Networking - 1.1 - The intermediary devices and their roles


  • Network Access Devices (Hubs, switches, and wireless access points)
  • Internetworking Devices (routers)
  • Communication Servers and Modems
  • Security Devices (firewalls)

Network Media

Communication across a network is carried on a medium

The signal encoding is different for each media type.

  • Metallic wires, the data is encoded into electrical impulses
  • Fiber optic cables - pulses of light, within either infrared or visible light ranges.

Wireless transmission, electromagnetic waves
Criteria for choosing a network media are:

  • The distance the media can successfully carry a signal.
  • The environment in which the media is to be installed.
  • The amount of data and the minimum required speed.
  • The cost of the media and installation

Services and Processes

Processes running on the intermediary network devices perform these functions:

  • Regenerate and retransmit data signals
  • Maintain information about what pathways exist through the network and internetwork
  • Notify other devices of errors and communication failures
  • Direct data along alternate pathways when there is a link failure
  • Classify and direct messages according to QoS priorities
  • Permit or deny the flow of data, based on security settings

Networking Representations