Caller (FROM) ID on divert/forward

[brendanf]

I am calling from one SIP extn (9000) to a SIP extn (4025) which, when not answered, is configured on the 3CX to forward the call on no answer to a different SIP registered extn (4000). I would like to know if there is any way that the device receiving the diverted/forwarded call (at 4000) could receive info relating to the "unanswered" extn (i.e. 4025). The SIP INVITE packet only contains called (TO) party of 4000 and calling party (FROM) of 9000. Is there any way to get the PBX to send the diverted party info? Is this a limitation of the "free" 3CX version, or is it the case with all commercial releases of the soft PBX?

 

[archie]

No. It is limitation of SIP protocol. There's no standard way to place divertion info into INVITE.

 

[brendanf]

In which case, I guess that the only means of providing such information might be to emulate DTMF (string representing party involvement) over RTP? Seems a bit crazy when considering the wealth of information that is communicated during the SIP initiation sequence...!?!

 

[archie]

SIP is quite flexible protocol still, and we can make extensions to it easily. But the problem is an absence of standard way of doing this. So, even if we will make some extension - it will not be understood by SIP phones, so they will just ignore it.

 

[brendanf]

Yes, but an end node processing SIP in not necessarily a "phone", hence could benefit from the additional info, but I understand what you are saying. On the same subject (of extra call info), if an "external" incoming call (say, from the PSTN) hits a SIP proxy (3CX for example) and is forwarded directly to an internal SIP enabled device -- is there a way of providing the CPI/CLI info (assuming incoming caller's number is provided by telco) to the SIP device (eg. for display on the device's LCD)?

 

[archie]

On the same subject (of extra call info), if an "external" incoming call (say, from the PSTN) hits a SIP proxy (3CX for example) and is forwarded directly to an internal SIP enabled device -- is there a way of providing the CPI/CLI info (assuming incoming caller's number is provided by telco) to the SIP device (eg. for display on the device's LCD)?

Yes, it is possible. If you know at which field your PSTN gateway sends CLI info - you can adjust Inbound parameters of your device (in web interface of 3CX) to read $CallerNum from that field. Than it will be passed to extension as a user part of From field and phone will show it properly as a caller ID.

 

[brendanf]

Can the "diverted from" party information not be passed in the same fashion i.e. in the FROM info field?

 

[brendanf]

The more I dig around on this subject, I am finding that diversion info is sent quite frequently in SIP Invite headers, though as Archie stated, in the absence of any defined 'standard'. Is this something 3CX would consider in the near future?