L.2 Use cases

33.3283GPPIP Multimedia Subsystem (IMS) media plane securityRelease 17TS

As fax has a special legal status in many countries and enjoys continuing support, specification of secure fax is important. As most faxes are still connected to PSTN, the primary use case is seen as a fax call between an IMS UE and a PSTN/CS fax terminal. In order to support this use case media protection needs to start at the IMS UE and be terminated before or at the PSTN GW. Fax calls between two IMS UEs is another possibility but is not as common, and in this case there exist other alternatives like attaching the fax in an email or instant message using ITU-T recommendation T.37.