As the Internet grows, more and more applications are being networked. In this thesis, we use the Nemesis operating system to provide networked applications with service guarantees from both the network and the end system. The Nemesis operating system is designed from scratch to provide applications with service guarantees. Nemesis allows applications to reserve resources such as CPU time, transmit bandwidth on network interfaces and disk I/O bandwidth. We have implemented communication protocols in Nemesis. The ability of Nemesis to reserve CPU time enables applications to run the protocol stack within a guaranteed time and the ability to reserve transmit bandwidth enables applications to transmit data into the network at guaranteed rates. Experiments with the Nemesis TCP show, that networked applications with CPU time and transmit bandwidth reservations transmit at desired rates even when several applications contend for both CPU time and transmit bandwidth. We have also implemented the resource reservation protocol RSVP that reserves resources in the network. Nemesis is thus able to provide networked applications with end-to-end service guarantees.

As the need for greater bandwidth in local-area networks grows, wavelength-division multiplexing (WDM) is gathering attention as a viable successor to Gigabit Ethernet technologies. In this paper we introduce a new WDM optical LAN architecture based on the waveguide grating multiplexer (WGM) rather than the traditional passive star coupler (PSC). An N-port WGM allows N N connectivity via only N physical wavelengths, due to its inherent space-division multiplexing property. Wavelengthrouted networks based on the WGM promise to be signi cant components of future LAN and WAN technologies not only because of their ecient use of wavelengths, but also because they have been implemented as integrated devices. We propose simple, low-complexity TDM schedules for interconnecting MN nodes (M nodes per port) with a WGM in a local environment. Each node is equipped with a single tunable transmitter and a single tunable receiver (both of which can access all N wavelengths). Various transmitter and receiver tuning latencies are considered. We show that, for negligible tuning latencies, aggregate network throughput approaching min(MN ,N ) can be achieved, and for tuning latencies on the order of a packet length or more, throughput on the order of N can be achieved. Since these performance metrics are vastly superior to that of an equivalent PSC-based system (whose maximum throughput is limited by the number of wavelengths, N ), we propose that the WGM be considered as an alternative to the PSC for enabling WDM LANs and multiprocessor interconnects.

This paper presents a methodology for assessing the quality of service (QoS) provision for campus network. The author utilizes the Staffordshire University’s network communications infrastructure (SUNCI) as a testing platform and discusses a new approach and QoS provision, by adding a component of measurement to the existing model presented by Walker [1]. The QoS provision is assessed in light of users ’ perception compared with the network traffic measurements and online monitoring reports. The users ’ perception of telecommunications ’ network infrastructure QoS provision is critical to the successful business management operation of any organization. The computing environment in modern campus networks is complex employing multiple heterogeneous hardware and software technologies. In support of highly interactive user applications, QoS provision is essential to the users ’ ever increasing level of expectations. This paper offers a cost effective approach to assess the QoS provision within campus network. K e y w o r d s: quality of service provision, campus network, user’s perception, network communications infrastructures, the performance parameters and measurements, the survey questionnaire 1

This paper is concerned with the analysis, design and validation of a congestion cooperative rate control for communication networks. A sufficient condition for network stability in presence of multiple bottleneck and heterogeneous sources with different time delay is given and it is used for controller parameter design. The stability condition and the resulting cooperative control performance in terms of fairness, link utilization, packet loss and fault tolerance are validated firstly by Matlab/simulink tool and then by discrete packet simulator.

With multimedia applications, the Internet traffic increased a lot in volume, but also suffered major alterations in its nature, requesting other network services besides the current best-effort service. To satisfy this new situation, network architectures QoS-oriented such as the Integrated Services and Differentiated Services architectures have been discussed in several IETF groups. In this work we propose a methodology to implement packet schedulers, an element of fundamental importance to the new services, based on fuzzy control. The main innovation of this proposal is the employment of rule induction algorithms as C4.5 to infer the fuzzy controller's main rules. The approach has several advantages over the current ones, specially flexibility, efficiency and the possibility of being applied in several environments. 1.

This paper analyzes the performance of the existing Electrical Engineering network at Texas Tech University for different network configurations and under different load conditions. The networks that have been modeled and simulated using the OPNET Modeler are the Ethernet model, the IP over ATM model, and the LANE model. The results obtained from these simulations have been compared to the statistics obtained from the switches in the actual network using SNMP.

In this paper, we study the use of IEEE 802.11b networks for VoIP troic. Due to the large fixed overhead in IEEE 802.11b, the bandwidth available at the payload sizes typical for VoIP troic is far less than the bandwidth available when using the network for data troic. We analyze the maximal number of VoIP connections possible for different codecs in 802.11b and verified our results by experiments. The experiments indicate that the maximal number of simultaneous VoIP connections in a single cell of an IEEE 802.11b network when using the G711 a-Law codec with 10 ms audio data packets is six. We also study the effect of spatial distribution of wireless clients on the maximum number of VoIP calls. The maximum number of VoIP calls that can be sent over a single access-point with PingTel SIP based softphones (G711 codec, 20 msec audio payload per RTP packet) lies between 3 and 12. With Avaya's DEFINITY R2 phones (G711 codec with 30 msec payload), the number of supported connections is between 4 and 17 depending on the spatial distribution of the wireless clients around the access-point. Our analysis indicates that the use of a larger payload per frame is an effective solution to increasing the efficiency of the network and thus the number of VoIP calls.

This is a survey paper on Quality-of-Service(QoS) based routing. In this paper, we first introduce the concept of Quality-of-Service and its background. Second, we discuss the concepts of QoS-based routing, its objectives and main issues. After that, several types of QoS based routing algorithms are compared, and the advantages and disadvantages of each type discussed. Then, the relations between QoS based routing and some relevant techniques are studied, including traffic engineering, high level admission control, resource reservation protocols(e.g. RSVP), differential services(DiffServ) and MPLS (MultiProtocol Label Switching).