2.12.4 S9 AF/pCSCF Topology Hiding

S9 AF/pCSCF topology hiding is concerned with hiding the identity of a Protected Home Network’s AF/pCSCFs, as well as the number of AF/pCSCF’s in the network, when it exchanges messages with Untrusted Networks. An AF/pCSCF identity is embedded in the Origin-Host and Session-Id AVPs sent in Request messages and the Origin-Host AVP sent in Answer messages. This is associated with the Diameter Rx application messages overt he S9 Reference point. This AF/pCSCF Topology Hiding feature encompasses:

• 9 AF/ pCSCF Topology Hiding (inbound roaming use case) – Hiding of AF/pCSCF host names in Rx messages over the S9 Reference Point in Local Breakout (LBO) roaming architecture with the AF in the Visited Network where the Visited PCRF is implemented as a Proxy of Rx messages to/from the Home PCRF.

The technique to hide and restore S9 AF/pCSCF identities is similar to as described in S6a/S6d MME Topology Hiding.