[SR-Users] SIP Auth Realm - From domain or Request domain ?

I have a questions in regards to SIP Auth, and specifically how Asterisk 13 with PJSIP appears to send Invites. It seems that the typical Kamailio config sends the SIP auth challenge with the from domain as the auth realm. however in the case of the Asterisk 13 ( PJSIP ) invite, the from domain is an RFC1918 IP address and I would have to use the domain from the request. What im wanting to know is what the consensus is on where the auth realm comes from. does everyone 100% agree that you send auth using the SIP From header, or is this something that some do Request domain ? What im considering doing is to use the from domain, but if from domain = RFC1918 then use request domain. Im just after everyone's opinion on how to best handle this invite, from a auth_challenge perspective. ( not so much if the Asterisk 13 PJSIP module is doing the right or wrong thing ) INVITE sip:555111222333@sip.mytestdomain.com:5060 SIP/2.0 Via: SIP/2.0/UDP 180.111.222.333:5060;rport;branch=z9hG4bKPjafb111a9-aaaf-4c9e-b456-748514855a06 From: <sip:555111222333@172.18.90.1 To: <sip:555111222333@sip.netsip.net.au> Contact: <sip:9d43c8df-6378-4266-89c1-0a0bb0e1d0d1@180.111.222.333:5060> Call-ID: b7da52e2-dfd1-434e-a2c2-b28e1683ce0e -- Sincerely Jay