Analysis and Modeling of VoIP Servers: A Linear Programming Approach

The SIP protocol was standardized by the IETF at the application layer for initiating, managing, and terminating multimedia sessions and has been widely used as the main signaling protocol on both the Internet and VoIP networks. Most challenges in this protocol are overload and lack of proper state distribution. These challenges cause a wide range of next-generation network users to face a sharp decline in service quality. In this article, we define the state distribution problem between several nodes where the state maintenance is accompanied by considerable consumption of resources leading to overload. For the problem solution, the goal is to increase the overall throughput of calls and the availability of servers. First, we provide a framework based on software-defined networking technology, and then we formulate the problem as an optimization problem and implement and evaluate it as a module on the proposed controller. This leads to a more scalable SIP network that dynamically determines the number of SIP requests for which the server is modeled while delegating the state maintenance to its downstream server for the rest of the requests. This is in contrast to existing SIP servers because they are statically configured to be either stateless or stateful, resulting in non-optimal call throughput. Performance evaluation is performed at two levels of infrastructure and control and the results are presented.