Thursday, 26 April 2012

WEEK 5- Cabling

Cable is the medium through which information usually moves
from one network device to another. Several types of cable are
commonly used with LANs.In some cases,a network will utilize only one type of cable, other networks will use a variety of cable types.There are four types of cables namely :

  1.      Unshielded Twiested Pair (UTP) 
  2.      Shielded Twisted Pair (STP) 
  3.      Coaxial Cable
  4.      Fiber Optic Cable
  5.      Wireless LANs

      Unshielded Twiested Pair  (UTP)

  •   four pairs of wires inside the jacket
  •    each pair is twisted with different twist per   inch to help eliminate  interference from adjacent pairs and other electrical devices.

 Shielded Twisted Pair (STP) 

  •  consists of two individual wires wrapped in a foil shielding to help provide a more reliable data communication. 
  • suitable for environments with electrical interference but the extra shielding can make the cables quite bulky. 
  • often used on networks using Token Ring topology.
Coaxial Cable

  • Coaxial cabling has a single copper conductor at its center. 
  • A plastic layer provides insulation between the center conductor and a braided metal shield. 
  • The metal shield helps to block any outside interference from fluorescent lights, motors, and    other computers.
  • The most common type of connector   used with coaxial cables is the Bayone-Neill-Concelman (BNC) connector. 

  • Fiber Optic Cable  consists of a center glass core surrounded by several layers of protective materials and transmits light rather than electronic signals eliminating the problem of electrical interference. 
  • Fiber Optic Cable is ideal for certain environments that contain a large amount of electrical interference. 
  • It is able to transmit signals over much longer distances than coaxial and twisted pair.

Summary of Ethernet cabling 

10BaseT : Unshielded Twisted Pair : 100 meters
10Base2 : Thin Coaxial : 185 meters
10Base5 : Thick Coaxial : 500 meters

10BaseF : Fiber Optic : 2000 meters'

Cable and typology 

   Linear Bus : Coax, twisted pair, Fiber : Ethernet, Local talk
   Star : Twisted pair, fiber : Ethernet, Local talk
   Star-wired Ring : Twisted pair : Token ring
   Tree : Coax, twisted pair, fiber ; Ethernet

Ok, that's all from me today, thanks for visiting ^^

Saturday, 7 April 2012

Week 4- Typology, Protocol and Architecture

Today, we learn about typology, protocol and architecture. Typology can be classified into two; 
Physical and Logical typology.

Physical Typology- mapping of links and notes into a geometrical     shape.

Logical Typology- mapping of the flow of data.

Physical typology can be classified into five types

  • linear bus
  • ring
  • star
  • star -wired ring 
  • tree
Linear bus typology consist of a main cable and terminator at both end. All notes is connected to the main cable. Linear bus typology is easy to be connected and need less wire but may the whole system may malfunction if the main cable is broken. Ethernet and local talk uses linear bus typology.

Ring typology is similar to linear bus in many aspects. The only difference is that bus typology do not have terminator as all notes is interconnected with each other. 

Star typology is designed so that each nodes is connected to a hub/concentraterEthernet and local talk uses linear bus typology . Star typology is easy to add new nodes and will not malfunction if one of the nodes breaks down. However, it need more cable length and cost more compare to linear bus. 

Star-wired is externally same as star typology. Internally, the MAU (multiststion access unit) allows the information to pass from a device to a ring or circle. The Token Ring uses star- wired typology.

A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable. Tree typology allows point to point wiring for each nodes but  the overall length of each segment is limited by the types of cable used. 

In this lesson, we also learn about protocols. Protocols is a set of rules that governs the communication the computers in a network. It can be divided into
  1. Ethernet
  2.  Localtalk
  3. Token Ring
  4.  Fiber Distributed Data Interface (FDDI )

We also learn about the types of architecture:
  • Peer to peer 
  • client/server

In peer to peer, all computers are considered equal and have the same tendency to share information . Peer to peer network lacks security as there is no central computer to control the network.

In client/ server network, there are a central network that governs the transfer of data between the computers. The server is the heart of the system , providing security and access to information.  

Lastly, our homework of the day is to find out the definition of Asynchronous Transfer Mode (ATM)  . It encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that use variable sized packets or frames.  

That's all from me this lesson. Thanks 4 spending time to read it ^^