The VoIP Peering Puzzle�Part 39: SBC Architectures�Ditech Networks

Ditech Networks, Inc., headquartered in Mountain View, California, produces equipment for global communications networks, serving the needs of mobile and wireline operators using both circuit and packet technologies.

The company’s forte is voice processing, SIP, and security technologies that enable service providers to deliver consistently clear, secure, end-to-end communications to their customers over mobile, VoIP, and wireline networks. These voice quality solutions improve the sound of voice communications, transforming network distortions and environmental background noise into clear, high quality communications that lead to greater customer satisfaction, increased usage, and higher retention rates.

Ditech Networks has been serving the needs of telecommunications service providers for over 15 years, and in that time its echo-cancellation and voice-quality-improvement products have been deployed in more than 34 countries on 6 continents, and used on over 7million voice channels (DS0s). Ditech has approximately 225 employees, offices worldwide, and 2006 revenues of approximately $55 million.

In addition to the voice processing systems, Ditech Networks provides media processing and session control technologies for wireless and wireline service providers, including network solutions for both TDM and VoIP networks. Some of these products are very innovative, including voice quality solutions that allow cellular carriers to encode voice information at lower rates (thus extending the economic lives of their network infrastructures), and algorithms that provide bidirectional noise reduction and bidirectional acoustic echo cancellation.

Ditech Networks’ product portfolio was enhanced when the company acquired privately held Jasomi Networks, a developer of session border controllers, in 2005. By joining forces—combining the Ditech voice processing expertise with the Jasomi session border controller systems—the company positioned itself to provide a completed border services solution to carriers. The resulting product offering, named the PeerPoint C100, is an SBC targeted at smaller carriers that require up to 1,000 simultaneous channels per node.

The PeerPoint C100 is positioned as an access SBC with enhanced security, service assurance, high availability, management services, and legal compliance capabilities.

The Security group functions protect the core network with a media-stateful firewall; a media configurable port range; SIP-request-storm protection; a signaling stream access control black/white list; Real Time Protocol (RTP) packet inspection; network topology hiding including the removal and insertion of SIP application headers and fields (such as the ROUTE and VIA constructs); plus encryption, which includes encryption enforcement policies, and both Transport Layer Security (TLS) and media (RTP) encryption.

The Service Assurance group functions provide the far-end Network Address Translation (NAT) transversal, media path optimization; automatic session termination; and Quality of Service (QoS) enforcement.

The High Availability group includes failure detection based upon the VRRP (Virtual Router Redundancy Protocol, defined in RFC 3768, see ); plus remote server redundancy, load balancing and prioritization.

The Management Services group includes authentication using RADIUS (the Remote Authentication Dial-In User Service); multiple levels of read/write privileges; external reporting of call statistics, NAT information, and system logs; support for SNMP (Simple Network Management Protocol) and a private Ditech Management Information Base (or MIB); plus an internal SIP log for forensic applications.

For Legal Compliance, the system includes media and signaling stream duplication and routing, plus an interface for CALEA (the Communications Assistance for Law Enforcement Act). The unit includes an 8-port interface for 10/100/1000 Ethernet connections, and is supplied in a 19-inch rack-mounted chassis.

One of the most notable customers for the Peerpoint C100 SBC is the Free World Dialup (FWD) network (see ), the world’s first real-time, person-to-person IP network, supporting over 3 million users from over 136 carriers around the world. FWD supports many users’ applications, including voice, video, presence, and instant messaging.

FWD selected the Peerpoint C100 to solve the NAT and firewall challenges presented by this public carrier with so many end users. In this application, the SBC sits on the public side of the network, in the direct flow of all signaling and media connections. The SBC advertises a public IP address, and then translates the public/private IP addresses between the incoming and outgoing communication streams in order to complete the call (the NAT challenge).

The SBC also keeps the SIP devices registered, so that their ports are not closed due to any inactivity, and insures that all calls initiate from behind the firewall, thus maintaining the security of the network (the firewall challenge). The system was also found to be interoperable with many of the other devices deployed on the FWD network, thus minimizing technical support concerns.

Further details on the Ditech Networks 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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