Thursday, 11 October 2012

Networking Concept


An internetwork consists of two of more networks connected to each other. These networks are joined using cables and devices. Several factors determine the type of network. In each type of network, the devices are connected in a specific way. For communication between the networks different models, such as OSI, exist defining the manner in which the communication between network occurs.

Line configuration

1.  Point to Point configuration:
In Point to Point configuration, A dedicated like exists between two devices. A dedicated Link implies that the full capacity of the channel is reserved for communication between the two connected devices.
2. Multipoint Configuration:
In multipoint configuration, more than two devices share a link. In this configuration, several devices are connected on the same link and hence the capacity of the channel is shared between the device.

Types of Topologies

Topology refers to the configuration of computers and network devices. The two types of topologies are : -
  • Physical Topology : –  Represents the physical layout of devices on a network. It refers to the arrangements of the devices on the network and the way they communicate with each other. The five basic physical topologies are Bus, Star, Tree, and Mesh.
  • Logical Topology : –    Represents the way the data in transferred from one device to the next, irrespective of the physical interconnection of the devices.

Bus Topology

In Bus topology, all the devices are connected to a single cable know as the bus. The devices of the nodes are connected to the main bus with the help of :
  • Drop Line : –  Provides connection between the main cable and device.
  • Tap : – Creates contact between the drop line and the metallic core of the cable by puncturing the sheath of cable.
Bus Topology is easy to install as the devices need to be connected only with the bus. Also, it is cost effective, as the cabling required is less. If one device in the network fails, then the network in not affected as the communication is not dependent on any other device in network.
In Bus Topology the fault isolation is difficult, as break in the cable is difficult to identify. Also entire network is affected if the cable breaks.

Star Topology

In Star Topology all the devices are connected to a central hub. The devices are not connected to each other directly. In a star topology, when a device transfers data from one device to another, the date passes through the hub to reach the destination. The hub is responsible to manage and control the network.
Star Topology easy to install and manage, as a new device just requires to be connected to the central hub. It is easier to detect faults as each device is directly connected to the hub.
Star Topology requires a hub, which makes it expensive. Also, if the central hub fails then the entire network is disabled. Also congestion may occur in the network as all the traffic is routed through the hub

Ring Topology

In Ring Topology, all the devices are connected in a closed loop. Each device is connected through point-to-point line configuration to another device. There are no terminated cables in Ring Topology as in bus topology.
The fault isolation is easier in Ring Topology, as you can identify the device through which the data is not transmitted further.
Ring Topology is expensive as a lot of cabling is required. If one device in the network fails, entire networks is affected.

Tree Topology

Tree Topology has a group of star-configured workstations, which are connected to a linear cable. The difference between in Tree and Star topology is that in tree topology all the devices are not directly connected to the central hub. Several secondary hubs are present, which are connected to the central hub.
In Tree Topology the distance that a signal can travel between devices increases as hubs are present. The hub acts as a repeater, which amplifies the signal if it is weak.
Congestion my occur in Tree Topology as all the data is router through the hub. If the central hub fails then entire network is affected.

Mesh Topology

In Mesh Topology, every device has a dedicated link to every other device in the network. The link has to carry the traffic only between the devices, which it connects. If tere are n devices in the network then    [n (n-1)]/2    are the number of links needed to connect the device.
In Mesh Topology the traffic problem is eliminated as each device has a dedicated link to very other device. This also ensures security, as the data is directly routed to the destination devices.
In Mesh Topology more cabling is required, which makes it expensive to implement.

Type Of Networks

A network is a collection of computers connected to each other with the help of networking devices. A network is classified on the basis of its size, ownership, distance covered, and physical architecture. The different types of network are Local Area Network (LAN), Man Area Network (MAN), Wide Area Network (WAN).

Local Area Network (LAN)

A Local Area Network is spread over a small area. LAN s are used when you want to connect the computers in a building or group of group of buildings. Each computer on a LAN has its own Central Processing Unit (CPU), but they can share expensive devices, such as a printer, and modem. Computers on a LAN can also share data among themselves. The rate of transferring data over a lan is vary fast.

Metropolitan Area Network (MAN)

A Metropolitan Area Network is spread over a larger geographical area as compared to LAN. MAN is used to connect computers is a town or a city. MAN provides high speed connectives using fibre optic cable.

Wide Area Network (WAN)

A Wide Area Network enables long transmission of Data, Voice, Image, and Video information. A WAN is larger than a MAN network. WAN is used to transfer data over large geographical areas, such as, a country, continent, or the entire world. For Example, the Internet is the largest WAN.

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