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In this paper we simulate an office LAN using IT Guru Opnet 9.1 and then we calculate the performance of this network under 10BaseT and 100BaseT Ethernet wiring standards with different frame size and finally we compare the results i.e. which standard perform better for which frame size. We find that numbers of collision counts at hubs are always more in 10BaseT, because of the nature of this standard. Hubs are always more utilized in 10BaseT, because of more retransmission attempts due to high number collisions under 10BaseT. Initially when frame size is 1500 Bytes, we find that 100BaseT standard is performing well because the switch filters more traffic. We again reduce the frame size to 1024 Bytes in this case performances are equivalent. When we further reduce frame size to 512 Bytes we get a shocking result because 10BaseT standard performs well and the switch filters more traffic. Then we come to point that if we have a low traffic LAN and we fix frame size to 512 Bytes then we have to use 10BaseT Ethernet wiring standard in the implementation of LAN because it will give us good performance as compares to 100BaseT. To our best knowledge this is the first paper that calculates the performance of a LAN under these assumptions. General Terms Guided Media, Unguided Media, Collision count, Utilization, Traffic Received and Traffic Forwarded.

MANETs have some special characteristics such as open network architecture, shared wireless medium and highly dynamic topology which make them much prone to different attacks. Denial Of service (DoS) attack, the most common of all, if occurs becomes difficult to detect and defend. One of such attacks is JellyFish attack which is further categorized as JF Reorder Attack, JF Periodic Dropping Attack and JF Delay Variance Attack. In JF delay variance attack, a JF attacker node intrudes into forwarding group and delays data packets unnecessarily for some amount of time before forwarding them which results in high end-to-end delay in the network. The performance of the network also becomes worse. JF Attack disrupts the whole functionality of Transmission Control Protocol (TCP) as in the presence of JellyFish Delay Variance Attack source retransmits packets again and again causing congestion in the network. Some amendments are required in TCP for JF Attack prone networks. In this paper a modified TCP which is capable of handling congestion in the network caused by JF Attackers is proposed. In the presence of this modified protocol named as Efficient Transmission Control Protocol (ETCP) the performance of the network (i.e. throughput, end-to-end delay etc) improves.

Wireless Sensor Networks (WSNs) are prone to various attacks in which Blackhole a kind of Denial of Service (DoS) attack is very difficult to detect and defend. In blackhole attack, an intruder captures and re-programs a set of nodes in the network to block the packets they receive instead of forwarding them towards the base station. As a result any information that enters the blackhole region is captured and not able to reach destination causing high end-to-end delay and low throughput. Previously little amount of work is done for detection and prevention of the Blackhole attack in the WSN making its detection and prevention very crucial as per network performance is concerned. In this paper initially the affect of Blackhole attack is measured on the network parameters followed by the proposal of a novel technique for the detection and prevention of Blackhole attack in WSN.

Constrained resources, the ad-hoc nature of deployment and the vulnerability of wireless media are some of the most challenging characteristics of Wireless Sensor Network (WSN) which pose a need for unique security solutions. WSNs are susceptible to various attacks, in which Misdirection a kind of Denial of Service (DoS) attack is very difficult to detect and defend. In Misdirection Attack, the intruder misdirects the incoming packets to a node other than the intended node which introduces high end-to-end delay (sometimes infinite) in the network. The performance of the network (i.e. throughput) is also degraded. Thus the detection and prevention of this attack becomes very crucial. In this paper we have proposed a novel Cluster Based Intrusion Detection and Prevention Technique for Misdirection Attack. The network parameters calculated by the use of this technique shows considerable amount of improvement in throughput while introducing small amount of delay.

Wireless Sensor Network (WSN) has a great potential to be deployed in wide range of applications like consumer, industrial and defense sectors. WSNs are susceptible to various attacks, in which misdirection a kind of Denial of Service (DoS) attack is very difficult to detect and defend. In misdirection attack, the intruder misdirects the incoming packets to a node other than the intended node. Due to this attack, high end- to- end delay (sometimes infinite) is introduced in the network and performance of the network (i.e. throughput) is degraded. In this paper we have done a topological analysis of WSN in the presence of misdirection attack and presented an algorithm for the prediction of delay and throughput. We observed that WSN performs better for tree network topology as compared to mesh topology.

In modern time people are not using 10BaseT Ethernet wiring standard in the implementation of a local area network (LAN), category 3 cables which is used for the implementation of that standard in a network is become obsolete now, it is only used in telephone lines. Our aim is to find out some parameters under which 10BaseT can work well as compare to 100BaseT standard. We want people to motivate to use 10BaseT standard because under some assumptions 10BaseT standard can work well as compare to 100BaseT. To support our idea we simulate an office LAN using IT Guru Opnet 9.1, then we calculate the performance of this network under 10BaseT and 100BaseT Ethernet wiring standards with increasing time and finally we compare the results i. e. which standard performs better. We find that numbers of collision counts at hubs are always more under 10BaseT, because of the nature of this standard. The hubs are more utilized under 10BaseT, because of more retransmission attempts due high number of collisions in 10BaseT. Hubs perform smartly in case of 100BaseT standard because they filter little bit traffic in this case but they did not filter any traffic in case of 10BaseT. Initially when time is less the switch performs better under 10BaseT because it filtered more traffic, but when we start increasing the time the performance of 100BaseT is going to improve and at one instance of time their performances are become equivalent then after that the performance of 100BaseT is become good. So in our simulation we find that if a LAN is used for a short duration of time, then we have to use 10BaseT standard in the implementation of a LAN because in this case switch filter more traffic so the performance of LAN is good here. When this LAN is used for the long time duration we have to use 100BaseT standard because in this case we got good results as compare to 10BaseT.