LAN Network topologies

Network topology is the name given to the way in which the devices (called nodes) are physically connected in a network.
There are three common network topologies, called ring, line (bus) and star.
You will be expected to briefly describe the features of each one, know their advantages and draw simple line diagrams to represent then.


Ring topology:

Network topologies - a RING network

In a ring topology, the nodes are connected in a ring and data travels in one direction using a control signal called a 'token'.


Advantages:
  • Not greatly affected by adding further nodes or heavy network traffic as only the node with the 'token' can transmit data so there are no data collisions.
  • Relatively cheap to install and expand.
Disadvantages:
  • Slower than a star topology under normal load.
  • If the cable fails anywhere in the ring then the whole network will fail.
  • If any node fails then the token cannot be passed around the ring any longer so the whole network fails..
  • The hardest topology to troubleshoot because it can be hard to track down where in the ring the failure has occurred.
  • Harder to modify or expand because to add or remove a node you must shut down the network temporarily.
  • In order for the nodes to communicate with each other they must all be switched on.

Bus (line) topology:

Network topologies - a BUS (LINE) networkNodes are connected to a main (bus) cable. If data is being sent sent between nodes then other nodes cannot transmit.  If too many nodes are connected then the transfer of data slows dramatically as the nodes have to wait longer for the bus to be clear.

Advantages:
  • The simplest and cheapest to install and extend.
  • Well suited for temporary networks with not many nodes.
  • Very flexible as nodes can be attached or detached without disturbing the rest of the network.
  • Failure of one node does not affect the rest of the bus network.
  • Simpler than a ring topology to troubleshoot if there is a cable failure because sections can be isolated and tested independently.
Disadvantages:
  • If the bus cable fails then the whole network will fail.
  • Performance of the network slows down rapidly with more nodes or heavy network traffic.
  • The bus cable has a limited length and must be terminated properly at both ends to prevent reflected signals.
  • Slower than a ring network as data cannot be transmitted while the bus is in use by other nodes.

Star topology:

Network topologies - a STAR networkIn this type of network, a central computer (server) usually forms the main node and the subsidiary nodes are connected to it and to each other through a switch or hub.
Advantages:
  • The most reliable because the failure of a node or a node cable does not affect other nodes.
  • Simple to troubleshoot because only one node is affected by a cable break between the switch and the node.
  • Adding further nodes does not greatly affect performance because the data does not pass through unnecessary nodes.
  • Easily upgraded from a hub to a switch or with with a higher performance switch.
  • Easy to install and to expand with extra nodes.
Disadvantages:
  • Uses the most cable which makes it more expensive to install than the other two topologies.
  • The extra hardware required such as hubs or switches further increases the cost.
  • As the central computer controls the whole system, the whole system will be affected if it breaks down or if the cable link between it and the switch fails.
  • If the switch, the link to the server or the server itself fails then the whole network fails.

LAN, MAN, WAN




LAN (Local Area Network) - a computer network confined to a relatively small area, such as a single building or a group of adjacent buildings.  A LAN can cover an entire campus, so long as the buildings are directly connected.  The nodes (computers, printers, servers, etc.) are connected via bridges and routers.  Devices can be connected by twisted-pair wire, coaxial cables, or fiber optic cables.
MAN (Metropolitan Area Network) - a data network designed for a town or city. In terms of geographic breadth, MANs are larger than local-area networks (LANs), but smaller than wide-area networks (WANs).  Some MAN networks do without connecting media altogether, communicating instead via radio waves, using dish antenna's on rooftops.
WAN (Wide Area Network) - a computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more local-area networks (LANs). Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

Results Trial SPM 2012

Tahniah kepada pelajar-pelajar cikgu yang mendapat keputusan cemerlang bagi subjek ICT  pada kali ini...Keep it up!!!!






1.
Poh Quan Xin
87%
A
2.
Goh Ai Hoon
85%
A
3.
Yap Yen Wen
77%
A-
4.
Yeo Jun Yan
77%
A-
5.
Gan Jie Shen
75%
A-

Kepada pelajar-pelajar yang lain, cikgu berharap agar kamu semua berusaha dengan lebih gigih lagi untuk berjaya dalam SPM sebenar nanti...
##Berita baik: semua lulus!!!
P/s : jangan ponteng sekolah....banyak latih tubi yang akan cikgu beri di kelas nanti...