OSI Layer 1: Physical Layer

The Physical Layer defines the Electrical, Mechanical, and functional specifications of the physical link used to connect the communication device on the network. This layer defines characteristics like voltage levels, data rates, maximum transmission distances, connectors etc.

The specifications in this Layer can be categorized as LAN or WAN:

LAN Specifications Examples:
• Ethernet
• FDDI
• Token Ring

WAN Specifications Examples:
• V24
• V35
• X21
• EIA/TIA-232