ts in common with an SP edge SBC; however, the integration with the existing UC infrastructure is a requirement that goes beyond that of an SP edge SBC. Chapter 5: Components of SIP Trunks Enterprise Network: IP Network Infrastructure The IP infrastructure requirements of an enterprise are almost identical to that of an SP, but there is one major difference. An SP generally needs to connect to thousands of end customers that might share a common overlapping IP address space. This interconnect is often in the form of VRF interworking. An enterprise generally needs to connect only with a few SPs that most likely do not have overlapping IP address spaces. Generally, the problem of the interconnecting of overlap- ping addresses spaces and connecting them via VRF interworking is one that is primarily seen only by SPs and not a primary issue for enterprise IP network infrastructure deploy- ments. However, there are some exception cases when VRF interworking is required for enterprise IP networks that are used as a foundation for SIP Trunks. The major issues of latency, delay, and jitter affect an enterprise and SMB network in the same way that they affect an SP. As such, the same effort should be used to ensure that a secure and robust IP networking infrastructure is provided as the foundation to ensure that any SIP trunk solutions can be successfully deployed. Enterprise Network-Enterprise Session Management A new trend that is developing in large enterprise UC deployments and is transitioning down to smaller deployments is the use of a Session Management layer to have a single point of control and interconnect for SIP trunks. The requirements of an enterprise ses- sion manager are similar to that of a call agent in an SP network; however, there are many distinct features that set them apart. Generally, an enterprise session manager is a B2BUA that acts as a central control point for the signaling aspects of SIP trunks and can provide some additional value-added capabilities. Cisco has offered the CUCM (Session Manage