Vendor Network Architectures�Part V: Sonus Networks, Inc.

The Internet bubble that burst in 2000 separated many technology startups into two categories: those in the history books and those still executing their business plans. Sonus Networks, Inc., founded in 1997, is one of those firms in the second category, focusing on their mission to provide VoIP infrastructure systems to the carrier market, including traditional telecom carriers, wireless network operators, Internet Service Providers (ISPs) and cable providers. Their customer base is worldwide, with Sonus equipment presently serving in 24 countries around the globe, and a customer list that includes familiar names such as AT&T, Bell South, Cingular Wireless, Global Crossing, Level 3, NTT, Qwest, Verizon, and many others.

From its inception, Sonus has focused on building a highly scalable, distributed network architecture, even before those terms became fixtures in popular technology culture. This design went against the more traditional switching model of earlier days, but with the advent of the current IP Multimedia Subsystem (IMS) standard (see earlier articles in this tutorial series IP Multimedia Subsystem and IP Multimedia Subsystem functions), this early vision has positioned Sonus as a carrier-class equipment provider since 1999, with a claim that their products carry more minutes of VoIP traffic than those of any other vendor.

Sonus products provide a single architecture, upon which advanced services can be deployed across a number of wireless and wireline technologies. Wireless support includes CDMA, 2GSM, 3GSM, and WiFi technologies; wireline support includes xDSL and cable networks. This architecture is based upon four key principles: distributed intelligence, where each Sonus component handles all of the processing required for that function; centralized subscriber database and routing, where all the subscriber and routing information is kept in a centralized databases that can queried as needed, thus simplifying network administration; call signaling, which is based upon the Session Initiation Protocol (SIP), and common applications, that can apply to all subscribers, regardless of the technology that they use to access the network.

The Sonus products are defined by their relationship to the four key functions that are defined by IMS: Border and Media Control, Session Control, Application Layer and Management and Charging.

The Border and Media Control products include the Network Border Switch (NBS), which delivers the IP network interconnect function, the PSTN Gateway, which provides the PSTN interface and signaling functions, and the Sonus Open Services Partner Alliance (OSPA) Media Server, which provides media services to the subscribers. These products are based upon a common hardware platform, called GSX, which allows future enhancements to be added as software upgrades. The GSX modules may then be equipped with a number of packet network and/or circuit network interfaces, including Gigabit Ethernet, DS1/DS3 and OC3.

The Session Control products include the HSX Home Subscriber Server (HSS), which is a central database of subscriber information; the SRX Serving Call Session Control Function (S-CSCF), which provides session coordination and call routing functions, and the PSX Breakout Gateway Control Function (BGCF), which routes calls from the IMS network to another network. The SRX S-CSCF is particularly interesting, as it provides a central coordination point for a wide variety of multimedia sessions, which may include video calling, videoconferencing, instant messaging, chat and push-to-talk over cellular (PoC) services. Inter-application, inter-subscriber and inter-network connections may be involved in this coordination function, adding to the complexities involved.

The Application Layer products include the ASX Feature Server, which provides traditional, Class 5 subscriber features, such as call waiting, call forwarding, caller ID, and so on; and the OSPA Application Servers, which are provided by third parties.

Finally, two products provide the Management and Charging layer functions: the Insight Element Management System (EMS), which is a complete, web-based management system for carrier-class packet networks; and the Insight DataStream Integrator, which is a comprehensive billing solution.

In summary, Sonus had the good fortune to anticipate the next wave in distributed communications architectures, and then safely ride that wave when the Internet bubble burst. Further details on the Sonus architecture and products can be found at Our next tutorial will continue our examination of vendors’ softswitch architectures.

Copyright Acknowledgement: © 2005 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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