Laudon & Laudon: Canadian Edition Chapter 7 Telecommunications – Part 1 In the continuing saga towards our greater understanding of management information systems, we will now discuss the concepts of telecommunications and networks. The importance of these topics cannot be overestimated since without telecommunications networks, communicating over long distances and sharing electronic information would not be possible. The ability to do both of these things is vital for and information society.

Information Systems for Management Outline Telecommunications Model Analog Signal Digital Signal Communication media (twisted wire, coaxial cable, fibreoptic, microwave, satellite signalling) Computer Network Local Area Network (LAN) Wide Area Network (WAN) Network Hardware Network Software Network Topology Packet and Circuit Switching Telecommunications Information Systems for Management

Information Systems for Management Telecommunications sender receiver relay electronic signal (message) channel Telecommunications: Electronic data transfer (communications) over some a channel (medium). Telecommunications system contains: Sender & Receiver Message - Data that is transmitted as a signal over a channel Channel - The medium by which data or voice are transmitted between sender and receiver (e.g., twisted wire, optical cable, air— microwave, satellite signaling) Other equipment (switch, relay, modem, gateway, etc.) Telecommunications Information Systems for Management

Types of Signals Analog signal Continuous waveform Can get all the ranges Use: voice communications Example: electrical light Digital signal Discrete waveform Two states: 0 and 1 (On-off electrical pulses) Use: data communications Example: computer, computer nets Modem (MOdulation / DEModulation) Converts digital into analog, and analog into digital signals Telecommunications Information Systems for Management

Telecomm Media & Transmission Speeds Total amount of data transmitted through a telecommunications channel measured as bits per second. Medium Speed Fiber optic cable 6 Tbps Coaxial cable 1Gbps Twisted wire Up to 1Gbps Microwave 600 Mbps Satellite bps=bits per second; Kbps=kilobits (103); Mbps=megabits (106); Gbps=gigabits (109); Tbps=terabits (1012) Telecommunications Information Systems for Management

Information Systems for Management Networks Network - A set of nodes (computers, printers, and other equipment) and linking media. Types of networks based on: Topology (configurations of nodes and links; e.g., star network) Geographic scope – LAN vs. WAN Communications method – Circuit vs. Packet Telecommunications Information Systems for Management

Information Systems for Management Star Network All computers are connected to a central node (e.g. hub, computer, switch, controller). All communications between computers must pass through the central node. Better communications control, but the central node is critical (high-risk). hub, switch, controller, or computer Telecommunications Information Systems for Management

Information Systems for Management Bus Network All computers are linked by a single circuit All messages are broadcast to the entire network Simple communications management as signals can travel both directions as needed, but collision possible. Telecommunications Information Systems for Management

Information Systems for Management Ring Network All computers are linked by a closed loop Data is passed in one direction from one node to another Better control and no collision, but communications management more complex than with bus. Telecommunications Information Systems for Management

Laudon & Laudon: Canadian Edition LAN vs. WAN Local Area Network (LAN) Network covering a smaller area (one or more buildings like campus) Wide Area Network (WAN) Network covering a larger area (a region, world) Examples: IBM’s SNET, Internet Many student labs will have Lans, shared printers, etc. Telecommunications Information Systems for Management

Information Systems for Management Circuit Switching Circuit Switching Entire message travels from switch to switch Used for analog signals (classical telephone network) Source: TechWeb Telecommunications Information Systems for Management

Information Systems for Management Packet Switching Packet Switching Sender breaks message into small packets Packets are routed in the most economical way by different routes Receiver reassembles the message Internet works this way Telecommunications Information Systems for Management

Information Systems for Management Network Hardware Router, Switch –most used today Devices for managing communications on a network Telecommunications Information Systems for Management

Information Systems for Management Network Software Network Operating System (NOS) Software that routes and manages communications & resources (e.g., Ethernet OS for bus network, IBM toke Passing Ring OS for ring network, Windows Server and Client NOS) Network Protocol Rules that govern communications between network nodes (e.g., how computers on a bus network communicate; TCP/IP – how computers on different networks communicate) NOS can support a certain protocol and more than one (TCP/IP today supported by most NOSes) Telecommunications Information Systems for Management

Transfer Control Protocol & Internet Protocol (TCP/IP) Defines the Internet – how different networks (NOSes, hardware, application and system software) communicate with each other. Four layers: Email (SMTP), file transfer (FTP, HTTP TCP IP Telecommunications Information Systems for Management

Information Systems for Management How Internet Works SENDER RECEIVER SMTP to TCP: “Take this message and send it to this email address”. TCP Breaks message into packets and passes to IP. IP Looks up Internet addresses and routers on the way to receiver. Puts address on each packet and passes to Network. Puts packets on com- munication medium. SMTP restores original format of message and presents it. TCP Put packets back to the Whole in proper orders and Checks sum of data received vs. sum sent. IP Accepts packets and reports back to routers. Gets packets off com- munication medium. See: How SMTP and TCP/IP work Telecommunications Information Systems for Management