This article originally appeared in the July/August issue of INTERNET TELEPHONY

Integrating robust policy control and enforcement capability with session management provides service providers and enterprises with an opportunity to both make money and save on operating costs. So what exactly is policy-enabled session management, and how does it help enterprises and service providers?

Session management is a term in the SIP lexicon that has been around for a couple of years. In its basic form, session management makes it possible for existing legacy systems to work together while also working with newly deployed SIP-based systems and have full access to common SIP-based services and applications. Session management saves money by extending the life of legacy systems, and provides the ability to generate new revenues with SIP-based services and applications.   

Policy plays an important role in session management solutions for current and future enterprise networks. A number of paradigm shifts in enterprise networks in recent years have made policy fundamental to a robust session management solution. These include cloud computing and virtualization, the emergence of bring your own device, and increased adoption of video (with stringent quality requirements and bandwidth demands), among many others. Effective enterprise-wide policies that govern the access to data and usage of services are essential to meeting the evolving and dynamically changing needs of enterprise networks.

Policy includes policy control/management, policy enforcement and optionally policy databases. Policy control determines how policies/rules are applied to each SIP session or IP flow. This action is triggered by policy requests received from the policy enforcement element. The policy enforcement element enforces policies/rules on SIP sessions, IP flows, etc., which it receives from the policy control element. A policy database serves as the repository for policies. The policy control element queries the policy database, if necessary, to determine the policy. Example: No one in the office is allowed to access non-business related websites between the hours of 9 a.m. and 5 p.m. The list of restricted sites is contained in the policy database.

A robust session management solution should support both network policies and subscriber-level application policies on a per-session basis. When a subscriber initiates a SIP session, specific policies can be applied to the session based on the identity of the subscriber, the application invoked by the subscriber and the network conditions. Typically, these policies fall into three categories: local policy, static policy and dynamic policy.

A local policy can be thought of as a sub-set of static policy, and applies to one specific node/subscriber/location; for example, a company does not want to allow voice or video calls in the main conference room of the company’s New York office. Or, it can be a policy applicable to a single PBX (News - Alert), UC device; for example, the UC terminal in the lobby does not allow video calls.

A static policy is one that is provisioned in a (static) policy database/repository. Session management does a lookup of the policy repository to determine the policies to be applied to a given session. For example, a subscriber invokes a SIP video session to stream videos from a content provider with restricted content; however, the session is blocked because the subscriber’s profile does not allow access to restricted content.  

A dynamic policy is one that can vary from session to session for a given subscriber. Dynamic policy may include dedicated policy applications running on top of (or as part of) the session management layer. For example, a subscriber initiates an intra-enterprise SIP voice call session; session management invokes a presence policy application that determines the current status of the called subscriber; and then it invokes a second location policy application (using service orchestration) to determine the current location of the called subscriber. Depending on the current location/status of the call request, specific policies are applied to the call request. Policies can include redirecting the call, blocking the call, sending the call to voicemail, etc.

Network policy complements subscriber-level application policies, and in combination, they create a powerful policy solution for session-based services within enterprises. Network policies include intelligent network routing based on various criteria, session screening, session blocking, quality of service enforcement, call and number translation. A least cost routing engine can also be part of the network policy management solution. Network policy typically supports routing of sessions based on origination or destination numbers, destination location, session type, least cost, time of day or day of week, and/or QoS requirements.

A fully integrated policy solution for session management should include application policies, subscriber-level policies, and network policies. For example, a subscriber initiates a unified communications audio/video session with another subscriber; session management invokes the location policy application to determine the called subscriber’s location; session management then invokes the network policy engine to determine the LCR to the subscriber based on their current location, as well as to apply QoS requirements to the audio/video session; and session management sets up the connection to the called subscriber.

So how does policy-enabled session management help enterprises and service providers? By enabling service differentiation; it allows tiered billing for services which can generate additional revenues. It facilitates the enforcement of SLA and fair use of resources, preventing few users from using up most of the bandwidth. It provides better control over the QoS for customers, which is especially important for video. It increases workplace productivity by allowing enterprises to define and enforce policies on non-business related activities at a very granular level on a per-application per-subscriber per-session basis. It provides better security and control over sensitive data. By intelligently routing traffic over optimal routes, policy-enabled session management reduces costs for enterprises and service providers.

Enterprises and service providers should consider deploying a policy-enabled session management solution in order to reduce cost and generate revenue. In a majority of the cases, this type of solution will fit into their existing network with minimal re-work and integration effort.

Mohan Palat (News - Alert) (News - Alert) is product marketing manager with Sonus Networks (News - Alert) .