Transcript Session 3
LBSC 690 Session 3 Networking Analog to Digital We live in an analog world: Sound, temperature, light, etc. Sensory inputs. Are continuous signals. Can assume all (essentially infinite) values in a given interval. Basis for analog computers: Uses electrical voltage/current to variables. to represent. Digital Discrete representation: assumes a finite number of values in a given interval. Basis for digital computers: Use 2 discrete values to represent data, & instructions. (Binary system). Analog signals converted to digital by Pulse Code Modulation (PCM). PCM Three step process: Analog signal is sampled: Nyquist’s Theorem. Samples are quantized. Quantized samples are encoded into binary digits, called “bits” for short. See handout. Evolution Computers initially stand alone. Need to communicate. Transmit data at a distance. Communications: Data communication. Telecommunication: Provides electrical communications at a distance. Service provided by a number of companies internationally. The “telecommunications industry.” Telecommunications Industry Carriers: LECs (RBOCs: 7 to 4); CLECs. IXCs. Internet Service Providers (ISPs). Vendors/Consultants & Manufacturers. Judicial/Political/Legislative: Regulatory agencies. Standards Making Organizations. Customers: business & residential. Technology and research. Networking Simplest form: Directly connect two communicating devices. Not practical solution. Problem of topology: How to deal with fully connected mesh. Need network. Nodes and segments. The Universal Seven Part Data Model DTE DCE DTE/DCE Interface DCE Transmission Channel DTE DCE/DTE Interface DTE: Data Terminal Equipment DCE: Data Communication Equipment Network (Cont’d.) S N “Local loop” NETWORK S S: Network Station N N N: Network Node S N S Network Types Switched Communication Network: Circuit-switched. Packet–-switched. Broadcast communication Network: Packet radio network. Satellite network. Local area network. Generic Switching Network Reference handout. Concepts: Bandwidth Measure of channel capacity: frequency range Radio Spectrum (Next Slide) Frequencies available for telecommunications Modulation Process of embedding intelligence in a carrier wave Multiplexing Process that combines multiple calls or messages on a single channel Examples; TDMA (Time Division Multiple Access), CDMA (Code Division Multiple Access) Spectrum A limited resource Government controlled: FCC & ITU, e.g. Some assigned frequencies: Am radio: 535-1635 KHz Analog cordless phones: 44-49 MHz TV channels 2-6: 54-88 MHz FM radio: 88-108 MHz TV channels 7-13: 174-216 MHz Cellular phones: 806-890 MHz PCS: 900-929 MHz Satellite TV (small dish): 11.7-12.7 GHz Cell Phones More than 115 million users in US 46,000 people subscribing every day Based on concept of cells 10 sq. mi. in area with a Base Station in it Low power: 0.3 & 6 watts Mobile Telephone Switching Office (MTSO). Special codes: electronic serial no. (ESN), mobile identif. no.(MIN, system ident, code (SID). Analog vs. digital. American vs. European approaches GSM (Global System For Mobile communication) TDMA vs. CDMA LANs What are they? Need & functions. Hardware/software components. Concept of packets. Ethernet and token ring. ANSI/ IEEE 802.3 (ISO 8802-3) Need to interconnect LANs. LANs Data communication facilities designed to provide high-speed switched connections between processors peripherals and terminals within a local area, e.g., buildings or a campus. LAN Functions File sharing Printer sharing CD ROM sharing On-line databases Groupware OPAC access Dial in & out Fax in & out Voice-video-multimedia E-mail Internet access LAN Benefits Shared access Increased security Application and data highway Adding new applications is done once (on server) Support services more effective and lower cost LAN Installation Network Operating System (NOS). Network Interface Cards (NIC). Cabling and connectors. Hubs/ Switches. Network Servers: File, Print, Communication, etc. Clients TRAINING Network Management: Network Administrator & Support Personnel. Certification. Continuing education. User training. Ethernet Developed in 1973 at Xerox Corporation’s Palo Alto Research Center (PARC). Developed by Bob Metcalfe. Uses the Ethernet Protocol. Protocol: A code prescribing strict adherence to correct etiquette and precedence. Communication protocols: symbols (Character set), rules for sequence and timing of messages, and procedures for error detection and handling. Messages broken into frames (packets). With source and destination addresses. Ethernet Broadcast network Carrier Sense Multiple Access/Collision Detection (CSMA/CD) Collision retry (random wait) Need for repeaters Hubs Basic, Smart, Intelligent, Switches Bridges Routers (internetting) Network Topology Bus Star Ring Mesh Hybrid Transmission Channels (Media) 4-wire phone UTP STP Coax Fiber optic 3Kbps 100Mbps 16Mbps 10Mbps 10Gbps 200 ft. 100 ft. 100 ft. 500 ft. 2-5 km. The Internet Historical development. TCP/IP Protocol Suite. Transmission Control Protocol/Internet Protocol Telnet. FTP. E-mail. Assignment 1: Two exercises. Packet switching. IP Addressing Packet Switched Networks General Switching Diagram: Reference Handout What is my IP Address? Go to “Start” menu Click on “Run” In window type WINIPCFG When gray window appears, lick on “More Info” Tracing a Message Click on MS-DOS prompt At the C:\WINDOWS> prompt type: tracert www.loc.gov Modems Function: Modulation – demodulation. Types and speeds: Standard ISDN. Cable TV. xDSL. Satellite World Wide Web (WWW) Historical development. HTTP. HTML. Multimedia. Trends Convergence. Voice over IP (VIP). Wireless. 3G (Third Generation) PCS (Personal Communication Services) Ubiquitous networking Remote device control.