.

 

If the other side hands up, the PSTN side may play back a busy tone; but that is not done on the signalling layer. This is done on the media layer. If that is the case then the PBX cannot do much about it and it is considered a feature.

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  • 2 weeks later...

The typical cases for the rollover are (1) that the lines on the primary PSTN gateway are busy and the PBX needs to access another SIP trunk to make an outbound call and (2) that the first SIP trunk is unavailable because the Internet connection is down and the call needs to be terminated with a local backup PSTN gateway.

 

In the first case the timeout should not matter because the gateway will send an error code back; this code should trigger the fail-over immediately. In the second case you need to explicitly tell the PBX how long the user should wait before the fail-over happens. 5-15 seconds seem realistic.

 

Ringback tone generally means that the called party is alerting its user. There is a lot of confusion out there about the meaning of ringback tone. IMHO it is wrong to play a ringback tone when the other phone has not even been reached yet. This is the case when the trunk is down; in that case it is better to play some "comfort noise", so that the line does not sound dead.

 

If the other side hands up, the PSTN side may play back a busy tone; but that is not done on the signalling layer. This is done on the media layer. If that is the case then the PBX cannot do much about it and it is considered a feature.

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Thanks for the reply. I was never notified, unfortunately.

 

Regarding your first point, it doesnt roll over immediately as there is no response. I wish it did but it doesnt. Without a timeout value, it doesnt work at all.

 

Regarding your second comment, no one is asking for a fake ring. We are only asking that if the first trunk doesnt work, the backup works as it does with the first. Therefore, the called phone is ringing yet the caller only hears dead air and has no idea the phone is ringing.

 

Regarding your last point, this is not a feature, but some misconfiguration in the sip setup. The trunk misinterprets the hangup as a busy signal. I dont believe this has anything to do with the PSTN, as the PSTN has no knowledge of the trunk failover setup and this only occurs during that setup. It does not happen otherwise.

 

It would be very useful to get this situation resolved.

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