rt myriad of different signaling methods that might be encountered by the SP. For the SP to serve the largest audience possible, it needs to interconnect with the widest variety of edge enterprise devices that support SIP trunks. The capability to translate the SIP messaging into a signal that is understood by the SP is accomplished by either the edge SBC or the Customer Premise Equipment (CPE) device that is traditionally provided by the SP. Due to the essential nature of the edge SBC in the SP network, it must be highly resilient and capable of achieving a five nines level of availability (for example, 99.999 percent uptime). This is usually accomplished by a combination of a redundant box-to-box hard- ware, deployed in either ACTIVE/ACTIVE or ACTIVE/STANDBY pairs to support Chapter 5: Components of SIP Trunks increased availability; and in-box redundancy in the form of redundant hardware that would provide protection from individual component failure, such as a failure of a central processing unit, forwarding plane, or power supply. Finally, a redundant software solution for the edge SBC that can support the rerouting of calls, in the event of any individual device failure, is essential for ensuring the required availability. Many SPs have a legal requirement to record phone calls and calling information and pro- vide this to the appropriate authorities. Compliance with this capability is often a require- ment that must be fulfilled to allow the SP to offer services. This functionality is usually referred to as lawful intercept and is often accomplished on the edge SBC through the use of media or signaling packet duplication to dedicated devices. Finally, the edge SBC is often the first place at an SP site that alarm information about a specific customer is captured. This is typically the case when an SP does not provide or monitor any CPE deployed for the service. In this case, the edge SBC must generate alarms in response to issues that affect individual customers. The general architecture and important inte