S3. IMS Session Initiation signalling flow —
origination in CS Network
mobile termination in home network
S3-3a. SIP PRACK request (UE1 to UE2):
from MGCF1 to S-CSCF2
(12 of 48)
MGCF sends a PRACK request without SDP, because there is not another set of codecs to the original SDP offer.
: Takes the value of either the IP address or FQDN of the originating MGCF.
: Takes a higher value than that in the previous request.