32.2993GPPCharging managementDiameter charging applicationsRelease 16Telecommunication managementTS
The IMS-Visited-Network-Identifier AVP (AVP code 2713) is of type UTF8String and contains the contents of the SIP P-header "P-Visited-Network-ID". with the value according to 3GPP TS 24.229 
– For the roaming architecture for voice over IMS with local breakout, the value of IMS-Visited-Network-Identifier AVP is a pre-provisioned string that identifies the network of the P-CSCF at the home network.
– For the roaming architecture for voice over IMS with home routed traffic, IMS-Visited-Network-Identifier AVP is a string that identifies the visited network of the UE including an indication that the P-CSCF is located in the home network.