Vendor Network Architectures�Part XXV: sentitO Networks

sentitO Networks of Acton, Massachusetts, was founded in 2000 to provide carrier-class VoIP switching and service delivery solutions to drive the migration of circuit switching networks to IP networks. sentitO’s architecture is named the Open Network Exchange, or ONX, which was designed from the ground up for VoIP applications. This architecture is designed to address four different application challenges:

  • VoIP Transport: enabling carriers to migrate their existing circuit switched network to an Internet Protocol (IP)-based packet network to deliver voice transport and services. Getting the IP traffic into the network at the earliest stage increases the economies of scale, and therefore reduces the transport and operational costs.
  • VoIP Termination: enabling wholesale carriers that provide VoIP termination services the ability to expand their network in a linear, economical fashion through the use of more efficient gateways.
  • PBX Trunking: many enterprise business customers are not yet ready to upgrade their legacy PBX and key systems, but have a continuing need for trunk circuits between locations. VoIP circuits can be used for that application to lower the cost of voice transport over existing ISDN Primary Rate Interface (PRI) connections.
  • Residential VoIP: local service providers have rolled out broadband, fiber optic, and wireless access networks, and are all competing to provide voice services to the same residential customers. Customers require the typical voice applications, but regulators also mandate support for E911, call intercept, and other required public services.

The ONX solution is a distributed architecture based on SIP (Session Initiation Protocol), XML (Extensible Markup Language), and MPLS (Multiprotocol Label Switching) standards, which are combined to create an innovative VoIP switching and service-delivery solution. This distributed and decentralized architecture mirrors the model of the Internet itself. It distributes the call control logic and processing functions that are typically associated with a media gateway controller to a scalable media gateway, and is designed to improve on the centralized architecture of most softswitches. For example, the ONX has no common or pooled Digital Signal Processing (DSP) resource cards, which allows a “pay-as-you-grow” model for traffic and service deployment. In addition, the system includes XML scripting of port, trunk, and subscriber profiles, plus support of MPLS routing. The architecture consists of three key elements:

  • Intelligent Voice Gateway (iVg): is a highly scalable, intelligent voice services gateway designed for the edge of carrier and service provider networks. The iVg combines media gateway, call control, and router technologies to improve voice quality and reliability, and is designed for the rigors of Tier 1 carrier requirements. It is a native IP platform, which utilizes SIP and XML to quickly create and alter routing parameters, trunk, port, and subscriber profiles, and facilitate third-party interoperability.
  • Proxy7 Signaling Gateway: combines a SIP proxy server with SS7 signaling intelligence to create a cost-effective bridge between emerging VoIP networks and the PSTN. It enables intelligent and scalable SIP/SS7 interworking to support transparent configuration and management of services across and between IP and TDM networks, and translates SS7 messages to SIP messages for interoperability at the network edge.
  • PreVision Network Manager: is a real-time, Web-based management platform for ONX products and services that supports standards-based network management via SNMPv3 and XML interfaces and tool sets. It provides a change-event drive model that provides immediate reconciliation with existing network parameters, and immediate notification of modifications to network elements.

In addition to support for the ONX product, sentitO has developed partnerships with key providers of SIP-based applications, features, and devices to enhance interoperability and conduct certification and testing. The ONX Alliance includes extensive interoperability testing of third-party products and solutions, to foster the interoperability of VoIP equipment and services, and to dramatically reduce the time to deployment and revenue for their customers. This alliance focuses on SIP-based applications and services, including media servers, session border controllers, billing systems, network management systems, IP telephones and softphones, plus integrated access devices.

Further details on the sentitO architecture and products can be found at Our next tutorial will continue our examination of vendors’ architectures.

Copyright Acknowledgement: © 2006 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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