Glossary

Session Boarder Controller is an IP-to-IP network element that resides at the edge of the network and manages sessions. A session in this context is any real-time IP communication be it voice, video or multimedia using common protocols such as SIP, H.323, MGCP, MEGACO even though some vendors extend its reach also to streaming protocols such as RTSP. An SBC may modify and control the signaling and media of a session functioning in many cases as a Back-to-Back User Agent (B2BUA) acting on behalf of the called party and creating a second call-leg to destination. The SBC is today widely used by fixed and mobile service providers and may also be deployed in large enterprise networks as well as in smaller configurations integrated into other access devices for small/medium enterprises.

SBC was initially required for mitigating SIP interoperability faults between networks and Firewall/NAT traversal. Since the SBC wasn't standardized for many years and even today it is still in standard discussions there are many shapes and form to an SBC thus, the SBC has evolved to be the Swiss Army Knife of VoIP typically providing functions such as:

• Firewall/NAT traversal
• Protocol translation (e.g. SIP-H.323 interworking)
• Media transcoding for voice and video
• Security protecting elements in the network
• Interoperability enhancement translating between different variations of SIP extending service reach
• Load balancing
• Billing and revenue assurance providing different billing mechanisms assuring session billing
• Quality-of-Service (QoS) assurance supporting implementation of Service Level Agreements (SLA)

Developer solutions for Gateways:

• SIP Developer Suite for development of any SIP product including SBC.
• SIP Server Framework and B2BUA development of SIP Server applications such as SBCs
• H.323 Stack for development of any H.323 product including the H.323 leg of the SBC.
• MEGACO/H.248 Stack designed for decomposed gateway architectures and is ideal for development of Media Gateways and Media Gateway Controller applications when adding media transcoding to the SBC
• SIP-H.323 interworking function for development of IP-to-IP Gateways bridging the transition from H.323 to SIP