7/12: Ch. 6 Telecommunications

• Business Value of Telecommunications

• Trends– Industry– Technology– Application

• Internet applications

• Network models– WANs, LANs, Internetworks, Intranets, Extranets,

Client/Server, Interorganizational

Business Value

• How businesses use telecommunications– enterprise collaboration– electronic commerce– internal business

• Business Value of Telecommunications– overcoming barriers:

geographical, time, cost, structural

Trends

• Industry– increased number of suppliers– deregulation act create more suppliers

• Technology– Open systems increase connectivity– Digital overtakes analog– Wireless

• Application– applying telecommunications to every aspect of

busines

Internet Applications

• origins: ARPANET – Defense Dept. project

• WWW – Tim Berners-Lee at CERN (Switz.)

• Email

• Usenet (newsgroups)

• IRC (chat rooms, AIM)

• FTP

• Telnet

Network Models

• basic model:– terminal – processor – channel – processor – terminal– includes software at most points

Network Models

• WAN – Wide Area Network

• LAN – Local Area Network– network servers, shared peripherals, etc.

• Internetworks – Networked LANs– using processors: switches, routers, hubs, gateways

• Intranets & Extranets – WWW for internal & external use -- VPNs

• Client/Server – applications reside on server– client programs reside on terminals (PCs)

Part 2: Alternatives

• Media choices– Twisted pair, coaxial cable, fiber optics, microwaves,

satellites, cellular phone systems, wireless LANs

• Processors– Modems, multiplexers, internetwork processors

• Software – common functions

• Network Topologies– Star, bus, ring

• Architecture & Protocols– TCP/IP, OSI

Media Choices

• Twisted Pair Wire– telephone wire

• Coaxial Cable– cable TV

• Fiber Optics– glass fibers use light to transmit data

images courtesy of mag-nify.educ.monash.edu.au, www.mars-cam.com, 3Com.com

Media Choices

• Terrestrial Microwaves– line-of-sight up to 30 miles apart

• Communication Satellites– DirectPC, DirectTV

• Cellular Phone Systems

• Wireless LANs– radio, infrared

images courtesy of mitsubishi.com

Processor Choices

• Modems– Analog modems (telephone)– ISDN, Cable, DSL modems

• Multiplexers– allow multiple users on same channel– FDM, TDM, STDM

• Internetwork Processors– switches, hubs - complete connections– routers, gateways – interfaces for networks

image courtesy of 3Com

Software

• Access control– autodialers, log-ins, etc.

• Transmission control– error checking (parity checking)– transmission of data, etc. (often file transfer)

• Network management– prioritizes traffic on network– prevents (or deals with) data collisions, etc.

• Security management– includes encryption, access validation

Network Topologies

• nodes, hubs, backbones, servers

• Star– central server control

• Bus– like a highway

• Ring– control gets handed

off from node to node

Architecture & Protocols

• circuit-switched networks– telephone conversation: whole circuit reserved

• packet-switched networks– shared passages, packets of information being sent– Internet: packet-switched (ex. TCP)

Internet Protocol (IP)

• address: 4 separate 3-digit numbers separated by periods

• looking up IPs at Internic.net– URLs are used to look up IP addresses at Domain

Name Servers (DNS)

165.134. 1 . 25

209.145.150. 10

Transmission Control Protocol (TCP)

• breaks message into manageable chunks and sends them separately

• like packing up a house’s contents to move

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