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(2-1) The most common scheme carefully chooses the bottleneck that most reduces the computer’s speed. Ideally, the cost is allocated proportionally to assure that the data rate is nearly the same for all parts of the computer, with the most costly part being the slowest. This is how skillful commercial integrators optimize personal computers such as smart cellphones.
(2-2) A computer system is one that is able to take a set of inputs, process them and create a set of outputs. This is done by a combination of hardware and software. Computer hardware consists of the physical components that make a computer go. Software, on the other hand, is the programming that tells all those components what to do. Windows and Photoshop and Web browsers are software. Knowing how to operate software is a bit like knowing how to drive a car: It’s what you use the computer for on a daily basis. But understanding hardware is like knowing how the car works.
(2-3) Computer software has to be “loaded” into the computer’s storage (such as the hard drive or memory). Once the software has loaded, the computer is able to execute the software. This involves passing instructions from the application software, through the system software, to the hardware which ultimately receives the instruction as machine code. Each instruction causes the computer to carry out an operation– moving data, carrying out a computation, or altering the control flow of instructions.
(2-4) In modern protocol design, protocols are “layered” according to the OSI 7 layer model or a similar layered model. Layering is a design principle which divides the protocol design into a number of smaller parts, each part accomplishing a particular sub-task and interacting with the other parts of the protocol only in a small number of well-defined ways. Layering allows the parts of a protocol to be designed and tested without a combinatorial explosion of cases, keeping each design relatively simple. Layering also permits familiar protocols to be adapted to unusual circumstances.
(2-5) No one actually owns the Internet, and no single person or organization controls the Internet in its entirety. It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies. The Internet carries an extensive range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web (WWW), the infrastructure to support email, and peer-to-peer networks.
(2-6) 802.11 networks are organized in two ways. In infrastructure mode, one station acts as a master with all the other stations associating to it. The master station is termed an access point (AP) and all communication passes through the AP; even when one station wants to communicate with another wireless station, messages must go through the AP. In the second form of network, there is no master and stations communicate directly. This form of network is commonly known as an ad-hoc network.
(2-7) A cellular network or mobile network is a radio network distributed over land areas called cells, each served by at least one fixed-location transceiver, known as a cell site or base station. In a cellular radio system, a land area to be supplied with radio service is divided into regular shaped cells, which can be hexagonal, square, circular or some other regular shapes, although hexagonal cells are conventional. Each of these cells is assigned multiple frequencies which have corresponding radio base stations. The group of frequencies can be reused in other cells, provided that the same frequencies are not reused in adjacent neighboring cells as that would cause co-channel interference.