Friday 6 April 2012

Topology, Protocol and Achitecture of Networks.

Time flies. We are already in week 7 and it is our fifth lesson with Dr. Dayang. In the previous lesson, we learn WHAT is computer network about and in today's lesson, we learn HOW is the computer network works. Basically, computer network is classified into 3 categories that are topology, protocol and architecture.






What is TOPOLOGY (LAN)?

  • Topology is the study of arrangement or mapping of the elements (links, nodes and etc,) of a network, especially the physical and logical interconnections between nodes.

Physical Topology (LAN)=) the  physical layout of devices on a network and how they communicate with each other.
 
Logical Topology (LAN)  =) the mapping of the flow of data between the nodes in the network determines the logical topology of the network.

BUT we are more emphasize on physical topology.


There are how many TYPES of physical topology?

 six. i) Linear Bus   ii) Star   iii)Star-wired   iv)Tree v)FDDI vi) Ring

i) Linear Bus
  • consists of main run of cable at each end.
  • the bus cable carries the transmitted message along the cable. The workstation will check whether the address destination match it or not. The workstation will not do anything if the destination address is not match.
  •  protocol used: Ethernet and Local Talk


Linear Bus



 ii) Star
  • is designed with each node (file server, workstation, and peripheral) connected directly to the central network hub or concentrator.
  • data on a star network passes through the hub/concentrator before continuing to its destination. The hub/concentrator manages and controls all the functions of the network. It acts a repeater for the data flow.
  • common cable used: twisted pair cable, coaxial cable or fiber optic cable.
  • protocol used: Ethernet and Local Talk.

Star


 iii) Star - wired
  • Externally same as star topology.
  • Internally, MAU (Multistation Access Unit) of a star-wired ring allows information to pass through from one device to another in a circle or in a ring.
  • protocol used: Token Ring


Star-wired


iv) Tree
  • combines characteristics of linear bus and star topologies.
  • consists of a group of star-configured workstations connected to linear bus backbone cable. This type of topology allows the expansion of network from the existing one.


Tree



v) Fiber Distributed Data Interface (FDDI)
  • normally implemented over fiber optic ( fast ethernet, UTP)
  • 100mbps
  • dual redundancy built in by use primary and secondary ring
  • automatic bypassing and isolation of faulty nodes.


FDDI


vi) Ring
  • Each system connects to its neighbour to form a ring.
  • this topology does not require termination as it is connected to each other in a loop. So, it does not have the beginning and end point not like the linear bus.
  • The configuration can be seen in FDDI.

Ring








What is Protocol?

  •  is a set of rules that governs the communications between computers on a network.
  • These rules include guidelines that regulate the following characteristics of a network:
           - access method
           - allowed physical topologies
           - types of cabling
           - speed of data transfer

  • There are protocols for Ethernet, Localtalk, Token Ring and FDDI.



What is Architecture?

  • is about how the data flow on the network.
  • 2 types: i) Peer to Peer       ii)Client/Server

Peer to Peer Network
- all the computers are considered equal, have the same abilities to use the resources available on the network.
- do not have a file server or a centralized management source.
- designed for small to medium local area networks.
- e.g. Appleshare and Windows for Workgroups.

Client/Server
- allow the network to centralize functions and applications in one or more dedicated file servers.
- file servers become the heart of the system, providing access to resources and providing security.
- individual workstations (clients) have access to the resources available on the file servers.
- e.g. Novell Netware and Windows 2000 Server.





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