S3. IMS Session Initiation signalling flow —
origination in CS Network
mobile termination in home network
S3-1a. SIP INVITE request (UE1 to UE2):
from MGCF1 to I-CSCF1
(2 of 48)
: Contains the international E.164 number from the user, as obtained from CS Networks signalling.
: Contains the IP address or FQDN of the originating MGCF.
: The MGCF inserts the TEL URL containing the subscriber number, as received from the CS network.
: The MGCF inserts this header and populates the icid parameters with a globally unique value.
: SIP URI that contains the IP address or FQDN of the MGCF.
: Contains a preconfigured set of codecs supported by the MGW.