Networking - The TCP/IP Five-Layer Model - The Physical Layer

The Physical layer of the TCP/IP model has essentially the same role as the Physical layer of the OSI model: it defines how individual bits are actually transmitted across a medium. It is concerned with voltages, light levels, radio frequencies, connectors, and timing, not with the meaning of the bits.

In particular, the Physical layer is responsible for:

Defining the physical characteristics of the medium (copper wire, fiber, radio, and so on),
Specifying mechanical and electrical interfaces (connectors, pinouts, signaling levels), and
Establishing how bits are encoded on the medium and how transmitters and receivers stay synchronized.

Common examples of technologies that belong primarily to the Physical layer include:

Ethernet physical standards (such as 10BASE-T, 1000BASE-T, and 10GBASE-SR),
Fiber channel and SONET/SDH optical standards, and
Wireless radio standards such as the physical portions of 802.11.

The Physical layer is responsible for several processes, each of which is responsible for a series of methods:

Physical Topology and Media
- Point-to-point and shared media connections,
- Star, bus, ring, and mesh cabling arrangements, and
- Choices among twisted pair, coaxial, fiber, and wireless media.
Signaling and Encoding
- Representing binary 0s and 1s as electrical or optical signals, and
- Using line coding schemes and clocking methods to allow the receiver to interpret the bit stream.
Bit Synchronization
- Asynchronous transmission with start and stop bits, and
- Synchronous transmission using shared clocks or guaranteed transitions in the signal.

Let us move on to layer 2, the Data Link Layer.

Nah, I want to skip around:

Introduction
Physical (Layer 1)
Data Link (Layer 2)
Network (Layer 3)
Transport (Layer 4)
Application (Layer 5)
Conclusion