The VoIP Peering Puzzle�Part 34: SBC Architectures�NexTone

NexTone Communications, Inc., headquartered in Gaithersburg, Maryland, develops intelligent session management and interconnect systems, marketing their products worldwide, and serving enterprise, existing service provider, and next-generation service provider customers.

By many accounts, they would be considered veterans in the IP interconnect industry, having shipped their first peering product in October 2001. Presently, the company is one of the Top 50 companies in Deloitte’s 2006 Technology Fast 500, a ranking of the 500 fastest-growing technology, media, telecommunications, and life sciences companies in North America. NexTone claims that their customers carry more than 50 percent of the United States/International VoIP traffic, and more than 550 service providers and enterprises worldwide have used NexTone’s IntelliConnect™ System. In addition, more than 60 service providers in the Voice Peering Fabric use NexTone to manage and route their VoIP traffic.

NexTone’s products form a distributed architecture, with the access and switching elements at the network edge, and the network management functions in the network core. This architecture, the IntelliConnect System, includes four key components:

  • The Session Border Controller (SBC), secures the bilateral interconnects.
  • The Multiprotocol Session Exchange (MSX) platform interconnects SIP and H.323 networks. This element provides access control, and performs private-to-public IP network address translation (NAT) in real time while also supporting NAT traversal, topology hiding, route enforcement, and the regulation of bandwidth consumption between networks.
  • The IP Multimedia Exchange (IMX) platform interconnects IP and IP Multimedia Subsystem (IMS) networks. It operates at the network edge to provide seamless connectivity between IMS networks and enable subscriber roaming. It can also control bandwidth usage, call rate, and call capacity at the network ingress and egress.
  • The Real-time Session Manager (RSM), controls these edge devices from the network core. It is a dynamic policy manager providing centralized Quality of Service (QoS) and Service Level Agreement (SLA) management and traffic engineering to VoIP and IMS networks, thus optimizing service quality, availability, and network capacity.

The NexTone SBC, a standalone session border controller, is implemented on industry-standard hardware, and runs on a Linux-based software architecture. The SIP and H.323 signaling intelligence of the SBC adapts session signaling at the network edge, and lets service providers successfully interconnect to any fixed or mobile IP network, with a future eye on IP Multimedia Subsystem (IMS) architectures.

The security features are especially strong, as the SBC is designed to defeat a wide variety of Internet threats meant to disrupt or disable a service provider’s VoIP or IMS network. Security facilities in OSI layers 2 through 5 protect against a myriad of threats including: flood attacks, Denial of Service (DoS) attacks, and SIP signaling attacks. Separate signaling and media interfaces provide signaling resiliency, enabling the SBC to sustain peak performance and call quality even while under a high level of attack. Intelligent Access Control Lists enable easy blacklisting of endpoints to counter recurring attacks. The SBC also provides access control and performs private-to-public IP network address translation (NAT) in real time, while also supporting NAT traversal, topology hiding, route enforcement, and the regulation of bandwidth consumption between networks.

The latest version of NexTone’s SBC was announced in March 2007. It includes improvements in H.323/SIP protocol interworking, media processing, security, accounting, service reach, and operational and management functions. The new product capabilities are extensive, with a service-provider-verified 150 calls per second performance rate, enhancements to the H.323 and Q.931 signaling standards to improve interworking support, Least Cost Routing (LCR) improvements, plus enhancements supporting the Communications Assistance for Law Enforcement Act (CALEA, which performs lawful interecept), Electronic Numbers (ENUM) and IP Security (IPSec).

To support the new version of the SBC, NexTone also expanded its policy enforcement platform, the RSM, to support over 2 million unique routes and policies. In addition, the RSM provides dynamic policy management, faster route generation, and a 500 percent increase in Call Detail Record (CDR) system performance. The RSM supports flow-through provisioning using a Web Services API that enables the Soap-XML programming language.

NexTone is also quite innovative in its product support and testing options. NexTone University is an education facility with an emphasis on the interconnection of VoIP, wireless, and IMS networks. The NexTone Lab is available to equipment manufacturers to certify the interoperability of their products with the NexTone architecture, and also for service providers to test their solutions before implementation.

Further details on the NexTone 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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