LEARNING OBJECTIVES
• Components of Telecommunications
System
• Calculate Capacity of
Telecommunications Channels &
Evaluate Transmission Media
• Types of Networks & Network
Services
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8.2
LEARNING OBJECTIVES
• Describe connectivity network
standards
• Identify applications for supporting
electronic commerce, business
• Analyze management problems of
networking
*
8.3
Communication Theories
Sender -> medium -> receiver
Coding -> transmit -> decoding
*
8.4
INFORMATION
SUPERHIGHWAY
Is this a good analogy?
Look for analogies of business
development after railroad, interstate
highways, and telephone.
*
SYSTEM COMPONENTS
•
•
•
•
Computers
Terminals (Input/Output Devices)
Communication channels (medium)
Processors (Modems; Multiplexers; Frontend Processors)
SYSTEM
• Network software
*
INPUT
PROCESS
FEEDBACK
OUTPUT
Dictionaries and
Protocols
• Dictionary: code conversion
• Protocol: rules and procedures used
for transmission
*
ANALOG SIGNAL
• Continuous waveform
• Voice Communications
*
DIGITAL SIGNAL
• Discrete waveform
• Two discrete states:
– 1-bit & 0-bit
– ON / OFF pulse
• The meaning of 32-bit, 64-bit, etc.
• Data Communications
*
Sampling
• Converting analog signals to digital
signals
• Increased flexibility for editing
• Smaller codes (.wav vs. .mid files)
COMMUNICATION
CHANNELS
Means by which data are transmitted:
• Twisted pair (Copper Wires)
• Coaxial cable: (Insulated Copper
Wires)
• Fiber-optic cable
• Microwave
*
FIBER OPTICS
• Super clear glass strands
• High bandwidth (up to ten billion bits
per second transmission)
• Full duplex (two-way communication)
*
SIGNAL
LASER
CABLE
PHOTO
DETECTOR
SIGNAL
LOW-ORBIT SATELLITE
MICROWAVE
TRANSMISSION
UPLINK
DOWNLINK
WIRELESS TRANSMISSION
TECHNOLOGIES
• PAGING SYSTEM: Small Page Beeps
when Receives Short Message
• CELLULAR TELEPHONE: Device
uses Radio Waves to Reach
Antennas Within Areas Called Cells
• MOBILE DATA NETWORKS: Radio based Data Network using Hand-held
Computers. Cheap, Efficient
*
WIRELESS TRANSMISSION
TECHNOLOGIES
• Personal Communication Service:
Cellular; Lower Power; Higher
Frequency. Smaller Phones not
Shielded by Buildings, Tunnels
• Personal Digital Assistant: Pen
Sized, Hand-held, Digital
Communicator
*
Communication Channels are
evaluated by:
• Transmission Speed: Bits per
Second (BPS) or Baud
• Bandwidth: Capacity of Channel;
Difference between Highest & Lowest
Frequencies
*
SPEEDS & COST OF MEDIA
MEDIUM
TWISTED PAIR
SPEED
300 BPS - 10 MBPS
MICROWAVE
256 KBPS - 100 MBPS
SATELLITE
256 KBPS - 100 MBPS
COAXIAL CABLE
56 KBPS - 200 MBPS
FIBER OPTICS
56 KBPS - 10 GBPS
BPS: BITS PER SECOND
KBPS: KILOBITS PER SECOND
MBPS: MEGABITS PER SECOND
GBPS: GIGABITS PER SECOND
COST
LOW
HIGH
8.18
COMMUNICATIONS
PROCESSORS
• FRONT- END PROCESSOR: minicomputer
manages communication for host
computer (secretary)
• CONCENTRATOR: computer collects
messages for batch transmission to host
computer
• CONTROLLER: computer controls
interface between CPU and peripheral
devices (traffic cop)
• MULTIPLEXER: allows channel to carry
multiple sources simultaneously
*
Network Topologies
how computers are tied together
USER
USER
STAR
HOST
USER
USER
Network Topologies
how computers are tied together
USER
USER
USER
USER
USER
USER
BUS (“Broadcast”)
Network Topologies
how computers are tied together
USER
USER
RING
USER
USER
Types of Local Networks
• Private Branch Exchange (PBX):
firm’s central switching system
• Local Area Network (LAN): dedicated
channels; limited distance; higher
capacity than PBX. Can share
expensive hardware & software
*
Local Area Network
• Server: stores programs, data; determines
access to network
• Gateway: connection to other networks
• Network Operating System (NOS):
manages file server; routes
communications on network
• Peer-to-peer vs. Client/Server
*
Wide Area Network (WAN)
• Spans large geographic distances
• Can include cable, satellite,
microwave
*
Dedicated Line vs.
Shared Line
• Cost and benefit of a dedicated line
• Additional arrangements (overhead)
needed for people to share the same
medium
NETWORK SERVICES
• Packet Switching (delivered bits and
pieces)
• Frame Relay (delivered in chunks)
• Asynchronous Transfer Mode (ATM)
• Integrated Services Digital Network (ISDN)
• Digital Subscriber Line (DSL)
• Cable modem
• T1 Line (high capacity phone line)
*
PACKET SWITCHING
(X.25):
• Breaks data blocks into small
packets (e.g.: 128 Bytes)
• Packets routed via the most
economical means
• Reassembled at destination
*
TCP/IP Model Components
Developed by Dept of Defense in 1972
• Application Layer
• Transmission Control Protocol (TCP):
Breaks Data into Datagrams
• Internet Protocol (IP): Breaks, Sends
Datagrams as Smaller IP Packets; Can
Repeat Transmission to Increase
Reliability
*
8.35
TCP/IP Model Components
• NETWORK INTERFACE: Handles
Addressing and Interface Between
Computer & Network
• PHYSICAL NET: Defines Electrical
Transmission Characteristics for Sending
Signal Along Networks to Destination
*
8.36
OPEN SYSTEM
INTERCONNECT (OSI)
INTERNATIONAL REFERENCE MODEL
FOR LINKING DIFFERENT TYPES OF
COMPUTERS & NETWORKS. LAYERS:
1. PHYSICAL: Transmission of Data over
Medium
2. DATA LINK: Packaging, Transfer of
Packets; Error Checking
3. NETWORK: Routing Packets Over WAN
*
OPEN SYSTEM
INTERCONNECT (OSI)
4. TRANSPORT: Ensures Reliable Data
Delivery
5. SESSION: Establishes Communication
Links on Network
6. PRESENTATION: Code Conversion for
Data Presentation
7. APPLICATION: Specialized User
Functions (e.g.: Operating System; File
Transfer; e-mail)
*
FACILITATING
APPLICATIONS
•
•
•
•
•
•
•
E-mail
Voice mail
Fax
Teleconferencing
Dataconferencing
Videoconferencing
Groupware
*
Groupware:
for collaborative works
•
•
•
•
•
Group writing and commenting
Email distribution
Scheduling
File/Database sharing
E-meetings
*
DIGITAL INFORMATION SERVICES
PROVIDER
TYPE OF SERVICE
AMERICA ONLINE
GENERAL INTEREST / BUSINESS INFORMATION
COMPUSERVE
GENERAL INTEREST / BUSINESS INFORMATION
PRODIGY
GENERAL INTEREST / BUSINESS INFORMATION
DOW JONES NEWS RETRIEVAL BUSINESS / FINANCIAL INFORMATION
QUOTRON
FINANCIAL INFORMATION
DIALOG
BUSINESS / SCIENTIFIC / TECHNICAL INFORMATION
LEXIS
LEGAL RESEARCH
NEXIS
NEWS / BUSINESS INFORMATION
Electronic Data Interchange
(EDI)
Computer-to-computer
Exchange between two organizations
of standard business transaction
documents
SELLER
CUSTOMER
*
ORDERS, PAYMENTS
COMPUTER
SHIPPING NOTICES, PRICE
UPDATES, INVOICES
COMPUTER
MANAGEMENT ISSUES &
DECISIONS
PROBLEMS:
• CONNECTIVITY
• LOSS OF MANAGEMENT CONTROL
• ORGANIZATIONAL CHANGE
REQUIREMENTS
• HIDDEN COSTS OF CLIENT/SERVER
COMPUTING
• RELIABILITY & SECURITY
*
MANAGEMENT ISSUES &
DECISIONS
TELECOMMUNICATIONS PLAN:
• KNOW LONG-RANGE PLANS
• AUDIT EXISTING CAPABILITIES
• IDENTIFY, PRIORITIZE CRITICAL
IMPROVEMENTS
• ENHANCE FIRM’S STRATEGIC POSITION
IMPLEMENT PLAN
*