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Tech Talk with SIP Print's Jonathan Fuld: What is a Session Border Controller and Who Needs One?

May 27, 2010

By TMCnet Special Guest
Jonathan Fuld, Chief Technology Officer, SIP Print,

A Session Boarder Controller, or "SBC," is a device at the edge of one network that has two main features:

  • Control the signaling of the session: telephone call, video or other media
  • Manipulate and manage the media translation between various networks

Traditionally VoIP and voice and video over IP, or "V2IP," pronounced "vtip," could not travel across NAT Routers, Firewalls and other devices.  The SBC's act to encode V2IP signaling and media encoding so that these devices can pass through these basic devices.

Over the past few years VoIP PBX's - Allworx, Zultys (News - Alert), AAstra, Asterisk and others - began to include NAT Router and Firewall capabilities as an All-in-One solution for the small medium business looking to control costs for data and telephony networks.  Eventually, these PBX (News - Alert) manufacturers included SBC functionality and feature sets into their PBX's.  The need for SBC exists at the private network level and is accommodated within a VoIP and V2IP PBX.  No market exists for a standalone SBC at this level.

At the other end of the market - Public Network to Public Network, ITSP to PSTN, North American to European and internal EMEA - the need for SBC's is huge.  And when a cloud or telephony as a service, or "TaaS," service provider is offering V2IP to an end user the service provider must have an SBC for the following:

  • Network security / Identity and Fraud Control
  • Bandwidth Control and Management
  • Quality of Service, or "QoS,"
  • Statistical and Billing reporting, off loading softswitch burden
  • Calea compliance - law enforcement monitoring
  • Encoding conversion: not only at the session layer from H.323 to MGCP or to SIP and back again, but also at the media layer from G.711 to G.729 to G.722 and of course manipulation of H.263 and H.264

The only time a private network might need an SBC is if that private network carrying V2IP traffic crosses several geographic locations and utilizes a virtual network on top of a public network - the cloud.  There is some debate as to whether a large enough private network really requires an SBC if that network incorporates a multi-protocol label switching, or "MPLS," scheme.

If you are a small to medium business with VoIP or V2IP, you already have SBC functionality built into your PBX and you shouldn't require a standalone SBC.  If you are running V2IP in the cloud to your customers, you already have several SBC's at the edge of your network.


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Edited by Kelly McGuire

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