Benoit,

Snip

- For those calls, you could deploy a lightweight, signalling-only B2BUA to solve these "looping" problems. SEMS has historically been recommended for this purpose often, but the community edition has fallen into a bit of disrepair. FreeSWITCH, Asterisk, Drachtio, and others make good alternatives.

Adding a B2BUA to your platform is also a moving part and introduces complexity. However, the call flow is extremely straightforward, the software componentry involved is very straightforward, and forwarding requests is a core competency of Kamailio that is very idiomatic. Compared to your solution of manipulating the Call-ID in baroque ways, it's much less internally complex, and runs in more well-worn grooves that will be more easily understood by other Kamailio operators and SIP experts in the future.

-- Alex