Quality of Service in Data Communication Network



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| | WRET3105 NETWORK AND DATA COMMUNICATION Assignment 4 Semester 1, session 2011/2012 Submitted by: Student | ๐Ÿ˜ Nadiah binti Zainudin| Student No. | ๐Ÿ˜ WET080011| Instructor| ๐Ÿ˜ Saeid Abolfazli| Date| ๐Ÿ˜ 2nd Nov 2011| ————————————————- Questions: 1. What is QoS? Why QoS is important and how QoS is measured? 2. What is management of QoS? ————————————————- ————————————————- Answers: 1. What is QoS? In telephony field, quality of service is a service that covers all aspects of necessity in the use of telecommunication service.

The necessities include service response time, loss, signal-to-noise ratio, echo, interrupts, frequency response, loudness level, and so on [1]. In the computer networking field, QoS is defined as the ability of the network to provide a service at an assured service level [2]. In Internet, QoS is a technology that acts as additional support to the best-effort service in handling data transfer during load congestions and superiorly response to more problems, such as latency, corrupted files, lost connection, jitter, out-of-order delivery, data loss or insufficient bandwidth [1,7].

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QoS provides priority to different applications, users or data flow based on the load service requirements, and network conditions to ensure that the most important data reach the destination first. QoS also provide high-quality support for IP voice and video services, improve the service provided in low-speed access devices (e. g. Internet mobile wireless devices), and provide differentiated Internet access service to client with different service-quality levels at different prices [5]. QoS can be differentiated, that is, QoS provided in the network can vary with load conditions [6].

Assigning the priority is actually the network administratorโ€™s duty. QoS enable applications to signal service requirement to network. When the service is provided, network then signals that service characteristics along with traffic condition status to the network administrator system. Network administrator then pass the signal to the administrator decision support system to decide what priority should be given that particular flow of the application and assign the priority This decision also affected by factors such as networkโ€™s parameter policy.

Below is the visual representation of how these interactions are made in providing the priority to the applications. DB Network layers Status Repository Policy rule repository Network administrator Applications Signal: Service requirements Signal: Service requirement + traffic status Priority Figure 1: QoS server interaction (signaling + prioritizing) Why QoS is important? Prioritize is one of the most highlighted service that makes QoS very important. For example, a user transfer 50 GB data files to another computer sing FTP transfer and at the same time, he also browsing webpage on the internet, and do voice communication (VoIP call) with his friend from his computer. Because of the heavy FTP transfer, he may face very slow web browsing and unclear or cannot make the VoIP call at all. This is because FTP is bulk traffic, that is, it floods the bandwidth and left no space for other traffic [8]. Here is where QoS is needed where QoS give high priority to the very important task, in this case is, VoIP, the real-time traffic to perform its task first before other tasks.

QoS also important in ensuring required throughput and services are given to the critical applications like payment-transaction system and order-entry system, so that the data able to be delivered within the required time [3]. QoS technology can secure the bandwidth from the flows that are affected by unwanted or unexpected new requirements which can cause problems to the network traffic by quarantine them [4]. Such requirement is for example, the e-mail viruses that propagate and grow very fast stealing the bandwidth. QoS is important because it offer cost-effective.

Due to the extensive services provided by QoS, we can fully utilize the network resources and problems are unlikely to occur, thereby delaying or reducing the need for upgrading and reducing cost for maintenance. How QoS is measured? QoS is measured based on QoE (Quality of End-user experience) result that is simply the evaluation of customer feedback about the service quality in terms of the usability, accessibility, retain ability (connection losses), and integrity [2]. The better the QoE, the better the QoS. QoS can be measured using either service level approach or network management system approach.

Service level approach is based on the QoE statistical sample of overall users by weighting the key applications; find QoE key performance indicators (KPIs); taking the KPI measurement, utilizing handsets, and give overall score (index) from KPI values. Network management is based on QoS performance metrics that are mapped onto user-perceptible QoE performance target. The process include identify the relationship between QoS KPIs and their effect on QoE, measure QoS KPIs in the network, and lastly, rating usersโ€™ QoE through measured QoS KPIs using mapping rules. 2. What is management of QoS?

Management of QoS is the process of managing and maintaining QoS within a network or in the system with taking consideration towards all three factors: the network (parameterization), the system (system status), and the applications (service requirements) [2,9]. The network parameters provide an estimate of network status and communication quality, whereas, system parameters provide system health information, and, finally, the applications level parameters provide metrics and indicators on the health, security, access, configuration, current status, and resource utilization [9].

QoS management are also can be classified into four categories: network planning, QoS provisioning, QoS-QoE monitoring and optimization. In some other findings, QoS management is to determine the level of QoS that can be adapted into a particular network and take appropriate corrective actions if the QoS performance is below expectations [10]. As the sum of all, QoS management do estimating the characteristic of the required elements, monitoring the values of QoS, maintain the actual QoS values close to the estimated QoS, control the targets, and evaluate upon some QoS information. ———————————————— References [1]| ITU-T Recommendations E. 800, โ€œTerms and definitions related to quality of service and network performance including dependability,โ€ 1994. Available from http://www. itu. int/rec/T-REC-E. 800-199408-S/en| [2]| Chuku Venkateswar Rao, C. G. P. , P Jagan Mohan Krishna, G Prathibha Priyadarshini โ€œThe Importance of QoS & QoE Management In Wireless Communication System,โ€ 2(3): p. 639-645. | [3]| โ€œWhat is QoS? : Quality of Service (QoS),โ€ 2011. Available from http://technet. icrosoft. com/en-us/library/cc757120(WS. 10). aspx| [4]| โ€œWhy QoS need to be applied? ,โ€ 2011. Why QoS need to applied? Available from http://opalsoft. net/qos/WhyQos-10. htm| [5]| Geoff, H. , Telstra, โ€œQuality of Service โ€“ Fact or Fiction? ,โ€ The Internet Protocol Journal, March 2000, 3(1): p. 27-33. Available from http://www. cisco. com/web/about/ac123/ac147/ac174/ac197/about_cisco_ipj_archive_article09186a00800c8314. html| [6]| M. G. Adnams, โ€œQoS Management Concept for CNS/ATM-1 Package,โ€ AERONAUTICAL TELECOMMUNICATIONS NETWORK PANEL, March

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