 CSN, and are managed by the home NSP; however, under certain conditions, the ASN and CSN operated by the visited NSP may process these protocols. The reference point R2 may further support IP Host Configuration Management running between the MS and the CSN. Reference Point R3 Reference point R3 consists of a set of control-plane protocols between the ASN and CSN to support AAA, policy enforcement, and mobility management capabilities. It also encompasses the bearer- plane protocols, including tunneling to transfer user data between the ASN and the CSN. Reference Point R4 Reference point R4 comprises a set of control and bearer-plane protocols originating and/or termi- nating in various functional entities of an ASN that coordinate MS mobility between ASNs and ASN- GWs, ensuring interoperability between similar or heterogeneous ASNs. Reference Point R5 Reference point R5 consists of the set of control and bearer-plane protocols for inter-networking between the CSN operated by the home NSP, and is operated by a visited NSP. Reference Point R6 Reference point R6 comprises a set of control and bearer-plane protocols for communication between the BS and the ASN-GW within a single ASN. The bearer-plane consists of intra-ASN data transfer between the BS and ASN-GW. The control-plane includes protocols for data plane establishment, modification, and release control corresponding to the MS mobility. Reference Point R7 Reference point R7 consists of an optional set of control protocols such as AAA and policy coordi- nation in the ASN-GW, as well as other protocols for coordination between the two groups of functions identified in R6. This reference point has been removed from mobile WiMAX network architecture specification Release 1.5 [12]. Tunneling refers to a mechanism that enables disjoint packet networks to exchange data or packets via intermediate networks, while concealing the protocol details from the intermediate networks. Tunneling is generically implemented by encapsulating an end-to-end network protocol within