is released [7]. REGISTRATION ASPECTS While the final steps for registration are still in process of consolidation at this writing, we can still outline the generic procedures from [7] as follows: The ROO architecture will allow the serving CSCFs to have different capabilities and/or access to different capabilities; e.g. a VPN CSCF or CSCFs as a network gets upgraded. Service providers or network operators will not need to reveal the internal network structure to another network. Which means that association of the node names of the same entity type and their capabilities, as well as the number of nodes will be kept within the operator's or service provider network. Nevertheless, disclosure of internal network architectures may occur on a per agreement basis. A network will not have to expose explicit IP addresses of its nodes, except those belonging to interconnection and security tasks, e.g. firewalls and border gateways. For practical purposes and operational simplicity it is desired that the UE will use the same registration procedure(s) within its home and visited networks. Likewise, it is desirable that the procedures within the network(s) are transparent to the UE, when it registers with the IM CN subsystem with either its home or visited CSCF. Finally, the serving CSCF will understand a service profile and the address of the functionality of the proxy CSCF. 9.6.1 Registration Flows A preliminary process for use in the architecture definition is described next. 9.6.1.1 Requirements and Assumptions 1. A serving CSCF gets assigned at registration, without precluding additional serving CSCFs (for FFS) or change or CSCF at a later date. Towards IP Based Networks 1. We assume that radio bearers are already established for signalling and a mechanism exists for the first REGISTER message to be forwarded to the proxy. 2. The I-CSCF will use the same mechanism in visited and home networks to deter- mine the serving CSCF address based on the required capabilities. 9.6.1.2 Registration Procedures The registration pr