309 research outputs found
Simulation and analysis of adaptive routing and flow control in wide area communication networks
This thesis presents the development of new simulation and analytic models for the performance analysis of wide area communication networks. The models are used to analyse adaptive routing and flow control in fully connected circuit switched and sparsely connected packet switched networks. In particular the performance of routing algorithms derived from the L(_R-I) linear learning automata model are assessed for both types of network. A novel architecture using the INMOS Transputer is constructed for simulation of both circuit and packet switched networks in a loosely coupled multi- microprocessor environment. The network topology is mapped onto an identically configured array of processing centres to overcome the processing bottleneck of conventional Von Neumann architecture machines. Previous analytic work in circuit switched work is extended to include both asymmetrical networks and adaptive routing policies. In the analysis of packet switched networks analytic models of adaptive routing and flow control are integrated to produce a powerful, integrated environment for performance analysis The work concludes that routing algorithms based on linear learning automata have significant potential in both fully connected circuit switched networks and sparsely connected packet switched networks
Traffic Profiles and Performance Modelling of Heterogeneous Networks
This thesis considers the analysis and study of short and long-term traffic patterns of
heterogeneous networks. A large number of traffic profiles from different locations and
network environments have been determined. The result of the analysis of these patterns
has led to a new parameter, namely the 'application signature'. It was found that these
signatures manifest themselves in various granularities over time, and are usually unique
to an application, permanent virtual circuit (PVC), user or service. The differentiation of
the application signatures into different categories creates a foundation for short and long-term
management of networks. The thesis therefore looks from the micro and macro
perspective on traffic management, covering both aspects.
The long-term traffic patterns have been used to develop a novel methodology for network
planning and design. As the size and complexity of interconnected systems grow steadily,
usually covering different time zones, geographical and political areas, a new
methodology has been developed as part of this thesis. A part of the methodology is a new
overbooking mechanism, which stands in contrast to existing overbooking methods
created by companies like Bell Labs. The new overbooking provides companies with
cheaper network design and higher average throughput. In addition, new requirements like
risk factors have been incorporated into the methodology, which lay historically outside
the design process. A large network service provider has implemented the overbooking
mechanism into their network planning process, enabling practical evaluation.
The other aspect of the thesis looks at short-term traffic patterns, to analyse how
congestion can be controlled. Reoccurring short-term traffic patterns, the application
signatures, have been used for this research to develop the "packet train model" further.
Through this research a new congestion control mechanism was created to investigate how
the application signatures and the "extended packet train model" could be used. To
validate the results, a software simulation has been written that executes the proprietary
congestion mechanism and the new mechanism for comparison. Application signatures for
the TCP/IP protocols have been applied in the simulation and the results are displayed and
discussed in the thesis. The findings show the effects that frame relay congestion control
mechanisms have on TCP/IP, where the re-sending of segments, buffer allocation, delay
and throughput are compared. The results prove that application signatures can be used
effectively to enhance existing congestion control mechanisms.AT&T (UK) Ltd, Englan
Statistical multiplexing and connection admission control in ATM networks
Asynchronous Transfer Mode (ATM) technology is widely employed for the transport of network traffic, and has the potential to be the base technology for the next generation of global communications. Connection Admission Control (CAC) is the effective traffic control mechanism which is necessary in ATM networks in order to avoid possible congestion at each network node and to achieve the Quality-of-Service (QoS) requested by each connection. CAC determines whether or not the network should accept a new connection. A new connection will only be accepted if the network has sufficient resources to meet its QoS requirements without affecting the QoS commitments already made by the network for existing connections. The design of a high-performance CAC is based on an in-depth understanding of the statistical characteristics of the traffic sources
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