Call identification alternatives only trust Accept-Contact from same trust domain see P-Asserted-Identity model (RFC 3325) ? brittle or use Identity model ? signed by outbound proxy unfortunately, not covered by doesn’t help with UA rec/res model! creating a new header likely to have similar issues re-do mapping and ensure that URL matches server can learn list of “legal” URLs after a while can fail if mapping is dynamic (advertisement changes) then just replaces URL forces each outbound proxy to do mapping check external source that URL is indeed a PSAP use draft-ietf-sipping-certs for destination URL, but would need to have a role-based cert “this is a bona-fide PSAP” easy to posit, harder to deploy globally can incur significant delay but only needed when there’s service differentiation new TLD for PSAPs only ? |