Computer network devices

Computer network devices also known as communication devices and they constitute a data communication network.  These devices are routers, switches, hubs, LAN cards, gateway, modems, ISDN terminals and transceivers.  In an Ethernet or WAN network, the data communication cannot be performed without these devices.  Being an IT professional or a network administrator, you must have the good understanding of these devices. 

1. Repeater.

A wireless repeater.

A repeater is an electronic device that receives a signal and retransmits it at a higher level and/or higher power, or onto the other side of an obstruction, so that the signal can cover longer distances. Repeaters are often used in trans-continental and submarine communications cables, because the attenuation (signal loss) over such distances would be unacceptable without them. Repeaters are used in both copperwire cables carrying electrical signals, and in fiber optics carrying light.

2. Hub.

The central connecting device in a computer network is known as a hub. Every computer is directly connected with the hub.  Hub is a Non-Intelligent device, When data packets arrives at hub, it broadcast them to all the LAN cards in a network and the destined recipient picks them and all other computers discard the data packets. Hence there is a chance for data collision. Hub has five, eight, sixteen and more ports and one port is known as uplink port, which is used to connect with the next hub.

There are two types of Hubs

  1. Passive Hub
  2. Active Hub

Passive Hubs are the hubs which only broadcast the packets given by a Computer But, Active Hubs also amplifies the signal before its broadcasting.

Collision Domain: Collision Domain is an area of a network where there is chance for data collides with each another. A network collision occurs when more than one device attempts to send a packet on a network segment at the same time.

Collision Domain in HUB

The value of Collision Domain in Hub is 1. That is all the ports are in one collision domain. When we connect one or more hubs, the area of Collision domain is also increase.

Broadcast Domain: A broadcast domain is a logical division of a computer network, in which all nodes can reach each other by broadcast at the data link layer. A broadcast domain can be within the same LAN segment.

3. Bridge.

A bridge is a network communication device that is used to connect one segment of the network with another that uses the same protocol.  It operates at the Data link layer of the OSI layers model.  In the Ethernet network, the bridge is also known as IEEE 802.1D.  A bridge process the information at the data link layer of the OSI layers model.

The main advantages of the bridges include the following.

  • Inexpensive
  • Self Configuring
  • Reduced size of the collision domains.
  • Transmits the data based on the MAC address.
  • Supports relatively big networks.

Bridges are fast devices for forwarding the data but not as fast as the routers and switches.  A bridge cannot be used as a firewall device as a router.  In the bridged network, the messages are sent to all the nodes and are picked up only by the destined computers.  A bridged when combined with the router, known as a brouter.  Bridges has now replaced the switches and routers.

How Bridge reduce the Collision Domain?

Mainly there are 3 processes,

  1. Flooding
  2. Filtering.
  3. Forwarding.

Flooding: The MAC address learning process is known as Flooding.

Filtering: The Bridge keeps a MAC table according to its Ports and filters the un-wanted messages from entering the other port. This process is known as Filtering.

Forwarding:  When a packets from first port of a Bridge, which addressing a computer connected to the network in its second port, the bridge will forward that packets to its second port. This process is known as Forwarding.

4. Switches.

A switch is an intelligent device that maps the IP address with the MAC address of the LAN card.  Unlike the hubs, a switch does not broadcast the data to all the computers; it sends the data packets only to the destined computer.  Switches are used in the LAN, MAN and WAN.  In an Ethernet network, computers are directly connected with the switch via twisted pair cables.  In a network, switches use the three methods to transmit the data i.e. store and forward, cut through and fragment free.

Advantage of Switch:

  • Intelligent Device.
  • Transmits the data based on the MAC address.
  • Reduce collision domain.
  • Supports relatively big networks.
  • Self Configuring and can able to configure by an Administrator.

Switch has the same working principle of Bridge, that is

  1. Flooding
  2. Filtering.    and
  3. Forwarding.

5. Router.

A router is a communication device that is used to connect two logically and physically different networks, two LANs, two WANs and a LAN with WAN.  The main function of the router is to sorting and the distribution of the data packets to their destinations based on their IP addresses. Routers provides the connectivity between the enterprise businesses, ISPs and in the internet infrastructure, router is a main device. 

  • Router is a Layer 3 device.
  • Works based on IP address.
  • Keeps a Routing table to distribute the Packets.
  • Not a Self configuring device.

Cisco routers are widely used in the world.  Every router has routing software, which is known as IOS.  Router operates at the network layer of the OSI model.  Router does not broadcast the data packets.

6. WAP.

In computer networking, a wireless access point (WAP) is a device that allows wireless communication devices to connect to a wireless network using Wi-Fi, Bluetooth or related standards. The WAP usually connects to a router, and can relay data between the wireless devices (such as computers or printers) and wired devices on the network.

7. NIC.

LAN cards or network adapters are the building blocks of a computer network. No computer can communicate without a properly installed and configured LAN card. Every LAN card is provided with a unique IP address, subnet mask, gateway and DNS (if applicable).  An UTP/STP cable connects a computer with the hub or switch.  Both ends of the cable have the RJ-45 connectors one is inserted into the LAN card and one in the hub/switch.  LAN cards are inserted into the expansion slots inside the computer.  Different LAN cards support different speed from 10/100 to 10/1000.

8. Modems.

A modem is a communication device that is used to provide the connectivity with the internet.  Modem works in two ways i.e. modulation and demodulation. It covers the digital data into the analog and analog to digital

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