TDC 461/Session 5

Data Communications and the PSDN


  1. Announcements
    1. Reminder: Exams are due Friday, 7 August, at 5:00pm.
  2. Voice Processing
    1. Overview and Review
    2. Touch Tone and Voice Recognition
    3. Automated Attendant
    4. Automatic Call Distributors--5 main duties
      1. Prioritize calls
      2. Route the call to the appropriate agent
      3. Deliver any announcements, queue
      4. Direct busy calls to announcements
      5. Handle messages for call backs
    5. Voice Mail
    6. Interactive Voice Response
  3. Computer Telephony Integration
  4. Data Communications--Big Concepts:
    1. 6 Steps to Data Com
      1. Select and Deal with transmission media
      2. Use communicating devices that will preesnt the proper signal to the line
      3. Set up or abide by already-accepted rules (protocols)
      4. Use a pre-established alphabet that the devices can understand
      5. Ensure the integrity of information before, during, and after transmission
      6. Deliver information to the receiving device
    2. Big Concept #1: Standards
      1. =d->definition or description of a technology
      2. de facto
      3. de jure
      4. De facto standards often become de jure standards later down the line.
    3. Big Concept #2: Architectures
      1. =d->a coordinated set of guidelines that together constitute a complete description of one approach to building a communications environment.
    4. Big Concept #3: Protocols
      1. =d->provide the rules for communication between counterpart components on different devices.
      2. Protocols are usually written into software, but there are two notable hardware protocols, asynchronous and synchronous.
      3. Asynchronous Transmission Protocols: clocked or synchronized one byte at a time. Each byte is framed by one start bit, at least one stop bit, and an error checking bit (partity bit). 7-bit bytes (like ASCII) or 8-bit bytes (EBCDIC) require 10-11 bits for successful transmission.
        1. Asynchronous transmission has high overhead
        2. Nominal speed calculation-9600 bps/10 bits per byte=960 characters per second, in the best of all worlds
        3. Clocking is controlled by data terminal equipment(DTE) (PC)
        4. Most PCs and Minicomputers use asynchronous transmission
        5. Serial interfaces can only handle asynch transmission
      4. Synchronous Transmission Protocols
      1. clocked on blocks of bytes rather than a single byte
      2. bytes are sent in contiguous groups (blocks) of varying size
      3. much lower overhead than asynchronous transmission
      4. clocking is controlled by data communications equipment (DCE) (Modem)
      5. 2400+ bps modems are really synchronous "over the wire"
    5. Big Concept #4: Error Detection
      1. 3 modes of error control
        1. Recognition and Flagging
        2. Recognition and Retransmission
        3. Recognition and Forward Error Correction
      2. Echo Checking=>echoes sent signal back to senderís monitor for checking
      3. Parity Checking/Vertical Redundancy Checking=>
        1. Odd Parity=>
        2. Even Parity=>
        3. No parity=>
      4. Longitudinal Redundancy Checking
      5. Cyclic Redundancy Checking
    6. Big Concept #5: Plexing--Review
      1. Simplex
      2. Half Duplex
      3. Full Duplex
    7. Big Concept #6: Multiplexing
      1. Space Division Multiplexing
      2. Frequency Division Multiplexing
      3. Time Division Multiplexing
    8. Big Concept #7: Compression
      1. Why compress?
      2. Formatting
      3. Redundant Characters
      4. Commonly Used Characters
      5. Commonly used strings of characters
    9. Big Concept #8: Standards
  5. Public Switched Data Network
    1. Brief History
    2. 1950s
    3. 1960s
    4. 1970s
    5. 1980s
    6. 1990s
      1. WAN/MAN development
      2. Dataphone Digital Service
      3. Switched 56 Kbps (Digital Switched Access)
      4. Circuit-switched digital service applicable to same applications as DDS
  6. Digital Carrier Systems and Networks
    1. Carrier Systems
      1. =>systems that derive multiple logical channels from a single physical communications path, thereby supporting multiple communications.
    2. Digital Carrier
      1. introduced in 1957 in Newark, NJ.
    3. T-carrier (trunk carrier) refers to a specific set of cable pairs and digital repeaters every 6000 feet, for twisted pair. Much less for fiber.
    4. T-carrier concept
      1. Uses:
      2. Advantages:
    5. Channelized T-carrier
    6. Unchannelized T-carrier
    7. Fractional T1
    8. Encoding
    9. Framing
    10. Hardware
      1. Channel Service Units and Digital Service Units=>
      2. Multiplexers
      3. Nodal multiplexers=>
  7. X.25 (Packet-Switched) Networks
    1. Concept of packetization
    2. Concept of packet-switching
  1. ISDN
    1. SS7 protocol
    2. Basic-Rate Interface (BRI) ISDN
    3. Primary-Rate Interface (PRI) ISDN
    4. Applications of ISDN