The VoIP Peering Puzzle�Part 33: SBC Architectures�Sonus

Sonus Networks, Inc., headquartered in Westford, Massachusetts, is a leading provider of voice over IP (VoIP) infrastructure solutions for wireline and wireless service providers. Sonus addresses the full range of carrier applications, including residential and business voice services, wireless voice and multimedia, trunking and tandem switching, carrier interconnection, and enhanced services.

Sonus’ voice infrastructure solutions are deployed by major carriers, cable providers, and Internet service provider networks worldwide, including AT&T, Cingular, Level3, Qwest, and Verizon in the United States, Deutsche Telekom in Germany, KDDI and NTT Communications in Japan, China Netcom—plus new entrants into the voice industry, such as Vonage and Earthlink. Founded in 1997, Sonus has over 900 employees located at offices throughout North America, Europe, Asia and India, and posted 2005 revenues of $279 million dollars.

Perhaps as a result of all of this experience with large service providers, Sonus developers concluded that a different border control solution—one that went beyond current product offerings—was needed. In particular, Sonus concluded that first-generation session border controller architectures were falling short of industry requirements in several areas: limited performance and scalability, less than carrier-class reliability, and limited upgrade potential—plus limited integration with softswitches and routing engines. They also concluded that there was a need to integrate security, session control, and media services in a single, carrier-class platform.

In addition to the architectural issues, Sonus’ marketing research identified three market drivers—all related to network security—that needed industry attention. First, peering between network operators is on the upswing, as these operators seek to expand their market reach or grow through new service offerings. Second, a number of mergers and acquisitions have recently occurred within the carrier space, creating larger networks that must be fully integrated. Third, more network operators are providing Internet connectivity, which reinforces the need for enhanced security services.

This research inspired the development of the Sonus Network Border Switch (NBS), which provides IP interconnect in both carrier peering and carrier access configurations, and has thus far been adopted by 40 service providers around the world. The NBS also provides a path for carriers that are migrating toward next-generation converged networks based on the IMS/TISPAN standards (short for IP Multimedia Subsystem/Telecoms and Internet converged Services and Protocols for Advanced Networks, an effort to unite wireline and wireless networks, see ).

Sonus claims that the NBS is the only solution that integrates multiple border functions, such as session border control and PSTN media gateway operations, into a single, carrier-class system. The NBS is based on Sonus’s GSX Open Service Switch platform, a carrier-class VoIP processing platform that can scale from thousands to millions of ports, and is populated with a number of high-speed packet and circuit switching interfaces. The GSX9000, the largest member of that family, can handle up to 30,000 simultaneous peering sessions. Any given GSX9000 may be configured to support circuit-only borders as an Enhanced Media Gateway, packet-only borders as a Network Border Switch, or may simultaneously support both circuit and packet borders in a Hybrid configuration. As such, carriers can cost-effectively configure the GSX 9000 platform for TDM interconnect and IP interconnect functions, increasing or decreasing either function as their evolving network strategy dictates.

When you look under the hood of the NBS, its three general capabilities– security, session control, and media control—become clearer. The security functions provide for a split DMZ (De-Militarized Zone) for communication between trusted and untrusted networks, with topology hiding and Network Address Translation (NAT) support. The session control functions provide call admission control, on both a local and a network-wide basis, which can limit the maximum number of calls, the maximum bandwidth, the ingress call rate and the registration rate on a per-IP trunk group basis.

The NBS also provides for priority access (for E911 services) and automatic re-routing during periods of network congestion. The IP trunk groups can be provisioned for inbound only, outbound only, or two-way operation. Signaling interworking, such as SIP to/from H.323 conversions, is also provided. The media control functions manage the media flows through the switch; provide for media processing, such as transcoding between different codec variants (e.g., G.711 to/from G.723); handle tones and announcements; perform T.38 fax interworking functions; and process DTMF (Dual Tone Multifrequency) signals.

The NBS can be deployed in two different scenarios. The Carrier Peering deployment model provides wireless-to-wireline carrier peering, Class 4 and Class 5 carrier peering, and Application Service Provider (ASP) and trunking carrier peering. The Carrier Access deployment model enables access to the core network from broadband consumer networks, from enterprise networks, and from IP and TDM networks.

Further details on the SONUS IMS architecture and NBS product 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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