Hysteretic Control Technique for Overload Problem Solution in Network of SIP Servers

This paper contains research and development results concerning application of hysteretic control principles to solve SIP servers overload problem, which is known from a number of IETF standards and scientific papers published over the past few years. The problem is that SIP protocol, being the application layer protocol, by default has no build-in means of overload control, as, for example, SS7, MTP2 and MTP3 protocols. It was the SS7 network, where a threshold mechanism of hysteretic signalling load control was first implemented. In this paper we describe the main up-to-date solutions of an overload control problem in a signalling network, and develop analytical models of hysteretic control, which are useful in the development of load management functions of SIP servers. We also propose the design of Open SIP signalling Node (OSN) software architecture which is intended to be used for simulations and comparison of various overload control mechanisms

Comparison of LBOC and RBOC Mechanisms for SIP Server Overload Control

The purpose of this article is to analyze mechanisms of Loss-based Overload Control, LBOC and Rate-based Overload Control, RBOC for server overload control of the Session Initiation Protocol (SIP). Overloading occurs when a server is unable to process an entire incoming message flow due to a lack of resources. Standards of IETF SOC recommend several overload control mechanisms, including most important LBOC and RBOC. This article proposes the mechanisms of LBOC and RBOC and describes the results of the comparative analysis of these mechanisms based on the hysteresis control over incoming stream of signaling messages. The system resides in one of three modes (normal, overload, discard) based on thresholds and a size of an input queue. A signal message source implements the Markov-modulated Poisson process, MMPP-2 model. The leaky bucket algorithm is applied to limit the number of incoming messages in the implementation of RBOC mechanism. The comparison of results showed that RBOC mechanism based on the hysteresis control over incoming stream of signaling messages demonstrates higher effectiveness of the congestion control, as a result of which the average time in the overload mode is less than for LBOC mechanism. However, LBOC mechanism has the ability to maintain its high efficiency for all RTT values ​​on the same thresholds, while RBOC mechanism needs to have its own threshold dynamic control mechanism for different RTT values ​​to supply maximum efficiency. © Springer Nature Switzerland AG 2018