信息处理技术. chapter 5: internet and lan technology2 111chapter 4: file management, virus...

信息处理技术信息处理技术

Chapter 5: Internet and LAN Technology 2111Chapter 4: File Management, Virus Protection, and Backup

1Chapter 1: Computer, Internet, Web, and E-Mail Basics

Chapter 5: Internet and LAN Technology 3

After this chapter, you should be able to:– Describe the characteristics of various networks– Diagram Shannon’s model of a communications

network– List types of cables– List network devices– Describe the role of communications protocols and list

some protocols associated with the Internet and LANs– Explain packet switching and circuit switching– Recount the history of the Internet

Chapter 5 Preview


After this chapter, you should be able to:– Draw a conceptual diagram illustrating the Internet

backbone, NAPs, NSPs, routers, and ISPs– Explain Ping and Traceroute– Explain the differences between permanent IP

addresses, dynamic IP addresses, private IP addresses, and domain names

– Describe the advantages and disadvantages of dial-up, cable modem, DSL, ISDN, T1, T2, and wireless Internet access

– Explain when and why it is important to implement security measures such as antivirus software, firewalls, and Network Address Translation

Chapter 5 Preview


Chapter 5 Outline

• Section A– Network Building Blocks

• Section B– Local Area Networks

• Section C– Internet Technology

• Section D– Internet Access

Computer Concepts 8th Edition

Chapter 5Internet and LAN Technology

英特网及局域网技术

Section A: Network Building Blocks网络构架


Why is networking computers advantageous?

计算机网络优势何在 ?

• Reduce costs

• Provides access to a wide range of services and specialized peripheral devices

• Sharing data on a network is easy

• Networks enable people to work together regardless of time and place

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Do networks have disadvantages?网络也有弱点吗 ?

• Primary disadvantage is their vulnerability to unauthorized access// 非法非法访问访问 //

• More vulnerable// 易受易受……的攻击的攻击 // than standalone computers to malicious // 恶意恶意的的 //code

Page 226


How are networks classified?

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• Geographical scope

• Organizational structure

• Physical topology

• Network links

• Bandwidth

• Communications protocols


Why is geographic scope important?

• Wide Area Network

• Metropolitan Area Network

• Local Area Network

• Neighborhood Area Network

• Personal Area Network

Page 228


What is the difference between a client/server network and a peer-to-peer network?

• Client/server – contains servers and clients

• Peer-to-peer (P2P) – every computer is considered an equal

Page 229


How are devices on a network physically arranged?

Star Topology

Mesh Topology Bus Topology

Ring Topology

Tree Topology

Page 230


• Data can travel from one network device to another over a cable or through the air

• A communications channel is a physical path or a frequency for a signal transmission

• Wired network– Networks use different types of cables

• Wireless network

Network Links: What connects the nodes of a network?

Page 231


• Today’s networks use twisted-pair cables– UTP (unshielded twisted pair)– STP (shielded twisted pair)– Looks similar to telephone cable– Has square plastic RJ-45 connector

What are popular network cabling options?

Page 232


• Another option is coaxial cable– Resembles cable-TV cable– Round, silver BNC or F-type connector


Page 232


• Fiber-optic cable is a bundle of extremely thin strands of glass– Each optical fiber (strand) is thinner than a

human hair

• USB, serial, parallel, SCSI, and Firewire connections


Page 232


• Data can also travel airways in form of RF signals sent and received by a transceiver

• Microwaves provide another option for transporting data

• Radio and microwave transmissions cannot be bent around the surface of the earth to reach far-flung towers

• Communications satellites play an important part in long-distance communications

• A transponder on the satellite receives the signal, amplifies it, and retransmits the signal back to a ground station on earth

What are the options for wireless networks?

Page 233


What’s the difference between analog and digital signals?

• Digital signals are transmitted as bits using a limited set of frequencies

• Analog signals can assume any value within a specified range of frequencies

Page 233


What’s bandwidth?

• The transmission capacity of a communications channel

• High-bandwidth communications systems are sometimes referred to as broadband

• Systems with less capacity are referred to as narrowband

Page 234


• In 1948, Claude Shannon published an article that described a communication model

How does data travel over a network?

Page 234


How does data travel over a network?

Page 234


• A set of rules for efficiently transmitting data from one network node to another

• The best-known protocol is probably TCP/IP

What is a protocol?

Page 235


• When you transmit data, it is broken up into small pieces called packets

• A packet is a parcel of data that is sent across a network– Has the address of its sender– Has the address of the destination– Has some data

• When they reach the destination, they are put back together into original form

What’s a packet?

5


How does a protocol initiate a transmission?

• A synchronous protocol coordinates sending and receiving by using a clock signal

• Asynchronous protocols require the transmitting computer to send a start bit that indicates the beginning of a packet– Handshaking

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• Simplex – signal travels in only one direction

• Half duplex – signal travels in both directions, but only one direction at a time

• Full duplex – signal travels in both directions at the same time

How do protocols regulate the flow of data?

Page 237



Section B: Local Area Networks

局域网


• LAN technologies are standardized by the Institute of Electrical and Electronics Engineers

• IEEE designation numbers help identify compatible network technologies– IEEE 802.3

LAN Standards: What are LAN standards?

Page 238


What is ARCnet?

• One of the oldest, simplest, and least expensive LAN technologies

• Original ARCnet standard supported transmission rates of 2.5 Mbps

• Later versions supported 20 and 100 Mbps transmission rates

• Permits mixed transmission media

Page 238


What is Token Ring technology?

• Defined by the IEEE 802.5 standard

• Passes data around a ring topology using a signal called a “token” to control the flow of data

Page 238


What is the FDDI standard?

• Fiber Distributed Data Interconnect

• Offers 100 Mbps speeds over fiber-optic cables

• Popular campus network technology

Page 239


How does Ethernet work?

Page 239


How does Ethernet work?

Page 240


How fast is an Ethernet network?

Page 240


• An Ethernet card is a type of network interface card designed to support Ethernet protocols

• A hub is used to connect more than two computers– Each network device requires one of

the hub ports– You can add hubs using an uplink

port

What equipment is required for Ethernet installations?

Page 240


What equipment is required for Ethernet installations?

Page 240


• Wireless LANs are slower but eliminate unsightly wires

• Signals can be disrupted by large metal objects, cell phones, pagers, and other wireless devices

• Most popular is 802.11 sometimes called WiFi for “wireless fidelity”– Range of up to 150 feet

• Bluetooth– 1 Mbps, range of 30 feet

What is Wi-Fi?

Page 241

Wireless Campus

Wireless Networking• Wireless networks use radio signals

rather than cables to connect users.• Wi-fi is a popular wireless standard.

Wi-fi Wi-fi Access Access

PointPoint


• HomePNA uses a special NIC and cable to connect each computer to a standard telephone wall jack

• Network frequency is usually different from voice

• HomePLC uses special NIC to connect to standard electrical (power line) outlet

HomePNA and HomePNC Networks

Page 243


HomePNA and HomePNC Networks

Page 243


• First make sure every PC contains an Ethernet port

• Next, attach each workstation to a hub• With all workstations connected, turn them on• Windows should automatically detect the

Ethernet cards and establish a connection to the network

LAN Installation: How do I set up a simple LAN?

Page 244

Chapter 5: Internet and LAN Technology 41Page 244

How do I set up a simple LAN?


How do I access network resources?

Page 245


• Each workstation can specify whether its files will be accessible to other workstations on the network

• Drive mapping is Windows terminology for assigning a drive letter to a storage device that’s located on a different workstation

How do I specify which resources can be shared by other workstations?

Page 245



Section C: Internet Technology

英特网技术


• The United States created ARPA (Advanced Research Projects Agency).– To help scientists communicate and share

valuable computer resources– In response to the Soviet Union’s launch of

Sputnik in 1957, the first artificial satellite• The ARPANET, created in 1969, connected

computers at four universities

Background: How did the Internet get started?

Page 246


How is the Internet structured?

Page 247

Links maintained by AT&T

Links maintained by Sprint

High-speed AT&T routers

High-speed Sprint routers

NAP

NAP

To ISP To ISP


• Using Ping or Traceroute, you can discover how long data is in transit

• On average, data within the US usually arrives at its destination 110-120 ms (milliseconds) after it is sent

• Overseas transmissions require a little more time

Is it possible to track data as it travels over the Internet?

Page 248


Is it possible to track data as it travels over the Internet?

Page 248


• An ISP operates network devices that handle the physical aspects of transmitting and receiving data from your computer

• Many ISPs operate e-mail servers to handle incoming and outgoing mail for their subscribers and Web servers for subscriber Web sites

What kinds of network devices are part of an ISP?

Page 248


What kinds of network devices are part of an ISP?

Page 249


• Provides a standard that is fairly easy to implement, public, free, and extensible

• The Internet is not owned, operated, or controlled by any single entity

• TCP/IP is glue that holds the Internet together

Internet Protocols: Why does the Internet use TCP/IP?

Page 249


Is TCP/IP the only Internet Protocol?

Page 249


• The IP part of TCP/IP defines the format for the addresses that identify computers on the Internet

• These addresses are called IP addresses

• An IP address is a series of numbers, such as 204.127.129.001

– It is separated into four sections by periods

– Each section’s number cannot exceed 255

– Each address requires 32 bits (8 bits per section)

IP Addresses: Does the Internet use a special addressing scheme?

Page 250


• Static IP address – permanently assigned IP address

• Dynamic IP address – temporarily assigned

• ISPs need static IP addresses• Clients typically use dynamic IP addresses

as the IP addressing scheme provides approximately only 4.3 billion unique addresses

Do I need a permanent IP address?

Page 250


• People find it difficult to remember long strings of numbers, so host computers also have names called domain names

• Domain name – “fully qualified domain name” (FQDN), usually typed in all lowercase

– Key component of URLs and e-mail addresses

– www. msu.edu/infotech - www.msu.edu is the domain name

Domain Names: What’s a domain name?

Page 251


Domain Names: What’s a domain name?

Page 251

• Top-level Domains:– biz– com– edu– gov– info– int– mil– net– org


• Each name corresponds to an IP address• Domain name system – Huge database

that houses the names and IP addresses• Domain name servers – Computers that

house the database

How are domain names related to IP addresses?

Page 252


How do I get a domain name?

Page 253


• You can register a domain name for a minimal annual fee ($10 - $50)

• Some Internet entrepreneurs have registered high-profile domain names and resell them– team.com - $250,000– science.tv - $100,000

Is a fee required to obtain a domain name?

Page 253



Section D: Internet Access英特网访问技术


• While connected to your ISP, your call is routed through the telephone company’s local switch to the ISP

Local Switch

How does a dial-up connection work?

Page 255


• Modem – derived from modulate and demodulate

• Modulation – changing characteristics of a signal (digital to analog)

• Demodulation – changing signal back to original state (analog to digital)

How does a modem work?

Page 256


• Speed was measured as baud rate• Today, measure in terms of bits per second• V.90 – theoretical maximum speed of 56 Kbps• Even with perfect connection, a 56 Kbps

modem tops out at about 44 Kbps• Slightly faster speeds may be available with

the new V.92 and V.44 modem standards• Downstream vs. upstream

How fast is a modem?

Page 257


• Community antenna television – CATV• The satellite dish farm at which television

broadcasts are received and retransmitted is referred to as the head-end

• From the head-end, cabling system branches out and eventually reaches consumers’ homes

• Topology is similar to computer network

Cable Television Connections: How does a cable modem work?

Page 258


How can the cable TV system provide Internet access?

Page 258


• Lowest-capacity coaxial cable has far greater capacity than POTS lines

• Cable’s bandwidth is divided among 3 activities

Are television and data signals carried over the same cable?

Page 258


How do I set up a cable modem connection?

Page 259


• An always-on connection is always connected

• A hacker who discovers that your computer has a security weakness can easily find it again, and its high-speed access makes it a very desirable target

How do I set up a cable modem connection?

Page 259


What’s the significance of becoming part of a “neighborhood network”?

Page 260


• Several services such as DSL, ISDN, T1, and T3 take advantage of full capacity of the telephone connections

• Offers high-speed digital communications links for voice and data

DSL, ISDN, T1, and T3: What other options are available for high-speed Internet access?

Page 260


• DSL (Digital Subscriber Line) is a high-speed, always-on, Internet access technology that runs over standard phone lines

• Several versions exist – ADSL, SDSL, HDSL• xDSL – refers to entire group of DSL

technologies• DSLAM (DSL Access Multiplexor) – interpret

data signals

What is DSL?

Page 260


• T1 – high-speed 1.544 Mbps digital network– Consists of 24 individual channels (64 Kbps for

each)– Popular for businesses and ISPs

• T3 – 672 channels– Supports data rates of about 43 Mbps– Sometimes referred to as DS3 (Digital Service-3)

lines– Provide many of the links on the Internet

backbone

Who uses T1 or T3 service?

Page 262


• Direct satellite service (DSS) uses a geosynchronous or low-earth satellite to send television, voice, or computer data directly to a satellite dish

• Two-way satellite service ships both upstream and downstream data through the satellite– Offers 500 Kbps downstream– 40-60 Kbps upstream

How does satellite access work?

Page 262


How does satellite access work?

Page 262


Mobile Internet Access

• You can use a mobile Internet connection to surf the Web and check your e-mail

• A Wi-Fi hotspot is wireless broadband Internet service offered in public locations– WISPs maintain Wi-Fi hotspots

• WAP (Wireless Access Protocol) is a communications protocol that provides Internet access from handheld devices

Page 264


What kind of services are available from handheld devices?

• Short message service

• Multimedia messaging

• Music fingerprinting

• Games

• City guides

• E-mail

• News, sports, stocks, and weather

Page 265

Chapter 5: Internet and LAN Technology 77Page 267

What’s the best Internet connection?


You should now be able to:– Describe the characteristics of various networks– Diagram Shannon’s model of a communications

network– List types of cables– List network devices– Describe the role of communications protocols and list

some protocols associated with the Internet and LANs– Explain packet switching and circuit switching– Explain packet switching and circuit switching– Recount the history of the Internet

Conclusion


You should now be able to:– Draw a conceptual diagram illustrating the Internet

backbone, NAPs, NSPs, routers, and ISPs– Explain Ping and Traceroute– Explain the differences between permanent IP

addresses, dynamic IP addresses, private IP addresses, and domain names

– Describe the advantages and disadvantages of dial-up, cable modem, DSL, ISDN, T1, T2, and wireless Internet access

– Explain when and why it is important to implement security measures such as antivirus software, firewalls, and Network Address Translation

Conclusion

信息处理技术. chapter 5: internet and lan technology2 111chapter 4: file management, virus...

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