Jitter calculation in core - IEEE Xplore

Jitter Calculation in Core IMS (4)

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BA Alassane, (2)Konate Karim ,(3)Nikolay Ivanovich Chervyakov,

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Maxim Anatolievich Deryabin, (5)Mikhail Grigorievich Babenko, (6)Maria Nikolaevna Shabalina,(3-6 )

Laboratory of Computer, Network and Telecommunications, Department Mathematics and Computer ,(1-2)Cheikh Anta Diop University of Dakar, Dakar, Senegal, (1) [email protected], (2)[email protected], (3) [email protected]

Department of Applied Mathematics and Mathematical modeling, North Caucasian federal University,Stavropol,Russia, (4) [email protected],(5)[email protected] (6) [email protected]

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This paper is organized as follows: section 2 gives the traffic organization in an IMS session. After giving a basic architecture of IMS network in session 3, session 4 talk about jitter approach and definition. Work in section 5 and 6 concern respectively our previous work on topic and results. The paper concludes in Section 7.

Abstract—The IP Multimedia Subsystem (IMS) enables the convergence of voice, data, and multimedia services. IMS is well integrated with existing voice and data networks, while adopting many of their key characteristics. SIP (Session Initiation Protocol) provides a pathway to build a single unified network, bridging the gap that previously existed between the onceseparated Telecom and Internet networks. The Call Session Control Functions (CSCFs) servers are the key part of the IMS structure. They are the main components responsible for processing and routing signalling messages. For users and enterprise needs, network outages or significant degradations of the quality of service (QoS) become less and less tolerable. Our research works on improvement of the QoS in IMS networks. It is base in jitter calculation and proposal of reducing jitter for improving traffic.

II. THE IMS TRAFFIC Call Session Control Functions (CSCFs) are the session routing points in the IMS core network. They distribute incoming calls to the application services. The CSCFs handle initial subscriber authentication. Application services that receive a message from the CSCFs are defined to permit the processing of that call, and to perform additional service-related checks. The first point of contact for the user equipment (UE) to IMS network is the Proxy-CSCF. It forwards SIP to and from the home network and may also perform encryption and compression. The Interrogating-CSCF (I-CSCF) is the entry point to the home network. It may function similar to a firewall and hide the internal topology. At last, the Serving-CSCF (S-CSCF) is the main element in session control. It is fully responsible for registration and controlling of sessions to the UE. It also decides which Application Servers (AS) that needs to be triggered, depending on the Initial Filter Criteria (IFC). The IFC is part of the user profile which is held in the HSS (home subscriber server) and downloaded to the S-SCSF upon registration. The HSS is a database that contains all subscribers’ data, like the services that is allowed to access, the network in which he is granted to roam and the information about the location of the subscriber. Once information about the subscriber has changed, the entire profile is sent to the S-CSCF, making it always synchronized with the HSS. An important function of the HSS is to provide the encryption and authentication keys of the user: when a user registers himself in the network, he must provide the credentials to the S-CSCF and these are checked against the one stored in the HSS [1], [2], [3], [4], [5], [6].

Keywords— IMS, SIP, CSCF, QoS, JITTER

1 .INTRODUCTION IMS needs to offer high level of interaction for users. The fact of integrating different networks into one multifunctional IP needs to create a unified communication environment for fixed and mobile users, by offering enriched and integrated services. Those demands, with appropriate levels of quality, are not a simple task. The IMS core network use the protocol SIP to manage the multimedia sessions, and on the protocol IP for the transport and associated signalling traffic. In order to eliminate or reduce the problems of SIP server overload and improve QoS, various approaches have been proposed. Generally, the attributes of QoS are defined in terms of guaranteed of bit rate, waiting delay, loss rate and jitter. This work concern jitter calculations and proposals for improving traffic by reducing them. Jitter, is much more difficult to evaluate, but it is particularly important to manage the QoS of real-time service and other.

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Hamza Dahmouni , André Girard , Brunilde Sansò [16] have defined jitter in a single node queue by :

III. IMS BASIC ARCHITECTURE

: the total traffic load : exponential parameter queue distribution If

, we see that

as well. In other words,

is small, the jitter does not depend much on the when proportion of traffic. Suppose CSCFs servers (P-CSCF, I-CSCF, S-CSCF) are running on the same host. We can assume as single queue distribution node. Fig.1. IMS basic architecture

V. PREVIOUS WORK In our previous work [17] we such note that are four different QoS classes: conversational class, streaming class, interactive class and background class [10]. 1) Conversational class Applications which use this class include telephony speech, voice over IP and video conferencing. Real time conversation is always performed between groups of humans and so this is the only scheme where the required characteristics are strictly given by human perception. The maximum transfer delay is dictated by how much delay the humans can tolerate for audio and video. Therefore the bounds for acceptable transfer delay are very stringent, and if transfer delay is not low enough then it affects the quality. The transfer delay should be lower and stringent than the round trip delay for this class. 2) Streaming class Applications for this class includes listening to or looking at real time video (audio). This scheme is characterized by that the time relations between information entities within a flow shall be preserved, although it does not have any requirements on low transfer delay. The delay variation of the end - to - end flow should be limited to preserve the time variation between the information entities of the stream. 3) Interactive class Interactive traffic is a communication scheme which is characterized by the request response pattern of the end user. Round trip delay is the most important attribute for this class. Another important attribute is that the error rate should be very low in the data transfer. Applications for this class include browsing the web, database retrieval, access of server etc. 4) Background class This is a service class in which the applications run in the background, for example an e-mail program. It sleeps for most of the time and wakes up when an email arrives. Other examples include SMS, download of databases. Background traffic is characterized by that the destination is not expecting the data within a certain time. Thus, this class is less delay sensitive and contents should be delivered with low error rate.

IV. JITTER APPROACH AND DEFINITION Jitter is a measure of the packets’ transfer delay variation. It can depend on the packets routes and is caused by multiplexing several flows in the node queues. There are several definitions of jitter that try to capture the delay variation of packets. The IETF definition of jitter is based on the transit represent the delay experienced by packets going through a queue [8], [9], [4], [5], [13], [14], [15]. Let represent the delay experienced by the th packet going through a queue. The difference of transit time between two consecutive packets of a flow can be written as which can be positive or negative. The average end-to-end delay jitter is then given by the expected absolute value of this random variable

At each node, the tagged flow is multiplexed under the FCFS discipline. In the case of a network, let be the delay of th packet at node n. The end-to-end jitter for a tagged flow passing through N tandem nodes is given by

Using this model need some information like the number of input interfaces at the node, the link speed, and the traffic flow matrix and so. In our experimental IMS platform built under UBUNTU Unix distribution and using an open source tool named Wireshark we chose another approach definition.

We studied follow cases:

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Case

1:

Conversational and streaming classes represent 50 % of the traffic, Case

2:

Conversational and streaming classes represent 70 % of the traffic, Case 3: Conversational and streaming classes represent 80 % of the traffic, Case

Fig.4 Both classes represent 80 % of the traffic

4:

Conversational and streaming classes represent 90 % of the traffic. Result showed that when traffic is distributed in 70% to conversational and streaming class and 30% to interactive and background class, network is stable. It corresponds to case 2. VI.RESULT In a single node queue, let study jitter as given by Hamza Dahmouni, André Girard, Brunilde Sansò [17] where some y connections are represented by

. We have follow curves:

Fig.5 Both classes represent 90 % of the traffic

Jitter increase when traffic loading for some connections. Curve has the same start convex form. Summarizing in a single graph:

Fig.2 Both classes represent 50 % of the traffic

Fig.6 global traffic

Jitter decreases when the traffic load increases and give a concave function of load in case 2. It give also less level of jitter when traffic loading. In our previous work, when traffic is distributed in 70% to conversational and streaming class and 30% to interactive and background class, network is stable. We have confirmation in this study by a less than and decreasing jitter level in this case 2. Fig.3 Both classes represent 70 % of the traffic

V. CONCLUSION: Network delay jitter is an important QoS parameter for real-time services such as packet voice and packet video traffic. Voice and video service often have more restrictive QoS requirement on delay jitter than data transfer applications have. Delay jitter has little and decreasing impact on QoS when traffic in IMS network is distributed in 70% to conversational

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[8] Moshe Zukerman, Introduction to Queuing Theory and Stochastic Teletraffic Models, 2000-1012 [9] Winfried Grassmann,Modelling Markovian Queues and Similar Processes, Department of Computer Science University of Saskatchewan, CORS - SCRO 2000 ANNUAL CONFERENCE Energy, Natural Resources, and the Environment MAY 29-31, 2000, EDMONTON, ALBERTA [10] 3GPP 23.107 V7.4.0,"Quality of Service (QoS) Concept and Architecture," June 2006 [11] V.S. Abhayawardhana, R. Babbage, A Traffic Model for the IP Multimedia Subsystem (IMS), 2007 IEEE [12] B. Zhu. Analysis of SIP in UMTS IP multimedia subsystem. Master’s thesis, Computer Engineering, North Carolina State University, 2003 [13] Olivie Brun, Analyse et Optimisation de Performance des Réseaux de Communication, Habilitation à Diriger des Recherches délivrée par l’Université Toulouse III, février 2012 [14] Randall Landry, Study of delay Jitter with and without peak rate enforcement, Member, IEEE, and Ioannis Stavrakakis, Senior Member, IEEE, 1997 [15] Liren Zhang, Soo Ngee Koh Effect of delay and on voice/video over IP, ARTICLE in COMPUTER COMMUNICATIONS · JUNE 2002

and streaming class and 30% to interactive and background class and when CSCFs servers (P-CSCF, I-CSCF, S-CSCF) are running on the same host. Future research needs to work on multiple nodes case. REFERENCES [1] Hassan HASSAN, Jean-Marie GARCIA and Olivier BRUN LAAS-CNRS, Toulouse, France, Bandwidth Allocation and Session Scheduling using SIP, JOURNAL OF COMMUNICATIONS, VOL. 1, NO. 5, AUGUST 2006, [2] PETTER LINDGREN, Diameter service creation investigation and HSS, Evaluation, Master’s Thesis Supervisor: Stefan Östergaard, Kajsa Goffrich Examiner: Prof. Gerald Q. Maguire Jr, 2010-02-23 [3] Hassan HASSAN Modélisation et analyse de performances du trafic multimédia dans les réseaux hétérogènes, mémoire Doctorat de l’Université Paul Sabatier–Toulouse III 2007 [4] Mesud Hadžialić, Mirko Škrbić, Nerma Šečić, Mirza Varatanović, Elvedina Zulić, Nedim Bijedić University of Sarajevo , Problem of IMS modelling – Solving Approaches, CTRQ 2012 [5] Mlindi Mashologu, Performance optimization of IP Multimedia Subsystem, Dissertation.com, Boca Raton, Florida 2010 [6] C. Chi Bell Laboratories, Alcatel-Lucent chic, Hao Bell Laboratories, Alcatel-Lucent D.Wang Bell Laboratories, Alcatel-Lucent Z. Cao Institute of Information Science Beijing Jiaotong University, Modelling IMS Presence Server: Traffic Analysis &Performance, 2008 IEEE [7] JEREMIAH F. HAYES THIMMA V. J. GANESH BABU Modeling and Analysis of telecommunications network 2004 by John Wiley & Sons, Inc. All rights reserved

[16] Hamza Dahmouni · André Girard · Brunilde Sansò, An analytical model for jitter in IP networks, Ann. Telecommun. (2012) 67:81–90 DOI 10.1007/s12243-011-0254-y [17] BA Alassane, NIANG Boudal, Dimensioning traffic performance in IMS network, 2014 IEEE, 8th International Conference on Application of Information and Communication technologies-AICT2014, October 2014

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