The OSI Model Standards - Coursework Example

Introduction to the OSI Model OSI model is a conceptual design that indicates procedures and methods applied to a data packet at each layer. It is allocated in seven different layers. Each layer contributes to a successful delivery of a data packet. Moreover, “(Open Systems Interconnection model) The International Standards Organizations OSI model serves as a standard template for describing a network protocol stack” (OSI model. 2011). The Seven different payers are defined separately below: The Physical layer is associated with electronic signaling and medium on which the data will be transmitted i.e. cables The Data Link Layer is associated with the transmission of data packets from nodes on the network. Parameters for this layer are the destination addresses. The Network Layer is associated with routing and directing data to different networks. Likewise, Local area networks, Wide area networks and Metropolitan Area Networks. The Transport layer is associated with check and balance of data packets. It ensures complete delivery of data in terms of files or messages. The Session Layer is associated with maintaining data sessions between different nodes on the network. It also analyzes and prevents collisions between data channels by prioritizing them. The Presentation Layer is associated with presenting the data by converting protocols from data conversion techniques, encryption techniques, binary conversion techniques etc. The Application layer is associated with software including email software, client / server software, FTP software, and much more. Network Components Functionality A simple definition of regenerative repeater is available in network dictionary which states it as “a device which regenerates incoming digital signals and then retransmit these signals on an outgoing circuit” The regenerative repeaters are the network devices, installed within the network to regenerate signals that may become weak or unreachable to the destination, due to long distance. These devices are implemented in long distance wired networks for transferring data geographically from one network to the other. As signals, are evolved via network cables, they become weak and attenuated over a certain distance within the same network, resulting in unreachable signals to the destination. This is where regenerative repeaters are useful as they regenerate signals received on their ports and sends the regenerated signals to all the other ports connected on the other end. Moreover, regenerative repeaters do not maintain a database as compare to Ethernet switches and operates on Physical Layer of the OSI model. Furthermore, regenerative repeaters are not compatible for regenerating signals via two different networks. For instance, the regeneration of signals between a token ring network and Ethernet network is not supported. For example, there are two network locations, where the distance between the two is above 100 meters, repeaters are required to synchronize uninterruptible transmission of data from one network to the other. Otherwise, the attenuation may disturb the digital signals and may not reach the distance, which is above 100 meters. A simplest of definition for a network device known as bridge is as follows “Local Bridge is a bridge that directly interconnects networks in the same geographical area” (Local Bridge. 2007). Bridge has capabilities to develop network segments. The segments are developed to eliminate unnecessary broadcasting from some workstations or a department on the network. Consequently, the performance of the network will be efficient as bridges can segregate workstation from the network. As these devices operate on data link layer of the OSI model, it is implemented to amplify distance between network segments, allowing room for more workstations, to be attached within the same network. Moreover, the segregation of affected workstations from the network, eliminates network congestions and traffic choking. Bridges do not deal with the information available in the higher levels of the OSI model due to their presence at the data link layer. Bridge identifies each node by its network address, it is the devices that recognize which protocol and data pertains to them. Moreover, there is a component installed inside the bridge device known as RAM. The bridge’s ram is used to store routing tables of source addresses of all the nodes associated with the network. For example, two neighbors want to share their home network with each other, installation of the bridge device between these two home networks will connect them to each other, representing a single network. A comprehensive definition is available in network dictionary that says “Ethernet Hub or repeater is a device that accepts numerous Ethernet connections from network devices and cross-connects them, making them act as a single segment. Data arriving via the receive pair of one connection is regenerated and sent out on the transmit pair to all connected devices except for the device who originated the transmission. Ethernet Hub works at the physical layer of the OSI model. If a signal comes into two ports at the same time when a collision occurs, so every attached device shares the same collision domain. Hubs support only half duplex Ethernet, providing bandwidth which is shared among all the connected devices”. Hubs are normally implemented for connecting workstations with network interface cards (NIC). It operates on the physical layer 1 of OSI model. Moreover, hubs are of two types named as active hubs and passive hubs. Active hubs are also knows as repeaters, is a device that amplifies data transmission on the network along with forwarding signals to the destination. On the other hand, passive hub only transmits the signals to all ports (Active Hub. 2007). For example, if two or more than two workstations require file sharing, print sharing, and Internet connection sharing, they can use a proxy server for sharing internet services with each workstation by installing a hub device. A complete definition is available in network dictionary that defines router, as “Routers are physical devices or a software system within a switch operating a layer 3 of the OSI model. A router forwards and routes data packets along networks. A router connects at least two networks, commonly two LANs or WANs or a LAN and its ISP network. A router is located at any gateway where one network meets another, including each point-of-presence on the Internet”. Router is a processing device, consisting of various types including non-seed router, seed router, filtering router, level 1 router, level two routers, level four router, gigabit switch router, interior router and much more. Moreover, routers operate on the network layer 3 of OSI model. It takes data packets as input, analyzes them, and transmits them to their preferred location. Routers are more capable then hubs, repeaters, and switches as network engineers configure access control list in routers to restrict and allow access to specific users. If a home network is considered, router is directly connected to the WAN interface, and is the only device to allow or deny Internet access for one or more workstations in the home network. For example, in a corporate network environment, where there are more than 100 workstations, network engineer will configure the router to restrict or allow access of network services to specific employees as per policy. File Protection by Nested Folders In order to maintain and organize files on the computer, it is not a good idea to place all the secret and confidential files on the desktop. This is because, everyone can see, where all the confidential files are placed. The intruder has several ways to copy or delete these files. The intruder may access the remote desktop, which will display the desktop, and the secret file will be vulnerable. The intruders may gain access by the default file sharing that share, the desktop, my documents, and printers. It is better to secure secret files in nested folders. If the user wishes to access the secret file, nested folders will provide organization of files and folders in order to find the required file easily. Moreover, proving specific names to the folders may help things to become easier. For creating a nested folder in ‘My Documents’, Charlie will navigate via these folders: Double click My Computer  Double click C: Double Click ‘Document and Settings’ Double Click  ‘Charlie’ Double Click ‘My Documents’ Sharing Files Securely Charlie needs to configure the same workgroup name for both the workstations. The difference between the computer names will not affect the sharing procedure. Two services are mandatory to transfer files i.e. ‘File and Print Sharing for Microsoft Networks’ and ‘Client for Microsoft networks’. Both the users must log in, for creating a sharing session. Charlie will now right click on C drive and share the drive. However, Charlie will only allow access to the nested folder containing the file ‘TopSecret.odt’. Protocol Utilization Moreover, the protocols used to establishes file and print sharing is TCP/IP. The TCP/IP establishes a data channel between Marv and Charlie’s workstation and ensures the reliable delivery of data. The File transfer is initialized, by File transfer protocol (FTP) between the two workstations. For Wireless connectivity, two security protocols are used. If Charlie sends data from Wi-Fi network, the wireless router initialized Wi-Fi Protected Access (WPA). This protocol operates on wireless 802.11 networks from the Wi-Fi alliance established to enable migration from Wired Equivalent Privacy (WEP). WEP “Encrypts data at one end of a wireless link and decrypts it at the other end using either 64 or 128bit keys. WEP is used to secure wireless networks. WEP incurs a slight hit on network speed (because of the encryption) but for most applications this is will not be noticeable” (, Glossary definition for WEP )(, Glossary definition for WEP , , Glossary definition for WEP ). The WPA provides strong security by implementing a sophisticated key hierarchy in order to generate new encryption keys each time a workstation connects from an access point. For home users, WPA operates in pre shared keys (PSK) mode, so that whoever connects to the wireless network, must provide a secret key in order to establish connectivity (Edney, Arbaugh 2004). Utilization of Services ‘File and Print Sharing for Microsoft Networks’ creates a Microsoft network between the two workstations to access resources including file and print sharing and ‘Clients for Microsoft Networks’ allow the workstations to connect with each other by windows networking. The service mandatory for establishing the session is ‘Microsoft Server’. The wireless router is configured with Network Address translation because more than one workstations are connected in Charlie’s home network. The NAT translates IP addresses and is defined as “Network Address Translation (NAT) is a method by which IP addresses are mapped from one group to another, transparent to end users. The need for IP Address translation arises when a network’s internal IP addresses cannot be used outside the network either for privacy reasons or because they are invalid for use outside the network. Network topology outside a local domain can change in many ways”. When a request for establishing a connection with Mark workstation is transmitted, the NAT translates Charlie’s IP address from local to global IP address. Similarly, when Mark’s workstation receives the request, the session is created. System Inaccessibility Because Lola is not on the same network as Charlie and Marv has established a workgroup with the same name unknown to Lola and Lotta. The transmission between Charlie and Marv’s computer is encrypted by Microsoft network environment. References EDNEY, J. and ARBAUGH, W.A., 2004. Real 802. 11 security: Wi-Fi protected access and 802. 11i Boston, MA: Addison-Wesley. , Glossary definition for WEP . Available: http://www.cryer.co.uk/glossary/w/wep.htm [3/17/2011, 2011]. OSI model. 2011. Computer Desktop Encyclopedia, , pp. 1. Regenerative Repeater. 2007. Network Dictionary, , pp. 405-405. Local Bridge. 2007. Network Dictionary, , pp. 289-289. Active Hub. 2007. Network Dictionary, , pp. 21-21. Router. 2007. Network Dictionary, , pp. 419-419 Read More