 2410 and 2451. IP packets get transported over AAL5 accord- ing to RFC 2225 and RFC 1483. 9.4.4 Gn Reference Point (GGSN-SGSN) We use the Gn interface both for control signalling (i.e. mobility and session manage- ment) between SGSN servers and GGSN, as well as for tunnelling of end user data pay- load within the backbone network. The GTP-C protocol (running over UDP/IP) used for control signalling can also be in- cluded here. The interface is implemented according to TS 23.060 and TS 29.060. 9.4.5 Gm Reference Point (CSCF-UE) This interface allows the UE to communicate with the CSCF, e.g. register with a CSCF, call origination and termination and supplementary services control. The Gm reference point supports information transfer between UE and serving CSCF. The main procedures that require information transfer between UE and serving CSCF procedures related to serving CSCF registration; procedures related to user service requests to the serving CSCF; procedures related to the authentication of the application/service; procedures related to the CSCF's request for core network resources in the visited network. 9.4.6 Mc Reference Point (MGCF-MGW) The Mc reference point describes the interfaces between the MGCF and MGW, be- tween the MSC server and MGW, and between the GMSC server and MGW. It has the following features [7]: full compliance with the H.248 standard, baseline work of which is currently being carried out by ITU-T Study Group 16, in conjunction with IETF MEGACO WG; Towards IP Based Networks flexible connection handling which allows support of different call models and different media processing purposes not restricted to H.323 usage; open architecture where extensions/packages definition work on the interface may be carried out; dynamic sharing of MGW physical node resources; a physical MGW can be parti- tioned into logically separate virtual MGWs/domains consisting of a set of stati- cally allocated terminations; dynamic sharing of transmission resources between the domains as the MGW con- trols bearer