In recent years, Web services and applications are gradually shifting into cloud environments. These ever-increasing cloud services are being hosted on large scale computation and storage infrastructures called data centers (DC). A data center contains a large number of servers interconnected by a specifically designed network, named data center network (DCN). Today’s data centers host a variety of different applications that exhibit unique traffic characteristics. Some applications exhibit many-to-one communication pattern, some others follow ON-OFF pattern for flow arrivals resulting in bursty traffic. The many-to-one communication is a frequent pattern in data centers and may cause buffer overflow at the bottleneck link which ultimately results in throughput degradation of the flows; this problem is known as TCP Incast. In addition, data centers exhibit heavy tailed distribution for flow sizes; more than 80% of the data center flows have size less than 10 KB, called short flows, but around 90% of the traffic volume, in data center networks, is produced by long flows. Short flows are usually latency-sensitive and long flows demand high throughput. Short flows suffer to quickly increase their sending rates due to the existing long flows occupying most of the available capacity; this results in inefficient flow completion time (FCT) of short flows which ultimately results in degradation of the application’s performance. Furthermore, data centers employ scale-out model for growth to keep up with the rapid increase in the cloud services; thus, multiple paths exist between each pair of end-hosts. Load balancing of the traffic over the multiple path is required to improve network utilization. In addition, requirements like: i) high performance for applications, ii) scalability, and iii) robustness against topology changes, makes the load balancing task more challenging. This research thesis proposes queue length based solutions to the performance issues of TCP Incast and flow completion time of short flows. In addition, a queue length based traffic load balancing scheme is proposed to improve network utilization and applications’ performance. The proposed solutions are validated through implementation in network simulator and compared with the existing schemes. The results show that the proposed solutions significantly improve the performance of applications in the data centers.
والدین کی عظمت نحمدہ ونصلی علی رسولہ الکریم امّا بعد فاعوذ بااللہ من الشیطن الرجیم بسم اللہ الرحمن الرحیم معزز اسا تذہ کرام اور میرے ہم مکتب ساتھیو! آج مجھے جس موضوع پر گفتگو کرنی ہے وہ ہے’’عظمت ِوالدین‘‘ صاحب ِصد ر! والدین ایک عظیم نعمت ہیں ، ان کا وجود مسعود رحمت ہی رحمت ہے۔ ان کی موجودگی اولاد کے لیے باعث ِبرکت ہے، ان کی رضاء میں اللہ کی رضا ہے، ان کی ناراضی میں خدا کی ناراضی ہے۔ حدیث پاک میں ہے کہ جس نے یہ دیکھنا ہو کہ مجھ پر اللہ تعالیٰ راضی ہے یا ناراض تو وہ اپنے والدین کا چہرہ دیکھ لے اگر والدین خوش ہیں تو رب تعالیٰ بھی خوش ہے اگر والدین ناراض ہیں تو رب تعالیٰ بھی ناراض ہے۔ صدرِمحترم! قرآنِ پاک میں نصِّ قطعی سے ثابت ہے کہ اپنے والدین کے ساتھ بھلائی کرو، ان کا احترام کرو، اُن کے ساتھ اچھے طریقے سے گفتگو کرو، ان کو اُف تک نہ کہو ، والدین ایک ایسی ہستی ہیں کہ یہ اولاد کا کبھی بھی بُر انہیں سوچتے ،ان کے لیے مشکلات برداشت کرتے ہیں، پریشانیوں کو سینے سے لگاتے ہیں، اُن کی اعلیٰ تعلیم وتربیت کا انتظام کرتے ہیں۔ صدرِذی وقار! والدین کے چہرہ کو دیکھنا ایک عبادت ہے اللہ تعالیٰ مقبول حج کا ثواب عطا فرماتا ہے۔ حدیث پاکؐ میں ہے کہ کسی شخص نے پوچھا کہ مجھ پر سب سے زیادہ حق کس کا ہے آپؐ نے فرمایا کہ تیری ماں ، پھر پوچھا گیا آپؐ نے فرمایا کہ تیری ماں، پھر پوچھا تو آپؐ نے فرمایا کہ تیراباپ۔ معزز سامعین! ماں کے بارے میں کہا گیا کہ’’ جنت ماں کے قدموں کے نیچے ہے‘‘ ماں ایک ایسی نعمت غیر مترقبہ ہے کہ جس کا بدل دنیا میں ناممکن ہے۔ ماں آنکھوں کو...
Islam is a complete and perfect code of life. We find guidance from Islam on any aspect of life. This study aims to explore the evaluation of existing audit system in Islamic perspective. The study indicates the gaps and challenges in audit system keeping in view Islamic laws and principles. The study is qualitative in nature. Relevant documents have been analyzed keeping in view objectives of the study. Thematic content analysis has been used for the analysis of collected data. The study is significant for the researchers, policy makers and audit experts. Recommendation of the study are beneficial particularly for the Audit Department to overcome the existing gaps and challenges.
This study investigates predictability of returns in Pakistan stock market. The first essay investigates the profitability of momentum strategies in Pakistan stock market over the period 2001 to 2015 and over a sub-period 2007 to 2015. By constructing equally weighted winner- loser portfolios using partial rebalancing technique, the study finds that momentum profits are highly significant in all investment horizons for the complete period as well as for the sub-period. The most successful zero cost strategy is selecting the stocks based on their returns of past 6 months, and holding the portfolio for 6 months. Furthermore, the portfolios are sorted on the basis of risk factors to find the effect of liquidity and size on strength of momentum profits. We find that momentum returns are significant for all investment horizons in both high and low volume portfolios. However, the momentum returns of low volume portfolios are on average 0.2 percent higher than those of high volume portfolios. Finally, when stocks are sorted on the basis of size of firm, results indicate that the returns are significant for all investment horizons in both large and small size portfolios. Furthermore, the momentum profits are stronger for small rather than large size portfolios. Therefore, it is possible to earn super normal profits in Pakistan stock market by using momentum strategies.The second essay examines the predictability of returns through assessing the lead-lag relationship between stock returns in Pakistan Stock Market. It investigates the existence of cross-autocorrelations and lead-lag relationships between stock returns in Pakistan stock market. By using cross-autocorrelations and vector auto-regressions, our research finds that given the firms have low volume of trading, lagged returns of large cap portfolios significantly impact current returns on small cap portfolios, while the opposite is not true. In the high volume category, lagged returns of large (small) cap portfolios do not affect the current returns on small (large) cap portfolios. Also, the ability of lagged returns of low volume portfolios to predict current returns of high volume portfolios is better than the ability of lagged returns of high volume portfolios to predict current returns of low volume portfolios. This result is contrary to the existing theory on lead-lag effects which suggests that high volume portfolios lead the returns on low volume portfolios, as heavily traded stocks quickly absorb market information. The study is important in understanding the return irregularities which exist in Pakistan stock market. Investors can make use of this study to formulate such trading strategies which help them to earn abnormal profits. The research is of particular importance to regulators, as they can examine the inefficiencies in the market and formulate policies to reduce them. Academicians can also make use of this study to explore directions for further research