Unit 5- Computer Networking

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Purpose of this Module

The purpose of this training module is to provide information/knowledge to the learner with the basic skills about communication among computing devices through Computer Network. Definition of Computer Network

A computer network is a group of computer systems and other computing hardware devices like Hubs, Switches which are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Networks are commonly categorized based on their characteristics. Networks are used to: Facilitate communication via email, video conferencing, instant messaging, etc. Enable multiple users to share a single hardware device like a printer or scanner Enable file sharing across the network Allow for the sharing of software or operating programs on remote systems Make information easier to access and maintain among network users Types of Network Fig: Local Area Networks (LAN) There are many types of networks, including: ·   Local Area Networks (LAN):  A local area network (LAN) is a computer network within a small geographical area such as a home, school, computer laboratory, office building or group of buildings.           A LAN is composed of inter-connected workstations and personal computers which are                 each capable of accessing and sharing data and devices, such as printers, scanners and data           storage devices, anywhere on the LAN. LANs are characterized by higher communication             and data transfer rates and the lack of any need for leased communication lines. ·      Metropolitan Area Networks (MAN):  A metropolitan area network (MAN) is similar to a local area network (LAN) but spans an entire city or campus. MANs are formed by connecting multiple LANs. Thus, MANs are larger than LANs but smaller than wide area networks (WAN). Fig: Metropolitan Area Networks (MAN) MANs are extremely efficient and provide fast communication via high-speed carriers, such as fiber optic cables. ·    Wide Area Networks (WAN): A wide area network (WAN) is a network that exists over a large-scale geographical area. A WAN connects different smaller networks, including local area networks (LANs) and metro area networks (MANs). This ensures that computers and users in one location can communicate with computers and users in other locations. WAN   implementation can be done either with the help of the public transmission system or a private network. Fig: Wide Area Networks (WAN) Virtual Private Network (VPN):  A virtual private network (VPN) is a technology that creates a safe and encrypted connection over a less secure network, such as the internet. VPN technology was developed as a way to allow remote users and branch offices to securely access corporate applications and other resources Fig: Virtual Private Network (VPN) Network Topology Bus Topology: In local area networks where bus topology is used, each node is connected to a single cable, by the help of interface connectors. This central cable is the backbone of the network and is known as the bus (thus the name). A signal from the source travels in both directions to all machines connected on the bus cable until it finds the intended recipient. If the machine address does not match the intended address for the data, the machine ignores the data. Alternatively, if the data matches the machine address, the data is accepted. Because the bus topology consists of only one wire, it is rather inexpensive to implement when compared to other topologies. However, the low cost of implementing the technology is offset by the high cost of managing the network. Additionally, because only one cable is utilized, it can be the single point of failure. In this topology data being transferred may be accessed by any node. Fig: Bus Topology Star Topology: In local area networks with a star topology, each network host is connected to a central hub with a point-to-point connection. So it can be said that every computer is indirectly connected to every other node with the help of the hub. In star topology, every node (computer workstation or any other peripheral) is connected to a central node called hub or switch. The switch is the server and the peripherals are the clients. Fig: Star Topology The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters. Ring Topology: A ring topology is a bus topology in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (re transmit) the data to keep the signal strong. Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to re transmit data, it severs communication between the nodes before and after it in the bus. Fig: Ring Topology Advantages: When the load on the network increases, its performance is better than bus topology. There is no need of network server to control the connectivity between workstations. Disadvantages: Aggregate network bandwidth is bottlenecked by the weakest link between two nodes. Mesh Topology:  The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints. Fig: Mash Topology Hybrid Topology: Hybrid topology is also known as hybrid network. Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network (or star-bus network) is a hybrid topology in which star networks are interconnected via bus networks. However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected. Network Applications A network is a collection or set of computing devices connected to one another to establish communication and also share available resources. A network will comprise of software and hardware devices. You can have a network even if you are not connected to the internet. Computer networks make it possible for people to transfer files from one place to another and to communicate taking the shortest time possible. Computer network applications are network software applications that utilize the Internet or other network hardware infrastructure to perform useful functions for example file transfers within a network. They help us to transfer data from one point to another within the network. 1. Email programs They allow users to type messages at their local nodes and then send to someone on the network. It is a fast and easy way of transferring mail from one computer to another. Examples of electronic mail programs (Clients) are:- Pegasus mail Eudora Windows mail Fox mail Opera Poco mail Mozilla Thunderbird Windows mail Outlook express                                         Fig: Outlook Express, an email program 2. File transfer protocol (FTP) This application facilities transfer of files from one computer to another e.g. from a client to a server. There are 2 common processes involved in FTP Downloading: - This is the process of obtaining files from a server to a workstation or a client (for example when you download programs and music from a server). Uploading:- This is obtaining of files from a workstation to a server (for instance when you attach documents and upload them to a server, a good example being when you upload photos to Facebook). Examples of FTP programs are:- FTP in Unix FTP in Linux or FTP in Windows Fig: Process of File Transfer Protocol (FTP) 3. Terminal Emulation (TELNET) It allows a workstation to access the server for an application program. This enables you to control the server and communicate with other servers on the network. The workstation appears as a down terminal that is directly attached to the server. The user feels like he/she is using the server directly. TELNET enables PCs and workstations to function as dumb terminals in sessions with hosts on inter-networks. 4. Groupware These applications are used to automate the administration functions of a modern office for instance video conferencing and chatting. They facilitate the work of groups and improve on their productivity; they can be used to communicate, co-operate, coordinate, solve problems, compete and negotiate among others. (i) Video Conferencing: This is the process of conducting a conference between two or more participants at different sites by using computer networks to transmit audio and video data. For example, a point-to-point (two-person) video conferencing system works much like a video telephone. Each participant has a video camera, microphone, and speakers mounted on his or her computer. As the two participants speak to one another, their voices are carried over the network and delivered to the others speakers, and whatever images appear in front of the video camera appear in a window on the other participant’s monitor. (ii) Chatting: It is a real-time communication between two users via computer. Once a chat has been initiated, either user can enter text by typing on the keyboard and the entered text will appear on the other user’s monitor. The two must be online for a chat to be initiated. Most networks, cyber and online services offer a chat feature which enables computer users to chat as they go on with their work. Exercise for practical file: Q 1-  Explain types of Computer Networks. Also give your view to choose best network type. Q 2.- Discuss the applications of computer network you are using in your daily life. Important Note: Your comment is your attendance, so write your name and Enrollment No. in the comment section. Thanks You  The network does not necessarily have to resemble a star to be classified as a star network, but all of the nodes on the network must be connected to one central device. All traffic that traverses the network passes through the central hub. The hub acts as a signal repeater. The star topology is considered the easiest topology to design and implement. An advantage of the star topology is the simplicity of adding additional nodes. The primary disadvantage of the star topology is that the hub represents a single point of failure. Since all peripheral communication must flow through the central hub, the aggregate central bandwidth forms a network bottleneck for large clusters. Ring Topology: A ring topology is a bus topology in a closed loop. Data travels around the ring in one direction. When one node sends data to another, the data passes through each intermediate node on the ring until it reaches its destination. The intermediate nodes repeat (re transmit) the data to keep the signal strong. Every node is a peer; there is no hierarchical relationship of clients and servers. If one node is unable to re transmit data, it severs communication between the nodes before and after it in the bus. Fig: Ring Topology Advantages: When the load on the network increases, its performance is better than bus topology. There is no need of network server to control the connectivity between workstations. Disadvantages: Aggregate network bandwidth is bottlenecked by the weakest link between two nodes. Mesh Topology:  The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints. Fig: Mash Topology Hybrid Topology: Hybrid topology is also known as hybrid network. Hybrid networks combine two or more topologies in such a way that the resulting network does not exhibit one of the standard topologies (e.g., bus, star, ring, etc.). For example, a tree network (or star-bus network) is a hybrid topology in which star networks are interconnected via bus networks. However, a tree network connected to another tree network is still topologically a tree network, not a distinct network type. A hybrid topology is always produced when two different basic network topologies are connected. Network Applications A network is a collection or set of computing devices connected to one another to establish communication and also share available resources. A network will comprise of software and hardware devices. You can have a network even if you are not connected to the internet. Computer networks make it possible for people to transfer files from one place to another and to communicate taking the shortest time possible. Computer network applications are network software applications that utilize the Internet or other network hardware infrastructure to perform useful functions for example file transfers within a network. They help us to transfer data from one point to another within the network. 1. Email programs They allow users to type messages at their local nodes and then send to someone on the network. It is a fast and easy way of transferring mail from one computer to another. Examples of electronic mail programs (Clients) are:- Pegasus mail Eudora Windows mail Fox mail Opera Poco mail Mozilla Thunderbird Windows mail Outlook express                                         Fig: Outlook Express, an email program 2. File transfer protocol (FTP) This application facilities transfer of files from one computer to another e.g. from a client to a server. There are 2 common processes involved in FTP Downloading: - This is the process of obtaining files from a server to a workstation or a client (for example when you download programs and music from a server). Uploading:- This is obtaining of files from a workstation to a server (for instance when you attach documents and upload them to a server, a good example being when you upload photos to Facebook). Examples of FTP programs are:- FTP in Unix FTP in Linux or FTP in Windows Fig: Process of File Transfer Protocol (FTP) 3. Terminal Emulation (TELNET) It allows a workstation to access the server for an application program. This enables you to control the server and communicate with other servers on the network. The workstation appears as a down terminal that is directly attached to the server. The user feels like he/she is using the server directly. TELNET enables PCs and workstations to function as dumb terminals in sessions with hosts on inter-networks. 4. Groupware These applications are used to automate the administration functions of a modern office for instance video conferencing and chatting. They facilitate the work of groups and improve on their productivity; they can be used to communicate, co-operate, coordinate, solve problems, compete and negotiate among others. (i) Video Conferencing: This is the process of conducting a conference between two or more participants at different sites by using computer networks to transmit audio and video data. For example, a point-to-point (two-person) video conferencing system works much like a video telephone. Each participant has a video camera, microphone, and speakers mounted on his or her computer. As the two participants speak to one another, their voices are carried over the network and delivered to the others speakers, and whatever images appear in front of the video camera appear in a window on the other participant’s monitor. (ii) Chatting: It is a real-time communication between two users via computer. Once a chat has been initiated, either user can enter text by typing on the keyboard and the entered text will appear on the other user’s monitor. The two must be online for a chat to be initiated. Most networks, cyber and online services offer a chat feature which enables computer users to chat as they go on with their work. Exercise for practical file: Q 1-  Explain types of Computer Networks. Also give your view to choose best network type. Q 2.- Discuss the applications of computer network you are using in your daily life. Important Note: Your comment is your attendance, so write your name and Enrollment No. in the comment section. Thanks You