Network Simulator Essay Example for Free

Network Simulator EssayINTRODUCTIONIEEE 802.11 is the de facto standard for WLANs. It specifies both the medium access control (MAC) and the physical (PHY) layers for WLANs. The MAC layer operates on top of bingle of several physical layers. Medium access is performed utilization Carrier Sense Multiple Access with Collision Avoidance. However, simple CSMA is susceptible to the enigmatical node problem, curiously in so called ad hoc net incomes where a node may communicate directly with every other node in range or using intermediate nodes as relays otherwise. Hidden nodes cause costly packet collisions and thus significantly affect network performance. In order to combat the enigmatical node problem, a mechanism known as Request to Send/Clear to Send (RTS/CTS) handshake is often used.RTS/CTS mechanism is supported in the IEEE 802.11 family of standards. The RTS/CTS mechanism was ab initio proposed in a protocol called Multiple- Access with Collision Avoidance (MACA). Fr om a network point of view, one of the primary reasons for using the RTS/CTS mechanism is to avoid network congestion resulting from frequent packet collisions. Figure 1 depicts a conceptual through and throughput versus Packet sizing curve for a network. In the presence of congestion, the throughput goes to zero as the Packet Size is increased beyond a certain economic value. A properly designed network, on the other hand, maintains the maximum throughput as the Packet Size goes to infinity.LITERATURE REVIEWThe IEEE 802.11 standard includes an optional feature of the RTS/CTS (Request to Send/Clear to Send) function to control seat access to the medium when collisions occur due to the hidden node. This option is also known as virtual carrier sensing. Through the proper use of RTS/CTS, you can fine-tune the operation of your wireless LAN since it solves the hidden node problem and provides additional protection against collisions. If you enable RTS/CTS on a particular station, it wi ll refrain from sending a data frame until the station completes a RTS/CTS handshake with another station, such as an access point. A station initiates the process by sending a RTS frame.The access point (AP) or another station receives the RTS and responds with a CTS frame. The station must receive a CTS frame before sending the data frame. The CTS also contains a time value that alerts other stations to hold off from accessing the medium while the station initiating the RTS transmitsits data. Thus, the use of RTS/CTS reduces collisions and improves the performance of the network if hidden nodes are present.SIMULATION ENVIRONMENTWe use Ns-3 as simulation tool. NS-3 is built using C++ and Python and scripting is available with both languages. The ns-3 library is wrapped to python thanks to the pybindgen library which delegates the parsing of the ns-3 C++ headers to gccxml and pygccxml to generate automatically the equal C++ binding glue. These automatically-generated C++ files are finally compiled into the ns-3 python module to allow users to interact with the C++ ns-3 models and core through python scripts. Graphical visualization of raw or processed data collected in a simulation is graphed using Gnuplot tool. Our experimental done in Ubuntu 11.10 with installation of all needed tools. Simulation environs based on the command below, sudo apt-get install build-essential g++ python mercurialNS-3 is available in (linux, osx, cygwin, mingw) and we deploy Development version http//code.nsnam.org/ns-3-dev. The development version is usually immutable a lot of people use it for daily work.RESULT ANALYSISThe results analysis are based on the spare-time activity factors* Enabling and disabling RTS/CTS* communications protocol bases, either UDP or TCP* WLAN standards which are IEEE 802.11a, IEEE 802.11b, IEEE 802.11g* Variation of Throughput, Packet Loss Ratio, Delay with Packet Size and wireless fidelity Nodes. From the graphs below result obtained through the f ollowing* Disabling and enabling RTS/CTS* UDP protocol used* IEEE 802.11b standard used* Variation of Packet Size (500-2200)Considering the second result with use of TcpTahoe, TcpNewReno, TcpReno and UDP transport protocols with the following* Disabling and enablingRTS/CTS* UDP protocol used* IEEE 802.11b standard used* Variation of Packet SizeFig. Tahoe 1Fig. Tahoe 2Fig. Tahoe 3Fig. Reno 1Fig. Reno 2Fig. Reno 3Fig. Newreno 1Fig. Newreno 2Fig. Newreno 3Considering the third result for different IEEE802.11 standards (802.11a, 802.11b and 802.11g).* Disabling and enabling RTS/CTS* TCP protocol used* IEEE 802.11a/ IEEE 802.11b/ IEEE 802.11g standard used* Variation of Wifi NodesFig. 802.11a (i)Fig. 802.11a (ii)Fig. 802.11a (iii)Fig. 802.11b (i)Fig. 802.11b (ii)Fig. 802.11b (iii)Fig. 802.11g (i)Fig. 802.11g (ii)Fig. 802.11g (iii)CONCLUSIONFrom the result analysis obtained above, it is clearly seen that IEEE 802.11a has better performance compared to other wireless standards due to the f ollowing reasons* Provides maximum data rate of about 54 Mbps.* It operates in 5GHz ISM band.* It is not subjected to interference from other products designed ,* It is characterized with higher throughput* It is suited for connectivity provision over densely populated user environment besides from the result analysis above, TCP Tahoe is the best TCP variant due to the following facts * It is characterized by fast retransmit.* It is characterized by fast recovery.* Reduce congestion windowpaneREFERENCES1. E. Ayanoglu, S. Paul, T. F. LaPorta, K. K. Sabnani, and R. D.Gitlin, AIRMAIL A link-layer protocol for wireless networks, ACMACM/Baltzer Wireless Networks J., vol. 1, pp. 4760, Feb. 1995. 2. A. Bakre and B. R. Badrinath, Handoff and system support for indirectTCP/IP, in Proc. 2nd Usenix Symp. Mobile and Location-IndependentComputing, Apr. 1995. 3. S. Keshav, REAL A Network Simulator, University of atomic number 20 at *Berkeley, Berkeley, CA, USA, Tech. Rep., 1988.*4. V. Naoumov a nd A. Gross, Simulation of Large Ad Hoc Networks, In Proceedings of the 6th ACM Workshop on Modeling, Analysis, and * Simulation of Wireless and Mobile Systems, 2003.