Approved for public release, distribution is unlimited / This thesis studies and discusses the development of the API, called the persistency API, for supporting the persistent data sessions. Without persistent session support, network applications often need to be restarted from the beginning when intermittent physical connection loss happens. Application programmers can use the persistency API to achieve the service continuity. The persistency API provides the interface that allows a program to continue retrieve data from the point the connection is lost after the physical connection is restored. The focus of this thesis is to develop a generalized persistency API that supports various types of applications. This thesis studies the persistent session support for two types of transport protocols, TCP and UDP, which are used by major network applications. An application that performs text file and video file transfer is implemented to demonstrate the persistent data transfer sessions for TCP and UDP, respectively. The study shows that the proposed APIs can support the data transfer continuity in the reconnection process. / Captain, Royal Thai Army

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 number of Web traffic flows dominates Internet traffic today and most Web interactions are short-lived HTTP connections handled by TCP. Most core Internet routers use Drop Tail queuing which produces bursts of packet drops that contribute to unfair service. This thesis introduces two new active queue management (AQM) algorithms, PISA (PI with Short-lived flows Adjustment) and PIMC (PI with Minimum Cwnd). These AQMs are built on top of the PI (Proportional Integrator). To evaluate the performance of PISA and PIMC, a new simple model of HTTP traffic was developed for the NS-2 simulation. TCP sources inform PISA and PIMC routers of their congestion window by embedding a source hint in the packet header. Using the congestion window, PISA drops packets from short-lived Web flows less than packets from long-lived flows. Using a congestion window, PIMC does not drop a packet when congestion window is below a fixed threshold. This study provides a series of NS-2 experiments to investigate the behavior of PISA and PIMC. The results show fewer drops for both PISA and PIMC that avoids timeouts and increases the rate at which Web objects are sent. PISA and PIMC improve the performance of HTTP flows significantly over PI. PISA performs slightly better than PIMC.

This research is motivated by the recent developments in the Internet Engineering Task Force (IETF) to support seamless integration of moving networks deployed in vehicles to the global Internet. The effort, known as Network Mobility (NEMO), paves the way to support high-speed Internet access in mass transit systems, e.g. trains; buses; ferries; and planes; through the use of on-board mobile routers embedded in the vehicle. One of the critical research challenges of this vision is to achieve high-speed and reliable back-haul connectivity between the mobile router and the rest of the Internet. The problem is particularly challenging due to the fact that a mobile router must rely on wireless links with limited bandwidth and unpredictable quality variations as the vehicle moves around. In this thesis, the multi-homing concept is applied to approach the problem. With multi-homing, mobile router has more than one connection to the Internet. This is achieved by connecting the mobile router to a diverse array of wireless access technologies (e.g., GPRS, CDMA, 802.11, and 802.16) and/or a multiplicity of wireless service providers. While the aggregation helps addressing the bandwidth problem, quality variation problem can be mitigated by employing advanced traffic engineering techniques that dynamically control inbound and outbound traffic over multiple connections. More specifically, the thesis investigates traffic engineering solutions for mobile networks that can effectively address the performance objectives, e.g. maximizing profit for mobile network operator; guaranteeing quality of service for the users; and maintaining fair access to the back-haul bandwidth. Traffic engineering solutions with three different levels of control have been investigated. First, it is shown, using detailed computer simulation of popular applications and networking protocols(e.g., File Transfer Protocol and Transmission Control Protocol), that packet-level traffic engineering which makes decisions of which Internet connection to use for each and every packet, leads to poor system throughput. The main problem with packet-based traffic engineering stems from the fact that in mobile environment where link bandwidths and delay can vary significantly, packets using different connections may experience different delays causing unexpected arrivals at destinations. Second, a maximum utility flow-level traffic engineering has been proposed that aims to maximize a utility function that accounts for bandwidth utilization on the one hand, and fairness on the other. The proposed solution is compared against previously proposed flow-level traffic engineering schemes and shown to have better performance in terms of throughput and fairness. The third traffic engineering proposal addresses the issue of maximizing operator?s profit when different Internet connections have different charging rates, and guaranteeing per user bandwidth through admission control. Finally, a new signaling protocol is designed to allow the mobile router to control its inbound traffic.

There is a growing range of IP-based data and voice applications using mobile devices (e.g. 3rd , 4th generation mobile phones and PDAs) and new access technologies (e.g. Bluetooth, 802.11, GPRS, ADSL). This growth is driving a desire to support mobility at the IP level � in other words, allowing an IP host to keep on communicating with other hosts while roaming between different IP subnetworks. Mobile IPv6 allows hosts to move their physical and topological attachment points around an IPv6 network while retaining connectivity through a single, well-known Home Address. Although Mobile IPv6 has been the subject of simulation studies, the real-world dynamic behavior of Mobile IPv6 is only gradually being experimentally characterised and analysed. This thesis reviews the use of Mobile IPv6 to support mobility between independent 802.11b-attached IPv6 subnets, and experimentally measures and critically evaluates how long an end to end IP path is disrupted when a Mobile IPv6 node shifts from one subnetwork to another (handoff time). The thesis describes the development of an experimental testbed suitable for gathering real-world Mobile IPv6 handoff data using publicly available, standards compliant implementations of Mobile IPv6. (An open-source Mobile IPv6 stack (the KAME release under FreeBSD) was deployed). The component of handoff time due to 802.11b link layer handoff is measured separately to assess its impact on the overall Mobile IPv6 handoff time. Using Mobile IPv6 handoff results, the likely performance impact of Mobile IPv6 handoff on a common webcam application and a bulk TCP data transfer is also evaluated. The impact of handoff on these applications clearly shows that a default Mobile IPv6 environment would be highly disruptive to real-time and interactive applications during handoff events, even if the underlying link-layer handoff was instantaneous.

The future Internet will need to cater for an increasing number of powerful devices and entire groups of networks to roam in heterogeneous access networks. The current approach towards meeting such requirements, which is to retrofit mobility solutions to different layers of the protocol stack, has given rise to an increasingly fragmented network control layer. Furthermore, retrofitting solutions in an ad-hoc manner to the protocol stack does not provide consistent support from the network to different applications. This lack of a common control layer for facilitating roaming in heterogeneous networking environments represents a crucial challenge both technically and from a user perspective. To this end, a novel mobility architecture forms the basis and the first part of this dissertation. The work on investigating current network mobility solutions and improving these solutions if deemed necessary, in order to reuse within the novel mobility architecture constitutes the second part of this dissertation. The IETF standard protocol for network mobility was implemented and its performance was analysed on a real networking environment. This enabled to identify problems in the standard which affect the handover and routing performance. To address the identified routing and protocol header overheads of the standard network mobility protocol a novel optimal routing framework, OptiNets was proposed. To address the handover latency issues, optimizations to IPv6 network attachment were incorporated and also an access technology independent multiple interface Make-Before-Break handover mechanism was proposed. The viability of the OptiNets framework and the handover optimizations were demonstrated by analysis and by implementation. A more general external factor that affects the performance of mobile networks which is bandwidth scarcity of Wireless Wide Area Networks was addressed, by proposing a bandwidth fuelling architecture for on-board mobile networks. The feasibility of the bandwidth fuelling architecture was analysed by implementing a prototype and evaluating its performance.

Existen numerosos trabajos que estudian o tratan la realización software de los protocolos de comunicaciones para el acceso a la Internet-TCP/IP. Sin embargo, no conocemos ninguno que modele de forma general y precisa la ejecución de este software.La presente tesis aporta una caracterización detallada de la ejecución de la realización software de los mencionados protocolos sobre un computador personal y bajo un sistema operativo UNIX. Esta caracterización muestra cómo varía el rendimiento del sistema en función de la velocidad de operación de la CPU, las características del subsistema de memoria, el tamaño de los paquetes y otras variables de importancia para la remisión, autenticación y cifrado de paquetes IP.En otros trabajos se proponen adecuaciones o extensiones a la realización software de los mencionados protocolos que permiten que un software router provea de comunicaciones con diversos niveles asegurados de calidad mediante el uso de mecanismos de planificación para la unidad central de procesamiento. Sin embargo, en dichos trabajos no se contempla la planificación del uso del bus de entrada/salida. Los resultados derivados de nuestro modelo demuestran que, para sistemas que usan CPUs con frecuencias de reloj superiores a 1 GHz, la planificación conjunta de la CPU y el bus de entrada salida es indispensable para la provisión de comunicaciones con diversos niveles asegurados de calidad. Dichas frecuencias de reloj son comunes en los sistemas comerciales actuales, por lo que consideramos que es un problema de gran interés. En la tesis proponemos un mecanismo que consigue garantías de utilización del bus de entrada/salida mediante la modificación de los drivers de los interfaces de red. / Three are the main contributions of this work. In no particular order:" A detailed performance study of the software implementation of the TCP/IP protocols suite, when executed as part of the kernel of a BSD operating system over generic PC hardware." A validated queuing network model of the studied system, solved by computer simulation." An I/O bus utilization guard mechanism for improving the performance of software routers supporting QoS mechanisms and built upon PC hardware and software.This document presents our experiences building a performance model of a PC-based software router. The resulting model is an open multiclass priority network of queues that we solved by simulation. While the model is not particularly novel from the system modeling point of view, in our opinion, it is an interesting result to show that such a model can estimate, with high accuracy, not just average performance-numbers but the complete probability distribution function of packet latency, allowing performance analysis at several levels of detail. The validity and accuracy of the multiclass model has been established by contrasting its packet latency predictions in both, time and probability spaces. Moreover, we introduced into the validation analysis the predictions of a router's single queue model. We did this for quantitatively assessing the advantages of the more complex multiclass model with respect to the simpler and widely used but not so accurate, as here shown, single queue model, under the considered scenario that the router's CPU is the system bottleneck and not the communications links. The single queue model was also solved by simulation.Besides, this document addresses the problem of resource sharing in PC-based software routers supporting QoS mechanisms. Others have put forward solutions that are focused on suitably distributing the workload of the CPU-see this chapter's section on "related work". However, the increase in CPU speed in relation to that of the I/O bus-as here shown-means attention must be paid to the effect the limitations imposed by this bus on the system's overall performance. We propose a mechanism that jointly controls both I/O bus and CPU operation. This mechanism involves changes to the operating system kernel code and assumes the existence of certain network interface card's functions, although it does not require changes to the PC hardware. A performance study is shown that provides insight into the problem and helps to evaluate both the effectiveness of our approach, and several software router design trade-offs.