Herein is a research paper which depicts the use of emulation for testing purpose to illustrate the propagation of signals in the satellite communication. With the software NIST Net we could emulate any kind of links and get the results with actual packets in consideration. The procedure testing any network related protocol, link or equipment it is first simulated and if the results are satisfactory then the emulation is done which is in actual a real test bed so if the outputs are satisfactory then it is directly used as a part of the existing network. With Linux as the operating system installed in three computers and one of them acting as router which has NIST Net installed in it we could generate all the parameter that need to be considered in satellite communication. We can change the bandwidth, delay, drop rate with respect to congestion etc so that we could consider the parameters of actual links that will be involved and can get the idea of the throughput with the system and hence we could get the idea of the output we will be getting before hand. All new protocols go through this testing procedure before getting into implementation.
Keywords: TCP, FTP, LEO, MEO, GEO, NIST Net, Congestion, Corruption.
[...] NIST Net has been used for emulation up to line rate over 100Mbps Ethernet with typical “throw-away” machines (200 MHz Pentium-class processors and PCI-based 10/100 Ethernet cards). On current generation machines, NIST Net has been successfully used at line rate with gigabit Ethernet cards and 622 Mbps OC12 interfaces. Emulation, as defined here, is a combination of two common techniques for testing network code: simulation, which we can define as a synthetic environment for running representations of code; and live testing, a real environment for running real code. [...]
[...] In a sense, emulation can then minimize the intellectual “investment” required for network testing. NIST Net extends this metaphor by deliberately simplifying its installation and basic usage. Thousands of people throughout the world have successfully installed and used the emulator for a wide variety of projects, even those with no prior experience with Linux. It has proven particularly useful in academic settings for class laboratories and student research projects. In this paper, we discuss the features and design of the emulator, emphasizing the approaches taken to ensure simple installation and use, and to minimize processing overhead, while still providing useful network emulation facilities. [...]
[...] EMULATION RESULTS Table 1 : DELAY 400ms(MEO) Size Drop rate Drop rate 1MB 1.1 e + 02 .95e + sec 11 sec 2MB 1.2 e + 02 1e + sec 20 sec 5MB 1.3 e + e + sec 0.001 sec By the readings achieved we conclude that there has been a decrease in the data rates when we increase the drop rates to which will cause reduction in the speed of communication. The actual TCP was made for wired communication but when using in satellite communication it gives results [...]
[...] DRD does have shortcomings compared to more complex router congestion control mechanisms such as Random Early Detection , principally because DRD can result in coordination of packet drops and retransmissions across multiple flows after certain types of instantaneous traffic bursts. However, these shortcomings are not relevant for NIST Net, where each flow is treated separately, and hence cross-flow-coordinated drops do not occur. In this situation, DRD's computational simplicity makes it the preferred choice. The NIST Net implementation makes the minimum and maximum thresholds for DRD, and hence the steepness of the drop probability ramp, settable parameters. [...]
[...] Herein the first one is assigned the ip and it is connected via a cross cable link to the second one which is having the ip address the second ip address of the second pc is so that it represents the pc of different network and the last pc is assigned the ip so that they represent terminals of different networks and the emulation software is installed in the center pc default gateway for the first pc is given the ip address of 3. [...]
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