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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>