Layer 1 Media, Connections, and Collisions

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Layer 1 Media, Connections, and Collisions

• Shawn Shuoh-Ren Tsai
• Cisco Academy Training Center
• David Ta-Wei Shih
• CGUIC

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STP

• Each pair of wires is wrapped in metallic foil.
• The 4 pairs of wires are wrapped in an overall
  metallic braid or foil.
• STP reduces electrical noise, both within the
  cable (pair to pair coupling, or crosstalk) and
  from outside the cable (electromagnetic
  interference -- EMI -- and radio frequency
  interference -- RFI).

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UTP (Unshielded twisted-pair cable )

• is a four-pair wire medium - composed of pairs of
  wires - used in a variety of networks
• relies solely on the cancellation effect,
  produced by the twisted wire pairs, to limit
  signal degradation caused by EMI and RFI.
• Advantages less cost, easy to install
• Disadvantages more prone to electrical noise and
  interference

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Coaxial Cable

• Is more difficult to install

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OSI Model

• ensured compatibility and interoperability
• standards for networking media that have been
  developed and issued by the following groups
• IEEE - Institute of Electrical and Electronics
  Engineers
• UL - Underwriters Laboratories
• EIA - Electronic Industries Alliance
• TIA - Telecommunications Industry Association
• The latter two organizations, jointly, issue a
  list of standards that you will frequently see
  listed as the TIA/EIA standards

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The TIA/EIA standards address six elements

• horizontal cabling
• backbone cabling
• telecommunications closets
• equipment rooms
• work areas
• entrance facilities

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Horizontal Cabling

• This lesson will focus on TIA/EIA-568-A standards
  for horizontal cabling
• These are category 1 (CAT 1), category 2 (CAT 2),
  category 3 (CAT 3), category 4 (CAT 4), and
  category 5  (CAT 5) cabling.
• Only CAT 3, CAT 4, and CAT 5 are recognized for
  use in LANs.
• CAT 5 is the one most frequently recommended and
  implemented in installations today.

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Making and testing cable

• Cable testers
• Wire maps
• Straight-through cable
• A / A (B / B)
• Crossover
• A / B
• Roll over
• A / A (B / B)

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Collisions and Collision Domain

• A situation that can occur, when two bits
  propagate at the same time on the same network,
  is a collision
• The area within the network, where the data
  packets originated and collided, is called a
  collision domain, and includes all shared media
  environments

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Segments the Collision Domains