Understanding the characteristics of Internet traffic and designing an efficient RaptorQ-based data transport protocol for modern data centres

This thesis is the amalgamation of research on efficient data transport protocols for data centres and a comprehensive and systematic study of Internet traffic, which came as a result of the need to understand traffic patterns and workloads in modern computer networks. The first part of the thesis is on the development of efficient data transport pro- tocols for data centres. We study modern data transport protocols for data centres through large scale simulations using the OMNeT++ simulator. We developed and experimented with an OMNeT++ model of NDP. This has led to the identification of limitations of the state of the art and the formulation of research questions with respect to data transport protocols for modern data centres. The developed model includes an implementation of a Fat-tree topology and per-packet ECMP load bal- ancing. We discuss how we integrated the model with the INET Framework and validated it by running various experiments that test different model parameters and components. This work revealed limitations of NDP with respect to efficient one-to-many and many-to-one communication in data centres, which led to the de- velopment of SCDP, a novel and general-purpose data transport protocol for data centres that, in contrast to all other protocols proposed to date, natively supports one-to-many and many-to-one data communication, which is extremely common in modern data centres. SCDP does so without compromising on efficiency for short and long unicast flows. SCDP achieves this by integrating RaptorQ codes with receiver-driven data transport, in-network packet trimming and Multi-Level Feed- back Queuing (MLFQ); (1) RaptorQ codes enable efficient one-to-many and many- to-one data transport; (2) on top of RaptorQ codes, receiver- driven flow control, in combination with in-network packet trimming, enable efficient usage of network re- sources as well as multi-path transport and packet spraying for all transport modes. Incast and Outcast are eliminated; (3) the systematic nature of RaptorQ codes, in combination with MLFQ, enable fast, decoding-free completion of short flows. We extensively evaluated SCDP in a wide range of simulated scenarios with realistic data centre workloads. For one-to-many and many-to-one transport sessions, SCDP performs significantly better than NDP. For short and long unicast flows, SCDP performs equally well or better compared to NDP. In the second part of the thesis, we extensively study Internet traffic. Getting good statistical models of traffic on network links is a well-known, often-studied problem. A lot of attention has been given to correlation patterns and flow duration. The distribution of the amount of traffic per unit time is an equally important but less studied problem. We study a large number of traffic traces from many different networks including academic, commercial and residential networks using state-of-the-art statistical techniques. We show that the log-normal distribution is a better fit than the Gaussian distribution. We also investigate a second, heavy- tailed distribution and show that its performance is better than Gaussian but worse than log-normal. We examine anomalous traces which are a poor fit for all tested distributions and show that this is often due to traffic outages or links that hit maximum capacity. Stationarity tests showed that the traffic is stationary at some range of aggregation times. We demonstrate the utility of the log-normal distribution in two contexts: predicting the proportion of time traffic will exceed a given level (for link capacity estimation) and predicting 95th percentile pricing. We also show the log-normal distribution is a better predictor than Gaussian orWeibull distributions

Evaluating modern data centre transport protocols in OMNeT++/INET

In this paper we present our work towards an evaluation platform for data centre transport protocols. We developed a simulation model for NDP1, a modern data transport protocol in data centres, a FatTree network topology and per-packet ECMP load balancing. We also developed a data centre environment that can be used to evaluate and compare data transport protocols, such as NDP and TCP. We describe how we integrated our model with the INET Framework and present example simulations to showcase the workings of the developed framework. For that, we ran a comprehensive set of experiments and studied different components and parameters of the developed models

Polyraptor: embracing path and data redundancy in data centres for efficient data transport

In this paper, we introduce Polyraptor, a novel data transport protocol that uses RaptorQ (RQ) codes and is tailored for one-to-many and many-to-one data transfer patterns, which are extremely common in modern data centres. Polyraptor builds on previous work on fountain coding-based transport and provides excellent performance, by exploiting native support for multicasting in data centres and data resilience provided by data replication

SCDP: systematic rateless coding for efficient data transport in data centres

In this paper we propose SCDP, a general-purpose data transport protocol for data centres that, in contrast to all other protocols proposed to date, supports efficient one-to-many and many-to-one communication, which is extremely common in modern data centres. SCDP does so without compromising on efficiency for short and long unicast flows. SCDP achieves this by integrating RaptorQ codes with receiver-driven data transport, packet trimming and Multi-Level Feedback Queuing (MLFQ); (1) RaptorQ codes enable efficient one-to-many and many-to-one data transport; (2) on top of RaptorQ codes, receiver-driven flow control, in combination with in-network packet trimming, enable efficient usage of network resources as well as multi-path transport and packet spraying for all transport modes. Incast and Outcast are eliminated; (3) the systematic nature of RaptorQ codes, in combination with MLFQ, enable fast, decoding-free completion of short flows. We extensively evaluate SCDP in a wide range of simulated scenarios with realistic data centre workloads. For one-to-many and many-to-one transport sessions, SCDP performs significantly better compared to NDP and PIAS. For short and long unicast flows, SCDP performs equally well or better compared to NDP and PIAS

Menopause Awareness, Symptoms Assessment and Menqol Among Bahrain Women

Menopause is a normal physiological process of the permanent cessation of ovarian hormone reproduction, thereby offending the regular menstrual cycle. Critical period in women’s life occurs 40 to 60 years. Frequently reported symptoms are physiological disturbances, psychological complaints including mood swings and& other changes that may impair the overall quality of life. Menopausal symptoms significantly reduce the Quality of Life (QOL) and further worsens with more severity of the condition. The aim of this study was to assess the menopausal awareness and related symptoms that affects the quality of life. Methods: A cross-sectional community survey design was adopted among 128 women through convenience sampling by using Menopause awareness scale and MenQol. Results: The domain-wise prevalence of symptoms score on vasomotor was 51.5%(66), psychosocial 35.2%(45), 44.5%(57), sexual 25.8%(33) and others 44.5%(57). Overall score was 40.6%(52). In relation to menopause awareness, low 7.8 % (10), Moderate 82.0% (105) and high 10.2%(13).Conclusion: Menopause awareness programs need to be initiated at the community level for better health and the Quality of Life. Keywords: Menopause, Bahraini women, Menopause related QOL, Awarenes

The Forgotten Hemodynamic (PCO2 Gap) in Severe Sepsis

Background. Central venous-arterial carbon dioxide difference (PCO2 gap) can be a marker of cardiac output adequacy in global metabolic conditions that are less affected by the impairment of oxygen extraction capacity. We investigated the relation between the PCO2 gap, serum lactate, and cardiac index (CI) and prognostic value on admission in relation to fluid administration in the early phases of resuscitation in sepsis. We also investigated the chest ultrasound pattern A or B. Method. We performed a prospective observational study and recruited 28 patients with severe sepsis and septic shock in a mixed ICU. We determined central venous PO2, PCO2, PCO2 gap, lactate, and CI at 0 and 6 hours after critical care unit (CCU) admission. The population was divided into two groups based on the PCO2 gap (cutoff value 0.8 kPa). Results. The CI was significantly lower in the high PCO2 gap group (P=0.001). The high PCO2 gap group, on admission, required more administered fluid and vasopressors (P=0.01 and P=0.009, respectively). There was also a significant difference between the two groups for low mean pressure (P=0.01), central venous O2 (P=0.01), and lactate level (P=0.003). The mean arterial pressure was lower in the high PCO2 gap group, and the lactate level was higher, indicating global hypoperfusion. The hospital mortality rate for all patients was 24.5% (7/28). The in-hospital mortality rate was 20% (2/12) for the low gap group and 30% (5/16) for the high gap group; the odds ratio was 1.6 (95% CI 0.5–5.5; P=0.53). Patients with a persistent or rising PCO2 gap larger than 0.8 kPa at T = 6 and 12 hours had a higher mortality change (n = 6; in-hospital mortality was 21.4%) than patients with a PCO2 gap of less than 0.8 kPa at T = 6 (n = 1; in-hospital mortality was 3%); this odds ratio was 5.3 (95% CI 0.9–30.7; P=0.08). The PCO2 gap had no relation with the chest ultrasound pattern. Conclusion. The PCO2 gap is an important hemodynamic variable in the management of sepsis-induced circulatory failure. The PCO2 gap can be a marker of the adequacy of the cardiac output status in severe sepsis. A high PCO2 gap value (>0.8 kPa) can identify situations in which increasing CO can be attempted with fluid resuscitation in severe sepsis. The PCO2 gap carries an important prognostic value in severe sepsis

The Prevalence and Major Causes of Low Vision among Children in Gaza strip, Palestine

Low vision is a serious public health problem and is significantly increasing globally in the past couple of decades. However, there is no available data in the literature about the prevalence of low vision among children in Palestine. This study aimed to determine the prevalence and etiology of low vision at Al-Noor center of the visually impaired, Gaza Strip, Palestine. This retrospective analysis was based on the observation of 423 files, using a convenience sampling method. The information extracted from the files includes: date of first consultation, gender, age, systemic diseases, parental congruity, causes of visual impairment as diagnosed by an ophthalmologist and types of optical aids prescribed. The majority of patients 202 (47.7%) were from the age group between 6-12 years old. Two hundred and twelve (50.1%) of the subjects were males and 211 (49.8%) females. The main causes of low vision were amblyopia among patients in the zero to five years age group, retinitis pigmentosa among the 6-12 years age group and cataract, macular dystrophies and ocular albinism among the 13-18 years of age. The prevalence and etiology of low vision in children in Gaza Strip is high compared to other countries. It is recommended that regular checks of visual acuity be conducted for all children of age 0-18 years, who attend the visually impaired center

Is Re-introducing Major Open and Minimally Invasive Surgery during COVID-19 Safe for Patients and Healthcare Workers? An International, Multi-centre Cohort Study in the Field of Oesophago-gastric Surgery

Introduction: The COVID-19 pandemic has resulted in unparalleled changes to patient care, including the suspension of cancer surgery. Concerns regarding COVID-19-related risks to patients and healthcare workers with the re-introduction of major complex minimally invasive and open surgery have been raised. This study examines the COVID-19 related risks to patients and healthcare workers following the re-introduction of major oesophago-gastric (EG) surgery. Patients and Methods: This was an international, multi-centre, observational study of consecutive patients treated by open and minimally invasive oesophagectomy and gastrectomy for malignant or benign disease. Patients were recruited from nine European centres serving regions with a high population incidence of COVID-19 between 1 May and 1 July 2020. The primary endpoint was 30-day COVID-19-related mortality. All staff involved in the operative care of patients were invited to complete a health-related survey to assess the incidence of COVID-19 in this group. Results: In total, 158 patients were included in the study (71 oesophagectomy, 82 gastrectomy). Overall, 87 patients (57%) underwent MIS (59 oesophagectomy, 28 gastrectomy). A total of 403 staff were eligible for inclusion, of whom 313 (78%) completed the health survey. Approaches to mitigate against the risks of COVID-19 for patients and staff varied amongst centres. No patients developed COVID-19 in the post-operative period. Two healthcare workers developed self-limiting COVID-19. Conclusions: Precautions to minimise the risk of COVID-19 infection have enabled the safe re-introduction of minimally invasive and open EG surgery for both patients and staff. Further studies are necessary to determine the minimum requirements for mitigations against COVID-19