An Enhanced Queue Management Scheme for Eradicating Congestion of TFRC over Wired Environment

To accomplish increasing real time requirements, user applications have to send different kinds of data with different speeds over the internet.  To effectuate the aims of the computer networks, several protocols have been added to TCP/IP protocol suite.  Transport layer has to implement emerging techniques to transfer huge amount of data like multimedia streaming. To transmit multimedia applications, one of the suitable congestion control mechanisms in transport layer is TCP Friendly Rate Control Protocol (TFRC).  It controls congestion based on its equation. To get more smoothed throughput, intermediate nodes (like Routers. etc.) have to use suitable procedures in all real time situations. To eradicate the level of congestion in the network, we introduce enhanced Holt-Winters equations to RED queue management algorithm and applied to TFRC. The simulation results have shown that this strategy reduces packet loss and increases throughput

Seamless multimedia delivery within a heterogeneous wireless networks environment: are we there yet?

The increasing popularity of live video streaming from mobile devices such as Facebook Live, Instagram Stories, Snapchat, etc. pressurises the network operators to increase the capacity of their networks. However, a simple increase in system capacity will not be enough without considering the provisioning of Quality of Experience (QoE) as the basis for network control, customer loyalty and retention rate and thus increase in network operators revenue. As QoE is gaining strong momentum especially with increasing users’ quality expectations, the focus is now on proposing innovative solutions to enable QoE when delivering video content over heterogeneous wireless networks. In this context, this paper presents an overview of multimedia delivery solutions, identifies the problems and provides a comprehensive classification of related state-of-the-art approaches following three key directions: adaptation, energy efficiency and multipath content delivery. Discussions, challenges and open issues on the seamless multimedia provisioning faced by the current and next generation of wireless networks are also provided

Seamless Multimedia Delivery Within a Heterogeneous Wireless Networks Environment: Are We There Yet?

The increasing popularity of live video streaming from mobile devices, such as Facebook Live, Instagram Stories, Snapchat, etc. pressurizes the network operators to increase the capacity of their networks. However, a simple increase in system capacity will not be enough without considering the provisioning of quality of experience (QoE) as the basis for network control, customer loyalty, and retention rate and thus increase in network operators revenue. As QoE is gaining strong momentum especially with increasing users' quality expectations, the focus is now on proposing innovative solutions to enable QoE when delivering video content over heterogeneous wireless networks. In this context, this paper presents an overview of multimedia delivery solutions, identifies the problems and provides a comprehensive classification of related state-of-the-art approaches following three key directions: 1) adaptation; 2) energy efficiency; and 3) multipath content delivery. Discussions, challenges, and open issues on the seamless multimedia provisioning faced by the current and next generation of wireless networks are also provided

Dual-Mode Congestion Control Mechanism for Video Services

Recent studies have shown that video services represent over half of Internet traffic, with a growing trend. Therefore, video traffic plays a major role in network congestion. Currently on the Internet, congestion control is mainly implemented through overprovisioning and TCP congestion control. Although some video services use TCP to implement their transport services in a manner that actually works, TCP is not an ideal protocol for use by all video applications. For example, UDP is often considered to be more suitable for use by real-time video applications. Unfortunately, UDP does not implement congestion control. Therefore, these UDP-based video services operate without any kind of congestion control support unless congestion control is implemented on the application layer. There are also arguments against massive overprovisioning. Due to these factors, there is still a need to equip video services with proper congestion control.Most of the congestion control mechanisms developed for the use of video services can only offer either low priority or TCP-friendly real-time services. There is no single congestion control mechanism currently that is suitable and can be widely used for all kinds of video services. This thesis provides a study in which a new dual-mode congestion control mechanism is proposed. This mechanism can offer congestion control services for both service types. The mechanism includes two modes, a backward-loading mode and a real-time mode. The backward-loading mode works like a low-priority service where the bandwidth is given away to other connections once the load level of a network is high enough. In contrast, the real-time mode always demands its fair share of the bandwidth.The behavior of the new mechanism and its friendliness toward itself, and the TCP protocol, have been investigated by means of simulations and real network tests. It was found that this kind of congestion control approach could be suitable for video services. The new mechanism worked acceptably. In particular, the mechanism behaved toward itself in a very friendly way in most cases. The averaged TCP fairness was at a good level. In the worst cases, the faster connections received about 1.6 times as much bandwidth as the slower connections

Adaptive delay-constrained internet media transport

Reliable transport layer Internet protocols do not satisfy the requirements of packetized, real-time multimedia streams. The available thesis motivates and defines predictable reliability as a novel, capacity-approaching transport paradigm, supporting an application-specific level of reliability under a strict delay constraint. This paradigm is being implemented into a new protocol design -- the Predictably Reliable Real-time Transport protocol (PRRT). In order to predictably achieve the desired level of reliability, proactive and reactive error control must be optimized under the application\u27s delay constraint. Hence, predictably reliable error control relies on stochastic modeling of the protocol response to the modeled packet loss behavior of the network path. The result of the joined modeling is periodically evaluated by a reliability control policy that validates the protocol configuration under the application constraints and under consideration of the available network bandwidth. The adaptation of the protocol parameters is formulated into a combinatorial optimization problem that is solved by a fast search algorithm incorporating explicit knowledge about the search space. Experimental evaluation of PRRT in real Internet scenarios demonstrates that predictably reliable transport meets the strict QoS constraints of high-quality, audio-visual streaming applications.Zuverlässige Internet-Protokolle auf Transport-Layer erfüllen nicht die Anforderungen paketierter Echtzeit-Multimediaströme. Die vorliegende Arbeit motiviert und definiert Predictable Reliability als ein neuartiges, kapazitäterreichendes Transport-Paradigma, das einen anwendungsspezifischen Grad an Zuverlässigkeit unter strikter Zeitbegrenzung unterstützt. Dieses Paradigma wird in ein neues Protokoll-Design implementiert -- das Predictably Reliable Real-time Transport Protokoll (PRRT). Um prädizierbar einen gewünschten Grad an Zuverlässigkeit zu erreichen, müssen proaktive und reaktive Maßnahmen zum Fehlerschutz unter der Zeitbegrenzung der Anwendung optimiert werden. Daher beruht Fehlerschutz mit Predictable Reliability auf der stochastischen Modellierung des Protokoll-Verhaltens unter modelliertem Paketverlust-Verhalten des Netzwerkpfades. Das Ergebnis der kombinierten Modellierung wird periodisch durch eine Reliability Control Strategie ausgewertet, die die Konfiguration des Protokolls unter den Begrenzungen der Anwendung und unter Berücksichtigung der verfügbaren Netzwerkbandbreite validiert. Die Adaption der Protokoll-Parameter wird durch ein kombinatorisches Optimierungsproblem formuliert, welches von einem schnellen Suchalgorithmus gelöst wird, der explizites Wissen über den Suchraum einbezieht. Experimentelle Auswertung von PRRT in realen Internet-Szenarien demonstriert, dass Transport mit Predictable Reliability die strikten Auflagen hochqualitativer, audiovisueller Streaming-Anwendungen erfüllt

A Survey of Protocol-Level Challenges and Solutions for Distributed Energy Resource Cyber-Physical Security

The increasing proliferation of distributed energy resources (DERs) on the smart grid has made distributed solar and wind two key contributors to the expanding attack surface of the network; however, there is a lack of proper understanding and enforcement of DER communications security requirements. With vendors employing proprietary methods to mitigate hosts of attacks, the literature currently lacks a clear organization of the protocol-level vulnerabilities, attacks, and solutions mapped to each layer of the logical model such as the OSI stack. To bridge this gap and pave the way for future research by the authors in determining key DER security requirements, this paper conducts a comprehensive review of the key vulnerabilities, attacks, and potential solutions for solar and wind DERs at the protocol level. In doing so, this paper serves as a starting point for utilities, vendors, aggregators, and other industry stakeholders to develop a clear understanding of the DER security challenges and solutions, which are key precursors to comprehending security requirements

An Introduction to Computer Networks

An open textbook for undergraduate and graduate courses on computer networks

Performance Modeling, Design and Analysis of Transport Mechanisms in Integrated Heterogeneous Wireless Networks

Recently, wireless access to Internet applications and services has attracted a lot of attention. However, there is no single wireless network that can meet all mobile users’ requirements. Con-sequently, integrated heterogeneous wireless networks are introduced to meet diverse wireless Internet applications and services requirements. On the other hand, integrated heterogeneous wireless networks pose new challenges to the design and development of reliable transport mechanisms. Wireless Application Protocol version 2 (WAP 2.0) is one of the promising trans-port mechanisms. It uses wireless profiled TCP (WP-TCP), which is fully compatible with TCP, as one of the reliable transport protocols to cope with the wireless link impairments. For WAP 2.0 to continue providing reliable and efficient transport services in the future, one of the key is-sues is to thoroughly study, understand, and improve its performance in integrated heterogeneous wireless networks. In this thesis, we develop analytical frameworks and propose a solution to respectively study and improve the performance of WP-TCP in integrated heterogeneous wireless networks. Spe-cifically, we consider WP-TCP short- and long-lived flows over integrated wireless local area network (WLAN) and wireless wide area network (WWAN), where WLAN can be static or mo-bile. In order to facilitate the analysis of WP-TCP performance in integrated WLAN and WWAN, we first construct a novel WLAN link model, which captures the impact of both uncor-related and correlated transmission errors, and derive mathematical expressions that describe packet loss probability and packet loss burst length over WWAN-WLAN link. Then, we develop analytical frameworks for studying the performance of WP-TCP short- and long-lived flows. Differently from those reported in the literature, our analytical framework for WP-TCP short-lived flows takes into account both correlated and uncorrelated packet losses. Furthermore, our analytical framework for long-lived flow can be used to study the short-term (during vertical handover) and long-term performances of WP-TCP and it captures the effects of vertical handover, such as excessive packet losses and sudden change in network characteristics, which are commonly experienced in integrated static WLAN and WWAN. By using the devel-oped analytical frameworks, we extensively analyze the performance of WP-TCP flows and in-vestigate the optimal protocol design parameters over a wide range of network conditions. Finally, based on our analytical studies, we propose a receiver-centric loosely coupled cross-layer design along with two proactive schemes, which significantly improve the vertical hand-over performance. The proposed solution is easy to implement and deploy, compatible with tra-ditional TCP, and robust in the absence of cross-layer information. Extensive simulations have been conducted to confirm the effectiveness and practicability of our schemes

Making broadband access networks transparent to researchers, developers, and users

Broadband networks are used by hundreds of millions of users to connect to the Internet today. However, most ISPs are hesitant to reveal details about their network deployments,and as a result the characteristics of broadband networks are often not known to users,developers, and researchers. In this thesis, we make progress towards mitigating this lack of transparency in broadband access networks in two ways. First, using novel measurement tools we performed the first large-scale study of thecharacteristics of broadband networks. We found that broadband networks have very different characteristics than academic networks. We also developed Glasnost, a system that enables users to test their Internet access links for traffic differentiation. Glasnost has been used by more than 350,000 users worldwide and allowed us to study ISPs' traffic management practices. We found that ISPs increasingly throttle or even block traffic from popular applications such as BitTorrent. Second, we developed two new approaches to enable realistic evaluation of networked systems in broadband networks. We developed Monarch, a tool that enables researchers to study and compare the performance of new and existing transport protocols at large scale in broadband environments. Furthermore, we designed SatelliteLab, a novel testbed that can easily add arbitrary end nodes, including broadband nodes and even smartphones, to existing testbeds like PlanetLab.Breitbandanschlüsse werden heute von hunderten Millionen Nutzern als Internetzugang verwendet. Jedoch geben die meisten ISPs nur ungern über Details ihrer Netze Auskunft und infolgedessen sind Nutzern, Anwendungsentwicklern und Forschern oft deren Eigenheiten nicht bekannt. Ziel dieser Dissertation ist es daher Breitbandnetze transparenter zu machen. Mit Hilfe neuartiger Messwerkzeuge konnte ich die erste groß angelegte Studie über die Besonderheiten von Breitbandnetzen durchführen. Dabei stellte sich heraus, dass Breitbandnetze und Forschungsnetze sehr unterschiedlich sind. Mit Glasnost habe ich ein System entwickelt, das mehr als 350.000 Nutzern weltweit ermöglichte ihren Internetanschluss auf den Einsatz von Verkehrsmanagement zu testen. Ich konnte dabei zeigen, dass ISPs zunehmend BitTorrent Verkehr drosseln oder gar blockieren. Meine Studien zeigten dar überhinaus, dass existierende Verfahren zum Testen von Internetsystemen nicht die typischen Eigenschaften von Breitbandnetzen berücksichtigen. Ich ging dieses Problem auf zwei Arten an: Zum einen entwickelte ich Monarch, ein Werkzeug mit dem das Verhalten von Transport-Protokollen über eine große Anzahl von Breitbandanschlüssen untersucht und verglichen werden kann. Zum anderen habe ich SatelliteLab entworfen, eine neuartige Testumgebung, die, anders als zuvor, beliebige Internetknoten, einschließlich Breitbandknoten und sogar Handys, in bestehende Testumgebungen wie PlanetLab einbinden kann

Cross-layer Assisted TCP Algorithms for Vertical Handoff

The ever expanding growth of the wireless access to the Internet in recent years has led to the proliferation of wireless and mobile devices to connect to the Internet. This has created the possibility of mobile devices equipped with multiple radio interfaces to connect to the Internet using any of several wireless access network technologies such as GPRS, WLAN and WiMAX in order to get the connectivity best suited for the application. These access networks are highly heterogeneous and they vary widely in their characteristics such as bandwidth, propagation delay and geographical coverage. The mechanism by which a mobile device switches between these access networks during an ongoing connection is referred to as vertical handoff and it often results in an abrupt and significant change in the access link characteristics. The most common Internet applications such as Web browsing and e-mail make use of the Transmission Control Protocol (TCP) as their transport protocol and the behaviour of TCP depends on the end-to-end path characteristics such as bandwidth and round-trip time (RTT). As the wireless access link is most likely the bottleneck of a TCP end-to-end path, the abrupt changes in the link characteristics due to a vertical handoff may affect TCP behaviour adversely degrading the performance of the application. The focus of this thesis is to study the effect of a vertical handoff on TCP behaviour and to propose algorithms that improve the handoff behaviour of TCP using cross-layer information about the changes in the access link characteristics. We begin this study by identifying the various problems of TCP due to a vertical handoff based on extensive simulation experiments. We use this study as a basis to develop cross-layer assisted TCP algorithms in handoff scenarios involving GPRS and WLAN access networks. We then extend the scope of the study by developing cross-layer assisted TCP algorithms in a broader context applicable to a wide range of bandwidth and delay changes during a handoff. And finally, the algorithms developed here are shown to be easily extendable to the multiple-TCP flow scenario. We evaluate the proposed algorithms by comparison with standard TCP (TCP SACK) and show that the proposed algorithms are effective in improving TCP behavior in vertical handoff involving a wide range of bandwidth and delay of the access networks. Our algorithms are easy to implement in real systems and they involve modifications to the TCP sender algorithm only. The proposed algorithms are conservative in nature and they do not adversely affect the performance of TCP in the absence of cross-layer information.Käytämme enenevissä määrin kannettavia päätelaitteita (esim. matkapuhelin, kannettava tietokone) erilaisiin sovelluksiin kuten sähköpostin lukemiseen, verkon selaamiseen, musiikin lataamiseen ja kuuntelemiseen, pelien pelaamiseen ja laskujen maksamiseen riippumatta olinpaikastamme tai liikkuvuudestamme. Pystymme yhdistämään laitteemme Internetiin milloin tahansa missä tahansa. Langattomat verkot, jotka mahdollistavat laitteen kytkemisen Internetiin radion kautta käyttävät moninaisia teknologioita ja eroavat laajalti ominaisuuksiltaan. Esimerkiksi langaton lähiverkko (WLAN), jota voidaan käyttää rakennuksen sisällä, on matkapuhelinverkkoa (esim. GPRS) nopeampi verkko, kun taas GPRS-kenttä voi ulottua kokonaisen kaupungin tai maan alueelle ja laajemmallekin. Kannettava päätelaite, jossa on monia radioliittymiä, voi siirtyä käyttämään mitä tahansa monista saatavilla olevistaverkoista riippuen olinpaikasta tai käytettävän sovelluksen tarpeista. Verkonvaihto viittaa tähän verkosta toiseen siirtymiseen, ja se tunnetaan vertikaalisena verkonvaihtona, kun siirtymisen kohteena olevien verkkojen teknologia eroaa toisistaan. TCP on tietoliikenneohjelmisto, jota sekä tiedon lähettäjä että vastaanottaja käyttävät kuljettamaan sovelluksen tiedon luotettavasti. TCP säätelee tiedon lähetysnopeutta riippuen Internetin resurssien saatavuudesta. TCP:n käyttäytyminen riippuu päästä-päähän polun ominaisuuksista ja erityisesti pullonkaulayhteydestä, siitä yhteydestä, jolla on minimikapasiteetti polulla. Langaton yhteys, joka yhdistää kannettavan laitteen Internetiin on usein pullonkaulayhteys, ja äkillinen muutos sen ominaisuuksissa vertikaalisen siirtymän aikana vaikuttaa merkittävästi TCP:n suorituskykyyn ja siten koko sovelluksen laatuun. Tämä työssä on keskitytty tutkimaan TCP:n toimintaa vertikaalisessa verkonvaihdon yhteydessä ja suunnittelemaan algoritmeja, jotka parantavat sen suorituskykyä vertikaalisen verkonvaihdon yhteydessä. Suunnitellut algoritmit käyttävät hyväksi tietoa vertikaaliseen verkonvaihtoon liittyvien langattomien yhteyksien ominaisuuksista. Ensimmäinen tapaustutkimuskohde liittyy WLAN-GPRS -ympäristöön, jossa TCP saa minimimäärän tietoa verkonvaihtoon liittyen. Tulokset näyttävät, että TCP:n suorituskykyä voidaan parantaa huomattavasti. Tutkimusta on laajennettu kattamaan verkonvaihto yleisemmässä tapauksessa käyttäen karkeita arvioita ko. verkkojen ominaisuuksista. Kehitettyjen algoritmien toiminnallisuus on evaluoitu simulaatiokokeilla kattaen laajan joukon ominaisuuksiltaan erilaisia verkkoja. Tulokset osoittavat, että TCP-suorituskykyä voidaan parantaa vertikaalisen verkonvaihdon yhteydessä huomattavasti tätä lähestymistapaa käyttäen. Kehitetyt algoritmit voivat olla hyödyksi etsiessämme ratkaisuja kannettavien laitteiden todellisen käytön tarpeisiin