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  1. 1. Jashanpreet Kaur, Amoldeep kaur / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.585-588 Evaluating Data drop in Wireless LAN using TTL and Fragmentation Jashanpreet Kaur*, Amoldeep kaur ** *(Department of Computer Science, Punjabi University, Patiala) ** (Department of Computer Science, Punjabi University, Patiala)ABSTRACT Wireless network refers to thetransmission of data and voice over radio waves.The demand for reliable delivery of data inWireless Local Area Networks (WLANs) isbecoming ever more important due to the trendtowards converged communication networks.The size of the packets is a very importantperformance factor. Too small packets yield poorefficiency; too large packets are likely to getdropped. We evaluate data dropped performancemetric with and without the use of our technique.OPNET has been used to evaluate the varioussimulation results. Simulation has been carriedfor both the scenarios i.e. flow of data packetswith TTL and fragmentation and without it. Thedata drop is reduced to great extent with the useof TTL and Fragmentation and also gives ahigher throughput.Keywords - Data Dropped, Fragmentation,OPNET, Time-to-Live, Wireless LANI. INTRODUCTION A wireless LAN or WLAN is linking of Fig. 1 Wireless LAN Networktwo or more computers without using wires. AsWLANs eliminate the need of wires for connecting The data packet size is a major factor in reliableend users, they provide a very easy, viable access to delivery of data. If the data packet size is too small,the network and its services. WLAN utilizes spread- it yields poor efficiency and if the size is too large itspectrum modulation. It enabled mobile is likely to be dropped. The data drop will thuscommunication and Wireless networking. WLANs result in poor results. So it is must that the dataallow users in a local area, such as a university packet should reliably reach its destination. To getcampus or library; to form a network or gain access this thing done TTL and Fragmentation are the internet [1].WLAN is standardized as 802.11 The simulation result is evaluated in a form ofby IEEE. The most prominent specifications for graph.wireless LANs were developed by the IEEEworking group. The paper is organized around four sections. SectionIn a typical WLAN configuration a radio I discusses paper’s introduction. In Section II, wetransmitter/receiver (transceiver) called a Wireless study the related work. Section III tells about theAccess Point (WAP), connects to a wired network simulation technology and the results thereafterfrom a fixed location using a standard Ethernet obtained with the use of TTL and Fragmentation.(IEEE 802.3) cable connection. At a minimum, the The conclusion has been summed up in section IV.access point receives, buffers, and transmits databetween the WLAN and the wired network II. RELATED WORKinfrastructure. Figure 1 shows the basic wireless Wireless local area networks (WLANs)LAN network. based on the IEEE 802.11 standard are one of the fastest growing wireless access technologies in the world today. The low-cost and high-speed WLANs can be integrated within the cellular coverage to provide coverage for high-speed data services, thus 585 | P a g e
  2. 2. Jashanpreet Kaur, Amoldeep kaur / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.585-588becoming an integral part of next generation They compute a value for each bundle as a functionwireless communication networks. The performance of the priority of the bundle. Then, they compute theof Wireless local area network (WLAN) degrades, risk rate of the bundle as the risk divided by thewhen congestion conditions occurs with many real value. They also keep records regarding theapplications due too large packet size or other aggregate risk and the aggregate value of thereasons. These effects are a serious hurdle for the bundles accepted so far to compute the mean riskdeployment and advancement of wireless and the mean value. If the risk rate of an incomingtechnologies and, therefore, a congestion control bundle exceeds the mean risk rate over the bundle’sremedy is needed [2]. residual TTL, then the bundle is rated as the abovePeter Dely and Andreas Kassler have discussed average risk bundle and they refuse it. Otherwise,about the overhead which is induced by sending the they accept the bundle.small packets. Due to large MAC layer overhead,applications such as Voice over IP, which send III. SIMULATION METHODOLOGY ANDmany small packets, show poor performance in RESULTSWMNs [3]. Packet aggregation increases the OPNET modeler 14.5 is used to developcapacity of IEEE 802.11-based WMNs by the simulation and analysis for this paper. Theaggregating small packets into larger ones and performance metric that is used here is data droppedthereby reducing overhead. In this work, they have ( retry threshold limit) . A snap shot of the systempresented FUZPAG, novel packet aggregation simulation model is captured in Figure 2. Thearchitecture for IEEE 802.11-based wireless mesh proposed scenario consists of a wireless Networknetworks. It uses fuzzy control to determine the implemented as a WLAN network, which wasoptimum aggregation buffer delay under the current modeled within an area of 600 m*400 m. It consistschannel utilization. For different network topologies of 50 nodes and simulation goes for total one hour.they show that FUZPAG outperforms standard The steps used to make the above network are asaggregation in terms of end-to-end latency under a follows:wide range of traffic patterns. 1. A subnet in hexagonal shape is designed byBecause medium contention occurs for each packet using subnet designing module.that is transmitted in a IEEE 802.11 wireless 2. The LAN is populated with mobilenetwork, transmission of a large number of small wireless workstations (wlan_station_adv)packets can be particularly detrimental to taken from the wireless_lan_adv module ofperformance. As a result of contention overhead, the object pallet of the OPNET.end-to-end delay and energy dissipation increase 3. An access point (wlan_ethernet_slip4_adv)and the medium utilization decreases. Ramya is deployed in the LAN to theRaghavendra, Amit P. Jardosh proposed a protocol communication happen between all theto reduce contention through concatenation of nodes. The access point is a wireless lanseveral small packets into a single large packet, and based router with one Ethernet and 4 SLIPsubsequently transmit this large packet [4]. They interfaces.proposed IPAC, an IP-based packet concatenation 4. To generate data, Applications are definedprotocol that adaptively selects an appropriate by using “Application Config” node for apacket size based on the route quality. cell or subnet. 5. To configure the applications “ProfileIn [5], Burleigh et. al. proposed a proactive config” node is used for a cell.congestion control mechanism, named AutonomousCongestion Control (ACC), based on a financialmodel. The proposed solution has a set ofpredefined rules based on the local information,such as remaining storage capacity, bundle’spriority, and bundle’s TTL, for accepting orrejecting the incoming bundles. They accept theincoming bundle if the storage overrun does notoccur, that is, the projected growth of storage spaceoccupancy over the bundle’s residual TTL perioddoes not exceed the total storage space capacity ofthe node. If the above condition fails, they computethe bundle’s acceptance risk to give the bundle asecond chance. The risk of accepting a bundle is theworst-case number of byte-seconds of storage spacethat the bundle will consume. It is simply theproduct of the bundle size and its residual TTL. 586 | P a g e
  3. 3. Jashanpreet Kaur, Amoldeep kaur / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.585-588 Bytes(Constant) Fragmentation 1024 Bytes Threshold Simulation time 1 hour Now we consider the two scenarios and analyze the scenarios based on data drop. First we take in consideration the data drop without the use of TTL and Fragmentation and then using them. Fig. 2 Simulation Network ModelIn this proposed methodology, we have fragmentedthe packets flowing from sender to receiver intosmaller chunks and applied the Time-to-Liveconstraint on the packets. Simulation has beencarried for both the scenarios i.e. flow of datapackets with TTL and Fragmentation and flow ofpackets without them and results have beencalculated. Three different applications file transferprotocol (FTP) for high load, hypertext transferprotocol (HTTP) for image browsing and high videoresolution are being used to analyze the Fig. 4 Overlaid graph for Data dropped (Retryperformance. Simulation focuses on metric data Threshold)drop of network using TTL (Time-to-Live) andFragmentation. WLAN Network Parameters and The above graphs shows us that the data drop isValues for the scenarios are illustrated below: reduced to great extent with the use of TTL and Fragmentation whereas, large amount of data is TABLE 1 SIMULATION PARAMETERS dropped when there is no use of TTL and Fragmentation. The use of TTL and fragmentation Network Value results in reduced buffer overflow as the packets are Parameters fragmented into chunks. The data drop in the starting is less with the use but it goes high around Size 600*400 meters after 10 minutes. The Data drop rate after this never goes high with the use of TTL and Fragmentation. Model family WLAN IV. CONCLUSION Network scale Office In this paper, we analyze the network Data rate 54 mbps performance in terms of data dropped. Simulation results show that the performance of the network Technology WLAN could be improved with TTL and fragmentation for large packets be chosen. If the value of TTL is kept Nodes 50 high then the probability of occurrence of congestion in network becomes very high and if the Operational mode 802.11 values of TTL is very less then the data loss in the network would increase. The data packets using Packet interval time Constant(1 sec) TTL and fragmentation flowing in the network performs better giving higher throughput. Packet 4096 There is always a scope to improve the concluded results by calculating the proper values of the 587 | P a g e
  4. 4. Jashanpreet Kaur, Amoldeep kaur / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue 5, September- October 2012, pp.585-588fragmentation size and TTL and other parametersthat are required for the good performance of thenetwork.REFERENCES [1] “Introduction to Wireless LAN ", Website: [2] “The Medium Access Control Sublayer”, Computer Networks- Andrew S. Tanenbaum, Fourth edition, pp. 293 [3] Peter Dely, Andreas Kassler, Nico Bayer, Hans-Joachim Einsiedler, Dmitry Sivchenko Deutsche Telekom Laboratories, “FUZPAG:A Fuzzy- Controlled Packet Aggregation Scheme for Wireless Mesh Networks”, pp-778-782, 2010. [4] Raghavendra R, Amit P.Jardosh, “IPAC- An IP based Adaptive Packet Concatenation for Multihop Wireless Networks” in the conference on System Signals and Computer, 2006. [5] S. Burleigh, E. Jennings, and J. Schoolcraft, “Autonomous congestion control in delay-tolerant networks,” in SpaceOps, 2006, pp. 70–79. 588 | P a g e