Network Devices : Routers | Repeaters | Bridges | Gateways

Network devices, also known as networking hardware, are physical devices that allow hardware on a computer network to communicate and interact with one another.

For example: Repeater, Hub, Bridge, Switch, Routers, Gateway and NIC, etc.

Routers in Computer Network:

Routers are networking devices operating at layer 3 or a network layer of the OSI model. They are responsible for receiving, analysing, and forwarding data packets among the connected computer networks. When a data packet arrives, the router inspects the destination address, consults its routing tables to decide the optimal route and then transfers the packet along this route.

Features –

Routers have various features such as: -

1. A router is a layer 3 or network layer device.
2. It connects different networks together and sends data packets from one network to another.
3. A router can be used both in LANs (Local Area Networks) and WANs (Wide Area Networks).
4. It transfers data in the form of IP packets. In order to transmit data, it uses IP address mentioned in the destination field of the IP packet.
5. Routers have a routing table in it that is refreshed periodically according to the changes in the network. In order to transmit data packets, it consults the table and uses a routing protocol.
6. In order to prepare or refresh the routing table, routers share information among each other.
7. Routers provide protection against broadcast storms.
8. Routers are more expensive than other networking devices like hubs, bridges and switches.

Hubs:

A hub is a physical layer networking device which is used to connect multiple devices in a network. They are generally used to connect computers in a LAN.

A hub has many ports in it. A computer which intends to be connected to the network is plugged into one of these ports. When a data frame arrives at a port, it is broadcast to every other port, without considering whether it is destined for a particular destination or not.

Switches:

A switch is a data link layer networking device which connects devices in a network and uses packet switching to send and receive data over the network.

Like a hub, a switch also has many ports, to which computers are plugged in. However, when a data frame arrives at any port of a network switch, it examines the destination address and sends the frame to the corresponding device or devices. Thus, it supports both unicast and multicast communications.

Difference between Hub and Switch:

Repeaters in Computer Network:

A repeater is a dynamic network device used to reproduce the signals when they transmit over a greater distance so that the signal’s strength remains equal. It can be used to create an Ethernet network. A repeater that occurs as the first layer of the OSI layer is the physical layer.

Features –

Features of repeaters are as follows: -

1. These repeaters are linked to each other at the physical layer.
2. It sends the signals for the unsteady areas to enlarge the system signals.
3. These repeaters link the various network signals to convert the data between the two devices.
4. These repeaters can eliminate the distance between the two devices.
5. The repeaters can frequently monitor the signals that are created between the two LANs.
6. Repeaters can support dynamic networking.
7. The IP network links all the repeaters with an IP site relation network.
8. This IP network can support a fast response to any issue in the repeater network.
9. These receptors can support 100 % digital communication so that they do not require to wait for analogue voice calls.

Advantages –

Advantages of repeaters are as follows: -

1. The signals get weaker as they transit to greater distances. The repeater provides the stability of the signals.
2. These repeaters are cost-effective and easy to use.
3. The repeaters don’t influence network performance.
4. It is not all signals that can be linked using physical media.
5. These repeaters can retransmit the information and improve the weak signals.

Disadvantages –

Disadvantages if repeaters are as follows: -

1. They cannot connect two distinct networks.
2. While amplifying the signals, the repeaters also amplify the level of noise in those signals.
3. If we enhance the extent of the web by only using the repeaters. In that case, the signal propagation time will grow to a considerable level, and the network’s performance will collapse.

Bridges in Computer Network:

Bridges are used to connect two subnetworks that use interchangeable protocols. It combines two LANs to form an extended LAN. The main difference between the bridge and repeater is that the bridge has a penetrating efficiency.

Working of Bridges –

Bridges work in the following ways: -

1. MAC (Media Access Control) Address Learning –

When a frame arrives at the bridge, it reads the source MAC address of the sender and adds this information to its internal MAC address table. 

2. Filtering and Forwarding –

The bridge then looks at the destination MAC address in the frame.

1. Local Traffic: If the destination MAC address is on the same network segment as the sender, the bridge will not forward the frame to other segments, as it knows it would only cause unnecessary traffic.
2. Remote Traffic: If the destination MAC address is on a different segment, the bridge will forward the frame only to that specific segment.
3. Unknown Destination: If the destination MAC address is not in its table, the bridge will broadcast the frame to all segments (except the one it arrived from) to find the device.

3. Segmentation –

By forwarding traffic only where it's needed, the bridge creates separate collision domains, effectively dividing a larger network into smaller, more manageable segments with reduced overall traffic and improved network performance. 

Uses of Bridges –

The main uses of bridges are: -

1. Bridges are used to divide large busy networks into multiple smaller and interconnected networks to improve performance.
2. Bridges can also increase the physical size of a network.
3. Bridges are also used to connect a LAN segment through a synchronous modem relation to another LAN segment at a remote area.

Gateways in Computer Network:

A gateway is a network node that forms a passage between two networks operating with different transmission protocols. The most common type of gateways, the network gateway operates at layer 3, i.e. network layer of the OSI (open systems interconnection) model. However, depending upon the functionality, a gateway can operate at any of the seven layers of OSI model. It acts as the entry – exit point for a network since all traffic that flows across the networks should pass through the gateway. Only the internal traffic between the nodes of a LAN does not pass through the gateway.

Features of Gateways -

Features of Gateways include: -

1. Gateway is located at the boundary of a network and manages all data that inflows or outflows from that network.
2. It forms a passage between two different networks operating with different transmission protocols.
3. A gateway operates as a protocol converter, providing compatibility between the different protocols used in the two different networks.
4. The feature that differentiates a gateway from other network devices is that it can operate at any layer of the OSI model.
5. It also stores information about the routing paths of the communicating networks.
6. When used in enterprise scenario, a gateway node may be supplemented as proxy server or firewall.
7. A gateway is generally implemented as a node with multiple NICs (network interface cards) connected to different networks. However, it can also be configured using software.
8. It uses packet switching technique to transmit data across the networks.

Types of Gateways –

Gateways can be categorised on the following two bases:

On basis of direction of data flow, gateways are broadly divided into two categories:

1. Unidirectional Gateways − They allow data to flow in only one direction. Changes made in the source node are replicated in the destination node, but not vice versa. They can be used as archiving tools.

1. Bidirectional Gateways − They allow data to flow in both directions. They can be used as synchronization tools.

On basis of functionalities, there can be a variety of gateways, the prominent among

them are as follows: -

1. Network Gateway − This is the most common type of gateway that provides as interface between two dissimilar networks operating with different protocols. Whenever the term gateway is mentioned without specifying the type, it indicates a network gateway.

1. Cloud Storage Gateway − It is a network node or server that translates storage requests with different cloud storage service API calls, such as SOAP (Simple Object Access Protocol) or REST (Representational State Transfer). It facilitates integration of private cloud storage into applications without necessitating transfer of the applications into any public cloud, thus simplifying data communication.

1. Internet-To-Orbit Gateway (I2O) − It connects devices on the Internet to satellites and spacecraft orbiting the earth. Two prominent I2O gateways are Project HERMES and Global Educational Network for Satellite Operations (GENSO).

1. IoT Gateway − IoT gateways assimilates sensor data from IoT (Internet of Things) devices in the field and translates between sensor protocols before sending it to the cloud network. They connect IoT devices, cloud network and user applications.

1. VoiP Trunk Gateway − It facilitates data transmission between plain old telephone service (POTS) devices like landline phones and fax machines, with VoIP (voice over Internet Protocol) network.