Understanding the Physical Layer of Networking

Oct 1, 2024

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Cisco Introduction to Networks: Physical Layer

Overview

  • Focus on the physical layer of the OSI model.
  • Objective: Explain how physical layer protocols, services, and network media support communications.
  • Topics covered:
    • Purpose and functions of the physical layer.
    • Physical layer characteristics.
    • Types of cabling: Copper, UTP, fiber optic, and wireless media.

Physical Layer Characteristics

  • Part of the OSI model (bottom layer).
  • Responsible for transmitting bits across network media.
  • Encodes frames from the data link layer as signals on local media.

Standards

  • Governed by organizations such as ISO, EIA, TIA, IEEE, ANSI.
  • OSI model includes the physical layer.

Components and Functions

Physical Components

  • Hardware devices, media, and connectors that transmit signals.
  • Examples: NICs, cabling materials, cable design.

Encoding

  • Converts data streams into predefined codes (bits: 0s and 1s).
  • Binary zeros and ones can be represented by voltage levels (copper) or light intensity (fiber optic).

Signaling

  • Method of representing bit values (1 & 0) on the medium.
  • Varies based on medium type (e.g., light pulses for fiber optics).

Bandwidth

  • Refers to the capacity of a medium to carry data.
  • Measured in bits per second (bps).
  • Influenced by media properties, technology, and physics.

Latency, Throughput, and Goodput

  • Latency: Time delay for data to travel from source to destination.
  • Throughput: Measure of bit transfer across media.
  • Goodput: Usable data transfer rate, excluding traffic overhead.

Types of Cabling

Copper Cabling

  • Common, inexpensive, easy to install.
  • Limitations: Signal attenuation, susceptible to EMI and RFI, and crosstalk.

Mitigation Techniques

  • Adherence to cable length limits.
  • Shielding and grounding for EMI/RFI.
  • Twisted pairs to mitigate crosstalk.

Types

  • UTP (Unshielded Twisted Pair): Common, terminated with RJ45, color-coded.
  • STP (Shielded Twisted Pair): Better noise protection, uses shielding.
  • Coaxial Cable: Used in wireless and cable internet installations.

Standards and Connectors

  • Standards established by TIA/EIA.
  • Includes cable types, lengths, connectors, termination, and testing.

Fiber Optic Cabling

  • Transmits data over long distances with high bandwidth.
  • Immune to EMI/RFI, lower signal attenuation.

Types

  • Single Mode Fiber (SMF): Small core, long distance, high cost.
  • Multimode Fiber (MMF): Larger core, short range, lower cost.
  • Used in enterprise networks, FTTH, long-haul networks, submarine cables.

Wireless Media

Properties

  • Carries electromagnetic signals using radio or microwave frequencies.
  • Offers mobility but has limitations like coverage area, interference, security.

Standards

  • Governed by IEEE: Wi-Fi (802.11), Bluetooth (802.15), WiMAX, ZigBee.

WLAN Devices

  • Wireless Access Point (AP): Connects wireless signals to network.
  • Wireless NIC Adapters: Enable wireless capabilities for hosts.

Summary

  • Key components and functions of the physical layer.
  • Characteristics and types of cabling and wireless media.
  • Importance of standards and potential issues in network setups.

Note: Remember the terms and definitions for exams, especially focusing on differences between UTP and fiber optic cables, and the various wireless standards.