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Data Communications Applications

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Collect data during day, transmit at end of day. 6. Data Application Evolution ... Polling. Master TTY polls (asks) remote (slave) TTY if it has a message ... – PowerPoint PPT presentation

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Title: Data Communications Applications


1
Chapter 4
  • Data Communications Applications

2
Categories of Applications
  • Human-machine interaction
  • Type of information
  • Timeliness

3
Human-Machine Interaction
  • Person-to-person
  • Machine can be in the middle
  • Ex. phone call
  • Person-to-machine, machine-to-person
  • User interfaces to computer through terminals
  • Computer responds to user
  • ATM transaction
  • Machine-to-machine
  • File transfer between computers
  • Automated instrumentation communicating to
    computers

4
Information Types
  • Voice
  • Structured data
  • Has records and fields
  • Used in data processing apps
  • Unstructured data
  • Word processing
  • Images
  • Video, photographs, FAX

5
Timeliness
  • Online, realtime (fast)
  • Timesharing computers
  • Airline reservations
  • Store and forward (delayed)
  • Voice mail
  • e-mail
  • Batch (offline)
  • Collect data during day, transmit at end of day

6
Data Application Evolution
  • Teletype machines (TTY) - electronic typewriters
  • Connected in networks to transmit information

7
Administrative Message Switching
  • Connecting teletypes using telecom lines
  • Point-to-point
  • Teletypes in branch offices connect directly to a
    teletype in main office, one-to-one
  • Messages received by one teletype had to be typed
    into another to relay it
  • Improvement
  • Store messages on paper tape
  • Relay using paper tape- dont have to retype

8
Administrative Message Switching
9
Administrative Message Switching
  • Multi-point line
  • More than one TTY on a line
  • Messages seen by all TTYs on the line
  • Polling
  • Master TTY polls (asks) remote (slave) TTY if it
    has a message
  • Avoids message collisions
  • Requires address information in message
    (overhead)
  • Slaves must wait their turn

10
Administrative Message Switching
11
Computers and AMS (1960)
  • First
  • Computer could read messages on one line and
    transmit on another like router
  • Second
  • Computers grew more powerful
  • Added storage and calculation capabilities
  • Third
  • Users interacted on-line with computer
  • Fourth
  • Multiple users timeshare with computer

12
Computers and AMS (1960)
13
Distributed Processing
  • Began in late 1970s
  • Applications executed in parts on different
    computers
  • Didnt work well

14
Client-Server Computing
  • Server computers have data bases or run
    applications that Client computers access or use.
  • High-speed connections needed between clients and
    servers to handle multimedia
  • Most LANs use client-server model

15
Small LAN
16
Structured Data Applications
  • Delta Airlines reservation system (1985)
  • 4000 voice lines, 18 reservation centers
  • 66 data lines handling 350 transactions/second
    peak
  • 23,000 terminals in data network, including
    terminals in 2800 travel agencies
  • Automatic teller network
  • Retail checkout system
  • Point of sale terminals
  • Data collection at night
  • Accounting and inventory info updated in HQ
    computer

17
Airline Reservation System
18
Automatic Teller Machine Network
19
Retail Checkout System
20
Unstructured Data Applications
  • E-mail
  • Host computer holds user electronic mailboxes
  • Disk space is big issue
  • Security - company can read e-mails
  • TCP/IP uses Simple Mail Transfer Protocol (SMTP)
  • Disadvantages
  • Cannot send executable file with e-mail
  • Limited e-mail size
  • No foreign character sets
  • Multipurpose Internet Mail Extension (MIME) is an
    extension of SMTP

21
Unified Messaging System
  • Some e-mail software allows
  • E-mail
  • Voice mail
  • Fax
  • Sends to single phone number or mailbox
  • Computer or phone can access
  • System can read e-mail message if you access
    via phone

22
Image Application
  • Video conferencing
  • Meetings conducted between locations using
    cameras and TVs in conference rooms
  • One-way or two-way
  • Full motion or freeze frame
  • Freeze frame uses occasional updating
  • Reduces data rate
  • Corporate environment
  • Conference room with camera for people and camera
    (or computer) for slides
  • Compression technology helps data rate

23
Data Communication Considerations
  • Response time
  • Security
  • Especially for business
  • Planning for failures
  • Have backup for computer/system
  • Disaster recovery - long term failure
  • Needs planning
  • Test the plan!

24
Disaster Recovery Plan
25
WTC Disaster
26
Case Study Dows Applications That Use
Telecommunications
  • Dow Corning minimizes the number of mainframes
    used for business apps
  • Use a few computer centers accessed throughout
    company by telecom network
  • Unit cost of computing is cheaper even though
    telecom cost is higher percentage of total
  • Manufacturing centers use smaller computers
    linked to mainframes

27
Case Study Dows Applications That Use
Telecommunications
  • Business apps
  • Customer order processing
  • Inventory management and control
  • Manufacturing planning and scheduling
  • Finance and accounting
  • Personnel and human resource management
  • Planning and budgeting
  • Mainframes handled e-mail starting in 1983
  • Intranets growing
  • Voice mail and video conferencing
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