TELECOMMUNICATIONS
Moving Information through Networks

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Table of Contents for Module 8

• Learning objectives for Module 1.
• 8.1 The OSI Model
• 8.2 Some key terms and concepts
• 8.3 LAN's and WAN's.
• Return to Course Home Page

Learning objectives for Module 8

• Upon successful completion of this module, students should be able to:
  1. Define key telecommunications concepts & terms.
  2. Have a broad understanding of the OSI model.
  3. Be able to present a general design for LAN's & WAN's.

8.1 OSI model.

• The (ISO) International Standards Organization's 7 layer (OSI)open systems Interconnection reference model for network comunications. An abstract conceptual model.

• All vendor network products (hardware & software) fit into the ISO standards.

• The following diagram is a gross simplification of the OSI Reference Model.

• For more details on the OSI Reference Model, check the following links.
  1. http://home.pi.net/~jdewolde/osimodel.htm
  2. http://www.primenet.com/~matador/osi.htm
  3. A look at the OSI model
  4. OSI Model
  5. Overview of the OSI model

8.2 Some key terms and concepts.

• For communication to take place, you need a media type.
  1. Radiated Media
     1. Radio frequency
        1. Broadcast
        2. Microwave
     2. Satellite
     3. Light frequency
        1. Infrared
  2. Conducted Media
     1. Electrical (less cost, more errors)
        1. UTP
           1. Cat 3 LANs up to 10 Mbps
           2. Cat 4 LANs up to 16 Mmps
           3. Cat 5 LANs up to 100 Mbps
        2. Coaxial cable
     2. Light (more cost, less errors)
        1. Fiber optic - Very high speed
• PC ports
  1. Serial
  2. Parallel
• Connectors
  1. RJ-11
  2. RJ-45
  3. DB-9
  4. DB-25
  5. Etc.
• Transmission lines
  1. Switched
  2. Leased
• Transmission speeds
  1. Dial-up (modem)
     1. 14.4 kbps
     2. 28.8 kbps (today's standard)
     3. Faster modems are starting to appear on the market.
  2. Direct connect
     1. 56 kbps (fractional T1)
     2. T1 (DS-1) - 1.5 Mbps
     3. T2 (DS-2) - 6.3 Mbps (could be fiber)
     4. T3 (DS-3) - 44 Mbps (usually fiber)
     5. T4 (DS-3) - 300 Mbps (fiber)
     6. Etc.
• TCP/IP - the Internet protocol, supports:
  • WWW
  • Telnet protocol
  • FTP
  • SMTP (Simple Mail Transfer Protocol).
  • Etc.
• ATM - the new kid on the block
• LAN protocols
  • Ethernet 10BaseT - 10 Mbps
  • Fast Ethernet - up to 100 Mbps
  • Token Ring - 44.746 Mbps.
  • Appletalk
  • Etc.
• Signal transfer equipment
  • Repeater - just repeats the "bit" signal.
  • Bridges - Ethernet bridges pass ethernet data packets unmolested to the remote side. Most ethernet bridges filter the 48-bit ethernet addresses, and not IP addresses.
  • CSU/DSU - Channel Service Unit/Digital Service Unit. A device which converts between disparate transmission protocols or signal formats (e.g., ethernet and T1).
  • Routers - Routers look at IP addresses, and decide which ones to pass through, and which ones to block.
  • Gateways - Usually a computer, usually used to transfer data from one type of network to a different network. For example, a company with a "private" national network may have a "gateway" to the Internet.
• Firewall - Generally speaking, a "firewall" is an attempt to prevent network users from accessing information they should not access. The more sophisticated the "gateway" control between your network and the outside world, the more security you have. The best firewall is a gateway computer that is specifically programmed to let only authorized users onto your system.

8.3 LAN's & WAN's.

• There are numerous designs for local area networks (LAN's) and wide area networks (WAN's)using a wide variety of vendor hardware and software.

• The following Ontario Central School diagrams are typical LAN designs.

• For more information on LAN's/WAN's, review the following links.

  1. LAN's

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