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Session Management:

Building a Foundation for VoIP and Beyond

By Dan Dearing


Personal communication has changed significantly from ten years ago, when people relied on the phone system to talk to one another, access the Internet, and send faxes. Today, people use a combination of text, voice, and multimedia communications to best meet their needs based on what they are doing and where they are. Service providers and other IP network operators are rapidly moving to harness the flexibility and efficiencies of the converged IP network to cost effectively offer the mix of services consumers now demand; however, the use of one network to deliver multiple services creates new complexities and challenges in managing service connectivity and resources. Session management technology provides network operators with a technology strategy to manage the complexities of this new networking environment by giving IP network operators a foundation for VoIP and beyond. Session management is providing the underpinnings for a new network economy where sessions traversing the IP network � not bandwidth or usage minutes � are the currency.

The importance of IP network interconnects is growing since many of the complexities of converged IP environments manifest themselves at the edge of the network. Service providers have long been concerned with security at the network edge but are now finding that to scale their next generation services, they must also enforce a wider set of policies at the session layer that include security, session management, and the business performance of their network and its associated services. Service providers today can use network-to-network IP interconnects and corresponding user-to-network IP interconnects to adapt session traffic as it enters and leaves their network. These interconnects also provide a natural place for service providers to monitor traffic for both quality and accounting purposes.

Session management technologies provide network operators with a comprehensive facility to monitor and manage a VoIP network end-to-end for maximum quality of service and availability. Furthermore, session management enables interconnection across a variety of disparate VoIP networks and legacy systems while providing centralized voice and data management, thus enabling carriers to scale their VoIP services and expand their services revenues. More important, session management technology provides carriers with a strategy to diversify and grow revenues by facilitating the seamless introduction of new, revenue-generating services with little or no effect on underlying networks. The technology also enables service providers to leverage their investment in next generation technology as a stepping-stone to IMS.

Session management addresses not only the technology issues that exist at the network edge but also the commercial issues because it enables service providers to manage, monitor, and bill for VoIP, multimedia, and other real-time sessions that flow through their IP network. This advanced session-layer technology uses a continual process of policy optimization, thus enabling network operators to implement dynamic policies that can be enforced at the edge of their network, simplifying network operation and service rollout; more important, it gives them visibility into network behavior. By gathering and processing information such as session detail records and alarms in real time, session management technology allows network operators to use network feedback to dynamically adjust policies to changes in interconnect capacity, quality, and availability. The ability to adjust is essential for scale and reliability because it allows service providers to proactively and dynamically change policies to address time-critical revenue issues that relate to quality and reliability. Dynamic session management information empowers service providers to more effectively manage their service business by proactively addressing issues that affect customer satisfaction and loyalty (Figure 1).

In next generation networks, service providers use session border controllers (SBCs) to address many of the technical aspects of interconnecting networks and their real-time services; however, the SBC has a limited view of the session at a single network point and little visibility of the session end-to-end. For example, the SBC cannot tell a service provider the best route to connect two session endpoints, nor can it tell if there are problems within the network that may impact service quality. Session managers address these network- and session-wide issues with added intelligence to monitor sessions end-to-end and dynamically change the policies that control them based on current network and session status.

Session management consists of three layers of functionality and intelligence (Figure 2). The SBC layer provides session transport and performs the mechanics of interconnecting networks, including capabilities such as security, QoS assurance, and signaling interworking. The SBC also collects basic layer-three data such as packet delay, jitter, and lost packets. This information is not really relevant by itself at the SBC layer, but provides valuable network feedback for the higher layers.

The session control and enforcement layer treats sessions as unique connections between user and application endpoints. Tasks performed here include the setting up of a connection between two endpoints, enforcing policy about which endpoints can use the network, and determining which services sessions are allowed to access. This layer also collects feedback information that describes the duration and quality of the session, including call hold time, post-dial delay time, and mean opinion score.

The session management and analysis layer collects and analyzes information from the lower layers and then dynamically updates policies established by operator business and engineering teams to control network interconnects. These policies regard issues such as how calls are routed and service level agreements are maintained. To provide comprehensive visibility into service and network quality, this session management intelligence provides a detailed view of session activity across network interconnects. Information gathered from session detail records, log files, and alarms is summarized here for further analysis and action by operators. This layer also provides a facility to provision and manually update policies and to arrange for automatic notification of any dynamic changes to network policies.

As service providers scale and diversify their offerings, they need added operational visibility, interconnect flexibility at the OSI session layer for greater networking efficiencies, and maximum return on their investment in next-generation technology and applications. The added intelligence of the session manager, deployed in conjunction with an SBC, gives service providers a complete system that provides the underpinnings for exciting new IP services. This advanced capability empowers service providers to connect sessions more easily, securely, and scalably, giving the dynamic control needed to scale and adapt sessions to current network conditions.

Service providers today are using intelligent interconnects, powered by dynamic session management, to address practical issues such as recovering from a catastrophic service outage or adding additional connectivity between VoIP networks. More importantly, service providers are using intelligent interconnects as a stepping stone to the IMS architecture, enabling them to quickly expand their service offerings and deliver the mix of services and mobility users want most. With the migration to VoIP well underway, service providers are using intelligent interconnects to address a wider set of customers, linking fixed and mobile devices into a single network. This intelligent network edge enables service providers to offer traditional voice services along with new multimedia services such as mobile interactive gaming and video sharing. Service providers can fast-track these offerings by flexibly and securely interconnecting with application service providers (ASPs) at VoIP and IMS peering points and leveraging the outsourcing capabilities of the ASP.

Intelligent IP interconnects are creating a new networking economy where service providers, each having a specialty, are interconnecting their offerings to provide their customers a wider variety of IP-based services. We are witnessing tremendous service provider investments in IP, IMS, and wireless networks; however, many organizations do not have the economic backing to execute a �go it alone� approach. Intelligent interconnects enable different types of providers to interact and cooperate for expanded service offerings, greater service reach, and more flexible service delivery. The use of intelligent interconnections enables service providers to extract value from the promise of IMS and the converged IP network. This new networking model creates a new and innovative environment that is a win/win for both users and service providers. IT

Dan Dearing is vice president of marketing for NexTone Communications. For more information, please visit the company online at

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