RFC 4904 Compliance in Asterisk

Is it supported?

If so, is there any information on how to implement it?

Thanks in advance.

What is RFC 4904?

Selection of a trunk group in an Asterisk acting as a PSTN gateway has to be done explicitly in the dialplan. A gateway node can obviously look at the raw SIP headers to detect any trunk group selection parameter. I doubt that there is any explicit support for a SIP to SIP node to relay this information. Headers can obviously be detected and added on the output side. I can’t remember if URI atrributes can be added.

I suspect this is a sufficiently rare requirement that your best chance of getting an answer as to the support for relaying this information is to look at the source code.

In a legacy internal network, any explicit trunk group selection would be achieved by adding prefix digits, and relaying switches would not need to know that they were special.