With the rising popularity of Voice over IP (VoIP) services, understanding the effects of a global network on Quality of Service is critical for the providers of VoIP applications. This thesis builds on a model that analyzes the round trip time, packet delay jitter, and packet loss between endpoints on an Autonomous System (AS) level, extending it by mapping AS pairs onto an Internet topology. This model is used to produce a mean opinion score estimate. The mapping is introduced to reduce the size of the problem in order to improve computation times and improve accuracy of estimates. The results of testing show that estimating mean opinion score from this model is not desirable. It also shows that the path mapping does not affect accuracy, but does improve computation times as the input data grows in volume.

International Telemetering Conference Proceedings / October 26-29, 1998 / Town & Country Resort Hotel and Convention Center, San Diego, California / This paper describes a distributed network client-server system developed for researchers to perform real-time or near-real-time analyses on ensembles of telemetry data previously done in post-flight. The client-server software approach provides extensible computing and real-time access to data at multiple remote client sites. Researchers at remote sites can share similar information as those at the test site. The system has been used successfully in numerous commercial, academic and NASA wide aircraft flight testing.

Audio networking is a rapidly increasing field which introduces new exiting possibilities for the professional audio industry. When well established, it will drastically change the way live sound systems will be designed, built and used. Today's networks have enough bandwidth that enables them to transfer hundreds of high quality audio channels, replacing analogue cables and intricate installations of conventional analogue audio systems. Currently there are many systems in the market that distribute audio over networks for live music and studio applications, but this technology is not yet widespread. The reasons that audio networks are not as popular as it was expected are mainly the lack of interoperability between different vendors and still, the need of a wired network infrastructure. Therefore, the development of a wireless digital audio networking system based on the existing widespread wireless technology is a major research challenge. However, the ΙΕΕΕ 802.11 standard, which is the primary wireless networking technology today, appears to be unable to handle this type of application despite the large bandwidth available. Apart from the well-known drawbacks of interference and security, encountered in all wireless data transmission systems, the way that ΙΕΕΕ 802.11 arbitrates the wireless channel access causes significantly high collision rate, low throughput and long overall delay. The aim of this research was to identify the causes that impede this technology to support real time wireless audio networks and to propose possible solutions. Initially the standard was tested thoroughly using a data traffic model which emulates a multi-channel real time audio environment. Broadcasting was found to be the optimal communication method, in order to satisfy the intolerance of live audio, when it comes to delay. The results were analysed and the drawback was identified in the hereditary weakness of the IEEE 802.11 standard to manage broadcasting, from multiple sources in the same network. To resolve this, a series of modifications was proposed for the Medium Access Control algorithm of the standard. First, the extended use of the "CTS-to-Self" control message was introduced in order to act as a protection mechanism in broadcasting, similar to the RTC/CTS protection mechanism, already used in unicast transmission. Then, an alternative "random backoff" method was proposed taking into account the characteristics of live audio wireless networks. For this method a novel "Exclusive Backoff Number Allocation" (EBNA) algorithm was designed aiming to minimize collisions. The results showed that significant improvement in throughput can be achieved using the above modifications but further improvement was needed, when it comes to delay, in order to reach the internationally accepted standards for real time audio delivery. Thus, a traffic adaptive version of the EBNA algorithm was designed. This algorithm monitors the traffic in the network, calculates the probability of collision and accordingly switches between classic IEEE 802.11 MAC and EBNA which is applied only between active stations, rather than to all stations in the network. All amendments were designed to operate as an alternative mode of the existing technology rather as an independent proprietary system. For this reason interoperability with classic IEEE 802.11 was also tested and analysed at the last part of this research. The results showed that the IEEE 802.11 standard, suitably modified, is able to support multiple broadcasting transmission and therefore it can be the platform upon which, the future wireless audio networks will be developed.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / As part of NASA’s goal to reduce costs for satellite telemetry and command ground support, the ground network has installed two autonomous ground terminals known as Low Earth Orbiter - Terminal’s, or LEO-T’s. These systems are highly automated and were developed to prove the feasibility of supporting multi-mission satellites in a handsoff mode.

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In recent years the telemetry community has encountered a growing demand for bandwidth from users and a corresponding loss of spectrum. The Advanced Range Telemetry (ARTM) Program has responded to this situation with an initiative to develop, demonstrate, and improve the management and control of telemetry resources using demand assigned multiple access (DAMA) techniques. This initiative has proceeded along two paths. The first path is in the development of an expert system to facilitate the scheduling of telemetry missions and the deconfliction of their frequencies. This system emphasizes the graphical manipulation of mission data and uses a genetic algorithm to search for an optimal set of mission frequencies. The second path is the development of a bidirectional command and control link to remotely control and configure the frequency of a telemetry link. This link uses the simple network management protocol (SNMP) over a wireless Internet Protocol (IP) network implemented with Digital Communications Network System (DCNS) units.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / The advent of COTS based network-centric data systems brings a whole new vocabulary into the realm of instrumentation. The Communications and computer industries have developed networks to a high level and they continue to evolve. One of the basic techniques that has proven itself useful with this technology is the use of a “layered architecture.” This paper is an attempt to discuss the basic ideas behind this concept and to give some understanding of the vocabulary that has grown up with it.

ITC/USA 2011 Conference Proceedings / The Forty-Seventh Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2011 / Bally's Las Vegas, Las Vegas, Nevada / This paper presents the design for secure IP multicasting in an iNet environment using public key cryptography. Morgan State University has been conducting research to improve the telemetry network by improving network performance, implementing IP (Internet Protocol) multicasting and providing a stronger security system for the iNet environment. The present study describes how IP multicasting could be implemented to provide more secure communication in the iNet environment by reducing traffic and optimizing network performance. The multicast of data is closely tied to the key management center for secure applications. This paper develops a means of delivering keys between two or more parties showing a relationship between the multicast network and the Key Management Center (KMC). The KMC is an element of the system which distributes and manages session keys among multicast members. A public key encryption method is used to address the distribution of session keys in the multicast network. The paper will present a system level design of multicast and key management with dual encryption of session keys for the iNet system.

Les progrès en informatique permettent désormais d'effectuer des téléopérations via des réseaux informatiques. Par exemple, l'Internet a déjà été utilisé ces dernières années dans le cadre de téléopérations à longue distance. Il a l'énorme avantage d'être très répandu, accessible, fiable et économique. Le but de ce travail est de mettre en œuvre une plate-forme de téléopération à longue distance via des réseaux informatiques présentant les mêmes limitations que l'Internet : présence de retards, qui plus est variables dans le temps à petite (ms) et grande échelle de temps (mn), pertes de données, asymétrie des retards. Nous avons donc élaboré dans un premier temps un modèle mathématique d'une boucle de téléopération classique en partant d'expérimentations sur notre manipulateur mobile. Nous avons ainsi construit un simulateur qui nous a permis de nous attaquer à différents problèmes inhérents à une téléopération à longue distance. Enfin, nous développons un schéma de commande intégrant les diverses évolutions proposées applicable sur un bras manipulateur. Pour valider ce schéma expérimentalement, nous avons développé un ensemble logiciel de téléopération pour PC sous Microsoft Windows.

<p>When using Voice over IP (VoIP) in Wireless Mesh Networks the overhead induced by the IEEE 802.11 PHY and MAC layer accounts for more than 80% of the channel utilization time, while the actual payload only uses 20% of the time. As a consequence, the Voice over IP capacity is very low. To increase the channel utilization efficiency and the capacity several IP packets can be aggregated in one large packet and transmitted at once. This paper presents a new hop-by-hop IP packet aggregation scheme for Wireless Mesh Networks.</p><p>The size of the aggregation packets is a very important performance factor. Too small packets yield poor aggregation efficiency; too large packets are likely to get dropped when the channel quality is poor. Two novel distributed protocols for calculation of the optimum respectively maximum packet size are described. The first protocol assesses network load by counting the arrival rate of routing protocol probe messages and constantly measuring the signal-to-noise ratio of the channel. Thereby the optimum packet size of the current channel condition can be calculated. The second protocol, which is a simplified version of the first one, measures the signal-to-noise ratio and calculates the maximum packet size.</p><p>The latter method is implemented in the ns-2 network simulator. Performance measurements with no aggregation, a fixed maximum packet size and an adaptive maximum packet size are conducted in two different topologies. Simulation results show that packet aggregation can more than double the number of supported VoIP calls in a Wireless Mesh Network. Adaptively determining the maximum packet size is especially useful when the nodes have different distances or the channel quality is very poor. In that case, adaptive aggregation supports twice as many VoIP calls as fixed maximum packet size aggregation.</p>

Port scanning is the first activity an attacker pursues when attempting to compromise a target system on a network. The aim is to gather information that will result in identifying one or more vulnerabilities in that system. For example, network ports that are open can reveal which applications and services are running on the system. How a port responds when probed with data can reveal which protocol the port utilises and can also reveal which implementation of that protocol is being employed. One of the most valuable pieces of information to be gained via scanning and probing techniques is the operating system that is installed on the target. This technique is called operating system fingerprinting. The purpose of this research is to alert computer users of the dangers of port scanning, probing, and operating system fingerprinting by exposing these techniques and advising the users on which preventative countermeasures to take against them. Analysis is performed on the Transmission Control Protocol (TCP), User Datagram Protocol (UDP), Internet Protocol (IPv4 and IPv6), and the Internet Control Message Protocol (ICMPv4 and ICMPv6). All the software used in this project is free and open source. The operating system used for testing is Linux (2.4 and 2.6 kernels). Scanning, probing, and detection techniques are investigated in the context of the Network Mapper and Xprobe2 tools. / Thesis (M.Sc. - Computer)-University of KwaZulu-Natal, Durban, 2007.