Physical Layer

Now we would explain the last of OSI layer, the first/lowest of OSI layer.

Physical layer consists of the basic networking hardware transmission technologies of a network.
Physical layer is a fundamental layer underlying the logical data structures of the higher level functions in a network.
This layer is the most complex layer in the OSI architecture.
In this layer, it defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. the bit stream may be grouped into code words or symbols and converted to physical signal that is transmitted over a hardware transmission medium.
for example, data transfer in modem (signal to digital).

The example device that work in this device is Hub, repeater, network interface card.

The main function of this layer :
1. Definition of Hardware Specifications: The details of operation of cables, connectors, wireless radio transceivers, network interface cards and other hardware devices are generally a function of the physical layer

2. Encoding and Signaling: The physical layer is responsible for various encoding and signaling functions that transform the data from bits that reside within a computer or other device into signals that can be sent over the network.

3. Data Transmission and Reception: After encoding the data appropriately, the physical layer actually transmits the data, and of course, receives it. Note that this applies equally to wired and wireless networks, even if there is no tangible cable in a wireless network!

4. Topology and Physical Network Design: The physical layer is also considered the domain of many hardware-related network design issues, such as LAN and WAN topology.