The Cisco Network Route Director (NRD) is a high-performance Session Initiation Protocol (SIP) Route Proxy for inter-carrier, inter-call management server (CMS), and on-net or off-net routing. It is typically a centralized function in the communications network. It can be deployed in multiple points of presence (POPs) and is usually deployed as a cluster of servers for scalability and high availability. Route requests can be received from any SIP server in the network. The Cisco NRD forwards SIP requests to other SIP-based applications or networks or routes the request to other SIP-based applications or networks. Typical SIP interactions include those with public-switched-telephone-network (PSTN) gateways, other SIP networks and session border controllers (SBCs) that manage connectivity to a peer provider, or to a local Media Gateway Controller Function (MGCF) such as the Cisco PGW 2200 Softswitch. The Cisco NRD is intended to support IP Multimedia Subsystem (IMS) as the Cisco implementation of the Interrogating Call Session Control Function (I-CSCF) and Breakout Gateway Control Function (BGCF).