This Layer defines logical addressing (e.g IP address) in order to identify each endpoint in a network and provide end-to-end delivery of packets. Think of the Network Layer as the postal service in a country. When you want to send a letter to a friend, you just need to know the destination postal address (e.g [...]

The Data Link Layer provides error detection and error recovery of the data flowing across the physical network link. The Specifications in this OSI Layer define network and protocol characteristics such as Physical addressing, network topology, error notification, flow control etc. The physical addressing defined in this layer determines how devices are addressed on the [...]

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:
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