Archive for 2012

MESH TOPOLOGY

Sunday, May 13, 2012
Posted by Unknown

MESH TOPOLOGY

In a Mesh Topology, every node has a dedicated point-to-point link to every other node. Messages sent on a mesh network can take any of several possible paths from source to destination. A fully connected mesh network has n (n-1)/2 physical links to link n devices.

Advantages of Mesh Topology

§  The use of large number of links eliminates network congestion.

§  If one link becomes unusable, it does not disable the entire system.

Disadvantages of Mesh Topology

§  The amount of required cabling is very large.

§  As every node is connected to the other, installation and reconfiguration is very difficult.

§  The amount of hardware required in this type of Topology can make it expensive to implement.

TREE TOPOLOGY

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TREE TOPOLOGY

A Tree Topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a bus backbone cable.



Advantages of Tree Topology

§  The distance to which a signal can travel increases as the signal passes through a chain of hubs.

§  Tree Topology allows isolating and prioritising communications from different nodes.

§  Tree Topology allows for easy expansion of an existing network, which enable organizations to configure a network to meet their needs.

Disadvantages of Tree Topology

§  If the backbone line breaks, the entire segment goes down.

§  It is more difficult to configure and wire than other Topologies.

STAR TOPOLOGY

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STAR TOPOLOGY

In Star Topology devices are connected via a centralised network component known as hub or concentrator. The hub acts as a central controller and if a node wants to send data to another node, it boosts up the message to the intended node. This topologies commonly uses twisted pair cable, however, coaxial cable or fiber optic cable can also be used.

Advantages of Star Topology

§  Star Topology is easy to install and wire.

§  The network is not disrupted even if a node fails or is removed from the network.

§  Fault detection and removal of faulty parts is easier in Star Topology.

Disadvantages of Star Topology

§  It requires a longer length of cable.

§  If the hub fails, nodes attached to it are disabled.

§  The cost of the hub makes the network expensive as compared to bus and Ring Topology.

RING TOPOLOGY

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RING TOPOLOGY

In Ring Topology, computers are placed on a circle of cable. Every node has exactly two neighbors for communication purposes.

                                                                              All messages travel through a ring in the same direction (clockwise or counterclockwise) until it reaches its destination. Each node in the ring incorporates a repeater. When a node receives a signal intended for another device, its repeater regenerates the bits and passes them along the wire.





Advantages of Ring Topology

§  Ring Topology is easy to install and reconfigure.

§  Every computer is given equal access to the ring. Hence, no single computer can monopolies the network.

Disadvantages of Ring Topology

§  Failure in any cable or node breaks the loop and can take down the entire network.

§  Maximum ring length and number of nodes are limited.

BUS TOPOLOGY

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BUS TOPOLOGY


Bus topology uses a common bus or backbone (a single cable) to connect all devices with terminators at both ends. The backbone acts as a shared communication medium and each node (file, server, workstations, and peripherals) is attached to it with an interface connecter. 


                                                   Whenever a message is to be transmitted on the network, it is passed back and forth along the cable, past the stations and between the two terminators, from one end of the network to the other. As the message passes each station, the station checks the message’s destination address. If the address in the message matches the station’s address, the station receives the message. If the address does not match, the bus carries the message to the next station, and so on.


Advantages of BUS Topology

§  Connecting a computer or peripheral to a linear bus is easy.

§  This topology requires least amount of cabling to connect the computers and, therefore, less expensive than other cabling arrangement.

§  It is easy to extend a bus since two cables can be joined into one longer cable with a connector.

Disadvantages of Bus Topology

§  Entire network shuts down if there is a failure in the backbone.

§  Heavy traffic can slow down a bus because computers on such networks do not coordinate with each other to reserve time to transmit.

NETWORK TOPOLOGY

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NETWORK TOPOLOGY

Network topology is the study of the arrangement or mapping of the elements (links, nodes, etc.) of a network, especially the physical (real) and logical (virtual) interconnections between nodes. The term topology refers to the way a network is laid out, either physically or logically. A topology can be considered as the network’s shape.

There are five basic topologies: Bus, Ring, Star, Tree, and Mesh.
  • BUS TOPOLOGY
  • RING TOPOLOGY
  • STAR TOPOLOGY
  • TREE TOPOLOGY
  • MESH TOPOLOGY

WIDE AREA NETWORK

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WIDE AREA NETWORK

Wide Area Network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries).      



                                                                                                                                                                                                                          Several options are available for WAN connectivity:

Option:
Description
Advantages
Disadvantages
Bandwidth range
Sample protocols used
Point-to-Point connection between two computers or Local Area Networks (LANs)
Most secure
Expensive
A dedicated circuit path is created between end points. Best example is dialup connections
Less Expensive
Call Setup
28 Kb/s - 144 Kb/s
Devices transport packets via a shared single point-to-point or point-to-multipoint link across a carrier internetwork. Variable length packets are transmitted over Permanent Virtual Circuits (PVC) or Switched Virtual Circuits (SVC)
Shared media across link
Similar to packet switching, but uses fixed length cells instead of variable length packets. Data is divided into fixed-length cells and then transported across virtual circuits
best for simultaneous use of Voice and data
Overhead can be considerable

Transmission rate usually range from 1200 bits/second to 6 Mbit/s, although some connections such as ATM and Leased lines can reach speeds greater than 156 Mbit/s.  Typical communication links used in WANs are telephone lines, microwave links & satellite channels.
METROPOLITAN AREA NETWORK

A MAN, or Metropolitan Area network, is a network of computers spread over a ‘metropolitan’ area such as a city and its suburbs.
Some technologies used for this purpose are ATM, FDDI, and SMDS. These older technologies are in the process of being displaced by Ethernet-based MANs (e.g. Metro Ethernet) in most areas. MAN links radio, or infra-red laser links.
DQDB, Distributed Queue Dual Bus, is the Metropolitan Area Network standard for data communication. It is specified in the IEEE 802.6 standard. Using DQDB, networks can be up to 30 miles long and operate at speeds of 34 to 155 Mbit/s.

LOCAL AREA NETWORK

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LOCAL AREA NETWORK

A local area network (LAN) is a computer network covering a small geographic area, like a home, office, or groups of buildings e.g. a school.

LAN configurations consist of:

§  A file server - stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network.

§  A workstation - computers connected to the file server (Mac or PCs). These are less powerful than the file server

§  Cables - used to connect the network interface cards in each computer.

*     Ethernet over unshielded twisted pair cabling, and Wi-Fi are the two most common technologies currently for LAN, but ARCNET, Token Ring and many others have been used in the past.

*     Usually LAN offers a bandwidth of 10 to 100 Mbps.

Networking

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Networking
==========================================

A computer network is a collection of two or more computers, which are connected together to share information and resources. Computers in a network are interconnected by telephone lines, coaxial cables, satellite links, radio and/or some other communication technique. A network can be as few as several personal computers on a small network or as large as the internet, a worldwide network of computers.
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Advantages of NETWORK

Speed. Sharing and transferring files within Networks are very rapid. Thus saving time, while maintaining the integrity of the file.

Cost. Individually licensed copies of many popular software programs can be costly. Networkable versions are available at considerable savings. Shared programs, on a network allows for easier upgrading of the program on one single file server, instead of upgrading individual workstations. 

Security. Sensitive files and programs on a network are passwords protected (established for specific directories to restrict access to authorized users) or designated as "copy inhibit," so that you do not have to worry about illegal copying of programs.

Centralized Software Management.  Software can be loaded on one computer (the file server) eliminating that need to spend time and energy installing updates and tracking files on independent computers throughout the building. 

Resource Sharing. Resources such as, printers, fax machines and modems can be shared. 

Electronic Mail. E-mail aids in personal and professional communication. Electronic mail on a LAN can enable staff to communicate within the building having tot to leave their desk. 

Flexible Access. Access their files from computers throughout the firm. 

Workgroup Computing. Workgroup software (such as Microsoft BackOffice) allows many users to work on a document or project concurrently.


 §  Server faults stop applications being available.
 §   Network faults can cause loss of data.
 §  Network fault could lead to loss of resources.
 §  User work dependent upon network.
 §  System opens to hackers.
 §  Decisions tend to become centralized.
 §  Could become inefficient.
 §  Could degrade in performance.
 §  Resources could be located too far from users.
 §  Network management can become difficult.
 
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