Lesson 3: Computer Network and the Internet
This lesson provides a broad overview of Computer Networking and the Internet. The lesson begins with an overview of the Internet and of networking protocols, introducing several key terms and concepts. We examine the 'edge' of a computer network, looking at the end systems and applications, and at the transport service provided to applications running on the end systems. We also examine the 'core' of a computer network, examining the links and switches that transport data. We then take a broader view of networking. From a performance standpoint, we study the causes of packet delay and loss in a computer network. We identify key architectural principles in networking, including layering and service models. We provide brief introduction history of computer networking.
Finally, we provide a brief overview of ATM, a networking technology that provides an important contrast with Internet technologies.
Starter:
How do you use a computer for your study?
What do you use the Internet for?
What is a computer network?
I. What is the Internet?
Here we use the public Internet, a specific computer network, as our principal vehicle for discussing computer networking protocols. But what is the Internet? We would like to be able to give you a one-sentence definition of the Internet – a definition that you can take home and share with your family and friends. The Internet is very complex, both in terms of its hardware and software components, as well as in the services it provides.
A. Translation each word below into the Lao language.
Public: ……………………
Principle: ……………………
Complex: ……………………
Definition: ……………………
Component: ……………………
Hardware: ……………………
Software: ……………………
Service: ……………………
Provide: ……………………
10. Share: ……………………
B. Put a letter after each word above (n) for a noun, (adj) for an adjective, and (v) for a verb.
II. What is the Internet: ‘Nuts and Bolts’ View.
Instead of giving a sentence definition, let us try a more descriptive approach. There are a couple of ways to do this. One way is to describe the nuts and bolts of the Internet, that is, the basic hardware and software components that make up the Internet. Another way is to describe the Internet in terms of a networking infrastructure that provides services to distributed applications.
The public internet is a worldwide computer network, that is, a network that interconnects millions of computing devices throughout the world. Most of these computing devices are traditional desktop PCs, Unix-based workstations, and so-called servers that store and transmit information such as Web (WWW) pages and e-mail messages. Increasingly, non-traditional computing devices such as Web TVs, mobiles, computers, pagers, and toasters are being connected to the Internet.
In the Internet jargon, all of these devices are called hosts or end systems. The Internet applications, with which many of us are familiar, such as the Web and e-mail, are network application programs that run on such end systems.
End systems, as well as most other ‘pieces’ of the Internet, run protocols that control the sending and receiving of information within the Internet. TCP (Transmission Control Protocol) and IP (Internet Protocol) are two of the most important protocols on the Internet. The Internet’s principal protocols are collectively known as TCP/IP.
End systems are connected together by communication links. Links are made up of different types of physical media, including coaxial cable, copper wire, fibre optics, and radio spectrum. Different links can transmit data at different rates. The link transmission rate is often called the link bandwidth and is typically measured in bits/second.
Usually, end systems are not directly attached to each other via a single communication link. Instead, they are indirectly connected to each other through intermediate switching devices known as routers. A router takes information arriving on one of its incoming communication links and then forwards that information on one of its outgoing communication links. The IP protocol specifies the format of the information that is sent and received among routers and end systems. The path that transmitted information takes from the sending end system, through a series of communications links and routers, to the receiving end system is known as a route or path through the network.
Rather than provide a dedicated path between communicating end systems, the Internet uses a technique known as packet switching that allows multiple communicating end systems to share a path, or parts of a path, at the same time. The earliest ancestors of the Internet were the first packet-switched networks.
The Internet is really a network of networks. That is, the Internet is an interconnected set of privately and publicly owned and managed networks. Any network connected to the Internet must run the IP protocol and conform to certain naming and addressing conventions. Other than these few constraints, however, a network operator can configure and run its network (that is, its little piece of the Internet) however it chooses. Because of the universal use of the IP protocol on the Internet, the IP protocol is sometimes referred to as the Internet dial tone.
A. Read the text again and answer these questions.
How many ways to describe the Internet based on the text? What are they?
What is the public internet?
What are non-traditional computing devices mentioned in the text?
4. What are the Internet’s principal protocols?
5. What do TCP/IP stand for?
6. What are physical media mentioned in the text?
7. What is the link transmission called?
8. How are intermediate switching devices called?
9. What does a route or path through a network mean?
10. What is the Internet dial tone?
B. Translate into Lao Language
a networking infrastructure that provides services to distributed applications
a worldwide computer network
interconnects millions of computing devices
servers that store and transmit information
network application programs
to control the sending and receiving of information
incoming communication links
outgoing communication links
earliest ancestors of the Internet
an interconnected set of privately and publicly owned and managed networks.
III. Language work
Present Simple Tense
Subject + Present Verb
When do we use the Present Simple Tense
We use the Present Simple Tense to express habits, general truths, repeated actions or unchanging situations, emotions and wishes:
For habits
He drinks tea at breakfast.
She only eats fish.
They watch television regularly.
For repeated actions or events
We catch the bus every morning.
It rains every afternoon in the hot season.
They drive to Monaco every summer.
For general truths
Water freezes at zero degrees.
The Earth revolves around the Sun.
Her mother is Peruvian.
For instructions or directions
Open the packet and pour the contents into hot water.
You take the No.6 bus to Watney and then the No.10 to Bedford.
For fixed arrangements
His mother arrives tomorrow.
Our holiday starts on the 26th of March
Passive Voice and Active Voice
We use the Present Simple to express the idea that an action is repeated or usual. The action can be a habit, a hobby, a daily event, a scheduled event or something that often happens. In passive voice, we focus attention on the person or thing affected by the action, when the subject is unknown, unclear or irrelevant.
To make statements with the Present Simple Passive, use:
am/is/are + the Past Participle form of the verb
Example:
I am visited
You are visited
He/she/it is visited
We are visited
You are visited
They are visited
Activity 1:
Write a paragraph associated with networking at least 50 words using the Present Simple Tense.
Activity 2:
Write 10 sentences in the Present Simple Passive.
IV. What is the topology of the Internet?
The topology of the Internet, that is, the structure of the interconnection among the various pieces of the internet, is loosely hierarchical. Roughly speaking, from bottom to top, the hierarchy consists of end systems connected to local Internet Service Providers (ISPs) through access networks. An access network may be a so-called local-area network within a company or university, a dial telephone line with a modem, or a high-speed cable-based or phone-based access network. Local ISPs are in turn connected to regional ISPs, which are in turn connected to national and international ISPs. The national and international ISPs are connected together at the highest tier in the hierarchy. New tiers and branches (that is, new networks, and new networks of networks) can be added.
At the technical and developmental level, the Internet is made possible through the creation, testing, and implementation of Internet standards. These standards are developed by the Internet Engineering Task Force (IETF).
The IETF standards documents are called Request For Comments (RFCs). RFCs started out as general requests for comments (hence the name) to resolve architecture problems that faced the precursor to the Internet. RFCs, though not formally standards, have evolved to the point where they are cited as such. RFCs tend to be quite technical and detailed. They define protocols such as TCP, IP, HTTP (for the web), and SMTP (for open-standards e-mail). There are more than 2,000 different RFCs.
The public Internet is the network that one typically refers to as the Internet. There are also many private networks, such as certain corporate and government networks, whose hosts are not accessible from (that is, they cannot exchange messages with) hosts outside of that private network. These private networks are often referred to as intranets, as they often use the same Internet technology (for example, the same types of host, routers, links, protocols, and standards) as the public Internet. The preceding discussion has identified many of the pieces that make up the Internet. Let us now leave the nuts-and-bolts description and take a more abstract service-oriented view.
The Internet allows distributed applications running on its end systems to exchange data with each other. These applications include remote login, file transfer, electronic mail, audio and video streaming, real-time audio and video conferencing, distributed games, the World Wide Web, and much, much more.
It is worth emphasizing that the Web is not a separate network but rather just one of many distributed applications that use the communication services provided by the Internet. The Web could also run over a network besides the Internet. One reason that the Internet is the communication medium of choice for the Web, however, is that no other existing packet-switched network connects more than 100 million computers together and has over 350 million users.
Activity:
Write a summarization of the topology of the Internet, not more than 150 words.