originating MCPTT client to originating participating MCPTT function (O-PF).

Request-URI contains PSI of O-PF.

P-Preferred-Identity may contain IMPU of originating user.

"mcptt-request-uri" contains the group identity.

PSI of O-PF configured for each client.

MCPTT-id of each client is never sent in session initiation.

O-PF to controlling MCPTT function (CF).

Request-URI contains PSI of CF.

P-Asserted-Identity contains IMPU of originating user.

"mcptt-request-uri" contains the group identity.

"mcptt-calling-user-id" contains MCPTT ID of originating user.

CF finds the MCPTT ID of the originating user from the stored IMPU-MCPTT ID binding and locates the PSI of the controller that serves the group identity.

O-PF contains configuration of the PSIs of the CFs.

CF to terminating participating MCPTT function (T-PF).

Request-URI contains the address of the T-PF.

P-Asserted-Identity contains the address of the CF.

"mcptt-request-uri" contains the MCPTT ID of the terminating user.

"mcptt-calling-user-id" contains MCPTT ID of originating user.

"mcptt-calling-group-id" contains the group identity.

For each client in the group, CF maps the MCPTT-ID of the terminator to the address of the T-PF.

If the terminator is in another domain, the CF can map the MCPTT ID of the terminator to a PSI identifying a interrogating function in the partner network that is able to find the T-PF using the MCPTT ID.

CF to non-controlling MCPTT function of an MCPTT group (NCF).

Request-URI contains the PSI of the NCF.

P-Asserted-Identity contains the PSI of the CF.

"mcptt-request-uri" contains the group identity.

"mcptt-calling-user-id" contains MCPTT ID of originating user.

–

T-PF to terminating MCPTT client.

Request-URI contains the IMPU of the terminating user.

P-Asserted-Identity contains the address of the CF.

"mcptt-request-uri" contains the MCPTT ID of the terminating user.

"mcptt-calling-user-id" contains MCPTT ID of originating user.

"mcptt-calling-group-id" contains the group identity.

T-PF finds the IMPU of the terminating user from the stored IMPU-MCPTT ID binding at the time of registration.

terminating MCPTT client to T-PF (response).

as in TS 24.229.

"mcptt-called-party-id" contains contacted client’s MCPTT ID.

–

T-PF to NCF (response)

as in TS 24.229

"mcptt-called-party-id" contains contacted client’s MCPTT ID.

–

T-PF to CF (response).

as in TS 24.229.

"mcptt-called-user" contains contacted client’s MCPTT ID.

–

NCF to CF (response)

as in TS 24.229.

–

In the case of trusted mutual aid, the NCF returns the identities of the group in a "resource-lists" MIME body.

CF to O-PF (response)

as in TS 24.229.

–

–

O-PF to originating MCPTT client (response)

as in TS 24.229.

–

–