The VoIP Peering Puzzle�Part 46: SBC Architectures�Comdasys

Comdasys AG is a fast growing start-up headquartered in Munich, Germany. Since its inception in 2004, the company has developed a unique competence for delivering feature-rich, vendor-independent, and secure converged VoIP networking solutions, for both the service provider and enterprise marketplace. In addition, the company has become a supplier of choice for large communication vendors such as Siemens.

The company’s mission is to make the widespread deployment of converged networks easier, less expensive, and more secure.

Comdasys has Research and Development operations in Munich, and sales offices in Munich, Milan, Italy, Zurich, Switzerland, and Montreal, Canada. The company is targeting sales of € 2 million (approximately $2.7 million) in sales by the end of 2007.

Comdasys has two lines of products that are based on a common software platform.

The Comdasys FMC (Fixed Mobile Convergence) Solution is designed to extend PBX extensions and services to the road, home, or any place with a cellular or WLAN connection. This product consists of two components. The FMC Server provides a bridge between the enterprise network, the cellular network, and the WiFi network, so that the mobile device behaves like any other node on the corporate PBX. The FMC Client is a software module that resides on the mobile user’s dual-mode handset, and communicates with the FMC Server. These two elements extend the mobile user’s enterprise telephony presence (including IP PBX number, call features, and mailbox), assuring that they can seamlessly move between networks.

The second is the Convergence product family, which enables enterprises and service providers to connect branch offices to central data centers or hosted service offerings. These products are specifically geared to support real-time communication requirements.

The Convergence series is designed for two key deployment scenarios: as a branch SBC, or as a centralized SBC for enterprise applications. In the branch application, the SBC provides the secure link between the Internet or enterprise WAN connection and the branch office switching system and associated IP telephones. The SBC provides multiple functions for this configuration, including data routing, firewall, SIP NAT handling, QoS and traffic shaping, call admission control, VoIP security, and call routing via a SIP Proxy. In the enterprise application, the SBC provides the link between the Internet or enterprise WAN connection and a SIP-based softswitch. The SBC protects that softswitch from unauthorized access, and also provides topology hiding, Layer 7 packet inspection for firewall pinhole functions, QoS and traffic shaping, and NAT handling. The enterprise and branch scenarios can be combined, thus providing a controlled, secure link between the branch office switching system and the centralized softswitch.

Several different models of the Convergence platform are available to address differing network requirements. All of the systems share some common functions, including a SBC with access control, SIP-aware NAT transversal, topology hiding in both signalling messages and media flow, plus real-time session management; VoIP survivability with load balancing for redundancy; security with support for VPN, the Secure Real-Time Protocol (SRTP, defined in RFC 3711, and SIP Transport Layer Security for communication requirements that extend beyond the enterprise network; SIP carrier termination for SIP Trunking, plus interoperability with the Comdasys FMC Solution for fully converged and integrated enterprise network solutions.

The Convergence 550 is designed as a universal network building block for small or home offices, and can support up to eight end users. This entry level unit goes beyond the capabilities of the typical branch office system in that it provides the SBC functions that control the real-time traffic flows in and out of the branch office, for either VoIP enterprise or VoIP centrex applications.

The Convergence 1600 provides connectivity for up to 50 users. It can support a number of voice calling scenarios, including voice over VPN, Voice NAT, call admission control based on available bandwidth, emergency call prioritization, Electronic Numbers (ENUM), and call accounting.

The Convergence 2600 provides security connectivity for medium-size offices with up to 150 end users. It includes a QoS/Traffic control process that can classify to physical port, virtual firewall rule, session or Layer 7 protocol in use, provide bandwidth guarantees and limits, and incorporate a number of queuing algorithms, including token bucket, stochastic fair queuing, random early detection, and others.

The Convergence 3600 is targeted at large offices, with connectivity for up to 1,500 end users. This unit also features a redundancy solution that permits using a second Convergence 3600 in a hot-failover mode for high availability networking requirements.

The Convergence 4600 is designed as a universal network building block for service providers and large enterprises. It can handle 10,000 simultaneous SIP users and scale up to 2,000 concurrent calls with call processing of over 750 calls per second. It can operate in conjunction with any softswitch, SIP IP-PBX, or any SIP server to provide SBC functionality, plus call admission control, SIP Routing ENUM lookup, and other services.

Further details on the Comdasys 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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