 customer's network has and interwork them with the IP address space of the SP. A second important feature of the edge SBC is securing the SP networks. The inherent requirement of an edge SBC is to ensure that any of the SP components behind the SBC are protected from any attacks that might occur. This security is inclusive of what would normally be provided by an edge firewall but extends deeper into the application-specific security issues. This implies that the edge SBC or the edge SBC in combination of a firewall and intrusion protection system ensures that no attacks from traffic generated at the enter- prise can infect or impact the SP. In addition, the edge SBC ensures that no harmful traf- fic from the SP can infect or impact the enterprise and that one enterprise's traffic cannot affect another. Attacks that the edge SBC is designed to prevent are in both the realm of signaling and media attacks. Signaling attacks occur when an INVITE or other SIP signaling messages are sent from a "rogue" device in the enterprise or SP network. These rogue signaling attacks use techniques similar to IP attacks to determine information about a network and vulnerabilities. An example of an attack would be a rogue device sending INVITES to sequential phone number ranges to determine what numbers are valid and what num- bers are not. Media-based attacks include sending random Real-Time Transport Protocol (RTP) traffic or flows to impact active calls. This random RTP traffic would "guess" at open RTP ports and sequence numbers and inject media to these open ports. Edge SBCs are usually large in scale and designed to support thousands of customers for a SP; however, large customers of a SP can have a dedicated edge SBC. The capability to hide IP addresses from the multi- ple customers that utilize the same SBC is an essential capability of the edge SBC and is often accomplished through the use of multiple Virtual Routing and Forwarding (VRF) routing tables. Another important component of an edge SBC is the capability to suppo