NETWORK DEVICES of Computer Network

• Router
• Switch
• Bridge
• Hub
• Gateway

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ROUTER

INTRODUCTION

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• A router in a computer network is a device connecting two or more networks or subnetworks that are packet-switched.

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• These are networking devices functioning at layer 3 or a network layer of the OSI paradigm.

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• The principal function of a router in networking is to manage traffic between these networks. It does so by forwarding data packets to their respective IP addresses and allowing numerous devices to use the same internet connection.�

A router in a computer network is used for the following purposes:

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• To ensure that data is flowing to the right destination, users send the emails to the correct recipient.

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• Routers defend against unwanted data, such as when an enormous file is delivered to each workstation on the network, and also increase network performance.

Uses of a Router

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1. Broadband Routers: These are one of the important kinds of routers. It is used to do different types of things. it is used to connect computers or it is also used to connect to the internet.

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• Wireless routers: These routers are used to create a wireless signal in your office or home. Wireless routers receive data packets over wired broadband, convert the packets written in binary code into radio signals that are picked up by electronic devices, and then convert them back into previous packets. 

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• Edge Routers: As the name indicates, these are located at the edges usually connected to an Internet Service Provider, and distribute packets across multiple packets.

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• Core Routers: Core routers distribute packets within the same network. The main task is to carry heavy data transfers.

Types of Router

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There are several types of routers available in the market. Some of them are mentioned below:

Working diagram of Router

• A router examines a packet header's destination IP address and compares it against a routing table to determine the packet's best next hop.

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• Routing tables list directions for forwarding data to particular network destinations, sometimes in the context of other variables, like cost.

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• They amount to an algorithmic set of rules that calculate the best way to transmit traffic toward any given IP address.

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• A routing table often specifies a default route, which the router uses whenever it fails to find a better forwarding option for a given packet. For example, the typical home office router directs all outbound traffic along a single default route to its internet service provider (ISP).

How a router works ?

SWITCHES

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• A network switch connects devices in a network to each other, enabling them to talk by exchanging data packets. Switches can be hardware devices that manage physical networks or software-based virtual devices.

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• A network switch operates on the data-link layer, or Layer 2, of the Open Systems Interconnection (OSI) model.

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• In a local area network (LAN) using Ethernet, a network switch determines where to send each incoming message frame by looking at the media access control (MAC) address.

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• Switches maintain tables that match each MAC address to the port receiving the MAC address.

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INTRODUCTION

What are the types of switches?

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• Unmanaged Switch − These are inexpensive switches commonly used in home networks and small businesses. They can be set up by simply plugging in to the network, after which they instantly start operating. When more devices needs to be added, more switches are simply added by this plug and play method.

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• Managed Switch − These are costly switches that are used in organisations with large and complex networks, since they can be customized to augment the functionalities of a standard switch. The augmented features may be QoS (Quality of Service) like higher security levels, better precision control and complete network management.

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• AN Switch − Local Area Network (LAN) switches connects devices in the internal LAN of an organization. They are also referred as Ethernet switches or data switches. These switches are particularly helpful in reducing network congestion or bottlenecks. They allocate bandwidth in a manner so that there is no overlapping of data packets in a network.

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• PoE Switch − Power over Ethernet (PoE) switches are used in PoE Gigabit Ethernets. PoE technology combine data and power transmission over the same cable so that devices connected to it can receive both electricity as well as data over the same line. PoE switches offer greater flexibility and simplifies the cabling connections

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Features of Switches

• A switch operates in the layer 2, i.e. data link layer of the OSI model.

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• It is an intelligent network device that can be conceived as a multiport network bridge.

• It uses packet switching technique to receive and forward data packets from the source to the destination device.

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• It is supports unicast (one-to-one), multicast (one-to-many), and broadcast (one-to-all) communications.

• Switches are active devices, equipped with network software and network management capabilities.

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Switches can perform some error checking before forwarding data to the destined port.

Bridge 

INTRODUCTION

• A bridge in a computer network is a device used to connect multiple LANs together with a larger Local Area Network (LAN). The mechanism of network aggregation is known as bridging.

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• The bridge is a physical or hardware device but operates at the OSI model’s data link layer and is also known as a layer of two switches. 

• Basically, a bridge in computer networks is used to divide network connections into sections, now each section has separate bandwidth and a separate collision domain.

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• Here bridge is used to improve network performance. 

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There are generally two types of bridges which are as follows −

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Types of Bridges

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• Transparent Bridges
• It is also called learning bridges. Bridge construct its table of terminal addresses on its own as it implements connecting two LANs. It facilitates the source location to create its table. It is self-updating. It is a plug and plays bridge.

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• Source Routing Bridge
• This sending terminal means the bridges that the frames should stay. This type of bridge is used to prevent looping problem.

The main uses of bridges are −

• Bridges are used to divide large busy networks into multiple smaller and interconnected networks to improve performance.

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• Bridges also can increase the physical size of a network.

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• Bridges are also used to connect a LAN segment through a synchronous modem relation to another LAN segment at a remote  area.

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Uses of Bridges

Working of Bridges

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A bridge accepts all the packets and amplifies all of them to the other side. The bridges are intelligent devices that allow the passing of only selective packets from them. A bridge only passes those packets addressed from a node in one network to another node in the other network.

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HUBS

• Hub in networking plays a vital role in data transmission, and broadcasting.

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• Hub is a hardware device used at the physical layer to connect multiple devices in the network.

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• Hubs are widely used to connect LANs. A hub has multiple ports and it is a non-intelligent device.

INTRODUCTION

• Unlike a switch, a hub cannot filter the data, i.e. it cannot identify the destination of the packet, so it broadcasts or send the message to each port.

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• This is why it is known as a non-intelligent or dumb device.

How Does a Network Hub Work?

• A hub is a multiport device, which has multiple ports in a device and shares the data to multiple ports altogether. A hub acts as a dumb switch that does not know, which data needs to be forwarded where so it broadcasts or sends the data to each port. 

Types of Network Hubs:

Networks hubs are of the following three types:

1. Active Hub: They have a power supply for regenerating, and amplifying the signals. When a port sends weak signaled data, the hub regenerates the signal and strengthens it, then send it further to all other ports.

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• Passive Hub: Passive hubs are simply used to connect signals from different network cables as they do not have any computerized element. They simply connect the wires of different devices in the star topology.

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• Intelligent Hub: Intelligent hubs as the name suggests are smarter than active and passive hubs. The intelligent hub comprises a special monitoring unit named a Management Information Base (MIB). Intelligent hubs work similarly to active hubs but with some management features. Like it can monitor the traffic of the network and the configuration of a port. 

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Hubs are the hardware device that operates in the physical layer of the OSI model. 

• It supports half-duplex transmission

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• It works with shared bandwidth and broadcasting.

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• The hub can provide a high data transmission rate to different devices. 

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• It can detect collisions in the network and send the jamming signal to each port. 

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• Hub does not support VLAN and spanning tree protocol.

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• It is unable to filter the data and hence transmit or broadcast it to each port. 

Features of Hubs

GATEWAYS

A computer that sits between different networks or applications. The gateway converts information, data or other communications from one protocol or format to another. A router may perform some of the functions of a gateway. An Internet gateway can transfer communications between an enterprise network and the Internet.

The most common type of gateways, the network gateway operates at layer 3, i.e. network layer of the OSI (open systems interconnection) model. 

INTRODUCTION

Types of Gateways

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

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• 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.

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

Features of Gateways

• Gateway is located at the boundary of a network and manages all data that inflows or outflows from that network.

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• It forms a passage between two different networks operating with different transmission protocols.

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• A gateway operates as a protocol converter, providing compatibility between the different protocols used in the two different networks.

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• The feature that differentiates a gateway from other network devices is that it can operate at any layer of the OSI model.

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• It also stores information about the routing paths of the communicating networks.