Tahir Nawaz Minhas

Evaluation of delay performance of traffic shapers

In network emulation, traffic shapers are used to shape the performance of the network. They are provided with certain inputs in a test environment to vary the network performance accordingly in order to investigate the effects of different network conditions on applications in real yet emulated scenarios. However, it is very important for the shapers to work as supposed in order to successfully realize the desired network conditions. They may make the results of network emulations unrealistic and unreliable if their functioning is not according to the desired specification. In this work, we evaluate the delay shaping of three traffic shapers, NIST Net, Netem and KauNet through the results obtained from a number of experiments. A comparison of the output of their delay shaping is presented. This comparison can enable us to select the most suitable shaper based on the required shaping. Effects of hardware platforms on the shaping are also filtered out by performing the experiments with shapers installed on Advance Micro Devices (AMD) and Intel platforms separately. Different Protocol Data Unit (PDU) sizes are used in the experiments to test the influence of packet sizes on the shaping. These delay evaluation results are then complemented by the Coefficient of Throughput Variation (CoTV) results.

Inferring User-Perceived Performance of Network by Monitoring TCP Interruptions

The fluctuating performance of wireless and mobile networks has triggered the need for smart algorithms to assess the user perception, resulting from the quality of network services. While efforts have been done to model the user experience resulting from the network performance, there is still the need for practical methods to assess the user-perceived performance, in the real environment. In this work, we present a set of criteria to observe the user behavior on the Web, passively from the network-level. The criteria are based on the monitoring of TCP control flags and HTTP requests. Thus, information about user actions performed in the web browser can be inferred by monitoring the TCP termination flags and by keeping track of the HTTP requests. Along the way, we also present some anomalies observed in the TCP connection termination process, which may result in performance degradation of Web transfers.

Evaluation of throughput performance of traffic shapers

Traffic shapers are used by researchers to emulate the behavior of networks and applications in test environments, typically with user-defined traffic shaping parameters such as throughput and loss. Also, traffic shapers are used for the enforcement of SLA, so they are of interest for Internet Service Providers. However, output given by traffic shapers may not be as accurate as desired. Therefore, it is important to assess the accuracy of the implementation of traffic shapers. In this paper, we evaluate two traffic shapers with regard to the performance of their throughput shaping. For this evaluation, traces were collected. The properties of the resulting throughput at the outlet of the shaper are compared to the properties of the throughput at the inlet in combination with the preset shaper parameters. In this sense, we also compare shapers installed on Advance Micro Devices (AMD) and Intel platforms, and we use different PDU sizes and load levels to test the influence of those parameters on the shaping. We are furthermore able to deduct internal shaper parameters such as packet rate and buffer size from our measurements, and we analyse the statistical properties of the packet departure process. The extensive measurement results in this paper allow for a detailed assessment of the question whether the shaper performance is up to mark for a desired timescale. In general, the performance of both shapers and hardware platforms can be considered satisfactory on the investigated time scales between 1 ms and 1 s, with a slight advantage for NetEm on AMD.

Classification of TCP connection termination behaviors for mobile Web

Many emerging smart applications and services employ Web technology, and users nowadays surf the Web from any device via any kind of access network. Typically, high page latencies trigger users to abort ongoing transfers, resulting in the abrupt terminations of the TCP connections. This paper presents a systematic study of the termination process of the TCP connections and identifies the reasons behind the observed sequences of termination flags. Monitoring and classification of the termination behavior of the TCP connections can provide indications about the user-perceived performance of Web transfers. From the results, it is observed that the TCP termination behavior is heavily-dependent on the client-side application. Therefore, a set of criteria is required to identify the abortions made by the user.

Quantification of packet delay variation through the coefficient of throughput variation

Packet delay variation plays an important role in network performance degradation and affects the user-perceptual quality, especially in case of real-time services such as video streaming, VoIP etc. Lightweight methods for detecting network performance issues are desirable as compared to task-intensive measurement and analysis. On this background, this paper discusses the applicability of the Coefficient of Throughput Variation (CoTV) to quickly and reliably detect bottleneck behavior between two arbitrary points in a network. The CoTV can be used as a Reduced Reference Metric. It is relatively simple to calculate, compare and interpret, yet powerful to provide control feedback when facing changes in network performance. In this paper, we demonstrate above mentioned properties of the CoTV through a formula relating it to the sample interval of the throughput and the variability of the delay. The latter is shown to be detectable on time scales that are significantly larger than that of the variability itself. This observation is a key enabler for reducing the load on the device that performs the analysis due to the possibility to use large sample intervals. We also describe how difference and ratio of CoTV at outlet and inlet can be used to identify network performance issues.

Assessment of the rating performance of ITU-T recommended video quality metrics in the context of video freezes

Video streaming and multimedia applications are getting popular with the growth of networks. In real-time video streaming, video quality can be degraded due to network performance issues. Among other artifacts, freezing and frame dropping are factors that influence user experience. Service providers, operators, and researchers are interested to measure the Quality of Experience objectively. Different algorithms have been proposed and implemented in this regard. Some of them are in the recommendation list of the ITU Telecommunication Standardization Sector (ITU-T). In this paper, we study the effect of the freezing artifact on user experience and compare the mean opinion score (MOS) of these videos with the results of two algorithms, Perceptual Evaluation of Video Quality (PEVQ) and Temporal Quality Metric, both being part of ITU-T Recommendation J.247 Annex B and C, respectively. Another contribution of this paper is the investigation of the impact of different resolutions and frame rates on user experience.

QoE rating performance evaluation of ITU-T recommended video quality metrics in the context of video freezes

In real-time video streaming, video quality can be degraded due to network performance issues. Among other artefacts, video freezing and video jumping are factors that influence user experience. Service providers, operators and manufacturers are interested in evaluating the quality of experience (QoE) objectively because subjective assessment of QoE is expensive and, in many user cases, subjective assessment is not possible to perform. Different algorithms have been proposed and implemented in this regard. Some of them are in the recommendation list of the ITU Telecommunication Standardization Sector (ITU-T). In this paper, we study the effect of the freezing artefact on user experience and compare the mean opinion score of these videos with the results of two algorithms, the perceptual evaluation of video quality (PEVQ) and temporal quality metric (TQM). Both metrics are part of the ITU-T Recommendation J.247 Annex B and C. PEVQ is a full-reference video quality metric, whereas TQM is a no-reference quality metric. Another contribution of this paper is the study of the impact of different resolutions and frame rates on user experience and how accurately PEVQ and TQM measure varying frame rates.

QoE based comparison of H.264/AVC and WebM/VP8 in an error-prone wireless network

Quality of Experience (QoE) management is a prime topic of research community nowadays as video streaming, online gaming and security applications are completely reliant on the network service quality. Moreover, there are no standard models to map Quality of Service (QoS) into QoE. HTTP media streaming is primarily used for such applications due to its coherence with the Internet and simplified management. The most common video codecs used for video streaming are H.264/AVC and Googles VP8. In this paper, we have analyzed the performance of these two codecs from the perspective of QoE. The most common end-user medium for accessing video content is via home based wireless networks. We have emulated an error-prone wireless network with different scenarios involving packet loss, packet delay and delay variation. The focus of this paper is evaluating the end user satisfaction with the multimedia content by subjective assessment using Mean Opinion Score (MOS). We have observed the overall superiority of H.264/AVC but the VP8 codec strongly gains ground in highly error-prone networks in terms of user satisfaction.