Physical Layers

Which layer or medium talks with computer in it’s binary language only deal with 0’s and 1’s at very bottom level.

The Physical Layer deals with the actual transmission of bits through a physical medium.

Ultimately, computers communicate using:

0 1 0 1 1 0 0 1 0 0 0 1 1 1 0 0 1 1 1...............

Those bits must physically travel somehow.

They can travel through:

• copper cable
• fiber optic cable
• radio waves
• Wi-Fi
• cellular networks

look in visual how data transmission happen at machine level in the electrical signal form and somewhere present the bits, computer plays around these bits by passing this signal Analog and Digital.

look at the wire and physical mechanism used to by pass the signal for computer work or compute.

Bit

The smallest unit using the computer machine process something:

0 or 1

Signal

A bit is represented physically through some signal.

For example:

Copper → electrical signal
Fiber → light pulses
Wi-Fi → radio waves

Bandwidth

The theoretical capacity of a communication channel.

For example: 1 Gbps , Mbps , Kbps , Tbps etc

doesn’t mean every application will actually transfer 1 Gbps.

That’s where throughput comes in.

Bandwidth vs Throughput

This is very important from your previous session.

Bandwidth = maximum potential capacity can passed data not guaranty for successful.
    for successful surety comes where throughput
Throughput = actual amount successfully transferred per unit time or per unit amount

Example:

Road capacity = 1000 cars/hour
Actual traffic = 700 cars/hour

Bandwidth ≈ road capacity.

Throughput ≈ actual traffic.

Latency at Physical Layer

Physical distance matters.

If a server is geographically far away:

Delhi
   ↓
Singapore
   ↓
USA

the signal has to travel a much larger distance.

Get Ayush Raj’s stories in your inbox

Join Medium for free to get updates from this writer.

Remember me for faster sign in

That contributes to latency.

Real-life analogy

Think about sending water through a pipe.

Pipe size → capacity
Water actually flowing → throughput
Time taken to reach destination → latency

Hub and Switch

A hub in the physical layer is a basic networking device that connects multiple Ethernet devices, making them act as a single network segment.
It operates exclusively at Layer 1 (Physical Layer) of the OSI model, meaning it has no intelligence to read MAC addresses or filter data. MAC Address we will know later….

• Hub is functioning as non-intelligent multi-port repeaters that broadcast electrical signals to all connected ports.

• Switches primarily operate at Layer 2 (Data Link Layer), using MAC addresses to intelligently forward data frames only to the specific destination port.

Physical layer topology

The Topology of a physical layer is the arrangement of network devices. You can work with five physical topologies, including the following.

Star topology

• Star topology is a network topology characterized by all devices connecting to a single central device or node.
• This central node can be either a switch or a hub that transmits data between the devices. This type of topology can be beneficial because it is robust against single cable failure.

Mesh topology

• Mesh topology connects each device to all other devices within the network. This type of system can prevent congestion in communication between devices because it provides a dedicated path between each device in the system.
• It also provides easy scaling, enabling devices to add without disrupting current communication channels. However, this type of topology can be more challenging to install because of the higher number of inter-device connections.

Bus topology

• Bus topology connects multiple devices along a single cable that acts as the “spine” of the system.
• It can be cost-effective compared to other topologies, but it can also lead to privacy issues because all devices use the same communication line. In addition to this, adding or removing devices poses challenges as it disrupts the current system.

Ring topology

• Ring topology connects all devices along a circular path. Devices can transmit data to devices on either side of them through the ring.
• This type of topology has relatively easy installation, but expansion or disruptions can affect all devices in the system..

Wireless topology

• Wireless topologies don’t need physical cabling between devices, which prevents disruptions due to cable breaks or the installation of new devices.
• This type of topology is especially useful for remote users and easily scales to accommodate more devices on the network. However, this type of system has certain security concerns and can have higher latency than wired topologies.

The Physical Layer handles the raw hardware transfer of unformatted bits (1s and 0s) between devices over wired or wireless mediums.

Key Attribute

Signal Conversion & Modulation:

• Converts digital data into physical signals (analog waves or digital pulses) using techniques like ASK, FSK, and PSK to maximize speed and reduce noise.

Transmission Mediums:

• Uses physical cables (Ethernet, copper, fiber) or wireless frequencies (Wi-Fi, Bluetooth).

Transmission Modes:
◦ Simplex: One-way only (e.g., keyboard → PC).
◦ Half-Duplex: Two-way, but one at a time (e.g., walkie-talkies).
◦ Full-Duplex: Two-way simultaneously (e.g., phone call).

Primary Services

• Controls bit rate and synchronizes timing between sender and receiver.
• Defines network topologies (star, bus, mesh) and physical connector interfaces.
• Handles signal processing and error correction at the hardware level.

Key Limitations

• Does NOT include: Cable production/installation, data formatting, encryption, session control, or error recovery (these belong to higher OSI layers).

Common Examples & Protocols

Ethernet, USB, Bluetooth, Digital Subscriber Line (DSL), and Controller Area Network (CAN).

you can see there global view of the networking how devices work , process and communicate.