Network Devices (All Layers)

A networking device (also called network hardware) is a physical or virtual piece of equipment used to connect computers, printers, phones, and other devices within a network. This lecture provides a comprehensive introduction to all major networking devices, categorized by OSI layers (1 to 7). It clearly explains what each device is and how it functions within a network.

Layer 1 (Physical Layer): Transmission of raw bits

The major devices used at the Physical Layer are given below

1. Hub

A basic device that connects multiple computers in a LAN and broadcasts incoming data to all ports, regardless of the destination. It has no intelligence and operates blindly.

2. Repeater

Regenerates and amplifies weakened or corrupted signals over long distances to extend network range without data loss.

3. Modem (Modulator-Demodulator)

Converts digital signals to analog for transmission over phone lines (modulation), and analog back to digital at the receiving end (demodulation). Commonly used for internet access.

4. Network Interface Card (NIC)

A hardware component in a device (like a PC) that provides the physical connection to the network and handles data framing.

5. Cables (Ethernet, Fiber, Coaxial)

Serve as the physical medium for data transfer between devices, using electrical (Ethernet), light (fiber), or radio signals.

6. Transceiver

A hardware device that can both transmit and receive signals on the network. Common in wireless and fiber connections.

7. Media Converter

Used to connect different types of cabling, such as converting between copper (Ethernet) and fiber optics.

Layer 2 (Data Link Layer): Node-to-node communication, MAC addressing

The major devices used at the data link Layer are given below

8. Switch

A smart device that connects devices in a LAN and forwards frames only to the correct destination, based on MAC addresses. It reduces collisions and improves speed. Layer 2 switch Performs switching based on MAC addresses and operates only at Layer 2, without IP-level routing.

9. Bridge

Connects two network segments and filters traffic to reduce congestion and divide a large network into smaller, more manageable sections.

10. Access Point (AP)

Acts as a wireless bridge between Wi-Fi devices and a wired LAN. It allows wireless clients to connect to the network.

11. MAC Address Table

Maintained by switches to map MAC addresses to physical ports, allowing accurate and efficient frame delivery.

Note: NIC also partially functions at this layer by handling MAC addressing.

Layer 3 (Network Layer): Routing and IP addressing

The major devices used at the Network Layer are given below

12. Router

Connects different networks (e.g., LAN to WAN) and determines the best path for data packets using IP addresses.

13. Layer 3 Switch

A device that combines routing and switching by routing packets within a network using IP addresses, offering high-speed performance.

14. Multilayer Switch

Operates at multiple OSI layers (Layer 2 and 3 or higher) and performs both switching and routing functions efficiently.

15. Brouter (Bridge + Router)

Functions as a bridge for non-routable traffic and as a router for routable traffic, acting based on the protocol used.

16. Wireless Router

Combines the functions of a router and wireless access point, offering both wired and wireless connections for home or small networks.

Layer 4 (Transport Layer): End-to-end communication and reliability

The major devices used at the Transport Layer are given below

17. Load Balancer

Distributes incoming traffic across multiple servers to optimize resource use, increase throughput, and ensure high availability.

18. Transport Layer Firewall

Filters traffic based on port numbers and session control, providing basic but important security between devices.

Layer 5–7 (Session, Presentation, Application Layers): End-user services, encryption, content handling

The major devices used at the Session, presentation and application Layer are given below

19. Gateway

Acts as a protocol translator between different network systems (e.g., TCP/IP to VoIP), allowing communication between otherwise incompatible networks.

20. Proxy Server

Sits between a user and the internet, handling requests, caching content, improving performance, or applying access restrictions.

21. Application Layer Firewall

Monitors and filters network traffic based on specific application data, offering deep packet inspection for advanced security.

22. Content Filter

Blocks access to inappropriate or restricted websites, content, or applications based on user roles or policies.

23. NAT Device (Network Address Translation)

Translates private IP addresses to a public IP for internet access, conserving IP address space and enhancing security.

24. VPN Concentrator

Establishes and manages multiple secure VPN connections, encrypting data between remote users and the internal network.