Session Initiation Protocol (SIP) Server Overload Control: Design and Evaluation

TL;DR

This paper addresses SIP server overload issues by proposing and evaluating new pushback control algorithms, aiming to prevent congestion collapse and ensure fairness under heavy or variable loads.

Contribution

It introduces three novel window-based feedback algorithms and a new overload control architecture, enhancing load regulation and fairness in SIP servers.

Findings

New algorithms outperform existing methods in load regulation.

The double-feed architecture effectively balances fairness and performance.

Algorithms require fewer tuning parameters for practical deployment.

Abstract

A Session Initiation Protocol (SIP) server may be overloaded by emergency-induced call volume, ``American Idol'' style flash crowd effects or denial of service attacks. The SIP server overload problem is interesting especially because the costs of serving or rejecting a SIP session can be similar. For this reason, the built-in SIP overload control mechanism based on generating rejection messages cannot prevent the server from entering congestion collapse under heavy load. The SIP overload problem calls for a pushback control solution in which the potentially overloaded receiving server may notify its upstream sending servers to have them send only the amount of load within the receiving server's processing capacity. The pushback framework can be achieved by either a rate-based feedback or a window-based feedback. The centerpiece of the feedback mechanism is the algorithm used to generate load regulation information. We propose three new window-based feedback algorithms and evaluate them together with two existing rate-based feedback algorithms. We compare the different algorithms in terms of the number of tuning parameters and performance under both steady and variable load. Furthermore, we identify two categories of fairness requirements for SIP overload control, namely, user-centric and provider-centric fairness. With the introduction of a new double-feed SIP overload control architecture, we show how the algorithms can meet those fairness criteria.