Network Devices

Introduction

Network devices, in their definition, are as simple as they sound. They are devices that allow us to form a functional computer network- they connect the hardware, such as fax machines, printers, and speakers, and facilitate intercommunication with each other in a computer network. Some common network device examples include Routers, switches, Hubs, etc.

In layman's terms, network devices in computer networks are like conjunctions in a sentence- they connect words and help form cohesive sentences.

This article will attempt to familiarise readers with the concept of network devices, their functions, and subsequently, their various types, subtypes, and examples.

Here is a basic network devices list, widely used network devices before we attempt to elaborate.

Repeater

A repeater strengthens and retransmits signals over the same network to avoid corrupt messages from being received.

Hub

A hub is essentially a multiport repeater on a given LAN that broadcasts messages to all connected devices without filtering data.

Bridge

A bridge is like a repeater that can filter data and connect two separate LANs.

Switch

Switches are multiport bridges with the ability to perform error checks and forward data to the intended port only.

Router

A router network device directs data packets between networks using their IP addresses, ultimately connecting LANs and WANs.

Other network devices include gateways, NICs, routers, etc.

Hubs and Types of Hubs

A hub is a device that makes room for multiple connections in a computer network between both computers and other hardware devices. It links all the stations and operates on the physical layer of the OSI model. For example, an aux hub allows multiple mics to connect to the speakers in a sound system.

However, hubs cannot filter the received information, only relay it. Packets are forwarded to all devices connected to the network. All connected hosts share the collision domain. This may lead to inefficiency.

Hubs are furthermore classified as below.

1. Active Hub: Like repeaters, active hubs regenerate and amplify received messages before broadcasting them to hosts. They have an internal power supply and are both connecting center and repeater. This allows them to expand the distance between nodes and increase LAN size.
2. Passive Hub: Connect nodes by collecting wiring from nodes and power supply from active hubs. Broadcasted messages are neither regenerated nor amplified, meaning that they cannot contribute to optimizing nodal distance and hence limit LAN size. They are just connectors.
3. Intelligent Hub: Active hubs that allow network management via traffic monitoring, providing flexible data rates, port configuration, etc.

Bridge and Types of Bridges

The bridge is a device that connects two separate LANs using different protocols or two segments of a LAN. It accepts all data packets and amplifies them before selectively relaying information to the intended host using the MAC addresses of the source and destination. Therefore it acts like an intelligent repeater that connects smaller networks to form extended LANs. It has singular input and output and is a two-port device.

It is important to note that bridges do not filter data; they relay information selectively based on addresses, reducing collision and traffic.

Bridges are generally classified into two types, as given below:

1. Transparent Bridges: The end systems on the network are oblivious to the existence of these bridges and their configuration; they act like 'plug-and-play' bridges. These are self-updating and maintain a table of terminal addresses. Disconnecting transparent bridges does not require reconfiguration.
2. Source Routing Bridges: Used in Token Ring networks, the source system performs the routing action while the frame specifies which route to follow. So effectively, not only does the frame contain source and destination addresses, but also the bridge address. The host can send a special discovery frame using all possible paths to the destination to discover the frame.

Switch and Types of Switches

Like the Bridge, the Switch also operates on the data link layer. As mentioned earlier, a switch is a multiport bridge that can error-proof packets before forwarding them. Along with being efficient due to reduced traffic as a multiport device, it is also more precise as it only forwards 'good' packets to the 'right' host destination. This segments the collision domain while the broadcast domain remains the same.

Switches can be classified and sub-classified as follows:

1. Unmanaged Switches: Plug-and-play switches that do not require configuration or to be watched. These are most commonly used in home networks or small-scale networks as they use small cable connections in limited spaces. For example, they connect a PC to a Printer in a home office. They may be used for expansion to a larger network. Unmanaged switches are the most cost-effective option.
2. Managed Switches: Designed to deliver the most comprehensive set of features such as the best application experience, highest levels of security, management of the network, and scalability. Centralized management makes this an ideal and necessary cost for large networks. Scalability makes it suitable for expanding networks.
3. 1. Smart Switch: Also known as partially managed switches, these switches are easily set up and managed. Typically suited for small- to medium-sized networks, it can accept VLAN(Virtual LAN) configuration. They offer limited levels of security.
   2. Enterprise Managed Switches: Going by the tag of fully managed switches, these can fix, copy, transform, and display different network configurations, along with a web interface SNMP agent and command-line interface. Best suited for organizations with a large volume of ports, nodes, and switches, these are significantly more expensive than smart switches.

3. LAN Switches: They connect points on a LAN and reduce network traffic by broadcasting a data packet to its recipient alone. They can also be called Ethernet Switches/Data Switches.
4. PoE (Power over Ethernet) Switches: Designed to disentangle the cabling process, PoE Switches allow data and power to be integrated on the same cable. Therefore devices can receive both power and data simultaneously.
5. Layer 2 Switches: These switches operate at the 2nd Layer- Data Link Layer of the OSI (Open Systems Interconnection) model. They relay data between devices on the same segment of a network.
6. Layer 3 Switches: These switches operate at the 3rd layer- The network Layer of the OSI model. With the ability to route data among separate segments in a network, Layer 3 switches are used in complex expanded networks.
7. Rack-Mounted Switch: designed to attach to data racks, rack switches are ideal for use at large networks and data centers.
8. Desktop Switches: Smaller than rack-mounted switches, desktop switches are to be used on desktops or small-network/ work environments.
9. Modular Switches: Easily manageable and customizable, these switches come with a modular design. They are useful in large data centers and networks.

That brings us to the end of Switches, but before we attempt to conclude, it might be useful to outline a few more devices.

Gateway is like a path or passage, as suggested by the literal meaning of the word, that allows separate networks to connect. Since these networks operate on separate networking models or protocols, a gateway converts data packets received from a system according to, before interpreting and transferring it to the other system. This is why they are also known as protocol converters.

Brouter stands for bridging router- meaning that it can work at Layer 2 (data link) or Layer 3 (network) by combining a router's and a bridge's functions. It can route packets as well as filter network traffic across a LAN.

And finally, the NIC, which is an interface card for the network, is a Layer 2 device that connects the host and the network itself. The card has a pre-inscribed distinct ID and a connector allowing the computer to connect to the router. The purpose of a NIC is to make room for setting up a LAN.

To Sum Up, What are Network Devices and their Functions?

Devices that act in a connecting capacity to facilitate the functioning and expansion of a computer network are called Network Devices. They are largely divided into Repeaters, Hubs, Bridges, and Switches and also consist of hardware such as Routers, Brouters, Gateways, and NICs. The purpose of most, if not all, of these devices, is to receive a signal or packets of data, interpret it, clean and segment it if possible, amplify it, and finally broadcast it to all relevant hosts.

They are essential in building computer networks and ensuring a smooth user experience.

FAQs

1. Do printers and computers count as Network Devices?

No, printers, fax machines, and computers are hardware devices but are not to be confused with network devices, which are the 'middlemen' that connect hardware devices in a network. Example: a network device is a hub connecting the host to a printer and speakers.

2. Can a repeater filter data packets to prevent corruption?

A repeater only amplifies the data/message it receives without cleaning it and, therefore, cannot help in selective data broadcast. In other words, it prevents corruption due to loss of amplitude.

3. At which layer does the Bridge operate?

The Bridge operates with MAC (media access control) addresses at Layer 2 or the data link layer of the OSI model.

4. What are Layers in the OSI model?

The Open Systems Interconnection (OSI) model defines 7 layers over which computer systems communicate over a network. The aforementioned 7 layers of the OSI model include the Physical, Data Link, Network, Transport, Session, Presentation, and finally, Application Layers.