s and manage resources according to the H.248 protocols. The functionality across the Mc reference point will require to support mobile specific functions, e.g. SRNS relocation/handover and anchoring. The current H.248/IETF Megaco standard mechanisms will enable these features. 9.4.7 Mg Reference Point (MGCF-CSCF) The SIP based Mg reference point allows the transfer of session related information between the CSCF and the MGCF. We use this interface to communicate between the IP multimedia networks and the legacy PSTN/ISDN/GSM networks. 9.4.8 Mh Reference Point (HSS-R-SGW) This interface supports the exchange of mobility management and subscription data information between HSS and R99 and 2G networks. We need this interface to support Release 2000 (R4 and R5) network users who are roaming in R99 and 2G networks, and we implement it with MAP/IP using SCTP and other adaptation protocols developed by the IETF SIGTRAN working group. 9.4.9 Mm Reference Point (CSCF-Multimedia IP networks) The Mm SIP based reference point stands as an IP interface between CSCF and IP net- works. We use the interface, e.g. to receive a call request from another VoIP call control server or terminal. A network in principle will support SIP/SDP between the CSCF and other multimedia networks, with SIP signalling compliant with RFC 2543 and subse- quent SIP releases, and with SDP compliant with RFC 2327 and also with its subse- quent releases. The interworking between SIP and other protocols, e.g. H.323, occurs at the edge of the IP multimedia network. 9.4.10 Mr Reference Point (CSCF-MRF) The Mr affords the CSCF to control the resources within the MRF, thus allowing a net- work to support communication between the CSCF-MRF with either SIP or H.248 de- pending on the selection by standards. There is interest in the acceptance of IETF proto- cols such as SIP, e.g. for Mr. 9.4.11 Ms Reference Point (CSCF-R-SGW) The Ms corresponds to the interface between the CSCF and R-SGW. It will most likely be implemented using M3UA/SCTP. The UMTS Network and 