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Networking research often relies on simulations to design, analyze and test various protocols and mechanisms. These simulations should be performed in environments similar to the ones in which the protocols will be deployed. As such, the workload with which these protocols are tested in the simulation environment should match the properties of the traffic that is encountered in the real network. Source-level modeling of traffic is one in which a set of applications, or a set of users, is simulated to generate traffic that is characteristically similar to the traffic found on real network. This type of modeling helps in conducting realistic simulations. The source-level a-b-t model and accompanying tmix traffic generator for testbeds was developed at the University of North Carolina by F. Hernandez Campos. We have implemented this tmix traffic generator in the popular ns-2 and GTNetS network simulators. We show that our module can replay the connection vectors generated by the a-b-t model and generate workloads that are characteristically similar to the traffic found on a real internet link. In this thesis we describe in detail the design and implementation of our tmix module in ns-2 an

Tmix: A Tool for Generating Realistic TCP Application Workloads in ns-2

In order to perform realistic network simulations, one needs a traffic generator that is capable of generating realistic synthetic traffic in a closed-loop fashion that “looks like ” traffic found on an actual network. We describe such a traffic generation system for the widely used ns-2 simulator. The system takes as input a packet header trace taken from a network link of interest. The trace is “reverse compiled ” into a source-level characterization of each TCP connection present in the trace. The characterization, called a connection vector, is then used as input to an ns module called tmix that emulates the socket-level behavior of the source application that created the corresponding connection in the trace. This emulation faithfully reproduces the essential pattern of socket reads and writes that the original application performed without knowledge of what the original application actually was. When combined with a network path emulation component we have constructed called DelayBox, the resulting traffic generated in the simulation is statistically representative of the traffic measured on the real link. This approach to synthetic traffic generation allows one to automatically repro-duce in ns the full range of TCP connections found on an arbitrary link. Thus with our tools, researchers no longer need make arbitrary decisions on how traffic is generated in simulations and can instead easily generate TCP traffic that represents the use of a net-work by the full mix of applications measured on actual network links of interest. The method is evaluated by applying it to packet header traces taken from campus and wide-area networks and comparing the statistical properties of traffic on the measured links with traffic generated by tmix in ns

Tmix: A Tool for Generating Realistic TCP Application Workloads in ns-2

In order to perform realistic network simulations, one needs a traffic generator that is capable of generating realistic synthetic traffic in a closed-loop fashion that "looks like" traffic found on an actual network. We describe such a traffic generation system for the widely used ns-2 simulator. The system takes as input a pa ket header tra e taken from a network link of interest. The tra e is "reverse ompiled" into a sour e-level hara terization of ea h TCP onne tion present in the tra e. The hara terization, alled a onne tion ve tor, is then used as input to an ns module alled tmix that emulates the so ket-level behavior of the sour e appli ation that reated the orresponding onne tion in the tra e. This emulation faithfully reprodu es the essential pattern of so ket reads and writes that the original appli ation performed without knowledge of what the original appli ation a tually was. When ombined with a network path emulation omponent we have onstru ted alled DelayBox, the resulting traffi generated in the simulation is statisti ally representative of the traffi measured on the real link. This approa h to syntheti traffi generation allows one to automatically reproduce in ns the full range of TCP connections found on an arbitrary link. Thus with our tools, resear hers no longer need make arbitrary decisions on how traffic is generated in simulations and an instead easily generate TCP traffic that represents the use of a net-work by the full mix of applications measured on a tual network links of interest. The method is evaluated by applying it to pa ket header tra es taken from ampus and wide-area networks and omparing the statisti al properties of traffi on the measured links with traffic generated by tmix in ns