The usage of an SBC (Session Border Controller) enables enterprises to extend SIP-based applications beyond the Enterprise network boundaries, e.g., when users of Lotus Sametime Unified Telephony are not all within the same IP network.
Users within each network may not have public IP addresses and/or NAT (Network Address Translation) devices may be deployed within the networks. In these cases, SBCs are used to allow SIP signaling to pass between the user devices and Lotus Sametime Unified Telephony. The SBC also provides network topology hiding.
An SBC is basically a SIP-aware firewall that also serves as a SIP proxy or B2BUA (Back-to-Back User Agent). The Acme Packet Net-Net 2600 and Net-Net 3800 SBCs behaves as a B2BUA while the Branch and Comdasys SBC behaves as a proxy. The SBC is given a publicly accessible URL and IP address, and SIP phones in the internet use this as the address of their SIP registrar and proxy. The SBC also has a second IP address, and a separate LAN connection, in the corporate LAN. Its function is to analyze, modify, and relay messaging between the phone and the Lotus Sametime Unified Telephony system. Only proper SIP and media (RTP, Real-Time Transport Protocol) packets are permitted through the firewall function.
Parent topic: SBC (Session Border Controller)