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Some applications of simulation require that the model state be advanced in simulation time faster than the wall-clock time advances as the simulation executes. This faster than real-time requirement is crucial, for instance, when a simulation is used as part of a real-time control system, working through the consequences of contemplated control actions, in(More)
The IEEE 802.11 standard is a widely used protocol for wireless communications. It is a moderately complex algorithm involving collision detection, dynamic backoffs, channel reservations, and acknowledgments. Detailed simulation of 802.11 requires some care, and considerable execution time. We are interested in developing a rapidly executable model of(More)
Delay Tolerant Networking (DTN) considers how to provide communication in contexts where it is unreasonable to assume end-to-end connectivity. Network devices exchange buffered messages when they come into communication range; messages may be buffered and carried physically several times before ultimately being received. Service characteristics of a DTN(More)
The bulk of Internet traffic is carried using variants of the TCP protocol. A realistic simulation-based performance study of any distributed application run over the Internet (e.g. reliable multicast) must therefore account for the impact that TCP background traffic has upon application behavior. Because TCP flows are shaped by other TCP flows, it is(More)
Concerns about noncompletion and the quality of the 1st-year student experience have been linked to recent changes in higher education such as modularisation, increased class sizes, greater diversity in the student intake and reduced resources. Improving formative assessment and feedback processes is seen as one way of addressing academic failure, of(More)
A number of network simulators are now capable of simulating systems with millions of devices, at the IP packet level. With this ability comes a need for realistic network descriptions of commensurate size. This paper describes our effort to build a detailed model of the U.S. Internet backbone based on measurements taken from a variety of mapping sources(More)
Partitioning is an important issue in a variety of applications. Two examples are domain decomposition for parallel computing and color image quantization. In the former we need to partition a computational task over many processors; in the latter we need to partition a high resolution color space into a small number of representative colors. In both cases,(More)
After several years of research, we n o w h a ve the capability of modeling the Internet at scales on the order of 100,000 multi-protocol hosts IP, TCP, clienttserver applications and routers OSPF, BGP-4, with long-range correlated IP packet traac 11. Getting to this point required the design of a scalable Internet modeling framework SSFNET, a scalable(More)