The VoIP Peering Puzzle�Part 35: SBC Architectures�Data Connection

Data Connection, Ltd., headquartered in the United Kingdom, was founded in 1981. It is a leading independent developer and supplier of next-generation protocol solutions, with expertise in IMS, SIP, Megaco/H.248, MGCP, SBC, IP Routing, MPLS, ATM, and SNA products.

The company’s MetaSwitch division supplies IMS switching and applications solutions to tier one carriers, independent and rural telcos, competitive service providers, and cable operators. They claim to have system deployments that range in size from a few hundred to over 500,000 subscribers.

The Internet Applications Division focuses on large-scale application requirements. It supplies the IMS-compliant UC-Portal messaging and application services platform, together with a comprehensive set of systems-integration engineering, migration, and support services, to tier one service providers for IMS and PSTN deployments. Data Connection presently has over 360 employees and had revenues of $66 million in 2005.

Data Connection’s session border controller (aptly named the DC-SBC) is built on a foundation of three other DC VoIP products: the DC-SIP, DC-MGCP and DC-Megaco/H.248 systems, which have been shipping since the year 2000. In particular, the interworking, call control, routing-policy server, and call-services components were previously developed and deployed in the Metaswitch Class 5 Softswitch, which has been field proven with over 300 installations. Data Connection claims that the DC-SBC system presently represents over 150 man-years of development time.

The DC-SBC product is part of the company’s family of IP Multimedia Subsystem (IMS) solutions, which support the 3GPP (see, ETSI TISPAN (see, IETF ( and ITU-T (see IMS standards.

The DC-SBC may be used in User-to-Network (UNI) and or Network-to-Network (NNI) applications to support all the necessary security, call control service creation, and reachability functions required for the IMS, including the Proxy-Call Session Control Function (P-CSCF), Interconnect Border Control Function (IBCF), Border Gateway Function (BGF) and Interconnect Border Gateway Function (I-BGF) applications.

Architecturally, the DC-SBC consists of two primary components, known as DC-SIG and DC-Media.

The DC-SIG element includes a call signaling plane, which provides call control processes, including routing, interworking, and NAT transversal; a call signaling layer, which supports SIP, H.323, MGCP, and H.248 signaling; a media signaling plane that provides bandwidth management, load balancing and quality control; plus a media gateway signaling layer for media gateway control.

The DC-Media element includes a media gateway manager for quality of service and policy management; a media gateway signaling element supporting H.248, and a platform-specific media packet forwarder. These two components have been designed in a modular fashion, allowing them to be integrated together as a complete solution, or deployed individually. Furthermore, each component may be distributed independently to separate hardware modules or geographical locations.

This modular architecture enables the DC-SBC and other Data Connection IMS solutions to be deployed in a wide variety of network architectures and in a very scaleable fashion.

The features of the DC-SBC can be divided into three general categories: security, reachability, and services.

The security area includes support for Denial of Service (DoS) detection and protection; bandwidth theft detection and protection; network topology and user hiding, including route stripping; plus encryption and authentication.

The reachability area handles signaling and media pinholing; SIP, H.323, MGCP, and Megaco/H.248 protocol processing; interworking between signaling protocols; IPv4 and IPv6 addressing; overlapping address resolution; firewall, and Network Address Translation (NAT) transversal; plus bad protocol detection.

The services part is responsible for: media transcoding, service-level agreement (SLA) policing, virtual private networks (VPNs) support; dual-tone multi-frequency (DTMF) interworking; policy-based routing; network congestion avoidance; quality of service, based upon either the differentiated services (DiffServ) or multiprotocol label switching (MPLS) models; lawful intercept, and support for the Communications Assistance for Law Enforcement Act (CALEA); E911 support, voice-, fax-, and modem over IP media bridging; and billing functions that include support for call detail recording, session timers, and the Remote Authentication Dial In User Service, or RADIUS.

The DC-SBC is also designed for carrier-grade reliability and capacity with hot software upgrades/downgrade capability and a capacity that is rated in the thousands of calls per second. The modular architecture makes it simple for implementers to distribute components over different hardware locations, allowing a massively scalable solution. In addition, the DC-SBC supports hundreds of thousands of concurrent sessions with a non-blocking design that allows highly scaled call control to run efficiently in both single and multi-threaded environments. Its redundant framework also enables fault tolerance and high availability, including non-disruptive fail-over to backups (1:1 or 1:N).

Further details on the Data Connection architecture and products can be found at Our next tutorial will continue our examination of vendors’ SBC architectures.

Copyright Acknowledgement: © 2007 DigiNet Corporation ®, All Rights Reserved

Author’s Biography
Mark A. Miller, P.E. is President of DigiNet Corporation®, a Denver-based consulting engineering firm. He is the author of many books on networking technologies, including Voice over IP Technologies, and Internet Technologies Handbook, both published by John Wiley & Sons.

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