Definition Data Communications - Assignment Example

Data Communications Name: Institution: Date: Question 1 (22 marks) – Transport Layer a) As we have seen, the Internet layer of TCP/IP has two protocols – IPv4 and IPv6. The transport layer provides two main protocols TCP and UDP (along with some special-purpose, minor protocols). But these are for very different reasons. Why are the Internet and Transport layers very different in providing two protocols? (8 marks) The transport layer has to protocols; the TCP and UDP. The exchange of data between the devices on in the communication channel may happen in two different ways depending on features of these two different protocols. These are the differences between the TCP and the UDP. The TCP is connected based, the data makes its way across from source to destination. The UDP is not connection based meaning that one system can send a load of data to another and the relationship ends (Kumar & Rai, 2012). The other important feature of TCP IS reliability that implies all data is acknowledged. On the other hand, UDP is unreliable and there is no data acknowledgement. In the IP protocols there are no two ways of identifying the source and the destination devices in the internet layer. Therefore, in the internet layer there is only one way of functioning whereas for the transport layer there are two and the transport is unique and different from the internet layer through providing two ways. b) Since UDP does very little that is different from IP, why do we even have a transport layer such as UDP? (7 marks) Even though the UDP does very little that is different from IP, there are many differences between the IP and the UDP that shows that UDP should still exist. The differences include, the UDP is suitable for applications that requires fast, efficient transmission. There are applications that can perform better in UDP than in TCP since there UDP does not use many servers like TCP. The error recovery is not attempted under the UDP, it is faster compared with the TCP. This happens because the UDP is a “best effort” protocol compared with the IP that has comparatively lower speed (Kumar & Rai, 2012). The UDP is also simple to use for networks because it requires less processing at the transmitting and receiving of hosts. c) Describe how DDoS attacks may be mounted against TCP and UDP services. In what way will being connection oriented be different for TCP and UDP? (7 marks)
 The DDOS has different ways of being mounted on different protocols depending on the features of these protocols and the propensity to errors in the implementation. The UDP has many features compared to TCP that makes it easier to mount a DDOS in it. The first feature of UDP is that it lacks the session context meaning that the majority of the transactions happening over this protocol are unencrypted. This make is possible for being tapped and an attack mounted. This happens when a third party, and not the intended recipient generates a response to dupe original querrier (Kumar & Rai, 2012). For the DDOS, the UDP servers need to answer all queries. For the TCP, the weakness in installation makes it possible to mount an attack. The TCP is connection-oriented meaning that when a message or a file is sent, it will get delivered unless the connection fails. Unlike TCP, the UDP is not connection-oriented and when data is sent, there is no assurance that it will be delivered. Question 2 (22 marks) – IP Addressing a) Perform the following boolean operations on the given bit patterns (3 marks) i. not 11100010 0001110 ii. 11100010 or 00001110 = 11100010 OR 00001110 =11101110 iii. 11100010 and 00001110 11100010 And 00001110 =00000010 b) What are the subnet masks for the following slash address blocks? (3 marks) i. /9 255.128.0.0 i. /17 255.255.128.0 ii. /31 255.255.255.255 c) Are the following address masks legal? If so, what are their slash forms? If not, why are they not legal? (4 marks) i. 255.255.248.0 Legal, the slash notation is /21 ii. 255.224.252.0 not legal, it has not used the fourth entirely to move to third. iii. 255.255.255.224 legal, slash notation is /27 iv. 255.255.156.0 not legal, it does not meet the notations for /17 or /18 d) How many computers are in networks with the following address blocks? (2 marks) i. /13 524,288 IP addresses. From 2^19 ii. /26 64 IP addresses from 2^6 e) A small company is assigned the class C network 205.67.35.0. You need to divide this network to provide subnets for three departments using fixed-length subnetting. The departments are approximately the same size. Show the network and broadcast addresses for each subnet. Show the slash notation. How many hosts are on each subnet? Are the resulting subnets class C networks? (10 marks)
 According to Singh (2015), Class C mask uses the last octet for host addressing. Thus, the last octet, the subset zero is utilized. The slash notation = /24 This gives 254 IP addresses for the hosts 254/3 = 85 hosts on each subnet This is class C subnets because they have been distributed from the last octet of the class network provided. Question 3 (20 marks) – Wireless a) Explain why CSMA/CD scheme used in traditional Ethernet LANs cannot be used in 802.11 wireless LANs. (5 marks) The CSMA/CD happens over the cables while 802.11 wireless LANs happens in te space as the medium. Among other number of reasons that include the mode of operation and the use of the network infrastructure, CSMA/CD cannot be used in the same way. When the medium is attached to different nodes, each node will monitor whether there is current flowing in the cables before it can transmit data. When the cable is declared free, then the node will transmit. There are instances when two or more nodes will transmit at the same instance and thus causing the collision. The CD stands for collision detention and happens when the scheme institutes the Collision Detection (CD) to ensure that when there is a collision in data streams. Most important is that this happens through the cable medium. When it comes to the 802.11 wireless LANs, this medium is not cables, it provides the basis for wireless network products through the use of the Wi-Fi brand (Kim & Lee, 1999). Therefore, CSMA/CD scheme that is used in traditional Ethernet LANs cannot be used in 802.11 wireless LANs because in the difference in the features and mode of operation. b) A supermarket uses WiFi to enable staff to check inventory levels and to perform price checks. Staff have complained that the wireless scanners they use to check stock levels do not work reliably in some isles. The supermarket manager has contracted you to diagnose the wireless problems and correct them.
 
 The supermarket is 60m by 40m.
 Assume that the useful range of WiFi within the warehouse will be 15m radius. 
The access points are organised into a grid with the following channel allocations: Ch1 Ch6 Ch1 Ch6 Ch1 Ch6 i. You have determined that the channel allocations are not optimal, how would you improve upon the current channel allocations? (10 marks) The reasons for the weak signal strength or interference of from other channels and the proposed optimization will seek to correct these weaknesses. The channel allocation and the dimensions of the space raises the possibility of channel interference. The optimization will seek to improve the access and the quality of the WiFi signal strength in every access point. In improving the quality, the signal that is estimated at each access point within the allocated channels should be ensured to be greater than the threshold with which the minimum rate is guaranteed. In this approach the maximum of channel utilization will be minimized at every channel allocation or access point. To correct the possibility of channel interference, it will also be ensured that for much allocated channel, there will be only one access point bandwidth that can be used by the clients to ensure there is not interference. It will also be ensured that the total traffic demand at every allocated channel will be less than the wireless link bandwidth that is provided by an access point (Lee, et al., 2002). The optimization will involve lowering the dimensions of the channels while the signal strength remain the same. ii. As you are reconfiguring the access points you notice that none of them currently have any security enabled. Is this a problem, and if so, what type of security would you recommend? (5 marks) This is a major problem because it poses threat to the company data from the malicious attackers who might perpetrate DDOS or accessing the network without the authority. The unsecure WLAN is open to accidental associations or casual eavesdropping that could jeopardize the company data. The securing of the company wireless network will protect the company from unwanted security concerns and will control the individuals who can access the wireless network (Phifer, 2014). Depending on the functions of each channel allocation, the company would like to exclude the other channels from access this network, therefore, security will be necessary. With security, it means that the inventory access point cannot access sales access point unless there is prior knowledge. The securing of the networks will also protect the irresponsible use of network by clients or unsecured “rogue” access points. However, addressing this will be easy because the WLAN comes with standard security with authentication and encryption that can be enabled to secure the network, these authentication and encryption features are disabled by default whenever the wireless network is implemented. Bibliography Kim, J. H. & Lee, J. K., 1999. Performance of Carrier Sense Multiple Access with Collision Avoidance Protocols in Wireless LANs. Wireless Personal Communications, 11(2), pp. 161-183. Kumar, S. & Rai, S., 2012. Survey on Transport Layer Protocols: TCP & UDP. International Journal of Computer Applications, 46(7), pp. 20-25. Lee, Y., Kim, K. & Choi, Y., 2002. Optimization of AP Placement and Channel Assignment in Wireless LANs. Seoul National University. Phifer, L., 2014. WLAN security: Best practices for wireless network security. Tech Target. Singh, A. K., 2015. Internet Protocol (IP) Address – Subnetting and Supernetting. International Journal of Emerging Trends & Technology in Computer Science (IJETTCS), 4(5(2)), pp. 87-90. Read More