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computer certification » software » network simulation » general simulators » ntcuns 1.0
DescriptionThe NCTUns 1.0 network simulator is a high-fidelity and extensible network simulator capable of simulating various protocols used in both wired and wireless IP networks. Its core technology is based on the novel kernel re-entering methodology invented by Prof. S.Y. Wang [1, 2] when he was pursuing his Ph.D. degree at Harvard University. Due to this novel methodology, the NCTUns 1.0 network simulator provides many unique advantages that cannot be achieved by traditional network simulators such as ns-2 [3] and OPNET [4].After obtaining his Ph.D. degree from Harvard University in September 1999, Prof. S.Y. Wang returned to Taiwan and became an assistant professor in the Department of Computer Science and Information Engineering, National Chiao Tung University (NCTU), Taiwan, where he founded his ¡§Network and System Laboratory.¡¨ Since that time, Prof. S.Y. Wang has been leading and working with his students to design and implement the NCTUns 1.0 (the NCTU Network Simulator 1.0) for more than three years. The NCTUns 1.0 network simulator has many useful features listed as follows: It can be used as an emulator. An external host in the real world can exchange packets (e.g., set up a greedy TCP connection) with nodes (e.g., host, router, or mobile station) in a network simulated by the NCTUns 1.0. Two external hosts in the real world can also exchange their packets via a network simulated by the NCTUns 1.0. This feature is very useful as the function and performance of real-world devices can be tested under various network conditions. It directly uses the real-life FreeBSD¡¦s TCP/IP protocol stack to generate high-fidelity simulation results. By using a novel kernel re-entering simulation methodology, a real-life UNIX (e.g., FreeBSD or Linux) kernel¡¦s protocol stack can be directly used to generate high-fidelity simulation results. It can use any real-life existing or to-be-developed UNIX application program as a traffic generator program without any modification. Any real-life program can be run on a simulated network to generate network traffic. This enables a researcher to test the functionality and performance of a distributed application or system under various network conditions. It can use any real-life UNIX network configuration and monitoring tools. For example, the UNIX route, ifconfig, netstat, tcpdump, traceroute commands can be run on a simulated network to configure or monitor the simulated network. It can simulate both wired and wireless networks. A wired network is composed of fixed nodes and point-to-point links. A wireless networks is composed of IEEE 802.11 (b) mobile nodes and access points (both the ad-hoc mode and infra-structure mode are supported). It can simulate various networking devices. For example, Ethernet hubs, switches, routers, hosts, IEEE 802.11 (b) wireless stations and access points, WAN (for purposely delaying/dropping/reordering packets), Wall (wireless signal obstacle), etc. It can simulate various protocols. For example, IEEE 802.3 CSMA/CD MAC, IEEE 802.11 (b) CSMA/CA MAC, learning bridge protocol, spanning tree protocol, IP, RIP, OSPF, UDP, TCP, HTTP, FTP, Telnet, etc. Its simulation speed is high. By combining the kernel re-entering methodology with the discrete-event simulation methodology, a simulation job can be finished quickly. Its simulation results are repeatable. If the chosen random number seed for a simulation case is fixed, the simulation results of the case will be the same. It provides a highly-integrated and professional GUI environment. This GUI can help a user (1) draw network topologies, (2) configure the protocol modules used inside a node, (3) specify the moving paths of mobile nodes, (4) plot network performance graphs, (5) playing back the animation of a logged packet transfer trace, etc. Its simulation engine adopts an open-system architecture and is open source. By using a set of module APIs that are provided by the simulation engine, a protocol module writer can easily implement his or her protocol and integrate it into the simulation engine. It supports remote and concurrent simulations. The NCTUns 1.0 adopts a distributed architecture. The GUI environment and simulation engine are separately implemented and use the client-server model to communicate. Therefore, a remote user using the GUI program can remotely submit his or her simulation job to a server running the simulation engine. The server will run the submitted simulation job and later return the results back to the remote GUI program for analyses. This scheme can easily support the server farm model in which multiple simulation jobs can be performed in parallel on different server machines. This can increase the total simulation throughput. It supports more realistic wireless signal propagation models. In addition to providing the simple (transmission range = 250 m, interference range = 550 m) model that is commonly used in the ns-2, the NCTUns 1.0 also provides a more realistic model in which a received bit¡¦s BER is calculated based on the used modulation scheme, the bit¡¦s received power level, and the noise power level around the receiver. At NCTU, Prof. S.Y. Wang and his students are working hard to continuously add more functionalities and features to the NCTUns 1.0 network simulator. They want to make the NCTUns 1.0 network simulator a high quality software tool and would like to contribute it to the networking community
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