Raghu, One note of caution: IMS is an emerging technology and roaming is a particularly immature portion of the standards. There really are no *definitive* answers to your question.
Having said that, the conventional wisdom for IMS roaming is that the P-CSCF will be located in homeB and userA's S-CSCF will be located in homeA. userA will need to register with the P-CSCF and the P-CSCF will forward the registration request back to the S-CSCF. There are several options for P-CSCF discovery. Operator policy will dictate which methods are actually used. a) The mobile device may be told who its P-CSCF when it's assigned an IP address on the visited network. b) The mobile device can use DHCP to ask whether there are any SIP servers in the visited network. c) The mobile device could send a SIP request to a multicast address to ask whether there are any SIP servers in the visited network. -- Gary Cote www.awardsolutions.com _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
