Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions from 23 to 30.
In general terms, the Internet is a way of accessing information from many different sources via a computer at home or connected to a local network. At its simplest, the Internet consists of individual computers linked via a network. The network consists of three basic items: backbones, Internet Service Providers (ISPs) and routers connected to servers that store and send data to and from people.
When people want to access the data, the information goes through four stages. First, their computer is connected to an ISP via a modem or a local area network (LAN). A modem is a piece of equipment for people using a computer at home which converts the signal of the telephone line to a digital signal. A local area network is a network of computers linked together with a digital line.
Next, the request for data is broken into pieces of information about 1 kilobit in size called packets. The next step is for these packets to be broken up into three parts. The head contains the sender's and receiver’s addresses, the data contain the information, and the footer comprises data which show the end of the packet and an error check.
The packets are subsequently transferred to a router - a specialised computer that sends information to its destination along thousands of pathways. Networks are connected through routers which make sure the packet is sent to the correct place and determine the best way for the packet to go. One router communicates with the next router to make sure the next part of the network is clear. If a network path or part of a network is busy, a different route may be chosen. Thus, information that is sent over the Internet travels in separate packets through several possible different routes.
(Adapted from Achieve IELTS)
