Network Devices - Introduction

Network Devices:

Network devices are devices which are used to connect computers or other devices with each other so that they can share files and their resources (printers/ fax machines, data/ information) with each other.

There are following types of network devices

  1. HUB
  2. Ethernet HUB’s
  3. Switches
  4. Bridges
  5. Routers
  6. Brouters
  7. Gateways
  8. Network card
  9. Network protocols
  10. ISDN (Integrated Services Digital Network)
  11. Modems

HUB

Hub is one of the basic networking devices which is used to connect multiple devices in single local area network. It works on physical layer of OSI model. Hub is considered as no-intelligent device. It only broadcasts the packets on all the devices connected with it. If more than one device sends packets at the same time then HUB can't handle situation and due to this data collides with each other and become unreadable and this situation is known as "COLLISION DOMAIN".

HUB


 Ethernet HUB’s

Ethernet HUB is same as simple HUB but it is an intelligent device due to Carrier Sense Multiple Access with Collision Detect (CSMA/CD) which controls multiple media access. This HUB communicate in Half-duplex mode.

ETHERNET HUB


 Switches

Switch is also like HUB but it is also an intelligent device. It is also use on Physical Layer of OSI model which is used to connect multiple end devices to create a local area network. Switch works on the basis of MAC-Address Table which it maintains in its memory. In this table switch stores the MAC-Address of device and port number on which that end device is connected.

When switch receives a packets it first of all matches the source and destination MAC-Address written in packet header with the table which maintained by switch. If source and destination MAC-Address matches with the table entries then switch sends that packet to the destination but if address doesn't match then switch holds the packet and first sends a broadcast message to all the devices to update its MAC table.

Switches also have ability to control the collision and broadcast domains.


SWITCH


 Bridges

Bridge is a network device which is used to connect other bridge networks using the same type of protocols. Bridge works at the Data Link Layer of the OSI Model. It connects other networks with each other so that they can communicate with each other and share their resources with each other. It connects two or more LAN's into larger logical LAN which uses same type of protocol. This device is used to develop the simple networks. It does not support the complex networks.

BRIDGE


 Routers

Routers are Network Layer devices of OSI Model. It is identified as Layer-3 device. It use logical address information in the header of the packet which are IP Addresses for processing. Router is used to develop the larger and complex networks and used to perform complex routing between the different networks.

Router maintains the two type of tables
  • APR Table (Address Resolution Protocol)
  • MAC-Address Table


APR Table:
In this table router stores the port number, mac-address and IP address of the end device.

MAC-Address Table:
In this table router only stores the port number and mac-address of the end device.

Router uses both tables for the communication between different networks.

Router performs two type of routing.


Static Routing:
In this type of routing all the network address are stored manually in the tables of routers. It is time taking task and get errors as well. This type of routing is only feasible in small networks where two or three routers are used because the number of routers increase the complexity also increase.

Dynamic Routing:
This is the replacement of Static routing. Dynamic Routing is used in complex networks where numbers of routers are more than two or three. There are different type of protocols which are used to perform dynamic routing. In dynamic routing, routers exchange their information with each other using the routing protocols.


ROUTER


Brouters

Brouters are the hybrid routers which mean they are the combination of "BRIDGE" and "ROUTER". They have the functionality of both bridge and routers. They work as bridge when data is forwarded between the networks and can also perform the routing when needed. It also provides the feature of security by providing the access only to the authorized data towards the local area network and blocks/ redirects unknown data.

BROUTERS


Gateways

Gateways are the devices which are used to connect multiple networks and transfer data between them. It acts like a path between different networking systems or computer programs. Gateway is a device which forms link between the different networks. Gateway allows the end devices to communicate or send data on same network or on different network. Router is also known as gateway, because it interprets data form one network protocol to another network.

GATEWAYS


 Network card

Network card is also known as Network Interface Cards (NICs) is hardware device which is used to connect end devices with the network. They are installed on the mother-board of the end device. Their main task is to develop the physical link between end device and network. It translates the data into electrical signals and sends that signals on the network.

There are two types of NICs
  • Wired NICs
  • Wireless NICs


Wired NICs:
This NIC is used to connect the end device with the network using cable having connector named RJ45. It uses electrical signals to transmit data over the network.

Wireless NICs:
This NIC is used to connect the end device with the network using wireless technology. It uses Radio Waves to communicate data over the network.


NETWORK CARD


Network Protocols

Network Protocols are the set of instruction which are used for communication between the network devices. It is compulsory for the devices which are connected with each other that they have same type of protocols on which they have working. Most common network protocols which are used in networks are HTTP and TCP/IP on which most of the internet standards works.

System Requirements:
  • Bus compatibility should be verified while installing the NIC.
  • Memory Input and output (I/O) addresses and IRQ are needed.
  • Drivers if not installed already.

ISDN (Integrated Services Digital Network)

ISDN (Integrated Services Digital Network) is used to send graphic and audio files over the network. It is a Wide area network technology which is used in place of Dial-up Links. The accessibility of ISDN depends upon the provisions given by the service provides. It provides high speed link than modem. ISDN has the ability to create more than one route on a single link.

ISDN

Modems

Modems are basically an old technology which is used to convert digital signals which are generated by end device into analog signals so that travelling on phone line can be enabled. The other name of modem is "MODULATOR-MODULATOR". It is used as a dial-up for LAN to connect it with ISP. Modems are in both types external and internal.

MODEMS

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