No description available.

Seamless middleware integration requires conversion of the message format from the source of the request to that of its target. A number of solutions have been proposed and implemented, but they lack wide applicability and ease of use. This thesis proposes an improved solution based-on dynamic protocol-level systems integration using configuration, rather than programming. This allows large complex enterprises to extend and enhance their existing systems more easily. The major components of this solution are a Middleware Protocol Definition Language (MPDL) based on the Object Management Group (OMG) Interface Definition Language (IDL) that can describe a wide range of protocols declaratively, and a run-time environment, The Ubiquitous Broker Environment (TUBE), that takes these protocol descriptions and performs the necessary mediation and translation. The MPDL can describe a range of synchronous, asynchronous, object-based, and binary and text-based protocols. Ea ch protocol need only be described once, and the framework provides a means to easily implement special extensions to the protocol. Further, this approach can be used as the basis for developing new middleware protocols; the protocol used internally by TUBE is itself defined and executed using this approach. TUBE has been implemented and successfully tested across a range of commonly used middleware, including synchronous, asynchronous, object-based, binary and text-based protocols. Key components of the system are currently in operation in a large Australian corporation.

This paper discusses current network technologies and protocols and presents a simulation study of the most common networking protocol used today, TCP/IP. The TCP/IP protocol stack has many inherent problems that will be shown through this simulation study. Using the SimpleScalar Toolset, the significance of the data copying and checksumming performed in TCP/IP will be shown along with the architecture needed to support the processing of TCP/IP. Solutions for these TCP/IP pitfalls including a zero-copy protocol and a design for an intelligent network interface card will also be presented. / Graduation date: 2000

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Border Gateway Protocol (BGP) prefix hijacking is a serious problem in the Internet today. Although there are several services being offered to detect a prefix hijack, there has been little work done to prevent a hijack or to continue providing network service during a prefix hijack attack. This thesis proposes a novel framework to provide defense against prefix hijacking which can be offered as a service by Content Distribution Networks and large Internet Service Providers. Our experiments revealed that the hijack success rate reduced from 90.36% to 30.53% at Tier 2, 84.65% to 10.98% at Tier 3 and 82.45% to 8.39% at Tier 4 using Autonomous Systems (ASs) of Akamai as Hijack Prevention Service Provider. We also observed that 70% of the data captured by Hijack Prevention Service Provider (HPSP) can be routed back to Victim. However if we use tunneling, i.e. trying to route data to neighbors of Victims which in turn sends the traffic to Victims, we observed that data can be routed to Victim 98.09% of the time. Also, the cost of such redirection is minimal, since the average increase in path length was observed to be 2.07 AS hops.

No description available.

Border Gateway Protocol (BGP) prefix hijacking is a serious problem in the Internet today. Although there are several services being offered to detect a prefix hijack, there has been little work done to prevent a hijack or to continue providing network service during a prefix hijack attack. This thesis proposes a novel framework to provide defense against prefix hijacking which can be offered as a service by Content Distribution Networks and large Internet Service Providers. Our experiments revealed that the hijack success rate reduced from 90.36% to 30.53% at Tier 2, 84.65% to 10.98% at Tier 3 and 82.45% to 8.39% at Tier 4 using Autonomous Systems (ASs) of Akamai as Hijack Prevention Service Provider. We also observed that 70% of the data captured by Hijack Prevention Service Provider (HPSP) can be routed back to Victim. However if we use tunneling, i.e. trying to route data to neighbors of Victims which in turn sends the traffic to Victims, we observed that data can be routed to Victim 98.09% of the time. Also, the cost of such redirection is minimal, since the average increase in path length was observed to be 2.07 AS hops.

This paper proposes a hybrid routing protocol based on the k-hop clustering structure for MANETs. The source sends packets to the destination directly if it is in the source¡¦s neighbor table; otherwise the source reactively sends the route request packet (RREQ) to trigger the routing process. Instead of adopting the nodes that forwards the RREQ as the route between the source and destination, the route reply packet (RREP) is broadcasted via the nodes in the clusters that the RREQ has ever passed to find the route. The route constructed in this way can avoid the clusterheads always being in the transmission route and collapsing due to overloading. In comparison with the Cluster Based Routing Protocol (CBRP), the proposed protocol can distribute the communication workload from the clusterheads to member nodes. Simulation results demonstrate that the proposed protocol has better packet delivery ratio and end-to-end delay time than that of CBRP.

The value of establishing design requirements is well-argued and the need for their clear representation in the material used to brief designers is recognised. However, very little attention has been given as to how the design requirements should be represented for use by industrial designers and whether, or how, such representations benefit design. The research presented in the thesis aims to explore approaches to the organisation and presentation of design brief requirements for effective use by designers. We first examined how design requirements are specified, organised and represented in theory and practice. The role of design requirements in the design problem-solving process was analysed to gain insight into how explicit requirement representation might benefit the design process. An experimental study, using protocol analysis, was then conducted to investigate the impact of explicitly representing design requirements in achieving the theoretical benefits for such representations. The results indicate the explicit representation of design brief requirements yields systematic enhancements including increased utilisation of design requirements and the production of solutions assessed as meeting design requirements more successfully. Thus, the findings support the proposition that the manner in which design requirements are represented will impact upon the design process and the designers' performance. In line with the research findings, recommendations are made about how the organisation and presentation of requirements may be manipulated to achieve maximum positive enhancement and minimal negative reduction in the quality of the design process

This thesis is concerned with the study of dynamic wavelength assignment in wavelength division multiplexed (WDM) passive optical networks (PONs), which is one option for implementing WDM in access networks. A discrete event simulation is developed using the Block Oriented Network Simulator (BONeS) package to compare a WDM PON using dynamic wavelength allocation with one utilizing fixed wavelengths. The model is used in conjunction with a traffic profile constructed using market research data to show bandwidth savings for dynamic assignment of between 4 and 20 % depending on the number of customers and the services distributed. It is shown that the alternative approach of using the Erlang laws underestimates these benefits. An upstream protocol for real-time services with a Fibre To The Cabinet (FTTCab) configuration is developed for single wavelength PONs. It is shown that using connectionbased information does not improve the performance of such a protocol. A segment based protocol which provides timing information on cell arrivals to reduce CDV is modelled and optimized. The results show that a frame of 766 ps divided into 10 segments allows the International Telecommunication Union (ITU) delay and cell delay variation (CDV) targets to be met. The protocol and modelling process is then extended to a WDM system with multiple service classes and non-negligible tuning times. A mechanism for masking tuning latencies which achieves a throughput efficiency of over 98% is designed and modeled. An improvement in performance is then demonstrated for rapid retuning at frame level compared with wavelength assignment at connection set-up. Finally, a new architecture for transferring the tunable devices from the optical network units (ONUs) to the optical line termination (OLT) is proposed. The reduction in the number of tunable components enables cost savings. The efficient transmission of broadcast and multicast traffic is demonstrated using this architecture.