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Why Session Management Matters

The move to the converged services model based on IP networks is well underway at network operators around the world, but the smoothness of the transition will depend in large part on those operators having the ability to manage IP services in a way that makes sense in the IP environment. This requires nothing less than a complete rethinking of the way carriers approach network design and management.

Builders of telecom networks have long envisioned their networks operating at the first four layers of the OSI model stack – the physical, data link, network, and transport layers, a.k.a. the "transport set" – while the higher layers – session, presentation, and application, a.k.a. the "application set" – were left to the data processing community that managed the applications on the data networks.

With converged IP networks and next-generation networks, however, all that is changing. Now the operators' core services, such as voice and video, are also applications on the IP network. The network can no longer be indifferent as to what is occurring above layer 4. The network layers need information about what is happening at the session layer and above, and the session layer needs information from the network layers in order to function properly.

This transformation of telecom network design and management is the focus of Heavy Reading's latest research report, Session Management, IMS, and the Future of Session Border Controllers. The report analyzes the changes required to support IP-based services in a world of converged IP networks and points to the key emerging technologies that will reshape the telecom network environment.

VOIP is now the main driver behind this network management revolution, with IPTV on the way. In order to establish a VOIP session, essential information that is carried in the signaling message (layer 5) is required to configure the network correctly. Signaling messages include information about the type of codec (which is layer 6), the type of client (layer 7), and the IP addresses and port (layers 3 and 4). How the network is configured is critical, since all services ride on a common IP network – and while latency and jitter may not be important for an Internet Web session, it is very important for voice and video. Furthermore, while a little bit of packet loss can be tolerated in a voice call, it is much more noticeable in a video session. Networks must be configured to provide the right quality of service (QOS) to support the applicable sessions.

Session border controllers (SBCs) perform a lot of the functionality at the edge of the network almost by default. SBCs initially were used to solve problems of firewall and network address translation (NAT) traversal, but they quickly began to incorporate a host of other features that network providers deem important. Our report includes results of an exclusive worldwide survey of 80 service provider professionals; as part of that survey, we asked respondents to rate the relative importance of 16 different SBC features in the areas of connectivity, security, QOS, regulatory requirements, call accounting, and policy-based routing. In that study, we found only a 15 percent difference between the average ratings for the most important feature (firewall) and the least important feature (media transcoding). Clearly, the survey participants see all of these functions as critical to their networks and today they see them contained within their SBCs.

Over time, as carriers implement common IP infrastructure, this functionality will be distributed throughout the network. Session management and session control will be essential to manage traffic across the core networks. With this network evolution, some of the session management functionality will move to the core; some will move to other network elements; and some will remain at the border security device. Standard interfaces will interconnect the network elements, over which they will be communicating information about the sessions, their requests for connections, their status, and disconnects. Information will include the amount of bandwidth required, which will vary greatly depending on whether it is voice or video; their relationship to other sessions in the case of multimedia; or their transfer across networks in the case of fixed and mobile convergence.

Gone are the days of service-specific networks, and gone with them are the ways those services were managed. In the world of converged IP networks and services, it's all about managing the quantity and quality of sessions: quantity (both in terms of number of sessions and bandwidth per session) to ensure that the network performance remains high and the costs are consistent with the service offered; quality to ensure customer satisfaction and to avoid wasting precious resources on the wrong applications. The winners in the future will be determined at least in part by how well they manage sessions.

— John Longo, Senior Analyst, Heavy Reading

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