Chapter 4: Telecommunications and Networking

Telecommunications & Networking v Telecommunications - communications (both voice and data) at a distance v Networking - the electronic linking of geographically dispersed devices

The Need for Networking v Sharing of technology resources v Sharing of data v Distributed data processing and client/server systems v Enhanced communications, including Electronic Data Interchange (EDI) and access to the Internet

Telecommunications & Networking: The Big Pieces v Analog vs. digital signals v Media v Topology v Network types v Protocols

Modem v An abbreviation for mo dulator/ dem odulator v A device that converts data from digital form to analog form so that it can be sent over the analog telephone network (as well as reconverts data after it has been transmitted)

Speed of Transmission v bandwidth - difference between highest and lowest frequencies (cycles per second) that can be transmitted on a particular medium - a capacity measure v Hertz - cycles per second v baud - signals sent per second v common measure - bits per second (bps)

Types of Transmission Lines v Private, or dedicated lines v Switched lines v Simplex transmission v Half-duplex transmission v Full-duplex transmission

Transmission Media v Twisted pair v Coaxial cable - baseband and broadband v Wireless, including microwave, radio frequency, infrared light v Satellite v Fiber optics

New Satellites v Over a dozen new projects proposed v 1,700 satellites to be launched in the next ten years, compared to the present 150 commercial satellites v Low earth orbit (LEO) satellites - only 400 to 1000 miles above the earth, compared to geosynchronous satellites at 22,000 miles above the equator

New Satellites (continued) v Iridium satellites to offer mobile telephony, paging, and data communications (Motorola, Lockheed Martin, Sprint) v Loral’s Globalstar - 48 satellites, similar services to Iridium

New Satellites (continued) v Teledesic satellites, Internet access, corporate networking, desktop videoconferencing (Craig McCaw, Bill Gates)

Telecommunications Transmission Speeds v Twisted pair - voice telephone14,400 bps -56,000 bps v Twisted pair - conditioned56 kbps kbps v Twisted pair - LAN4 mbps mbps v Coaxial cable - baseband10 mbps mbps v Coaxial cable - broadband10 mbps mbps v Radio frequency wireless LAN2 mbps - 8 mbps v Infrared light wireless LAN4 mbps - 16 mbps v Microwave / Satellite64 kbps - 50 mbps v Fiber optic cable100 mbps - 30 gbps

Topology of Networks v Bus topology v Ring topology v Star topology v Tree, or hierarchical, topology v Mesh topology v More complex topologies

Network Types v Computer telecommunications network v Private branch exchange (PBX) network v Local area network (LAN) v Backbone network v Wide area network (WAN) v Internet

Local Area Networks v Contention bus network (e.g., Ethernet) - uses CSMA/CD protocol v Token bus network v Token ring network

New LAN Technology v Fast Ethernet : Ethernet (contention bus) operating at speeds up to 100 mbps v Fiber Distributed Data Interface (FDDI): Token ring architecture delivered on a dual ring at speeds up to 100 mbps

Backbone Networks v Middle distance networks that interconnect LANs in a single organization with each other and with the organization’s WAN and the Internet v Employ high-end LAN technology, often operating at 100 mbps or more

Backbone Network Terminology v Hub - simple device connecting one section of a LAN to another v Bridge - connects two LAN segments when the LANs use the same protocols

Backbone Network Terminology (continued) v Router, or gateway - connects two or more LANs together; networks may use different protocols v Switch - connects more than two LANs that use the same protocol into a backbone network

Wide Area Networks v Direct Distance Dialing (DDD) v Wide Area Telephone Service (WATS) v Leased line (most common, T-1 lines) v Satellite (C-band, KU-band) v Value added network (VAN) v Integrated Services Digital Network (ISDN)

Value Added Network, or VAN v A data-only, private, nonregulated telecommunications network that uses packet switching v An organization may choose to buy the services of a VAN to implement its wide area network (WAN)

Packet Switching v A method of operating a digital telecommunications network in which information is divided into packets of some fixed length that are then sent over the network separately v Permits more efficient use of the network

ISDN - Integrated Services Digital Network v An emerging set of international standards by which the public telephone network will offer extensive new telecommunications capabilities - including simultaneous transmission of voice and data over the same line - to telephone users worldwide

ISDN - Integrated Services Digital Network v Offered over twisted pair wiring - “B” or bearer channels, “D” or data channels v Basic rate - two B channels of 64 kbps (thousand bits per second), one 16 kbps D channel - all over one twisted pair v Primary rate - 23 B channels of 64 kbps, one 64 kbps D channel - all over two twisted pairs

ISDN - Uses v Customer service application - customer’s records automatically sent to service representative’s workstation when a customer calls in v Economical and efficient way to solve dial-in headaches into a corporate network for telecommuters, branch offices

New WAN and LAN Technology v Asynchronous Transfer Mode (ATM) : Switching technology employing fast packet switching; an emerging standard for broadband ISDN, with speeds from mbps up to 622 mbps; many prognosticators believe that ATM represents the future for both LANs and WANs

Internet v Network of networks that use the TCP/IP protocol, with gateways (connections) to even more networks that do not use TCP/IP v Internet applications - , Usenet newsgroups, listserv, FTP, Gopher, Archie, Veronica, World Wide Web

Intranet v A network operating within an organization which employs the TCP/IP protocol v The organization uses the same Web browser, Web crawler, and Web server software as it would on the Internet, but the intranet is not accessible from outside the organization

Network Protocols v An agreed-upon set of rules or conventions governing communications among elements of a network (or, to be more precise, among layers or levels of a network)

Network Protocols v OSI (Open Systems Interconnection) Reference Model - an emerging standard v TCP/IP (Transmission Control Protocol/Internet Protocol) - standard used on the Internet and IU network v SNA (Systems Network Architecture) - an IBM standard

Changing Nature of Telecommunications/Networking v Decreasing price/performance ratio -- faster transmission, cheaper v More wireless options v Increased standardization v Increased usage of TCP/IP protocol v Greater management complexity due to anytime/anywhere access and support