irements The following technical items need to be answered during the process of selecting SIP providers and SBC vendors: Session management Interworking support Demarcation 162 SIP Trunking Security Operations and management System specification Performance/sizing Now, let's look into the details of each area. Session Management As the SBC is used mostly to connect SIP networks, some SIP-specific requirements need to be answered by the SBC vendor and SIP service provider. Signaling/Media Protocol The SBC should support multiple IP Telephony/Voice over IP (VoIP) protocols such as H.323, SIP, SIP-T, SIP-I, and Media Gateway Control Protocol (MGCP). SBC vendors can list the versions supported for the following protocols: H.323 SIP-T MGCP+ H.248 H.248+ Operational Modes Support An SBC can be operated in different modes. In general, enterprises see the SBC as a Back to Back User Agent (B2BUA) to enable centralized call management, interworking with alternative networks, management, monitoring of the entire call state, and SO on. You can check with your SBC vendors about the following modes of operations: B2BUA peering B2BUA access IMS P-CSCF Transaction stateful proxy mode Session stateful proxy mode Chapter 9: Questions to Ask of a Service Provider Offering and an SBC Vendor Stateless proxy mode NAT traversal mode SIP Features You can put the following SIP-specific features in your RFP. Vendors might not support all the features, but you can pick some of them according to your needs: IMS SIP capabilities RFC-3455 headers and procedures P-Associated-URI P-Charging-Vector P-Charging-Function-Address P-Called-Party-ID P-Visited-Network-ID P-Access-Network-Info RFC-3608 Service Route RFC-3327 Path header SIP Privacy (RFCs 3324, 3325, and 3326) RFC-3325 P-Asserted-ID for session agents P-Preferred-ID Multiple SIP ports per SIP interface (for example, port 5060 plus alternative listening ports) SIP L5 NAT/Topology hiding SIP dialogue transparency SIP media release intrarealm SIP media release intranetwork SIP distributed 