งานนำเสนอเรื่อง: "Chapter 6 Communication. 1. From Analog to Digital Analog Most phenomena in life are analog. Analog signals use wave variations, continuously changing."— ใบสำเนางานนำเสนอ:
Chapter 6 Communication
1. From Analog to Digital Analog Most phenomena in life are analog. Analog signals use wave variations, continuously changing. Sound, light, and temperature are analog forms. Traditional TV and radio use analog signals. Humans' vision operates in analog mode.
From Analog to Digital
Digital Computers use digital signals --> 0 and 1 --> off and on. All the data that a computer processes is a series of 0 and 1 Each signal is a bit.
For data transmission over telephone lines and cables, modems are needed to convert analog data into digital data that computers can use.
2. The Benefits of Networks Sharing Hardware Sharing Software Sharing Data and Information Better Communications Accessing Database Centralized Communications Security of Information
LAN (Local Area Network) WLAN (Wireless Local Area Network) LAN connects computers and devices in a limited geographic area such as one office, one building, or a group of buildings close together.
MAN (Metropolitan Area Network) MAN is a communications network covering a city or a suburb. Cellphone systems are MAN.
WAN (Wide Area Network) WAN is a communications network that covers a wide geographic area, such as a country or the world.
4. Network Architectures Peer to Peer Client-Server
Peer to Peer All computers on the network are "equal" and communicate directly with one another, without relying on a server. Easy to setup Less expensive Work effectively for up to 25 computers Slow down under heavy use
Client-Server Clients are microcomputers that request data. Servers are central computers used to supply data. File server is a computer acts like a disk drive, storing the programs and data files. Database server is a computer that stores data but doesn’t store programs. Print server controls one or more printers and stores the print-image output. Web server contains web pages. Mail server manages .
5. Intranet Intranet is an organization’s internal private network that serves employee only.
6. Extranet Extranet is private intranets that connect internal personnel and selected suppliers and other parties such as purchasing, production planning.
7. VPN (Virtual Private Networks) VPNs use a public network (usually the internet) plus intranets and extranets to connect an organization's various sites but on a private basis, via encryption and authentication; regular internet users do not have access to the VPNs data and information.
8. Firewall Protect Network from Intruders FIREWALL Networking Basic https://www.youtube.com/watch?v=- xnqC2aPb00 https://www.youtube.com/watch?v=- xnqC2aPb00 Software Firewall > One computer Hardware Firewall > Many computers
9.1 Host & Nodes Host computer controls the network Node is any device that is attached to a network. – Computer – Storage devices – Scanner – Printer
9.2 Packet A packet is a fixed-length block of data for transmission. A sending computer breaks an electronic message apart into packets, each of which typically contains bytes. https://www.youtube.com/watch?v=3_EHaM 3tr98 https://www.youtube.com/watch?v=3_EHaM 3tr98
9.3 Protocol Protocol is a set of conventions governing the exchange of data between hardware and software components in a communication network.
Switch A switch is a device that connects computers to a network and facilitates communication by sending message between sender and receiver nodes.
9.4.2 Bridge A bridge is a device used to connect two similar networks, LAN and LAN A bridge has a single connection point.
9.4.3 Gateway A gateway is an interface permitting communication between dissimilar network, LAN and WAN
9.4.4 Router Routers are specialized devices for transmitting data, physical devices that join multiple networks. Router calculates the best possible transmission path of data packets between networks.
9.5 Network Interface Card Network interface card enables the computer to send and receive messages over a cable network.
Star All computers and other communication devices are directly connected to a switch. The switch prevents collisions between messages. If a connection is broken, the rest of the devices will continue operating. If the switch goes down, the entire network stops.
Ring All computers and other devices are connected in a continuous loop. Messages are passed around the ring until they reach the destination. There is no central server. Messages flow in one direction. Thus, there is no collisions. If one node malfunctions, the entire network can stop working.
Bus All nodes are connected to a single wire. The bus has two endpoints, which stop the network signal. Advantage If some message collide, the sending device waits and tries to transmit again. Inexpensive, easy to use, good for small network Disadvantage Need extra software to avoid collision Limited to 20 devices Cannot exceed 185 meters in length
Tree A tree network is a bus network of star networks. Each department has its own star network. Every departments are then linked through the bus network.
Mesh Each node has more than one connection to the other nodes so that a message can take any possible shortest, easiest route to reach its destination. If a path between two nodes is disrupted, data can be automatically rerouted along another path.
Twisted-pair is slow, carrying data at the rate of megabits per second (normally 56 kbps) The telephone line is twisted-pair wire.
11.2 Coaxial Cable
Coaxial Cable Coaxial is used for television It can carry data up to 200 megabits per second
11.3 Fiber-optic Cable
Fiber-optic Cable A fiber-optic cable consists of dozens of thin strands of glass or plastic that transmit pulsating beams of light rather than electricity. A fiber-optic cable can carry data at the rate of 2 gigabits per second. It is not affected by electromagnetic interference. It has a much lower error rate than telephone wire. It requires less power to transmit signals than co- ax cable.
12. Wireless Communications Media 12.1 Infrared Transmission 12.2 Broadcast Radio 12.3 Cellular Radio 12.4 Microwave Radio 12.5 Communications Satellites
12.1 Infrared Transmission Infrared wireless transmission sends data signals using infrared-light waves at a frequency too low for human eyes to receive and interpret. Infrared port can be found on TV remote- control megabits per second
12.2 Broadcast Radio Broadcast radio is a wireless transmission medium that send data over long distances at up to 2 megabits per second. Broadcast radio is used in AM and FM radio station.
12.3 Cellular Radio Cellular radio is used for cellphones and wireless modems, using high-frequency radio waves to transmit voice and digital messages.
12.4 Microwave Radio Microwave radio transmits voice and data at 45 megabits per second through the atmosphere as super high-frequency radio waves.
12.5 Communication Satellite Communications satellites are microwave relay stations in orbit around Earth.
13. Long-Distance Wireless One-way Communication > GPS, Pager Two-way Communication > 4G
14. Short-Distance Wireless Local area networks > range feet > Wi-Fi Personal area networks > range feet > Bluetooth Home automation network > range feet > Insteon https://www.youtube.com/watch?v=YpuqceW 3qu8 https://www.youtube.com/watch?v=YpuqceW 3qu8