Week 3 Network 1 PDF

What is a Computer Network?  What is a Computer Network? A set of nodes (computers or electronic devices) which are connected together by communication links (communication pathway that transfer data from one device to another). A computer network is a collection of...

What is a Computer Network?  What is a Computer Network? A set of nodes (computers or electronic devices) which are connected together by communication links (communication pathway that transfer data from one device to another). A computer network is a collection of computers and computer resources connected together to permit communication between resources Resources include PCs, laptops, servers, mainframes Printers File servers Etc. Network usages 1. Data Sharing 2. Software sharing 3. Hardware sharing 4. Personal Information Sharing 5. E-commerce 6. Person – to – Person Communication 7. Entertainment 8. Game Playing 9. Client – Server applications 10.Remote Communications 11.etc. Advantages of Computer Networks Enables users to share hardware like scanners and printers. This reduces costs by reducing the number of hardware items bought. Allows users access to data stored on others' computers. This keeps everyone up-to-date on the latest data Can share access to the Internet. Advantages of Computer Networks Can even let users run programs that are not installed on their own computers but are installed elsewhere in the network. What Is Bandwidth in Networking? The network bandwidth definition can be confusing, but basically, network bandwidth is defined as It’s a measure of how much data can be sent and received at a time. Bandwidth is measured in bits, megabits, or gigabits per second.  Physical Topology The way in which a network is laid out physically.  Bus topology Bus topology (line topology) is a Multipoint connection where each computer and network device is connected to a single cable or backbone to link all the devices in a network.  The bus pattern connects a computer to the same communications line. Communications goes both directions along the line. All the computers can communicate with each other without having to go through the server or any other machine.  Bus topology Notes: There is a limit on the number of taps a bus can support and on the distance between those taps. As a signal travels along the backbone, it becomes weaker.  Bus topology Bus – computers connect via “t” connector to a line that connects all computers In essence, the network is one long cable Cheap network but not efficient if multiple computers attempt to use the bus at the same time, there is a collision and the computers must wait to try again Advantages of a Bus topology Ease of insulation Use less cabling than mesh or star. It works well when you have a small network. Disadvantages of a Bus topology 1. A fault in bus cable (break) stops all transmissions even between devices on the same side of the problem. The damaged area reflects signals back the direction of origin, creating noise in both directions 2. Reconnection It can difficult to add new devices (adding more require modification or replacement of the backbone). Disadvantages of a Bus topology 3. It can be hard to troubleshoot individual device issues. 4. Bus topology is not great for large networks. Star topology Each device has a dedicated point-to-point link only to a central controller (hub) Unlike a mesh , a star topology does not allow direct traffic between devices, if one device want to send data to another , it send it to the hub, which send it to other device  The star pattern connects everything to a host computer, a network switch, or a network hub, which handles the network tasks. All communications between computers go through the host/switch/hub.  Advantages of a Star topology 1.Easy to install and reconfigure and less expensive each device need only one link and I/O port to connect it to any other devices.) 2.Robustness: if one link fails, only that link affected and other links remain active. 3. identification and fault isolation  Disadvantages of a Star topology The dependency of the whole topology on one single point, the hub. If the hub goes down, the whole system is dead. Tree topology : is a variation of star - Not every device plugs directly into the central hub. The majority of devices connect to secondary hub that in turn is connected to the central hub. Tree topology : is a variation of star The advantages and disadvantages of tree topology are generally the same as those of star. - The addition of secondary hubs bring more advantage: allows for more devices to be attached to a single central hub, therefore increase the distance a signal can travel between devices.  Ring Topology Each device has a dedicated point-to-point connection only with the two devices on either side of it A signal is passed along the ring in one direction from device until it reaches its destination.  The ring pattern connects the computers and other devices one to the other in a circle. There is no central host computer that holds all the data. Communication flows in one direction around the ring. Ring Topology Each device in the ring incorporate as repeater Repeater is a device used to regenerates the signal it receives a weakened signal, creates a copy, bit for bit, at the original strength Ring Topology Advantages: Easy to install and reconfigure. Each device is linked only to its immediate neighbors. To add or delete a device requires hanging only 2 connections Fault isolation is simplified : A signal is circulating at all times (token) if one device does not receive a signal within specified period, it can issue an alarm. The alarm alerts the network operator to the problem and its location. Disadvantages Unidirectional traffic. A break in the ring (such as disabled station) can disable the entire network. This can be solved by use dual ring