Unit 1_ Network Hardware session 1.pptx
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This document provides definitions and explanations of key concepts in computer networks: - A computer network connects two or more devices to share resources and files using common protocols. - Networks have five basic components: messages, senders, receivers, transmission media, and protocols. - Communication can occur in simplex, half-duplex, or full-duplex mode depending on whether devices can transmit and receive simultaneously. - Important criteria for networks are performance, reliability, and security.
Unit 1_ Network Hardware session 1.pptx
- 2. • Network Hardware • Network Software • OSI • TCP/IP Reference models • Example Networks: ARPANET, Internet. • Physical layer : Guided Transmission media: twisted pairs, coaxial cable, fiber optics, Wireless transmission.
- 4. Definition 1: A Computer Network is a group of two or more interconnected computer systems that use common connection protocols for sharing various resources and files. Definition 2: A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. Definition 3: When we communicate, we are sharing information. This sharing can be local or remote. Between individuals, local communication usually occurs face to face, while remote communication takes place over distance.
- 5. Delivery: The system must deliver data to the correct destination. Data must be received by the intended device or user and only by that device or user. Accuracy: The system must deliver the data accurately. Data that have been altered in transmission and left uncorrected are unusable. Timeliness: The system must deliver data in a timely manner. Data delivered late are useless. Jitter: Jitter refers to the variation in the packet arrival time.
- 6. A data communications system has five components.
- 7. Message: The message is the information (data) to be communicated. Popular forms of information include text, numbers, pictures, audio, and video. Sender: The sender is the device that sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on. Receiver: The receiver is the device that receives the message. It can be a computer, workstation, telephone handset, television, and so on.
- 8. Transmission medium: The transmission medium is the physical path by which a message travels from sender to receiver. Some examples of transmission media include twisted-pair wire, coaxial cable, fiber- optic cable, and radio waves . Protocol: A protocol is a set of rules that govern data communications. It represents an agreement between the communicating devices.
- 9. Information today comes in different forms such as text, numbers, images, audio, and video. Text: Text is represented as a bit pattern, a sequence of bits (Os or Is). Numbers: Numbers are also represented by bit patterns . the number is directly converted to a binary number to simplify mathematical operations. Images: Images are also represented by bit patterns. In its simplest form, an image is composed of a matrix of pixels (picture elements), where each pixel is a small dot. Audio: Audio refers to the recording or broadcasting of sound or music. It is continuous not discrete . Video: Video refers to the recording or broadcasting of a picture or movie.
- 10. Communication between two devices can be •Simplex •Half-duplex •Full-duplex
- 11. In simplex mode, the communication is unidirectional, as on a one-way street. Only one of the two devices on a link can transmit; the other can only receive. The simplex mode can use the entire capacity of the channel to send data in one direction. Example: keyboard , monitor
- 12. In half-duplex mode, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The half-duplex mode is like a one-lane road with traffic allowed in both directions. Example: Walkie-talkies
- 13. In full-duplex, both stations can transmit and receive simultaneously. One common example of full-duplex communication is the telephone network. When two people are communicating by a telephone line, both can talk and listen at the same time. The full-duplex mode is used when communication in both directions is required all the time.
- 14. A network must be able to meet a certain number of criteria. The most important of these are Performance Reliability Security Performance : Performance can be measured in many ways, including transit time and response time. Transit time is the amount of time required for a message to travel from one device to another. Response time is the elapsed time between an inquiry and a response.
- 15. Reliability: In addition to accuracy of delivery, network reliability is measured by the frequency of failure, the time it takes a link to recover from a failure, and the network's robustness in a catastrophe. Security: Network security issues include protecting data from unauthorized access, protecting data from damage and development, and implementing policies and procedures for recovery from breaches and data losses.
- 16. For communication to occur, two devices must be connected in some way to the same link at the same time. There are two possible types of connections: point-to-point multipoint.
- 17. Point-to-Point : A point-to-point connection provides a dedicated link between two devices. The entire capacity of the link is reserved for transmission between those two devices. Multipoint : A multipoint (also called multidrop) connection is one in which more than two specific devices share a single link. In a multipoint environment, the capacity of the channel is shared, either spatially or temporally. If several devices can use the link simultaneously, it is a spatially shared connection. If users must take turns, it is a timeshared connection.