I’ve been reading a recent spec (see [1]) saying a second Identity header should be included in outbound INVITE when a Diversion or History-Info header is present in incoming INVITE.
Something I didn’t get when reading the document I referenced, is that the first Identity header is the original one signed by the original Telco, and verified by you !
Said differently : Alice calls Bob who forwards to Cory.
Alice’s ITSP sends a single Identity which is is forwarded by Bob’s ITSP.
Bob’s ISTP adds a ppt=div Identity while forwarding to Cory.
Cory’s ISTP has 2 Identity headers to validate.
So it seems ITSP should have a way to match incoming and outgoing call including a way to copy the Identity header.
Expanding my latest example with Alice calling Bob and Bob forwarding to Cory, if I were Bob’s ITSP, I would need:
a mean to tell if an incoming call is a forwarded one or not,
a mean to get Alice’s call Identity header
a mean to append Alice’s Identity header (when calling Cory)
a mean to tell Asterisk, “for this outbound call to Cory, use ppt=div instead of ppt=shaken when building Bob’s Identity header”
Having a database in which live calls details (Identity header, From header, the tag value within this from header, …) are stored, seems possible.
If I were Cory’s ITSP, I would need:
a way to check each Identity header individually (no matter if an Identity header either use ppt=shaken or ppt=div)
access each attestation’s details (for logging and reporting).
A dialplan function that would read Diversion or History-Info header in incoming channel and if appropriate, return a tag uniquely identifying the re-targeted call, would greatly help.
When Alice’s call is re-targeted from Bob to Cory, should the original From header be kept unchanged is the re-targeted call from Bob to Cory ?
If positive, theoretically, should the tag value within Alice’s call From header be unique enough to find Alice’s call among many live calls ? Should the whole From value be preferred to to search live calls database ?
Anyway, I would be very curious to read again about Asterisk capabilities toward this “ppt=div” Stir Shaken option.
@oza4h07 Go ahead and open an “Improvement” issue at Asterisk Issue Tracker and include everything you’ve described here as well as the link to the FFTelecoms document.