Overload control in SIP networks using no explicit feedback: A window based approach

The performance of SIP servers is largely degraded during overload conditions due to the built in message re-transmission mechanism of SIP. In this paper we propose adistributed and end-to-end adaptive window based overload control algorithm, by which upstream SIP servers control the amount of calls that are forwarded to a downstream SIP server in an attempt to prevent it from being overloaded. Our scheme uses the call establishment delay as a measure of the amount of load on the downstream server and unlike other methods does not rely on any explicit feedback from the downstream server. As a result the proposed algorithm imposes no additional complexity on the downstream server. Moreover, it requires no additional processing to be done at the downstream server, which is overloaded, making it a very robust approach. Using simulations we show that our proposed method achieves higher throughput than a commonly used overload control algorithm and is also fair among different upstream servers. It is also shown that compared with approaches using explicit feedback, the performance of our scheme is less sensitive to link delays. Furthermore, the effect of server queue size is also considered and a simple method for finding an upper bound on the queue size of the downstream server is given.

Controlling Overload in SIP Proxies: An Adaptive Window Based Approach Using No Explicit Feedback

The Session Initiation Protocol (SIP) has gained momentum and is being widely used both in the Internet and Next Generation Telecommunications network as the core signaling protocol. SIP operation relies on SIP servers which are responsible for forwarding of SIP messages. It has been shown that the performance of SIP servers is largely degraded during overload conditions due to the built in message retransmission mechanism of SIP. This is an obstacle in wide deployment of SIP for a realistic situation. In this paper we propose a distributed and adaptive window based overload control algorithm, which controls the amount of calls that are forwarded to a downstream SIP server in an attempt to prevent it from being overloaded. Our scheme uses the call establishment delay as a measure of the amount of load on the downstream server and unlike other methods does not rely on explicit feedback. Using simulations we show that our proposed method performs better than a commonly used overload control algorithm and exhibits fast convergence and is stable.

Overload control in SIP servers: Evaluation and improvement

It has been shown that the throughput of Session Initiation Protocol (SIP) proxies is largely degraded during overload conditions due to the built in message retransmission mechanism of SIP. Many overload control algorithms have been proposed with the objective of keeping SIP proxy throughput at an acceptable level when overload occurs. In this paper we view the overload problem as a Lyapunov stability problem. We consider the standard SIP trapezoid topology consisting of an upstream and downstream proxy operating in tandem. We provide a fluid flow model for the operation of this system under overload. We write state space equations for the tandem proxy system and using Lyapunov stability criterion derive stability conditions for it. We then propose an overload control algorithm that stabilizes the system by rejecting a fraction of SIP call setup requests. Backing our analysis with simulations we illustrate that our algorithm is able to restore proxy throughput when hit by overload. In addition, we show that rejection should be an integral part of any SIP overload control scheme and prove that the optimal rejection policy is to put the rejection burden on the upstream proxy as much as possible. Moreover, based on our mathematical model we show how to do optimal capacity provisioning for a SIP network in order to withstand overload. To the best of our knowledge this is the first work which addresses stability of SIP proxies using Lyapunov theory.

Stability analysis of tandem SIP proxies

Having facilities such as being in text form, end-to-end connection establishment, and being independence from the type of transmitted data, SIP protocol is a good choice for signaling protocol in order to set up a connection between two users of an IP network. Although utilization of SIP protocol in a wide range of applications has made various vulnerabilities in this protocol, amongst which overload could make serious problems in SIP servers. A SIP is overloaded when it does not have sufficient resources (majorly CPU processing power and memory) to process all messages. In this paper the window-based overload control mechanism which does not require explicit feedback is developed and implemented on Asterisk open source proxy and evaluated. The results of implementation show that this method could practically maintain throughput in case of overload. As we know this is the only overload control method which is implemented on a real platform without using explicit feedback. The results show that the under load server maintains its throughput at the maximum capacity.

Sip overload control testbed : design , building and evaluation

Session Initiation Protocol (SIP) is adopted as the main signaling protocol for the IP Multimedia Subsystem (IMS). Large deployment of SIP servers in Next Generation Networks (NGN) requires studying the behavior and performance of SIP servers under both normal and overload conditions, which may happen in such networks with a vast number of users. In this paper a measurement-based study is performed to assess SIP proxy server performance under different configurations, and for different underlying transport protocols, for both inter-domain and intra-domain calls. Test results show the effectiveness of configuration and distance on SIP signaling performance. Therefore a great attention must be paid during SIP servers deployment.

Configuration of a SIP Signaling Network: An Experimental Analysis

Summary

Carriers have adopted session initiation protocol (SIP) in their next generation networks. Providing carrier-grade service requires high availability in times of component failures, avalanche restart, flash crowds and denial of service attacks, which cause overload on SIP servers. Throughput of SIP servers is largely degraded during overload. We propose an SIP overload control (SIP-OC) solution for local and remote situations, working in hop-by-hop and end-to-end modes. Our local SIP-OC method uses a cross-layer approach with negligible performance impact, while the implicit nature of our remote SIP-OC allows detection of sophisticated overload conditions such as those caused by non-SIP entities. Our remote SIP-OC uses transaction response time as the basis for implicit overload detection. Coupling our local and remote SIP-OC schemes, we show that the range of ‘sustainable’ overload that can be imposed on the system improves significantly. Moreover, incorporating a 2-means filtering mechanism into our SIP-OC scheme makes it perform well under packet-loss. We also show that our proposed solution is robust to network latency and SIP server capacity fluctuations. All of our results are obtained from experiments over SIP testbeds including an experimental IP multimedia subsystem. Copyright © 2016 John Wiley & Sons, Ltd.

Mojataba Jahanbakhsh

Papers

Configuration of a SIP Signaling Network: An Experimental Analysis

Local and distributed SIP overload control solution improving sustainability of SIP networks