Call agents are very familiar with borders controllers. These devices control the call admissions to the network at the border of that network to help regulate the amount of calls where an agent is working. Session Border Controllers are Voice-over Internet Protocol (VoIP) devices, which can also perform many other necessary call control functions.

There are two main parts to a session border controller; the signaling and the media functions.

The signaling function of the session border controller controls access to the base of the network and can maneuver the details of the message. The media function of the session border controller controls access to the media bundles and obstructs any chance at theft.

A “session” is any real-time voice, video, presence, instant messaging or multimedia collaboration session using IP session-layer signaling protocols, such as SIP or H.323.

The “border” is any IP-IP network border and the “control” functions satisfy critical enterprise requirements in five major areas:

• Security—A Net-Net SBC secures the SIP/H.323 trunking border to service provider IP networks for PSTN/IP termination and hosted services, and the Internet border to remote offices, teleworkers and mobile employees. In extremely security-conscious organizations, a Net-Net SBC even secures the enterprise data center with mission-critical IP PBX or UC server resources where it connects to the private VPN connecting other sites and “untrusted” employees.
• Service reach maximization—The SIP and H.323 interworking capabilities of a Net-Net SBC ensure interoperability with-and-between IP endpoints, IP trunking services, hosted IP services, IP PBXs and UC servers.
• SLA assurance—A Net-Net SBC controls session admission, bandwidth utilization, IP PBX or UC server loads and overloads, IP network transport and SIP/H.323 session routing. Appropriately deployed, Net-Net SBCs provide a range of high-availability options ranging from disaster recovery for business-critical major sites to basic survivability for smaller sites.
• Regulatory compliance—Encryption for session privacy, call/session replication for recording and prioritized session control for E911 calls are supported by a Net-Net SBC.
• Cost management—A Net-Net SBC enables least cost routing and session/call accounting, and it enforces service authorization and polices bandwidth use.

Session Border Controllers also act as a firewall, preventing customers or other providers from learning the specific details about how the network is constructed or how the calls are routed.  Session Border Controllers can either be centralized or distributed depending on the company’s needs.