The VoIP Peering Puzzle�Part 42: SBC Architectures�AudioCodes

AudioCodes Ltd., with international headquarters in Lod, Israel, and U.S. headquarters in San Jose, California, has an impressive resume of innovations that have advanced voice over packet systems since the company’s establishment in 1993.

The overall AudioCodes line is quite diverse, ranging from algorithms and chip development, to communications boards and modules. The company is considered a market leader in voice compression technologies, and is the key originator of the ITU G.723.1 codec standard that is incorporated into many VoIP systems today.

In addition, they offer media gateway and media server platforms for packet networks in the wireline, wireless, broadband access, and media server markets. AudioCodes has over 700 employees—with about half engaged in research and development activities—and product deployments in more than 75 countries.

In August 2006, AudioCodes expanded its product portfolio by acquiring Plano, Texas-based Netrake, a provider of session border controllers and security gateways to fixed and mobile service providers. This acquisition added the Netrake nCite products to the AudioCodes line, which are used to deliver real-time control of voice and multimedia applications across all IP networks. There are two models in this product line: the nCite 1000 that is targeted at smaller service providers, and the nCite 4000 that is designed for larger carriers that need a scalable platform.

These products are designed for three key applications. The first is Carrier Peering for the Wholesale Market, with support for security, denial of service (DoS) prevention, digit-based routing, digit manipulation, load balancing, per-carrier service level agreement (SLA) enforcement, and protocol normalization across peering carriers.

The second application is for Hosted Business/IP Centrex, with SIP-to-H.323 interworking, hosted firewall network address translation (NAT) support, call detail recording (CDR), and other digit-based routing features for large enterprise and residential applications.

The third application is Hosted/Residential VoIP, where endpoints maintain communication with service providers behind firewalls using registration timers that are regulated by the SBC, plus assured interoperability between the residential firewalls and the SBC, and support for up to 150,000 subscribers per unit.

Moreover, multiple applications, including the three noted above, can be delivered on the same chassis.

The nCite 1000 is designed as a cost-effective platform for small and medium-size service providers and larger enterprises. The system integrates both signaling and media in a single platform, to securely and reliably deliver VoIP applications across IP network borders. The product’s session management and routing features include hosted firewall and NAT traversal, virtual routing domains, H.323/SIP interworking, support for electronic numbering (ENUM) and the Domain Name Service (DNS), plus geographic load balancing.

On the security side, the unit includes hardware-based Denial of Service (DoS) protection; protocol validation and fix-up; a media firewall; session-based bandwidth policing; topology hiding; support for both IPSec (IP Security) and TLS (Transport Layer Security); plus authentication based on the source/destination IP address, domain, port or protocol.

The system implements complete CALEA (Communications Assistance for Law Enforcement) functionality, including a provisioning interface for configuring the surveillance target, a Call Data Connection (CDC) interface, and a Call Content Connection (CCC) interface that allows the operator to implement CALEA functionality in the single network element.

The nCite 1000 is also designed for high availability, with support for active/stand-by or active/active (which allows the operator to load-balance traffic across two SBCs, while still providing redundancy) configurations, geographic redundancy across WAN links, and uninterrupted service in the case of device or link failure. This system can handle up to 4,000 concurrent sessions and up to 1 Gbps of bandwidth, with less than 31 milliseconds of latency.

The larger nCite 4000 system is designed for service provider deployments. It has similar technical characteristics, but with a capacity for up to 21,000 concurrent sessions (that can be scaled as high as 42,000), 2 Gbps of bandwidth (that can be scaled up to 4 Gbps), and less than 31 microseconds of latency.

Both the nCite 1000 and the nCite 4000 can be managed by the nCite Element Management System (EMS), which provides a comprehensive functionality set for managing the SBC real-time sessions, including defining and managing customer policies, automatic recognition of system alarms and events, and the monitoring of resource usage statistics to meet network and service planning requirements.

The system includes very strong support for service level agreements, with signaling information that includes call start/stop times, caller/callee IDs, protocol-specific identifiers, media information such as the average jitter and packet loss, plus network detail records for sessions, registrations and call failures, real-time session display, and performance statistics that can be generated at both the chassis and customer network level.

Further details on the AudioCodes 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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