Network Devices

 To transfer data via various transmission media and to set up networks with varying functionality, we need various devices such as Modem,Hub,Switch,Repeater,Router,Gateway, etc. Let us discuss them in detail.

Modem

Modem means 'Modulator Demodulator'. It is a device applied for conversion from analog signals to digital bits. We are aware that computers hold and process information in terms of 0s and 1s. Still, to transmit data from a sender to a receiver, or when accessing the internet, digital data are translated into an analog signal and the medium (whether free-space or physical media) transmits the signal to the receiver. Modems are attached to both the source and destination nodes. The modem at the sender's end is a modulator that translates the digital data into analog signals. The modem at thethe receiver's end functions as a demodulator which demodulatesthe analog signals into digital data for the destination node to comprehend.

Figure- Modem

Ethernet Card

Ethernet card or Network Interface Card (NIC card for short) is a network adapter employed in establishing a wired network.It is an interface between computer andthe network. It is a board mounted on the motherboard of a computer .The computer is connected to the network via NIC by an Ethernet cable.Ethernet cards may support data transfer between 10Mbps and 1 Gbps (1000Mbps). There is a

MAC address for every NIC, which assists in uniquely identifying the computer on the network.

Figure- Ethernet Card

 RJ45 

RJ 45 or Registered Jack-45 is an eight-pin connector that is utilized solely with Ethernet cables for networking.It is a standard networking interface that can be observed atthe end of all network cables.

In essence, it is a little plastic plug that fits into RJ-45 jacks of the Ethernet cards found in different

computing devices.

Figre- RJ45

Repeater

Data are transmitted in the form of signals through the cable. These signals can travel a specified distance (usually about 100 m). Signals lose their strength beyond this limit and become weak. In such conditions, original signals need to be regenerated. A repeater is an analog device that operates with signals on the cables to which it is attached. The weakened signal appearing on the cable is regenerated and placed retransmitted back on the cable by a repeater.

Hub

A network hub is a simple networking device used to connect more than one device in a Local Area Network (LAN) so that they can exchange information. Working at the physical layer (Layer 1) of the OSI model, a hub forwards incoming data packets to all the devices connected, irrespective of the destination. The broadcasting technique causes data collisions and inefficiency in the network, particularly as more devices are added.

An Ethernet hub is a networking device employed to link various devices via cables. Information coming on any of the lines are dispatched on all the others. The limitation of Hub is that if data from two devices come at the same time, they will collide.

Switch 

A switch is a network device that plays a crucial part in a Local Area Network (LAN). Similar to a hub, a network switch is utilized to join various computers or devices of communication. Upon receipt of data, the switch pulls the destination address off the data packet and refers it to a table to find out where to transmit the packet. Therefore, it transmits signals to just specific devices rather than sending to everyone. It can send several packets simultaneously. A switch does not send the noisy or corrupted signals. It discards such signals and requests the sender to resend it. Ethernet switches are common in

homes/offices to connect more devices thereby forming LANs or to access the Internet.

Router 

A router is a network appliance which canaccept the data, process it and forward it to othernetworks. A router connects a local area network to the internet. A router is superior to a hub or a switch since it has

advanced functionality as it is able to process the data carried over a network, determine/modify how it is packaged, and forward it to another network of a different nature. For instance, data has been broken into packets of a specified size. Assume these packets are to be transported on a different nature of network which does not support larger packets. In that case, the data is to be repackage as small packets and then forwarded over the network by a router.

Figure- Router

The router can either be wired or wireless. A wireless router can make smartphones and other devices have access to Wi-Fi. These kinds of routers mostly have some ports to deliver internet access via wired connections as well. Modern household Wi-Fi routers serve the function of a modem/switch as well as that of a router. They attach to incoming broadband lines, ISPs (Internet Service Providers), and transform them into digital information for computer units to process.

Gateway

Since the name "Gateway" implies, it is a major entry point which is a "gate" between an organisation's network and the external world of the Internet. Gateway is the entry and exit point of a network, since all data entering or exiting a network has to first pass through the gateway in order to use routing paths. Apart from routing data packets, gateways also keep information about the host network's internal connection paths and the identified paths of other foreign networks. If a node in one network needs to communicate with a node belonging to a foreign network, it will forward the data packet to the gateway,  and the gateway forwards it to the destination using the best route possible. 

Figure- Gateway

For basic Internet connectivity at homes, the gateway is typically the Internet Service Provider 

which gives access to the whole Internet. Typically, a router is configured to be used as a gateway device in computer networks. But a gateway can be implemented completely in software, hardware, or 

a combination of both. Because a network gateway is placed at the edge of a network,the firewall is usually integrated with it.