Pure Theory: 2010


Monday, October 25, 2010

How to do the project based on Computational Thinking:

The original blog link;

Take a minute to think back to some of your past science fair projects or lab experiments. What elements did they have in common? What elements were different?

While every project or experiment may have been unique in the problem they were trying to solve, they all followed the same basic template of title, problem, hypothesis, materials, procedure, data and results, and conclusion. This ability to notice similarities, differences and trends is called pattern recognition. The ability to then extract out the unnecessary details and generalize those that are necessary is called pattern generalization, which leads us to an abstraction.

These are just some of the problem-solving skills that we apply when we design and run an experiment. Other skills include decomposition (the ability to break down a tasks into sub-tasks, e.g., when we specify each of the materials that we’ll need to conduct the experiment) and algorithm design (the ability to build a repeatable, step-by-step process to solve a particular problem, e.g., when we create the procedure so that others can understand our process and run that same experiment).

Thursday, July 22, 2010

The basic difference between Route and Hub

Copyright@July 2010 By antonio081014.

These days, I was working on a network security of Cloud Computing, so those used to confuse me a lot are finally configured out. One of them is the difference between route and hub.

A computer, which is just a node in the network, connected to the Local Area Network(LAN). It has two addresses to identify the its identification. One is Media Access Control(MAC) address, which uniquely identifies each node in the network, and is stored on the network interface card(NIC) itself. Each NIC has a unique MAC address. It is the MAC address which are used by the Ethernet protocol while creating frames to transfer data from and to a computer, physically. The other address is the famous IP address, which is generated in the network layer, it can be used by the applications.

For hub (bridge), it just retransmits the coming package to all the connected nodes (Broadcast), and then if the package's MAC address is not matchable with the destination's MAC's address, it will drop directly. These operations are run on the Ethernet layer and Physical layer.

For Route, it usually has a route table embedded in the router. The route table keep the record of a mapping, which is the map between an IP address and the port of the router. When a pkg coming, the router will check the route table to identify which port maps to the destination's IP. Then it sends the package through that port. The route table is dynamic updated, which means the router will keep sending arp to all of the nodes. Then all the nodes will send the arp back, which tell the router the information of each node : 1)  The map of MAC address and the IP address, this will tell the which node(Each node's MAC is identified) has what IP address. 2) The map of IP address and the port number of router, this will tell which port to send when a package comes. These operations are run on the Network layer, Ethernet layer and Physical layer.