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

Statistical Analysis of Message Delay in SIP Proxy Server, Journal of Telecommunications and Information Technology, 2014, nr 4

Single hop delay of SIP message going through SIP proxy server operating in carriers backbone network is being analyzed. Results indicate that message sojourn times inside SIP server in most cases do not exceed order of tens of milliseconds (99% of all SIP-I messages experience less than 21 ms of sojourn delay) but there were observed very large delays which can hardly be attributed to message specic processing procedures. It is observed that delays are very variable. Delay components distribution that is to identied are not exponentially distributed or nearly constant even per message type or size. The authors show that measured waiting time and minimum transit time through SIP server can be approximated by acyclic phase-type distributions but accuracy of approximation at very high values of quantiles depends on the number outliers in the data. This nding suggests that modeling of SIP server with queueing system of GjPHjc type may server as an adequate solution

Statistical Analysis and Modeling of SIP Traffic for Parameter Estimation of Server Hysteretic Overload Control, Journal of Telecommunications and Information Technology, 2013, nr 4

The problem of overload control in Session Initiation Protocol (SIP) signaling networks gives rise to many questions which attract researchers from theoretical and practical point of view. Any mechanism that is claimed to settle this problem down demands estimation of local (control) parameters on which its performance is greatly dependent. In hysteretic mechanism these parameters are those which define hysteretic loops. In order to find appropriate values for parameters one needs adequate model of SIP traffic flow circulating in the network under consideration. In this paper the attempt is made to address this issue. Analysis of SIP traffic collected from telecommunication operator’s network is presented. Traffic profile is built. It is shown that fitting with Markov Modulated Poisson Process with more than 2 phases is accurate. Estimated values of its parameters are given

Structure and Bonding Nature of the Strained Lewis Acid 3-Methyl-1-boraadamantane: A Case Study Employing a New Data-Analysis Procedure in Gas Electron Diffraction

Vishnevskiy Y, Abaev MA, Rykov AN, et al. Structure and Bonding Nature of the Strained Lewis Acid 3-Methyl-1-boraadamantane: A Case Study Employing a New Data-Analysis Procedure in Gas Electron Diffraction. Chemistry. 2012;18(34):10585-10594.Base-free 3-methyl-1-boraadamantane was synthesized by starting from its known THF adduct, transforming it to a butylate-complex with n-butyllithium, cleaving the cage with acetyl chloride to give 3-n-butyl-5-methyl-7-methylene-3-borabicyclo[3.3.1]nonane and closing the cage again by reacting the latter with dicyclohexylborane. The identity of 3-methyl-1-boraadamantane was proven by 1H, 11B and 13C NMR spectroscopy and elemental analysis. The experimental equilibrium structure of the free 3-methyl-1-boraadamantane molecules has been determined at 100 degrees C by using gas-phase electron diffraction. For this structure determination, an improved method for data analysis has been introduced and tested: the structural refinement versus gas-phase electron diffraction data (in terms of Cartesian coordinates) with a set of quantum-chemically derived regularization constraints for the complete structure under optimization of a regularization constant, which maximizes the contribution of experimental data while retaining a stable refinement. The detailed analysis of parameter errors shows that the new approach allows obtaining more reliable results. The most important structural parameters are: re(B-C)av=1.556(5) angstrom, ${\angle }$e(C-B-C)av=116.5(2)degrees. The configuration of the boron atom is pyramidal with ${\sum \angle }$(C-B-C)=349.4(4)degrees. The nature of bonding was analyzed further by applying the natural bond orbital (NBO) and atoms in molecules (AIM) approaches. The experimentally observed shortening of the B?C bonds and elongation of the adjacent C?C bonds can be explained by the s(C-C)?p(B) hyperconjugation model. Both NBO and AIM analyses predict that the B?C bonds are significantly bent in the direction out of the cage

«Da qualche parte si veglia ancora...». La poesia «Сидзӕргӕс» di Kosta Chetagurov

Among the poems of Kosta Khetagurov included in the collection Iron F\u4d5ndyr (Ossetian Lyre), the one entitled \u201cSidz\u4d5rg\u4d5s\u201d (\u2018Widow\u2019, literally \u2018Mother of Orphans\u2019) deserves particular attention. Written probably at the end of the 1880s, the text describes a tragic familiar scene with an unhappy end. The portrait of a young woman, cooking a soup, and her five hungry children, sitting around the hearth and eagerly awaiting the dinner, is one of the most tearful and emotional scenes, well-known and beloved by all Ossetians. The present article presents a multi-layered analysis of the text. The introduction provides relevant biographical and historical information on \u201cSidz\u4d5rg\u4d5s\u201d and its historical, cultural and literary environment. The Italian literal translation is followed by an interlinear gloss: the first line contains a phonetic-phonological transcription of the text; the second features a semantic and morphosyntactic interpretation of the Ossetic text. In the appendices, beside a cognate poem, written by Kosta in Russian (\u201cV burju\u201d), the reader will find two previously unpublished typescript German translations of \u201cSidz\u4d5rg\u4d5s\u201d, from the archive of Gappo Baev (Berlin State Library)