Unit 7 Computer Network

计算机英语教程 教学课件

Contents• Part 1 Reading and Translating

– Section A: Ethernet

– Section B: Wi-Fi

– Section C: Location-based Service

• Part 2 Simulated Writing: Instructions

• Part 3 Listening and Speaking– Dialogue: Setting up Wireless Network

– Listening Comprehension: IPv6—the Next Generation

– Dictation: Router

1.1 Ethernet

1. Introduction

2. History

3. General Description

1.1 Ethernet• Complex Sentences

– Original: The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology..

– Translation: 以太网的用于将终端系统连接到网络的双绞线版本与用于场地主干网的光纤版本的组合，是最为广泛使用的有线局域网技术。

1.1 Ethernet• Complex Sentences

– Original: These systems replaced the coaxial cable on which early Ethernets were deployed with a system of hubs linked with unshielded twisted pair (UTP), ultimately replacing the CSMA/CD scheme in favor of a switched full duplex system offering higher performance.

– Translation: 这些系统用以非屏蔽双绞线链接的网络集线器系统替代了基于同轴电缆所部署的早期以太网，并最终选择一个能提供更高性能的可交换全双工系统替代了载波侦听多路访问 / 冲突检测模式。

1.1 Ethernet• Exercises

• I. Read the following statements carefully, and decide whether they are true (T) or false (F) according to the text.– ___1 ． The name “Ethernet” was derived from the similar

fundamentals between computers communicating over a shared coaxial cable and radio broadcast systems over the ether.

– ___2 ． Ethernet, token ring, FDDI and ARCNET LAN are all LAN standards.

– ___3 ． Data packets are blocks of data that are individually sent and delivered, via which Ethernet stations communicate with each other.

– ___4 ． A specific protocol can be identified via the packet type it uses in current Ethernet.

– ___5 ． Now, most manufacturers build smaller network card with decreasing cost and the reduced panel space in PC..

1.1 Ethernet

• II. Choose the best answer to each of the following questions.– 1 ． Which of the following has been outdated among

wired LAN technology?– A ． The shielded twisted pair B ． The fiber optic– C ． The coaxial cable D ． The unshielded twisted

pair

C

1.1 Ethernet

• II. Choose the best answer to each of the following questions.– 2 ． Which of the following is WRONG about the

comparison between the early version and the current version of Ethernet?

– A ． The original address fields in the experimental Ethernet have been changed in the current versions

– B ． The destination and source adresses have been overleapt in the current Ethernet versions

– C ． A switched full duplex system can offer higher performance than the CSMA/CD scheme used by the early Ethernet

– D ． The running speed of the current Ethernet is 100 times and beyond as fast as that of the early versions

D

1.1 Ethernet

• II. Choose the best answer to each of the following questions.– 3 ． What does the phrase “frame-based” mean

appearing at the beginning of the article?– A ． All generations of Ethernet conform to the multi-

layers structure of the OSI reference model– B ． All generations of Ethernet are built on improving

infrastructure from coaxial cable to twisted pair– C ． All generations of Ethernet base on the same

architecture formats and the same interfaces for higher layers

– D ． All generations of Ethernet base on the same physical layer as the underlying frame

B

1.1 Ethernet

• III. Translating.– 1. Original: Ethernet defines a number of wiring and signaling

standards for the physical layer, through means of network access at the Media Access Control (MAC)/Data Link Layer and a common addressing format.

– Translation:– 2. Original Adapters generally come programmed with a globally

unique address, but this can be overridden,either to avoid an address change when an adapter is replaced, or to use locally administered addresses.

– Translation:

1.2 Wi-Fi

1. Introduction

2. Uses

3. Advantages and Problems

1.2 Wi-Fi

• Complex Sentences– 1. Original: In business environments, just like other

environments, increasing the number of Wi-Fi access-points provides redundancy, support for fast roaming and increased overall network-capacity by using more channels or by defining smaller cells.

– Translation: 在商业环境中，正如其他环境一样，不断增加的 Wi-Fi 访问点数量通过使用更多的信道或定义更小的单元来提供冗余的、对快速漫游的支持以及更大的总网络容量。

1.2 Wi-Fi

• Complex Sentences– 2. Original: Over the years, Wi-Fi implementations have moved

toward “thin” access-points, with more of the network intelligence housed in a centralized network appliance, relegating individual access-points to the role of “dumb” transceivers..

– Translation: 经过多年， Wi-Fi 实现已经移向了“瘦”访问点，使用设在一个集中网络装置中的更多网络智能，将单独访问点降级到只是“哑的”无线电收发器的角色。

1.2 Wi-Fi• Exercises

• I. Read the following statements carefully, and decide whether they are true (T) or false (F) according to the text.– ___1 ． A Wi-Fi enabled device can connect to the Internet

when within range of any wireless network.

– ___2 ． A single Wi-Fi access point has a greater range indoors than outdoors.

– ___3 ． Wi-Fi connections can be disrupted by having other devices in the same area with an interference.

– ___4 ． Wi-Fi in the higher GHz frequency block has better range than in the lower GHz frequency block.

– ___5 ． There are about 800 million new Wi-Fi devices around the world now...

1.2 Wi-Fi

• II. Choose the best answer to each of the following questions.– 1 ． Which of the following description is WRONG

about Wi-Fi?– A ． Any standard Wi-Fi device will work anywhere in

the world with global operative set of standards– B ． Now most laptops are built with wireless network

adapters inside– C ． One can connect Wi-Fi devices in ad-hoc mode

for client-to-client connections without a router– D ． Communications between two devices need the

involvement of an access point with Wi-Fi

B

1.2 Wi-Fi

• II. Choose the best answer to each of the following questions.– 2 ． Which of the following types of wireless devices

has the highest power consumption?– A ． Bluetooth B ． ZigBee– C ． Wi-Fi D ． Not mentiond

C

1.2 Wi-Fi

• II. Choose the best answer to each of the following questions.– 3 ． Which of the following descriptions is WRONG

about the uses of Wi-Fi?– A ． A carrier wave is used to transmit the data in

packets– B ． The hardware provides indication to the sender

about whether the transmission was delivered– C ． Each station is constantly tuned in on the

channel– D ． All stations share a single radio frequency

communication channel

D

1.2 Wi-Fi

• III. Translating.– 1. Original: A Wi-Fi enabled device such as a personal

computer, video game console, smartphone or digital audio player can connect to the Internet when within range of a wireless network connected to the Internet.

– Translation:

1.2 Wi-Fi

• III. Translating.– 2. Original: TCP has been tuned for a wired network in which

packet loss due to noise is very rare and packets are lost almost exclusively due to congestion

– Translation:

1.3 Location-based Service

1. Introduction

2. History

3. Locating Methods

4. LBS Applications

1.3 Location-based Service

• Complex Sentences– 1. Original: Sometimes referred to as positioning, with control

plane locating the service provider gets the location based on the radio signal delay of the closest cell-phone towers (for phones without GPS features) which can be quite slow as it uses the “voice control” channel

– Translation: 有时也称为定位，用控制平面，定位服务提供商基于最近的手机塔的无线电信号延迟得到位置信息（用于无 GPS 功能的手机），由于使用“语音控制”信道，速度可能非常缓慢。

1.3 Location-based Service• Exercises

• I. Read the following statements carefully, and decide whether they are true (T) or false (F) according to the text.– ___1 ． This concept of location based systems follows the

standardized concept of real-time locating systems and related local services.

– ___2 ． LBS was originally developed by mobile carriers in partnership with mobile content providers.

– ___3 ． GPS and GSM can’t work indoors.

– ___4 ． LBS and SMS can be used in combination to provide location-based mobile advertising.

– ___5 ． Bluetooth, UWB, RFID and Wi-Fi can be used indoors as the alternatives.

1.3 Location-based Service

• II. Choose the best answer to each of the following questions.– 1 ． Which of the following facts happened latest

about the development of LBS?– A ． The first consumer LBS-capable mobile Web

device was released– B ． The first LBS service was launched– C ． The first mobile phones equipped with GPS was

launched– D ． The first commercial LBS service was launched

B

1.3 Location-based Service

• II. Choose the best answer to each of the following questions.– 2 ． Which of the following applications of LBS is

(are) mentioned in this article?– A ． Advertising B ． Logistics– C ． Emergency Medical Services D ． All above

C

1.3 Location-based Service

• II. Choose the best answer to each of the following questions.– 3 ． Which of the following locating methods does

GPS-based LBS belong to?– A ． GSM Localization – B ． Control Plane Locating– C ． Near LBS (NLBS) – D ． Operator-andGPS-independent location service

D

1.3 Location-based Service

• III. Translating.– 1. Original: A location-based service (LBS) is an information or

entertainment service, accessible with mobile devices through the mobile network and utilizing the ability to make use of the geographical position of the mobile device.

– Translation:

1.3 Location-based Service

• III. Translating.– 2. Original: The main advantage is that mobile users don’t have

to manually specify ZIP codes or other location identifiers to use LBS, when they roam into a different location.

– Translation:

2.1 Simulated Writing: Instructions

• Introduction

• Some Preliminaries

• Common Sections

• Format in Instructions

• Other Useful Information

• Sample

• Exercises

3.1 Dialogue: Setting up Wireless Network

• Creating a LAN Connection between Two PCs

3.2 Listening Comprehension IPv6—the Next Generation Internet Protocol

• Listen to the passage and the following 3 questions based on it. After you hear a question, there will be a break of 10 seconds. During the break, you will decide which one is the best answer among the four choices marked (A), (B), (C) and (D).

• Questions– 1. What is the most direct and powerful driving force behind the

development of IPv6?

– 2. How many unique IP addresses can be supported by IPv6 at most?

– 3. Why does IPv4 need to use the technique of network address translation?

3.3 Dictation: Router

• This passage will be played THREE times. Listen carefully, and fill in the blanks with the words you have heard.