Chapter 6. Telecommunications and Networks. Presentation Overview. The Evolution of Networking Data Transmission Characteristics Communications Media Network Classifications Network Topologies Network Hardware Network Software Communications Software and Protocols.
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Telecommunications and Networks
Telecommunications, combined use of computer hardware and communications software for sending and receiving information over communications media, enables computer users throughout the world to communicate.
What are the characteristics of transmitted data?
number of bits that can be transmitted per second
terms for measuring bandwidth
Analog and Digital Transmission
Modulate – sending modem changes digital signal into analog signal
Demodulate – receiving modem changes analog signal back into digital signal
Translating digital signals to analog signals
Internal modem – electronic board plugged into a slot on a computer’s motherboard
External modem – stand-alone device connected by cable to a computer
Parallel and Serial Transmission
Serial transmission sends 1 byte plus the parity bit one bit after another in a continuous line.
Parallel transmission sends 8 bits plus a parity bit at the same time over 9 separate paths.
Coaxial cable is an insulated center wire grounded by a shield of braided wire.
Twisted-pair cable is two parallel copper wires, individually wrapped in plastic and bound by another plastic casing.
Fiber-optic cable transmits beams of light through a glass or plastic core.
Wired Communications Media
Integrated Services Digital Network (ISDN) Lines are used to dial into the Internet and receive information at high speeds.
Digital Subscriber Lines (DSL) use existing phone lines and new switched connections to get faster speeds than traditional phone access.
T Linesare digital, high-speed, long-distance lines capable of carrying signals across the line.
Microwave systems transmit data through the atmosphere from one microwave station to another.
Communications satellite is a solar-powered, electronic device with specialized radios (transponders) for receiving signals from ground transmission stations. A satellite receives transmitted signals, amplifies them, and retransmits them to other ground locations.
Infrared technology allows data as infrared light waves to be transmitted from a special port in a computer to an infrared sensor in a printer.
Wireless Communications Media
Bluetooth technology offers short-range connectivity with other Bluetooth devices.
Devices form a small, temporary network that can transmit voice and data.
Wi-Fi-enabled devices use a broadband Internet connection through a wireless access point.
Signals sent by cell phones are transmitted and received from cell to cell until they reach their destination.
Networking paths allow networkedclient computers to send information to a server, which relays information back to the computer or to another on the network. Fax machines and printers are shared resources. The file server accesses a shared hard disk.
Local area network (LAN)is a private network using a file server that houses all networkresources.
Wide area network (WAN)spans a large geographical area connecting two or more LANs.
An intranetis a network within an organization to serve internal users.
A network interface card (NIC) is used for wired connections in a desktop PC.
A wireless NIC allows notebook computers to use Wi-Fi hotspots.
Network Interface Card (NIC)
connects each client computer to a network
In peer-to-peer architecture, computers act as both client and server.
Ring Topology has no hub, and each computer is connected to two other computers in a circular path.
Star Topology links multiple computers and devices to a central hub in a configuration resembling a star.
Hubs, Switches, Routers
devices that links computers in a network
A gatewayis a combination of hardware and software that allows dissimilar networks to communicate.
A bridge is a combination of hardware and software that enables devices on similar networks to communicate
Network Operating Systems (NOS)
Communication software programs can be used to
What are protocols?
With simplex data transmission, data flows only one way.
With half-duplex data transmission, data flows in both directions but only in one direction at a time.
With full-duplex data transmission, data flows in both directions at the same time.
Synchronous Transmission Protocols
blocks of bytes are wrapped in a start and stop byte called a synch byte.
Asynchronous Transmission Protocols
each byte of data is surrounded by control bits:
Local Area Network (LAN) Protocols
TCP/IPTransfer Control Protocol / Internet Protocol
Circuit Switching / Packet Switching
Internet and Web Protocols
Electronic Mail Protocols
Variations of the 802.11 protocol
802.11 n 2007 600 Mbps
Based on the information presented in this chapter and your own experience, what do you think is on the horizon?