No abstract

As a competitive alternative to traditional telephony is increasingly being used voice over internet protocol VoIP [1]. Although similar tract to transmit voice in case of VoIP than traditional voice telephony is not produced, but it is necessary to realize the conclusion of a communication session using the appropriate signaling protocol. While the end equipment manufacturers use many different protocols, but only a few of them are standardized and recognized by all equipment manufacturers. In the initial phase, the main communication protocol to establish connection has been used H.323 protocol [2], with both positive and negative features. Of the shortcomings that led to its limited use is caused by the complexity and by replacing it with Session Initiation Protocol SIP [2] and the increasing use of multimedia services over IP networks. SIP protocol is a major next-generation networks that use the IP Multimedia Subsystem IMS [3,4].In order to identify the characteristics of communication session, analytical [5] and simulation [6] methods are used. However, in both cases it is necessary to know the signaling message handling time statistical characteristics, including their distribution. Often in the theses are accepted, that application service time is distributed according to exponential distribution [5,6]. At the telephone networks that use circuit switching principle handling exponential distribution is valid for the duration of the call [7], but the IP networks that use packet transfer, it may be wrong. In order to determine the appropriate use real experimental results must be used.At time voice service is handled, signaling processing nodes accepts the different types of signaling messages and their processing length depends on the complexity of the process and the calculation of nodes resources (CPU, dynamic memory, internal bus) high-speed, productivity, etc.This work provides statistical characteristics of experimental signaling alarm service servicing at nodes time, used to service voice services, investigations.

SIP protocol is most often used for voice information transmitting over IP networks via communication session. Communication session process has been managed by SIP proxy server. In order to determine its operating characteristics, such as message service time, and message blocking probability, it is necessary to know the statistical features of the served traffic including the time interval of incoming message flow, the time interval distribution between arriving messages, mean value and their possible deviation. The statistic characteristics of time intervals of individual SIP messages and the total flow entering into SIP Proxy server have been experimentally determined in the paper. It has been found that the inter-arrival time of the sum total of SIP message flow does not correspond to the Poisson distribution thus General distribution should be used in the tests.