Computer Concepts 5th Edition Parsons/Oja Page 216 CHAPTER 5 Network Building Blocks Section A...

Computer Concepts 5th EditionParsons/Oja

Page 216

CHAPTER

5

Network Building BlocksSection A

PARSONS/OJA

Internet and LAN Technology


18

Section AChapter

5Network Building Blocks

Transmitting Data: Is it easy to transmit data?

A communications network is a collection of computers and other devices that communicate to share data, hardware and software


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What kind of coding process happens on a communication network?

Computers use several coding schemes based on binary digits ASCII EBCDIC Unicode Binary numbers


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Exactly what is transmitted when I send a message?

When data is transmitted, it usually takes the form of an electromagnetic signal

On a communication network, your data may be converted into several different types of waves


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Exactly what is transmitted when I send a message?


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Network Links: How do signals travel over a network?

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 frequency

Networks use different types of cables


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How do signals travel over a network?

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


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Another option is coaxial cable resembles cable-TV cable round, silver BNC connector


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Fiber-optic cable is a bundle of extremely thin tubes of glass Each optical fiber (tube) is thinner than a

human hair Consists of strong inner support wire, multiple

strands of optical fiber and a tough outer cable Transmit pulses of light

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


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Microwaves provide another option for transporting data

Radio and microwave transmissions are bent around the surface of the earth to reach 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


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Infrared light can also carry data signals, but for short distances with a clear line of sight Best for transmitting between notebook

computers and a printer, or between a PDA and a desktop computer

Laser light can also carry data signals, for a longer distance, but requires a clear line of sight Experimental, but possibly may be useful for

transmitting data between buildings


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What’s bandwidth?

Bandwidth is the transmission capacity of a communications channel

High-bandwidth communications systems, such as cable TV, are sometimes referred to as broadband

Systems with less capacity, such as the telephone system, are referred to as narrowband

The bandwidth of a digital channel is usually measured in bits per second (bps)


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Network Devices: What kind of equipment populates data communications networks?

Each device that is connected to a network is referred to as a node

The term workstation usually refers to a personal computer connected to a local area network (LAN), it is also called a client

A modem is a device that converts signals from a computer into a signal that can travel over a wide area network


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What kind of equipment populates data communications networks?

A network interface card (NIC) is the key hardware component for connecting a computer to a local area network. small circuit board that sends data to and from

workstation to network A server refers to any computer on a LAN or the

Internet that contains the software to manage and process files for other network nodes


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What kind of equipment populates data communications networks?

A host computer usually refers to any computer that provides services to network users

A hub is a device that connects several nodes of a LAN

A router is a device that is connected to at least two networks and makes decisions about the best route for data

A gateway is a device that performs functions similar to a router

A repeater amplifies and regenerates signals so they can retain the strength to reach their destinations


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Network Addresses: How does data find its destination?

Every node on a network has an address Every packet of data that travels over a network

also has an address which helps to route a packet to its destination


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Network Topology: Does a network require a certain configuration of nodes?

The layout of a network is referred to as its physical topology


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Does a network require a certain configuration of nodes?

A real-world network can make use of more than one topology


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Packet and Circuit Switching Technology: What’s a packet?

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


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Why not just send an entire message?

Engineers wanted a more robust communications link for computer networks

They devised packet switching in which a message was divided into several packets that can be routed independently to their destination to avoid out-of-service or congested links

Packet switching makes very efficient use of available bandwidth and provides a steady stream of data


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Communications Protocols: What is a communications protocol?

Communications protocol refers to set of rules for transmitting data from one node to another

Protocols allow two devices to negotiate and agree on how data will be transmitted

Scripts for dial-up modem


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How does a protocol initiate a transmission?

Protocols establish communications through handshaking

The devices decide on how to coordinate its transmission

Synchronous protocols are synchronized by a signal called a clock when sending and receiving data

Asynchronous protocols require the transmitting computer to send a start bit, then data is sent, and a stop bit to mark the end of the data


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Does data travel in both directions over the same channel?

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


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How does a protocol make sure that data arrives without errors?

Computers use error-checking protocols to make ensure accurate delivery of data (such as over the Internet) Parity bit – added to keep track of the number

of 1s and 0s Even parity protocol – requires number of 1s

to be an even number


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Network Classifications: How are networks classified?

Internetwork – a network composed of many smaller networks

Intranet – uses TCP/IP protocols but owned by a private business and does not typically allow remote access

Extranet – similar to intranet except that it allows remote password-protected access

WAN – (wide area network) covers a large geographical area and may consist of smaller networks


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How are networks classified?

LAN (local area network) – typically covers a very limited geographical area

Wireless network – uses radio frequencies HomeRF network – low-power wireless network

for home use HomePLC – uses building’s existing power line

cables HomePNA – uses existing telephone cables Novell – LAN that uses Novell Netware


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Ethernet – free for all


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Token Ring – connects nodes in a physical star configuration, but passes data around a logical ring using a technology called a “token”.

Wait for your turn…


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Client/server – contains servers and clients Peer-to-peer (P2P) – every computer is

considered an equal KaZaa: file sharing among peers


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5Internet Building Blocks

Background: How did the Internet get started?

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


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How did the Internet get started?

In early 1990s, software developers created new user-friendly Internet access tools Web browser: created at the University of

Illinois Today, the Internet connects computers all over

the globe and supplies information to people of all ages and interests


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Internet Hardware and Connections: What type of hardware populates Internet nodes?

Difficult to diagram due to over 100 million nodes and 350 million users


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What kinds of network devices are part of an ISP?

An ISP operates network devices that handle the physical aspects of transmitting and receiving data from your computer Modems Domain name server Router


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What kinds of network devices are part of an ISP?

An ISP links to other ISPs in a sort of ISP network

Network service Providers (NSPs) supply ISPs with access to high-speed transmission lines that form the backbone of the Internet Interstate highways of the Internet

NSPs also provide routers at network connection points


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How fast does data travel over the Internet?

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 transmission require a little more time


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

TCP/IP 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


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How does TCP/IP work?

It is a suite of protocols TCP (Transmission Control Protocol) – breaks

a message or file into packets IP (Internet Protocol) – responsible for

addressing packets so that they can be routed to their destination


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Is TCP/IP the only Internet Protocol?


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

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)


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Do I need a permanent IP address?

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


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Domain Names: What’s a domain name?

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.thex-files.com/episode236 - www.thex-

files is the domain name


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What’s a domain name?

A domain name ends with an extension that indicates its top-level domain


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How are domain names related to IP addresses?

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


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Do I need my own domain name?

Not for normal client-style Internet activities If you plan to operate your own Web server, you

may want a name


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How do I get a domain name?

ICANN (Internet Corporation for Assigned Names and Numbers) – global organization that coordinates the technical management of the Internet’s domain name system, allocation of IP addresses, and the assignment of protocol parameters

Organizations or individuals can select a domain name and register it by using an online registration service


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How do I get a domain name?

Click to start


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Is a fee required to obtain a domain name?

You can register a domain name for a minimal annual fee ($25 - $50)

Some Internet entrepreneurs have registered high-profile domain names and resell them Sell-videos.com - $35,000 Thelocallistings.com - $87,500


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5Internet Access

Dial-Up Connections: How does a dial-up connection work?

Uses POTS (plain old telephone service) to transport data between your computer and your ISP


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5Internet Access

How does a dial-up connection work?

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

Local Switch


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5Internet Access

How does a modem work?


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5Internet Access

Can I talk and send data at the same time?

When connected to ISP, data is transmitted in same frequencies used for voice conversations


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5Internet Access

How fast is a modem?

Speed was measured as baud rate, number of times per second that a signal in a communications channel varies speeds

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 Downstream vs. upstream


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5Internet Access

Cable Television Connections: How can the cable TV system provide Internet access?

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, and that is what is formed when you use cable TV as your ISP


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5Internet Access

How can the cable TV system provide Internet access?


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5Internet Access

Are television and data signals carried over the same cable?

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

Cable’s bandwidth is divided among 3 activities


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5Internet Access

How do I set up a cable modem connection?

Need an Ethernet NIC Need a cable modem,

which converts your computer’s signal into one that can travel over CATV cable


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5Internet Access

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

With CATV, your computer becomes part of a neighborhood data network

More people on the network, means slower service

Also, in early days your network neighborhood showed your neighbors


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5Internet Access

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

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


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5Internet Access

How do I secure an always-on connection?

Disable file and print sharing


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5Internet Access

How do I secure an always-on connection?

Shut down your computer when you are not using it

Install personal firewall software, which is designed to analyze and control incoming and outgoing packets Pick level – high, medium, or low


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5Internet Access

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

Several services such as DSL, ISDN, T1, and T3 take advantage of full capacity of the telephone connections (normal dial-up services do not)

Offers high-speed digital communications links for voice and data


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5Internet Access

What is DSL?

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


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5Internet Access

What is DSL?


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5Internet Access

What is DSL?

Speed varies, but most are rated at 1.5 Mbps downstream


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5Internet Access

How do I install DSL?

Telephone line connected to DSL switch at your house

Line connected to DSL modem which connects to your computer’s Ethernet card


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Who uses T1 or T3 service?

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

each) Popular for businesses and ISPs Not as fast as DSL

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


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5Internet Access

Wireless Internet Access: What are the options for wireless connections to the Internet?

Personal satellite connections – expensive, but sometimes only option (particularly in remote rural areas)

Cellular telephones – slowest, but provides mobile Internet access


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5Internet Access

How does satellite access work?

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


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5Internet Access

How does satellite access work?


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What’s the fastest Internet connection?


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5LAN Technology

LAN Services and Resources: What sort of resources does a LAN provide?

Main advantage of a LAN is that multiple users can share a limited number of resources

Can share a high-speed connection


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5LAN Technology

How do I access network resources?

When you boot your computer, OS looks to see if it can access a LAN Generally need to reboot after loosing network

connection The OS keeps track of network resources you

can access automatically Some network resources become available as

soon as your computer completes the boot process, and others after you use your networking utilities


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5LAN Technology

Can a LAN use existing phone or electrical wiring?

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

Network frequency is usually different from voice, so can use network at same time you place a call

You can not make a call when dial-up Internet connection is active however

HomePLC uses special NIC to connect to standard electrical outlet, but power fluctuations can adversely affect signal


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5LAN Technology

Can LANs use wireless technology?

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 s 802.11b 11 Mbps, spans 300 feet, and can be used

with Ethernet networks Bluetooth

200-400 Kbps, range of 35 feet


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LANs with wireless technology

Wi-Fi: Wireless Fidelity: Avoid expense of wiring installation for network Enjoy mobility Up to 100 times faster than dial-up connection

• 11 mps Range of 100 up to 1,000 feet Signals operate in the 2.4 and 5Ghz

radio bands, which are also used today by many cordless phones

Hot spot operators• Starbucks, hotels, airports, etc.

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