Networking BASICS 1

Wide Area Networks

Networking BASICS 2

Wide Area Network It connects computers and

LANs over a larger geographical area.

It crosses public thorough-fares such as roads, railroads, and water.

Networking BASICS 3

WAN vs. LAN GeographyOwnershipManagementSpeed Cost

Networking BASICS 4

Wired Analog Service It uses standard wired analog telephone

lines. It requires a modem to convert digital

signals to analog signals. Its top is speed 56 Kbps. Asymmetric – Some modems are

faster downloading than uploading.

Networking BASICS 5

Wired Analog Service

Networking BASICS 6

Digital Cellular It provides WAN data access to mobile users. Its coverage area is divided into smaller cells. Users “roam” into adjacent cells or “handoff”

into remote networks. The current technology is 2.5G with a

maximum speed of 384 Kbps.

Networking BASICS 7

Trunk-Based Leased Lines

The same type of lines are used to connect the telephone company’s switches.

They provide “always-on” high-speed connections.

The most common is T1, which oper-ates at 1.5 Mbps over twisted pair wires.

Networking BASICS 8

Trunk-Based Leased Lines

Networking BASICS 9

Digital Subscriber Lines (DSL)

They transmit at 1.5 Mbps over regular telephone lines.

They use the higher unused frequencies to send data.

Different versions of DSL: ADSL, G.list, HDSL, HDSL2

Networking BASICS 10

Digital Subscriber Lines (DSL)

Networking BASICS 11

Cable Modem It uses the same coaxial cable that brings in

cable TV signals. All cables for a neighborhood are connected

to a neighborhood splitter. The connection is shared among all users in

a neighborhood. Speed: 300 Kbps – 1.5 Mbps

Networking BASICS 12

Local Multipoint Distribution Service (LMDS)

Transmits: Maximum 155 Mbps downstream and 1.54 upstream

Range: 2 – 5 miles It is a low-cost option to laying fiber

optic cables. Its signals are susceptible to

interference from rain or fog.

Networking BASICS 13

Multichannel Multipoint Distribution Service (MMDS)

It uses lower-frequency signals than LMDS.

Range: up to 35 milesIts signals are less susceptible to

interference from rain or fog.

Networking BASICS 14

Satellites They have been used for over

40 years.They relay signals from one

point on earth to another.They are classified according to

the type of orbit.

Networking BASICS 15

Low Earth Orbiting (LEO)

They orbit at an altitude of 200 – 900 miles.

They circle the earth in 90 minutes. They have a small “footprint.” More satellites are needed to cover the

entire earth.

Networking BASICS 16

Low Earth Orbiting (LEO)

Networking BASICS 17

Medium Earth Orbiting (MEO)

They orbit at altitudes between 1,500 – 10,000 miles.

They circle the earth every 12 hours. They have a large “footprint.” Fewer are needed to cover the earth.

Networking BASICS 18

Remote Wireless Bridge It connects LANs located in different

buildings. The distance between buildings can be

up to 18 miles at 11 Mbps. It has similar characteristics to a

wireless LAN.

Networking BASICS 19

Free Space Optics (FSO)

It transmits up to 1.25 Gbps at a distance of 2.5 miles.

It uses low-powered infrared beams.

Its transmissions cannot be eavesdropped.

Networking BASICS 20

Virtual Private Network (VPN)

It uses the public Internet to transmit private data.

It encrypts data into a packet before sending.

There is no cost for setting up or using a VPN.

Networking BASICS 21

Virtual Private Network (VPN)

Networking BASICS 22

Public Switched Data Networks (PSDN)

Actual network itselfX.25Frame RelayAsynchronous Transfer Mode

(ATM)

Networking BASICS 23

Public Switched Data Networks (PSDN)Integrated Services Digital

Network (ISDN)Synchronous Optical Network

(SONET)Metro Ethernet Network (MEN)

Networking BASICS 24

Firewall It inspects incoming traffic. Packet-filter firewall – Inspects header

of each packet. Stateful packet-filter firewall –

Examines a packet’s source IP. Proxy firewall – Examines the contents

of a packet.

Networking BASICS 25

Network Address Translators (NAT)Disguises the internal IP by

substituting a fake IP and port number.

When a packet is returned, NAT replaces the fake numbers with the actual IP and port number.

Networking BASICS 26

PrivacyPrivacy is the right to be left alone

to the degree that you choose.It is a difficult problem to keep

personal data private.Identity theft is a major crime.

Networking BASICS 27

Networking BASICSThe Internet and Its Tools

Networking BASICS 28

The Internet It is not controlled or managed by

one person or group.Anyone can connect to the Internet.There is no control regarding what

can be posted.

Networking BASICS 29

History The U.S. was concerned that foreign

nations may attack. A computer network was needed that

could withstand an attack. The Internet was modeled after the

interstate highway system.

Networking BASICS 30

History ARPANET was launched in 1969 to link 4

sites. TCP/IP allowed multiple computers to

connect to each other. It was replaced by NSFNET in the 1980s. Hypertext Transport Protocol and browsers

opened up the Internet to anyone.

Networking BASICS 31

Domain Name System (DNS) It resolves (or finds) a Web site’s IP number

when given its name. It is a database organized as a hierarchy. It is organized into 3 different levels. DNS is distributed at multiple locations.

Networking BASICS 32

Domain Name System (DNS)

Networking BASICS 33

Web Browsers They allow users to view text, data,

pictures, animation, and video. A Web page contains instructions to a

browser about how to display items. Microsoft Internet Explorer is the most

popular browser.

Networking BASICS 34

E-Mail It is the most common Internet tool. They are either character-based or use

a graphical user interface. Documents are sent as attachments. File compression software reduces the

size of attachments.

Networking BASICS 35

Listserv It is also called a discussion list. It is an extension of an e-mail distribution list. Users subscribe and automatically receive

copies of all e-mail messages. Listserv address – Address of the

automated mailing program.

Networking BASICS 36

Listserv Etiquette Spend time reading before responding. Use a descriptive Subject heading. Include part of the original message

when replying. Use upper- and lowercase.

Networking BASICS 37

NewsgroupQuestions and answers are posted

in a central location.It is not necessary to save or sort e-

mail messages.It may require special software of

the client.

Networking BASICS 38

Newsgroup

Networking BASICS 39

Portals Portals are also known as an

online service.Portals are ready-made menus

of lists of information.Each selection narrows choices

until the information is located.

Networking BASICS 40

Search Engine The spider reads the Web pages and

stores information in an index. The search engine sifts through the

index to find the user’s requests. The ranking of pages is important.

Networking BASICS 41

Search Engine

Networking BASICS 42

Hypertext Markup Language (HTML)It is the standard way of

defining how text and graphics are displayed.

The browser reads HTML document instructions.

Networking BASICS 43

Hypertext Markup Language (HTML) Each page is made up of elements. The elements are indicated by tags. A tag is <, tag name, >. The ending tag contains a slash. <HTML> . . . </HTML>