Sem 2 Networking Programming Week 4 Physical Layer

Limitations of Electrical Signals

• Attenuation: electrical signals weaken over long distances
• Interference: susceptible to electromagnetic interference (EMI) and radio frequency interference (RFI) from two sources
• Crosstalk: interference between adjacent wires

Mitigation of Limitations

• Strict adherence to cable length limits to mitigate attenuation
• Metallic shielding and grounding in copper cables to mitigate EMI and RFI
• Twisting circuit pair wires together to mitigate crosstalk

Types of Copper Cabling

• Unshielded Twisted Pair (UTP):
  • Most common networking media
  • Terminated with RJ-45 connectors
  • Interconnects hosts with intermediary network devices
  • Key characteristics: outer jacket protects copper wires, twisted pairs protect signal from interference, color-coded plastic insulation electrically isolates wires
• Shielded Twisted Pair (STP):
  • Better noise protection than UTP
  • More expensive and harder to install than UTP
  • Terminated with RJ-45 connectors
  • Interconnects hosts with intermediary network devices
  • Key characteristics: outer jacket protects copper wires, braided or foil shield provides EMI/RFI protection, foil shield for each pair of wires provides EMI/RFI protection
• Coaxial Cable:
  • Consists of outer cable jacket, woven copper braid or metallic foil, flexible plastic insulation, and copper conductor
  • Used in wireless installations and cable internet installations
  • Commonly used with coaxial connectors

UTP Cabling

• UTP has four pairs of color-coded copper wires twisted together and encased in a flexible plastic sheath
• No shielding is used
• Relies on cancellation and variation in twists per foot to limit crosstalk

UTP Cabling Standards and Connectors

• Standards established by TIA/EIA (568) and IEEE
• Cable types, cable length, connectors, cable termination, and testing methods standardized
• Electrical standards rated by IEEE (Category 3, 5, 5e, 6)

Straight-through and Crossover UTP Cables

• Straight-through: both ends T568A or T568B, used for host to network device connections
• Crossover: one end T568A, other end T568B, used for host-to-host, switch-to-switch, and router-to-router connections

Fiber-Optic Cabling

• Less common than UTP due to expense
• Ideal for some networking scenarios
• Transmits data over longer distances at higher bandwidth than copper cabling
• Less susceptible to attenuation, and completely immune to EMI/RFI
• Made of flexible, extremely thin strands of very pure glass
• Uses laser or LED to encode bits as pulses of light

Physical Layer

• Purpose: establish a physical connection to a local network
• Connection can be wired or wireless
• Applies to corporate offices and home networks
• Network Interface Card (NIC) connects device to network
• Not all physical connections offer the same level of performance
• Transports bits across the network media

Bandwidth

• Capacity of a medium to carry data
• Digital bandwidth measures amount of data that can flow from one place to another in a given amount of time
• Physical media properties, current technologies, and laws of physics play a role in determining available bandwidth

Bandwidth Terminology

• Latency: amount of time, including delays, for data to travel from one point to another
• Throughput: measure of transfer of bits across the media over a given period of time
• Goodput: measure of usable data transferred over a given period of time

Characteristics of Copper Cabling

• Copper cabling is the most common type of cabling used in networks today
• Inexpensive, easy to install, and has low resistance to electrical current flow
• Very small core

Fiber-Optic Cabling Usage

• Fiber-optic cabling is used in four types of industry:
  • Enterprise Networks
  • Fiber-to-the-Home (FTTH)
  • Long-Haul Networks
  • Submarine cable Networks

Fiber-Optic Connectors

• Fiber patch cords: used to connect fiber-optic cables
• Yellow jacket for single-mode fiber cables and orange (or aqua) for multimode fiber cables