Networking Devices

Introduction

• A typical computer network, either LAN, MAN, or WAN is consists of a large number of communication devices along with communication medium or channels.
• To build a typical LAN, especially, we need to have computers, communication mediums or channels, NOS(Network Operating System), and networking devices such as Hubs, Switches, Network Adapters, NICs, Repeaters, Amplifiers, Bridges, Gateways, Internal/External Modems, different types of Connectors, Cable testers, clipping tools etc. 

Definition

• Networking devices are those basic hardware components that are used and help create a typical computer network.

Features

• Networking devices help to organize data transmission smoothly and successfully. 
• Examples of networking devices are –  NIC adapter card, Hubs, Switches, Repeaters, Amplifiers, Bridges, Modems, Gateway, Routers, Access Points, Proxy Server, Brouter, Firewall, Load Balancer, CSU/DSU(Channel Service Unit/Data Service Unit), Print Server, Ethernet Cable, Cable Connectors, Patch Panel, Cable Testers, Clipping Tools, etc.

Types

All the networking devices can be broadly categorised into two types of networking devices – 

(a) Intra Networking Devices and (b) Inter Networking Devices

(a) Intra Networking Devices:

• The networking devices used within a network connect its components, making it a typical network.
• These devices are typically components of LANs.
• Examples include NIC adapter cards, Hubs, Switches, Bridges, Repeaters, Amplifiers, Access Points, Ethernet Cable, Print Server, Cable connectors, Cable testers, and Clipping tools, among others.

(b) Inter Networking Devices:

• The networking devices that are used between two/more separate networks to connect them and make it a larger network.
• Examples are – Routers, Gateways, Modems, Brouters, Proxy Servers, Firewalls, CSU/DSU, etc.

(1.) NIC(Network Interface Card) Network Adapter Card/Network          Card/Ethernet Card/Network Interface Controller

• NIC is a hardware component that allows a computer or other related devices to connect to a network.
• The network interface card (NIC) provides the physical connection/link between the computer and the network.
• Actually, NIC provides the physical interface (port) to connect a device to a network (using Ethernet cables, Wi-Fi antennas, etc.).
• A NIC (Network Interface Card) works primarily at the Data Link Layer (Layer 2) of the OSI Model.
• NIC is the simplest intra-networking device that is used in data communication, i.e., it converts a computer’s data into signals that can be transmitted over the network and vice versa. It also handles the data link layer protocols (like Ethernet, Wi-Fi) for communication.
• The most common network interface connection today is Ethernet cards. Ethernet cards that contain connections for twisted pair cables have an RJ-45 connection. The Ethernet card is sometimes also called a network adapter card.
• Each NIC card is identified by a unique number called the Media Access Control (MAC) address, used for identifying the device on the network.
• NIC adapter card is attached/in-built to every computer that takes part in data communication.
• Most NICs are internal, with the card fitting into an expansion slot inside the computer. 
• A NIC is a piece of computer hardware (recently built with a motherboard or early controllers attached in motherboard expansion cards/ slots that plugged into a computer bus) to allow computers to communicate over a computer network.
• Network interface cards are a major factor in determining the speed and performance of a network.
• It allows users to connect, either by using cables or wirelessly.
• The network controller implements the electronic circuitry required to communicate using a specific physical layer and data link layer standard such as Ethernet, Wi-Fi, or Token Ring.
• NIC provides a base for a full network protocol stack, allowing communication among small groups of computers on the same LAN and large-scale network communications through routable protocols, such as IP.
• NIC is normally present in a Desktop computer, Laptop, Server, Network Printer, Embedded System, etc.  
• Types of NIC

• Advantages of NIC
  • Enables network communication and resource sharing.
  • Provides a unique identification (MAC address) for each device.
  • Supports high-speed data transfer.
• Components of a NIC
  • Controller Chip: Manages data transmission and reception.
  • Transceiver: Converts digital data to network signals and vice versa.
  • Connector/Port: For Ethernet cable (RJ-45), antenna (Wi-Fi), or fiber optic cable.
  • ROM/EEPROM: Stores the MAC address and configuration data.
• The NIC follows one or more of four techniques to transfer data:-
  • Polling – In this method, the CPU examines the status of the peripheral under program control.
  • Programmed I/O – In this method, the microprocessor alerts the designated peripheral by applying its address to the system’s address bus.
  • Interrupt-Driven I/O – In this method, the peripheral alerts the microprocessor that it is ready to transfer data.
  • Direct Memory Access – In this method, an intelligent peripheral assumes control of the system bus to access memory directly. This removes load from the CPU but requires a separate processor on the card.

(2.) Repeater

• • Actually, when a signal travels through a medium in a network, it loses its strength gradually, degrades, and finally becomes distorted (called attenuation), which is now not able to propagate further with proper speed and energy; hence, a repeater is required.
  • A repeater is a simple, physical-layer device used to extend the range of a network by allowing signals to travel farther by regenerating weak or corrupted signals.
  • A repeater is an electronic device that electrically amplifies the signal it receives and rebroadcasts/re-transmits it so that the signal can cover longer distances without degradation.
  • Typically, it is a digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.
  • It does not manage or filter data traffic, i.e., it cannot distinguish between different types of data; rather, it may repeat all signals, including noise.
  • It is best used for boosting signals over long distances in the same type of network.
  • It works with the actual physical signal and does not attempt to interpret/convert the data being transmitted.
  • Advantages of a Repeater

(3.) Amplifier

• An amplifier is an electronic device or circuit that increases the magnitude of voltage, current, or power of a signal, along with any noise present in the signal applied to its input.
• Amplifiers are used in wireless communications and broadcasting, and in audio equipment of all kinds.
• It increases the strength (amplitude) of a signal as it travels through a transmission medium (like copper wire or fiber optic cable).
• It is used to boost weak signals over long distances.
• An amplifier is the generic term used to describe a circuit that produces an increased version of its input signal.
• They can be categorized as either weak-signal amplifiers or power amplifiers.
• The purpose of an amplifier is to amplify or increase the input signal to produce an output signal that is much larger than that of the input, with a similar waveform to that of the input. The main change in the output signal will be the increase in the power level.
• This device operates at the Physical Layer (Layer 1) of the OSI model.
• This is used in analog transmission systems (e.g., traditional telephone lines, coaxial cables, optical fibre cable) to extend the range of the signal.
• An amplifier is different from a repeater, i.e., an amplifier boosts the entire incoming analog signal, including noise and distortion, whereas a repeater regenerates the original digital signal, removing noise and restoring the signal to its original shape i.e., amplifiers amplify analog signals along with noise, whereas a repeater removes noise from regenerated digital signals.
• Advantages of Amplifiers
  • Simple and Cost-Effective: Easy to implement in analog networks.
  • Extends Signal Range: Allows signals to travel longer distances without significant loss of strength.
• Disadvantages of Amplifiers
  • Amplifies Noise: Any noise or distortion in the signal is also amplified, which can degrade signal quality over long distances.
  • Not Suitable for Digital Networks: In digital communication, repeaters are preferred because they regenerate clean signals (noise-free).

(4.) Hub/Concentrator

• • In computer networking, a hub is a basic networking device that connects multiple devices in a Local Area Network (LAN), in which incoming data packets are broadcast to all connected ports, regardless of the intended recipient, i.e., every packet is sent out to every computer on the network; thus, there is a lot of wasted transmission and also every computer connected to the hub, sees everything that every other computer on the hub sees. 
  • A hub is a hardware device that contains multiple ports, which is used to connect multiple devices in a star topology.
  • When a packet arrives at one port in a hub, it is copied to all the ports of the hub. It simply copies the data to all of the Nodes connected to the hub (broadcast).
  • Hub operates at the Physical Layer (Layer 1) of the OSI model.
  • A hub is used to connect segments of a local area network (LAN) because a hub contains multiple ports.
  • Hubs are largely obsolete/outdated in modern networks due to least intelligent.
  • Advantages :
    • A hub is typically simple, inexpensive,  and the least complicated of routers and switches.
    • Easy to set up, i.e., plug-and-play.
    • Improves the performance, especially in the situation of bursty/heavy traffic and also of large files.
    • Use of Fast Ethernet hubs requires no hardware or software settings rather just plug and play them in. Thus, the hub offers ease of use. 
  • Disadvantages :
    • This is the least intelligent device, i.e., the biggest problem with hubs is their simplicity. Hence, every packet sent out to every computer on the network generates a lot of wasted transmission and can easily bog down the network.
    • Due to a simple device, it does not perform traffic/data filtering, i.e., A hub sends all data packets coming from one port to all other connected ports. It means that it does not filter or manage traffic; rather, it simply sends all incoming data/signals to all other connected devices. Hence, it is inefficient & insecure (all devices see all traffic). 
    • Hubs are typically used on small networks where the amount of data transmitted across the network is relatively low.
    • Not suitable for variable traffic because the hub has fixed bandwidth, and as network traffic grows, performance suffers.
    • It performs half-duplex communication, i.e., devices cannot send/receive data simultaneously while connected to the hub in a network.
    • Does not reduce collisions; rather creates unnecessary network congestion.
    • Requires Category 5 UTP cabling for each 100BaseTX connection.
  • Use/Applications
    • Rarely used today except in legacy systems or troubleshooting scenarios.

(5.) Switch

• A switch is a networking device that connects multiple devices (such as computers, printers, and servers) within a local area network (LAN) and intelligently forwards data only to the specific device(s) for which the data is intended.
• It operates mainly at the Data Link Layer (Layer 2) of the OSI model, but some advanced switches can also operate at the Network Layer (Layer 3).
• On busy networks, this can make the network significantly faster.
• A switch (or Switching Hub) is a device that can segment a larger local area network to reduce the traffic load.
• One should implement a switch when you have a network with 20 or more users that have bogged down the network due to excess traffic.
• It splits the network into two or more segments with devices that normally talk with each other.
• Conceptually, switching takes data from one interface and delivers it to another interface.
• Functions of a Switch
  • MAC Address Learning: Switches learn the MAC addresses of devices connected to each port and use this information to forward data only to the correct destination.
  • Frame Forwarding: When a data frame arrives, the switch checks its MAC address table and sends the frame only to the port where the destination device is connected.
  • Reduces Network Traffic: Unlike hubs, switches do not broadcast data to all devices, which reduces unnecessary network traffic and collisions.
  • Full-Duplex Communication: Supports simultaneous sending and receiving of data, increasing network efficiency.
• Types of Switch

Following types –

• • Unmanaged Switch:
    • Plug-and-play type of switch, no configuration needed.
    • Used in small networks or home environments.
  • Managed Switch:
    • Can be configured and monitored.
    • Supports features like VLANs, port mirroring, and network management.
    • Used in enterprise and large networks.
  • Layer 2 Switch:
    • Operates at the Data Link Layer.
    • Forwards frames based on MAC addresses.
  • Layer 3 Switch:
    • Operates at the Network Layer.
    • Can perform routing functions based on IP addresses.
• Advantages of Switch
  • Efficient Data Transfer: Sends data only to the intended device, not all like the Hub.
  • Reduces Collisions: Each port is its own collision domain.
  • Improves Network Performance: Supports higher bandwidth and full-duplex communication.
  • Scalable: Easy to add more devices to the network.
• Disadvantages of Switch
  • Cost: More expensive than hubs.
  • Complexity: Managed switches require configuration and management.
  • Limited to LAN: Primarily used within local networks, not for connecting different networks.

(6.) Modem

• The word Modem comes from modulator–demodulator.
• A modem (short for modulator-demodulator) is a hardware device that enables communication between computers over telephone lines/ phone lines, cable systems, fiber, or other communication channels. 
• A modem is a device that converts digital signals into analog signals and its vice-versa. Here, Modulation is the conversion of digital signals from a computer into analog signals for transmission over telephone lines, whereas Demodulation is the conversion of incoming analog signals back into digital signals for the computer to process.
• In other words, at the source station, modems convert digital signals to a form suitable for transmission over analog communication facilities (public telephone lines), i.e., into an analog signal. At the destination, modems again convert the analog signal back to a digital format.
• A modem in a computer network operates mainly at the Physical Layer (Layer 1) of the OSI model.
• A modem acts as a bridge or interface between a computer/local network and an ISP (Internet Service Provider).
• A modem enables internet access in homes and businesses using any type of channel/medium(analog or digital).
• The speed of a modem is measured in bits per second (bps) or megabits per second (Mbps).
• A modem must match the network type (DSL, cable, fiber, etc.)during transmission. In other words, it adjusts its transmission rate and modulation scheme based on the quality/nature of the transmission line.
• Many modems include basic error-correction mechanisms to ensure cleaner data delivery.
• Commercially, a modem may be External or Internal. External modems connect via USB or Ethernet, whereas Internal modems are installed inside the computer (e.g., PCI cards).
• Many devices today combine both Modem and Router into a single gateway unit.
• Types of Modems: The modems are of the following types –
  • Dial-up Modem: Uses standard telephone lines for low-speed internet access (up to 56 Kbps). Rarely used today.
  • DSL Modem: Uses standard telephone lines but transmits data at much higher frequencies (faster than dial-up). Allows simultaneous use of phone and internet.
  • Cable Modem: Uses coaxial cables (like TV cables) for broadband internet.
  • Fiber Optic Modem/ONT (Optical Network Terminal): Supports ultra-fast internet via fiber-optic cables by converting light pulses on fiber optic cables into Ethernet and vice versa.
  • Wireless/Cellular Modem: Uses cellular or Wi-Fi or mobile network standards (3G, 4G, 5G) to connect to the Internet.
  • Satellite Modem: Communicates via radio signals to a satellite dish system.

(7.) Bridge

• A bridge is an intra-networking device that connects and filters traffic between two or more similar network segments (use the same protocols and are on the same type of network architecture) at the data link layer (Layer 2) of the OSI model.
• Like a repeater, a bridge can join several LANs. However, a bridge can also divide a network to isolate traffic problems.
• Bridges are store-and-forward devices to provide error detection.
• They capture an entire frame before deciding whether to filter or forward the frame, which provides a high level of error detection because a frame’s CRC checksum can be calculated by the bridge.
• Bridges are rare in modern Ethernet LANs.
• Function of Bridges
  • Traffic Filtering: Checks each incoming frame’s MAC address and decides whether to forward, drop, or flood it.
  • Segmentation: Splits a network into segments, which reduces unnecessary traffic.
  • Learning MAC Addresses: Builds a MAC Address Table (or forwarding table) by listening to the source address of incoming frames.
  • Collision & Broadcast Domain Management: Reduces collision domains (good for performance).

• Working Mechanism of Bridges

• Advantages:
  • Reduces unnecessary traffic in network segments.
  • Easy to install and operate (no configuration in basic models).
  • Enables larger networks without overwhelming devices.
  • Works at the hardware level, which is generally faster than older software-based forwarding.

• Disadvantages:
  • A bridge cannot filter out broadcast traffic.
  • It introduces 20 to 30 % latency in the network.
  • A bridge shows lower performance than modern switches due to software-based forwarding in early bridges.
  • Mostly obsolete now(usually 2-4 ports, older, software-based), replaced by network switches (Multiple ports, hardware (ASIC)-based forwarding, faster due to hardware-accelerated brains).

(8.) Router

• A Router is one of the major inter-networking devices that forwards data packets between different networks, typically between a local network (e.g., in our home Wi‑Fi) and a wider network (e.g., the internet).
• A router is a device or special PC(a combination of both hardware and software) that is used to connect two or more different IP networks logically.
• The router works as a bridge between networks, making intelligent decisions on where data should go.
• The router selects the best path from available paths to route a message, based on the destination address and origin. Thus, the router can direct traffic to prevent head-on collisions and is smart enough to know when to direct traffic along shortcuts.
• Routers can even listen to the entire network to determine which sections are busiest. They can then redirect data around those sections until they are removed.
• If we have a LAN and we want to connect to the internet, we will need to purchase a router. In this case, the router serves as the translator between the information on your LAN and the Internet.
• Routers maintain a map of the physical networks on the Internet (network).
• The address of the router is referred to as the Default Gateway.
• When the Router receives a data packet, it checks its routing table
  • If the destination is local, send it directly.
  • If remote, send to the next hop (possibly another router closer to that network), and this will be repeated until the data reaches the receiver’s router, which finally delivers it to the receiver’s laptop.
• Components/Structure of the Router
  • CPU & Memory: The Main component of the Router for processing routing logic and maintaining tables.
  • Routing Table: A stored list of networks the router knows about and how to reach them.
  • Interfaces/Ports: These are the Physical (Ethernet, fiber) and wireless interfaces that connect different networks.
  • Firmware/OS: These are specialized software running the routing logic (e.g., Cisco IOS, Junos, MikroTik RouterOS).
• Types of Routers
  • Wired Router
    • This router connects devices via Ethernet cables.
  • Wireless Router
    • This router combines routing and a wireless access point for Wi‑Fi connectivity.
  • Core Router
    • This is a high-capacity backbone routers that operate inside major networks.
  • Edge Router
    • This router sits at the boundary of a network, connecting to external networks or ISPs.
  • Virtual Router
    • A software-based router running on a server or in the cloud.

(9.) Gateway

• In networking, a gateway is a device (or software) that connects two different networks (e.g., a network using TCP/IP and another using IPX/SPX, or Ethernet to ATM) that may use different protocols, architectures, or technologies, and translates the data so they can communicate.
• It acts as a translator among the networks so that data can be successfully transmitted and understood.
• Gateways can operate at all layers of the OSI model, but effectively, they operate on the application layer (Layer 7) of the OSI model. 
• The gateway translates protocols so both networks can communicate despite differences.
• If we are connected to the internet, we have to enter through a Gateway, i.e., a gateway connects a smaller network to the internet.
• Gateway Interconnects networks at higher layers than bridges or routers.
• Gateways, also called protocol converters, a gateway must convert one protocol into another before forwarding it.
• The job of a gateway is much more complex than that of a router or a switch.
• A router by itself transfers, accepts, and relays packets only across networks using a similar protocol.
• A gateway can be implemented in hardware, software, or both, but they are usually implemented by the software installed within a router.
• A gateway must understand the protocols used by each network linked to the router.
• Gateways are slower than bridges, switches, and (non-gateway) routers.
• A gateway may contain devices such as protocol translators, impedance matching devices, rate converters, fault isolators, or signal translators as necessary to provide system interoperability.
• A gateway is a network point that acts as an entrance point to another network.
• On the Internet, a gateway is a node or a stopping point node or a host (end-point) node. 
• In the enterprise network, a computer server acting as a gateway node is often simultaneously acting as a proxy server and a firewall server.
• A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.
• Function of Gateway
  • Protocol Conversion
    • Translates from one communication protocol to another (e.g., IPv4 ↔ IPv6, or email ↔ SMS).
  • Data Format Translation
    • Converts the format of the data so receiving systems can process it.
  • Route Control
    • Determines the best path to transfer the translated data to its destination.
  • Security and Filtering Enforcement
    • Often integrates with firewalls, filtering, and authentication systems to perform security and filtering.
  • Connecting Dissimilar Networks
    • Bridges LAN-to-WAN with different architectures, or enterprise networks to cloud services.
  • Compression & Encryption
    • Sometimes compresses or encrypts data for efficient and secure transmission.
  • Address Mapping
    • Translates addresses between different addressing schemes.
• Types of Gateway
  • Default Gateway

    • A default gateway is the IP address of a router (or similar device) on our connected network that forwards packets from our local network to destinations outside it.
    • It is considered the “first hop” out of our local network toward any other network.
    • It’s called “default” because it’s the route used when no other specific route matches the destination address in our computer’s routing table.
    • Example: In our home network, our ISP-provided router is our default gateway to the internet.

• Advantages of Gateway
  • Enables communication between incompatible network systems.
  • Can integrate protocol conversion, security, and traffic control at once.
  • Crucial for legacy systems to work with modern networks.
• Disadvantages of Gateway
  • More processing overhead due to translation.
  • Potential point of failure if it’s the only connection point between networks.
  • It can introduce latency if heavy conversions are involved.