Thesis (MSc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The Internet has experienced tremendous growth in the last three decades and has emerged as a platform to carryall forms of communications including voice, video and data. Along with this growth came the urgency for quality of service (QoS) controls in IP networks as different types of traffics have different service requirements. Although the IP protocol is able to scale to very large networks, it does not provide sufficient functionality for traffic engineering in order to enable QoS control. Multi-protocol label switching (MPLS) is a new routing technology that enhances IP with some QoS concepts from ATM and uses relatively simple packet forwarding mechanisms. MPLS has the ability to perform traffic engineering and QoS control by routing traffic flowson virtual connections called label switched paths (LSPs) which are assigned capacity. A large portion of the traffic carried on the Internet consists of data traffic in the form of TCP traffic. This thesis investigates several TCP models to find the ones most suitable to represent TCP traffic in MPLS networks. The models consist of three types. The first type models a single TCP source and the second type models a fixed number of TCP sources. The third type models an infinite number of TCP sources. The models were evaluated by comparing their throughput predictions and results obtained from simulation experiments that were done with the widely-used simulator ns. We also present a simple derivation of the 1/,;e law for the TCP congestion window size where e is the packet loss probability. / AFRIKAANSE OPSOMMING:In die afgelope drie dekades het die Internet beduidende groei ervaar, soveel so dat dit ontluik het as 'n medium om alle tipes van moderne kommunikasies te hanteer insluitend telefoon, video en data. Hierdie groei het gepaard gegaan met die behoefte na diensvlak (QoS) meganismes in IP netwerke aangesien verskillende tipe kommunikasies verskillende diens vereistes het. Alhoewel die IP protokol skalleerbaar is tot baie groot netwerke, voorsien dit nie voldoende funksionaliteit om QoS beheer toe te pas nie. "Multi-protocol label switching" (MPLS) is 'n nuwe roeterings tegnologie wat IP aanvul met QoS konsepte van ATM en dit maak gebruik van relatief eenvoudige pakkie versendings-meganismes. MPLS het die vermoe om netwerk-verkeer reeling en QoS beheer toe te pas deur verkeers-strome te roeteer op virtuele roetes genaamd "label switched paths" (LSPs) aan wie kapasiteit toegeken is. 'n Beduidende gedeelte van Internet-verkeer bestaan uit TCP-verkeer. Hierdie tesis ondersoek verskillende modelle van TCP om die te vind wat die mees geskik is om TCP verkeer in MPLS netwerke te verteenwoordig. Drie tipes modelle is ondersoek. Die eerste tipe moduleer 'n enkele TCP verkeersbron en die tweede tipe moduleer 'n vasgestelde aantal TCP verkeersbronne. Die derde tipe moduleer 'n oneindige aantal verkeersbronne. Die modelle is geevalueer deur hul voorspellings van die tempo van data transmissie te vergelyk met resultate van simulasies. Die simulasies is gedoen met die veelgebruikte simulator ns. Hierdie tesis bevat ook 'n eenvoudige afleiding vir die 1/,;e wet vir die TCP oorlading venster grootte met e die verlies waarskeinlikheid van 'n netwerk pakkie.

Peer-to-Peer(P2P)架構讓社群內的使用者收集分散在網路各處之資源，其中最為風行的P2P系統當屬P2P檔案分享系統。P2P檔案分享系統之架構可分為集中式及分散式，而分散式架構又可細分為結構化及非結構化兩種。採用分散式且非結構化之BitTorrent-like架構，因其可擴張性較佳而廣為風行。在經驗中發現，BitTorrent-like架構在非對稱網路之下雖擁有寬裕的下行頻寬，但是其頻寬使用率卻不高，我們分析其成因如下：(1) Fractional Upward Bandwidth (FUB) 、 (2)Blockage of Acknowledgement (BoA) 與 (3)Long Physical Paths 等。而其中的Blockage of ACK問題，現今尚未有研究學者提出完整解決方案。本研究之目的，即要針對此Blockage of ACK的問題，改良網路協定中的傳輸層 (Transport Layer) 協定以提昇P2P檔案分享系統之效能。我們改用UDP作為傳輸層協定，並在應用層加入自動重建遺失之封包、決定基本傳輸單位大小及決定資料傳送速率等機制，以彌補UDP之缺陷。文中並提供了傳輸協定運作時所需參數的估計法，並且也與其它傳輸協定做效能之比較。實驗結果發現，我們設計的傳輸協定確可改善P2P檔案共享系統的運作效能。 / Peer-to-Peer (P2P) architectures let participants gather resources form network and make participants acquire more computation resources than they could offer. One of the most prominent P2P systems is P2P file sharing system. P2P file sharing system could be classified into to 2 categories: centralized and decentralized model. BitTorrent-like (BT-like) model can be classified as decentralized and unstructured model. BT-like model is quit popular nowadays due to its scalability. Unfortunately, BT-like model has several shortcomings on performance over asymmetric networks, because of some problems, such as Fractional Upward Bandwidth (FUB), Blockage of Acknowledgement (BoA) and long physical paths. No complete solution is available yet to solve the BoA problem. We propose a new UDP-based protocol to alleviate this problem. Since UDP protocol is not able to guarantee the data-integrity nor to determine the proper transmission rate by itself. To offer a complete solution, we have to enhance UDP, to add extra capabilities such as packet loss recovery, segment size determination and data rate determination mechanisms. Experiments show that our proposed protocol has good improvement on performance.

行動隨意式網路(MANET)是一種具有高度動態拓撲結構的網路。每一個行動隨意式網路由一組移動節點(Node)組成，彼此之間互相支援轉送封包可以不依靠基地台建構成Intranet。此種網路中，因節點移動之緣故，連線不穩定、頻寬較窄，錯誤率亦較高。傳統的TCP傳輸協定在行動隨意式網路上的效能不免遭受重創。 傳統的TCP在封包遺失時，只能從傳送端進行重傳，而行動隨意式網路傳輸品質極不穩定，常常重送多次才可到達目的地，導致要耗費極長的時間才能將封包送達目的地，然而，在行動隨意式網路中，大量傳輸資料的需求並不大，反而是封包的快速送達更為重要，因此加速封包的送達成為比增大傳送量更為重要的目標。 為了使封包較快送達目的地端，我們提出了Hop-by-Hop TCP的方法，使每個節點使用當地重傳以保證封包成功的傳到下一個節點，遺失的封包不必重新由傳送端重傳，能更快反應封包遺失，並且提昇傳輸可靠度，使封包在高遺失率的情形之下能順利且較為快速的送達目的地端。 我們利用NS-2網路模擬器進行實驗，驗證我們的機制，實驗在不同的拓樸及負載等參數下進行，觀察傳輸成功率及封包傳輸時間，以及公平性。實驗結果指出，本方法在網路環境不穩定時吞吐量能有25.7%以上的提昇，而延遲時間也能有25%的提昇，亦有相當好的公平性。 / A Mobile Ad hoc Network (MANET) MANET is composed of a group of mobile computing devices (nodes) that are equipped with Wireless LAN (WLAN) capability. Nodes can transmit packets to each other to construct Intranet without any base station. In an MANET environment, the communication links are unstable due to various reasons. Error rate is higher and bandwidth is smaller than fixed networks. Running regular TCP protocol on MANET will suffer from serious performance degradation in MANET. To handle packet lost, regular TCP can only retransmit lost packets from the source. However, when error rate is high, several retransmissions may be needed to transmit a packet to its destination successfully. As a result, the effective bandwidth is much lower and the average time to transmit a packet will be much longer. Considering that most applications on MANET prefer shorter transmission time to higher bandwidth, this thesis proposes Hop-by-Hop TCP protocol aiming to accelerate the transmission of packets. Hop-by-Hop TCP makes every intermediate node in the transmission path running a local TCP to guarantee the transmission of each packet on each link. The retransmission of a lost packet is right at the transmitting end of the link where the packet is lost. It doesn't need to retransmit a lost packet from its source node. It takes less time in average to transmit a packet to its destination in a high error rate environment. We evaluate the performance of our approach by simulation using NS-2 simulator. Our experiments show that our proposed protocol outperforms TCP Reno by 25.7% in throughput and 25% reduction in average transmission time. The fairness requirement is also achieved while our proposed protocol coexists with other major TCP variants.

Approved for public release, distribution is unlimited / Inter-domain routing connects individual pieces of Internet topology, creating an integral, global data delivery infrastructure. Currently, this critical function is performed by the Border Gateway Protocol (BGP) version 4 [RFC1771]. Like all routing protocols, BGP is vulnerable to instabilities that reduce its effectiveness. Among the causes of these instabilities are those which are maliciously induced. Although there are other causes, e.g., natural events and network anomalies, this thesis will focus exclusively on maliciously induced instabilities. Most current models that attempt to predict a BGP routing instability confine their focus to either macro- or micro-level metrics, but not to both. The inherent limitations of each of these forms of metric gives rise to an excessive rate of spurious alerts, both false positives and false negatives. It is the original intent of this thesis to develop an improved BGP instability prediction model by statistically combining BGP instability metrics with user level performance metrics. The motivation for such a model is twofold. 1) To provide sufficient prior warning of impending failure to facilitate proactive protection measures. 2) To improve warning reliability beyond existing models, by demonstrably reducing both false positives and false negatives. However, our analysis of actual network trace data shows that a widely used BGP instability metric, the total number of update messages received in a time period, is not a good indicator of future user level performance. / Civilian, Department of Defense

This thesis report, focuses on the automation process of Electrical Substations, with the main objective of integration into SCADA systems for electrical equipment responsible for the operation within substations, these devices have different communication protocols, after concentration information substation SCADA system, the next step to realize is sending data to the regulatory body that is in a remote location away from the substation, this is achieved using communication protocols designed for this function. All this process requires an optimization for the response times to any event that may happen in the substations and with this an optimization in operation of generation, distribution and transformation of electrical energy

The IP Multimedia Subsystem (IMS) has gone from just a step in the evolution of the GSM cellular architecture control core, to being the de-facto framework for Next Generation Network (NGN) implementations and deployments by operators world-wide, not only cellular mobile communications operators, but also fixed line, cable television, and alternative operators. With this transition from standards documents to the real world, engineers in these new multimedia communications companies need to face the task of making these new networks secure against threats and real attacks that were not a part of the previous generation of networks. We present the IMS and other competing frameworks, we analyze the security issues, we present the topic of Security Patterns, we introduce several new patterns, including the basis for a Generic Network pattern, and we apply these concepts to designing a security architecture for a fictitious 3G operator using IMS for the control core. / by Jose M. Ortiz-Villajos. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. In the wired network, TCP performs remarkably well due to its scalability and distributed end-to-end congestion control algorithms. However, many studies have shown that the unmodified standard TCP performs poorly in networks with large bandwidth-delay products and/or lossy wireless links. In this thesis, we analyze the problems TCP exhibits in the wireless communication and develop TCP congestion control algorithm for mobile applications. We show that the optimal TCP congestion control and link scheduling scheme amounts to window-control oriented implicit primaldual solvers for underlying network utility maximization. Based on this idea, we used a scalable congestion control algorithm called QUeueIng-Control (QUIC) TCP where it utilizes queueing-delay based MaxWeight-type scheduler for wireless links developed in [34]. Simulation and test results are provided to evaluate the proposed schemes in practical networks. / by Gee Won Han. / Thesis (M.S.C.S.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite, which is used by major Internet applications such as World Wide Web, email, remote administration and file transfer. TCP implements scalable and distributed end-to-end congestion control algorithms to share network resources among competing users. TCP was originally designed primarily for wired networks, and it has performed remarkably well as the Internet scaled up by six orders of magnitude in the past decade. However, many studies have shown that the unmodified standard TCP performs poorly in networks with large bandwidth-delay products and/or lossy wireless links. In this thesis, we analyze the problems TCP exhibits in the wireless communication environment, and develop joint TCP congestion control and wireless-link scheduling schemes for mobile applications. ... Different from the existing solutions, the proposed schemes can be asynchronously implemented without message passing among network nodes; thus they are readily deployable with current infrastructure. Moreover, global convergence/stability of the proposed schemes to optimal equilibrium is established using the Lyapunov method in the network fluid model. Simulation results are provided to evaluate the proposed schemes in practical networks. / by Zhaoquan Li. / Thesis (Ph.D.)--Florida Atlantic University, 2013. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

Siu Chun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 66-68). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Thesis Overview --- p.3 / Chapter 2 --- Background and Related work --- p.4 / Chapter 2.1 --- Emergence of IP-over-ATM --- p.4 / Chapter 2.2 --- ATM architecture --- p.5 / Chapter 2.3 --- Scheduling issues in output-queued switch --- p.6 / Chapter 2.4 --- Scheduling issues in input-queued switch --- p.18 / Chapter 3 --- The Deadline-ordered Burst-based Parallel Scheduling Strategy --- p.23 / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Switch and queueing model --- p.24 / Chapter 3.2.1 --- Switch model --- p.24 / Chapter 3.2.2 --- Queueing model --- p.25 / Chapter 3.3 --- The DBPS Strategy --- p.26 / Chapter 3.3.1 --- Motivation --- p.26 / Chapter 3.3.2 --- Strategy --- p.31 / Chapter 3.4 --- The Deadline-ordered Burst-based Parallel Iterative Matching --- p.33 / Chapter 3.4.1 --- Algorithm --- p.34 / Chapter 3.4.2 --- An example of DBPIM --- p.35 / Chapter 3.5 --- Simulation results --- p.33 / Chapter 3.6 --- Discussions --- p.46 / Chapter 3.7 --- Future work --- p.47 / Chapter 4 --- The Quasi-static DBPIM Algorithm --- p.50 / Chapter 4.1 --- Introduction --- p.50 / Chapter 4.2 --- Quasi-static path scheduling principle --- p.51 / Chapter 4.3 --- Quasi-static DBPIM algorithm --- p.56 / Chapter 4.4 --- An example of Quasi-static DBPIM --- p.59 / Chapter 5 --- Conclusion --- p.63 / Bibliography --- p.65

"The Internet has assumed the role of the underlying communication network for applications such as file transfer, electronic mail, Web browsing and multimedia streaming. Multimedia streaming, in particular, is growing with the growth in power and connectivity of today's computers. These Internet applications have a variety of network service requirements and traffic characteristics, which presents new challenges to the single best-effort service of today's Internet. TCP, the de facto Internet transport protocol, has been successful in satisfying the needs of traditional Internet applications, but fails to satisfy the increasingly popular delay sensitive multimedia applications. Streaming applications often use UDP without a proper congestion avoidance mechanisms, threatening the well-being of the Internet. This dissertation presents an IP router traffic management mechanism, referred to as Crimson, that can be seamlessly deployed in the current Internet to protect well-behaving traffic from misbehaving traffic and support Quality of Service (QoS) requirements of delay sensitive multimedia applications as well as traditional Internet applications. In addition, as a means to enhance Internet support for multimedia streaming, this dissertation report presents design and evaluation of a TCP-Friendly and streaming-friendly transport protocol called the Multimedia Transport Protocol (MTP). Through a simulation study this report shows the Crimson network efficiently handles network congestion and minimizes queuing delay while providing affordable fairness protection from misbehaving flows over a wide range of traffic conditions. In addition, our results show that MTP offers streaming performance comparable to that provided by UDP, while doing so under a TCP-Friendly rate."