3/20: Telecommunications & Networking What is telecommunications? The hardware: physical components of telecommunications, inc. channels Standards: agreements on how to connect & communicate Network Topologies

Defining Telecommunications Communicating information via electronic means over some distance Information Superhighway: –National / worldwide high speed digital telecommunications accessible by general public

Elements of Telecommunications Computers Terminals (input / output devices) Communications channels Processors (modems; Multiplexers; Front-end processors) Communications software

Communication Channels The means by which data are transmitted. Twisted wires (copper wires) Coaxial cable: (insulated copper wires) Fiber-optic cable Wireless channels –Microwaves –Pagers, cell phones, mobile data networks

Channels: Fiber-Optics Super clear glass strands Fast, light, durable Billions of bits per second Expensive, harder to install Often used as backbone of networks

Channels: Microwaves Building-to-building Earth-to-satellite UPLINK MICROWAVE TRANSMISSION DOWNLINK

Channels: Other Wireless Channels PAGING SYSTEM: Pager receives short messages CELLULAR TELEPHONE: Uses radio waves to reach antennas within areas called cells MOBILE DATA NETWORKS: Radio-based data network using hand-held computers; cheap, efficient

Channels: Other Wireless Channels PERSONAL COMMUNICATION SERVICE: Cellular; lower power; higher frequency. Smaller phones not shielded by buildings, tunnels PERSONAL DIGITAL ASSISTANT: Handheld digital communicator SMART PHONE: Wireless, voice, text, Internet

Comparing Channels Transmission speed: bits/second (BPS) or baud Bandwidth: capacity of channel; Difference between highest & lowest frequencies Medium Medium Speed Speed Cost Cost Twisted wire Twisted wire 300 bps - 10 mbps 300 bps - 10 mbpsLow Land Microwave Land Microwave 256 kbps mbps 256 kbps mbps Satellite Satellite 256 kbps mbps 256 kbps mbps Coaxial cable Coaxial cable 56 kbps mbps 56 kbps mbps Fiber optics Fiber optics 500 kbps - 10 gbps 500 kbps - 10 gbpsHigh

Standards: Protocols Rules & procedures to govern transmission between components in a network Analog vs. Digital TCP/IP

Standards: Analog vs. Digital Recall: Analog signals –Continuous waveform –Passes thru system –Voice communications Digital signals –Discrete waveform –Two discrete states: on / off pulse –Data communication –Uses modem to translate analog to digital, digital to analog

Standards: TCP/IP Transmission Control Protocol / Internet Protocol Developed by Department of Defense in TRANSMISSION CONTROL PROTOCOL (TCP): Breaks data into datagrams 2.INTERNET PROTOCOL (IP): Breaks, sends datagrams as smaller IP packets; can repeat transmission to increase reliability

Standards: OSI Open System Interconnect International reference model for linking different types of computers & networks

Standards: Connectivity Measure of ability of computing devices to pass & share information without human intervention OPEN SYSTEMS: Software able to function on different computer platforms. Nonproprietary operating systems, applications, protocols

Network Topologies: Star Topology: Layout HOST HOST USER USER

Network Topologies: Bus USER USER

Network Topologies: Token Ring USER USER

Local Networks PRIVATE BRANCH EXCHANGE (PBX) –firm’s central switching system LOCAL AREA NETWORK (LAN) –dedicated channels –limited distance (less than 2000 foot radius) –higher capacity than PBX –Can share expensive hardware & software

Local Networks: LAN GATEWAY: Connection to other networks ROUTER: Forwards data to other networks NETWORK OPERATING SYSTEM (NOS): Manages file server; routes communications on network PEER - TO - PEER: In some small networks all computers have equal power

Wide-Area Networks: WANs A LAN that spans large geographic distances. Can include cable, satellite, microwave SWITCHED LINES: Route determined by current traffic DEDICATED LINES: Constantly available for high-volume traffic

Next Time: More on Telecom VANs Network Services –DSL, ISDN, Cable Modems, T1 lines, etc. –Which to use? X.25 and ATM E-Commerce & E-Business technologies EDI: Electronic Data Interchange – available services, etiquette