nclude a guarantee that not a single IP address can be leaked within the L5 headers. 172 SIP Trunking When a user connects to the outside network, its IP address and port needs to be proper- ly translated to protect its identity. The SBC should support the complete infrastructure topology, hiding at all protocol layers for confidentiality, attacking prevention security, and modifying, removing, or inserting call signaling application headers and fields. NAT Traversal NAT breaks end-to-end connectivity. Most NAT behavior-based techniques bypass enter- prise security policies. We prefer the techniques that explicitly cooperate with NAT and firewalls, enabling NAT traversal while still enabling marshalling at the NAT to enforce enterprise security policies. Many techniques exist, but no single method works in every situation because NAT behavior is not standardized. You can check at least the following support in the SBC: Does the product support NAT Traversal of the near end firewall? Does the product support NAT Traversal of the far end firewall? Session Routing Session routing is an integral part of session management. The routing database and rout- ing engine needs to perform some basic functions SO that your SIP network can accom- modate flexible call routing features as needed. You should check with your vendor whether the product supports the following routing features: Calling/From and Called/To address-based routing Least cost routing (time of day, day of week, cost) Answer Seizure Ratio (ASR)-based routing Routing by codec-traffic grooming Route advance/route hunting (SIP) Local policy route recursion override Configurable route recursion based on SIP response Routing capability based on source IP address Ability to act on redirect/REFER Trusted calling party name (CNAM) services Ability to run ENUM query Accounting and Billing The SBC should capture and generate the correct data for accounting and billing purposes. You also need to capture session data to protect against theft and abuse of service. You Ch