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