Transcript network layer model

Tech Guide B
The Details of Networking
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What We Will Cover
•
Network Architecture
•
Network Layer Model
•
Different Kinds of Networks
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NETWORK ARCHITECTURE
 A network architecture refers to the design of a
computer system or network. The term usually covers the
overall combination of the hardware and software that
makes up the network infrastructure.
◦ An open architecture is one where anyone can know the
design, thus allowing anyone to develop software and
hardware to work with it.
◦ A closed architecture network has a proprietary design, making
it difficult for outsiders to design programs that work with
the network.
 Most of today’s computer systems are open to allow for
easy growth.
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CLIENT/SERVER ARCHITECTURE
 The most common network architecture is
the client/server architecture.
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CLIENT/SERVER ARCHITECTURE
• Processing is shared among multiple small
computers known as clients that are connected via
a network to a host computer known as a server.
• Clients are typically PCs and workstations, a
type of high-powered small computer built for
specialized applications.
• Servers are computers running server software,
with each server typically focusing on a specific
task.
• Because both the client and the server are capable
of processing, it is shared between the two
computers.
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THREE-TIERED ARCHITECTURE
Three-tiered client/server architecture uses a
client, an application server, and a database server.
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TYPES OF SERVERS
Server Type Purpose
File
Provides both software and data files to users
Database
Application
Handles queries to a large database and
returns matching records
Handles high-speed processing
Web
Handles requests for web pages
Mail
Sends and receives e-mail for the entire
organization
Fax
Sends and receives faxes for the entire
organization
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SERVERS ON A NETWORK
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CLIENT/SERVER ADVANTAGES
AND DISADVANTAGES
Advantages
Disadvantages
Computing burden can be shared
among servers and clients
Programming relationship between clients
and servers is more complex
Servers can be specialized to one
particular type of task
System upgrades require that all clients
and servers be upgraded regardless of
location
Upgrading system can be done in
small steps
More complex computer and network
security issues due to increased numbers
of users and client machines with access
to networked resources, including data.
Loss of client does not stop other
clients from accessing server
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PEER-TO-PEER NETWORKS
• It is possible to set up a peer-to-peer network
where each computer in the network is on the
same level as other computers, and each
computer is equally responsible for overseeing
the functions of the network.
• Any two computers in a peer-to-peer network
can communicate directly with one another or
through intermediate peer computers.
• Peer-to-peer networks may be easier to setup,
but are not as efficient as client/server networks.
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COMPARING CLIENT/SERVER
AND PEER-TO-PEER NETWORKS
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NETWORK LAYER MODEL
A network layer model will help you
understand how the following three
elements work together.
 The simplified network layer models are:

◦ application software layer
◦ network connections layer
◦ data component layer
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NETWORK LAYER MODEL
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APPLICATION SOFTWARE LAYER
• Application software is the software on each computer
on the network that the user sees and uses to send and
receive messages and data between computers (Web
browsers, e-mail, etc.)
• Application layer protocols: simple mail transfer protocol
(SMTP) for e-mail, hypertext transfer protocol (HTTP),
electronic data interchange (EDI)
• Message may also be encrypted
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NETWORK
CONNECTION LAYER
The message from the application software
layer is formatted according to whatever
protocol will be used to send it over the
network.
 Transmission control protocol/Internet
protocol (TCP/IP) is commonly used.

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CONVERTING DATA
INTO PACKETS
An IP Address is a unique identifier given to
each device directly connected to the network.
• It consists of four groups of numbers in the
range 0 to 255 separated by periods.
• The message is divided into smaller digital units
called packets, each of which contains a
specific number of bytes.
•
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PACKET SWITCHING
Packet switching means that individual packets
are routed through the network based on the
destination address contained in each packet.
• The same data path can be shared among many
computers in the network, and if a computer on
the network is inoperable, the packet finds
another way to reach its destination.
• A router is a special type of computer that has
the sole purpose of accepting packets and
determining the best way to send them to the
destination computer.
• The sequence order allows the receiving
computer to reconstruct the message.
•
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THE FLOW OF PACKETS THROUGH
INTERMEDIATE ROUTERS
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DATA COMPONENT LAYER
•
•
•
•
•
Twisted pair: consists of twisted pairs of copper
wires; similar to that used in telephone systems
Coaxial cable: used to transmit cable television
signals into your home; widely used in networks
Fibre-optic cable: consists of hundreds of glass
fibre strands that can transmit a large number of
signals at extremely high rates of speed
Microwaves: high-frequency radio transmissions
that can be sent between two stations
Wireless: several technologies that allow data to
be transmitted without wires
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COAXIAL CABLE COMPARED
WITH GLASS FIBRE CABLE
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DATA COMPONENT MEDIA
Media
Cost
Error Rates
Speed
Twisted pair
Low
Low
Low-high
Coaxial cable
Moderate Low
Low-high
Fibre optics
High
Very Low
High-very high
Radio
Low
Moderate
Low
Infrared
Low
Moderate
Low
Microwave
Moderate Low-moderate
Moderate
Satellite
Moderate Low-moderate
Moderate
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SIGNAL TYPE

The signal type is how data are sent
over the network. A signal can be digital
or analog.
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ANALOG VS. DIGITAL DATA
TRANSMISSION
Advantages
Analog
• Reflect natural
phenomena; sound,
light, and electricity
are all analog
• Low-cost, existing
infrastructure for
analog transmission
Disadvantages • More susceptible to
noise, distortion, and
interference
Digital
• Less susceptible to noise,
resulting in a lower error rate
• Allows transmission of
multiple signals over one line at
the same time (called
multiplexing)
• Faster rate of transmission
• Less-complex and lower-cost
circuits
• Analog phenomena require
conversion to digital signals
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DATA RATE AND
BANDWIDTH ISSUES
• The data rate is measured in bits per second (bps).
• A digital subscriber line (DSL) transmits computer data in a
digital form along the same telephone line that is used for analog
voice communications.
• T-carrier circuits are dedicated digital lines that are leased from
a telecommunications company to carry data between specific
points.
• The term bandwidth is often used in relationship to data rate
and is a measure of how fast data flows on a transmission path.
o Baseband: only a single digital signal is carried through the
media
o Broadband: a variety of different analog signals are being
transmitted
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MAXIMUM DATA RATES
Transmission
Method
Maximum Data
Rate
Comments
Standard telephone 56 Kbps
service
Available everywhere
Digital Subscriber
line (DSL)
6 Mbps in; 640 Kbps
out
Becoming more available;
does not slow down as
more people sign up
Cable
As high as 55 Mbps,
Cable must support twobut averages between way communication;
200 Kbps and 2 Mbps available in many
locations but slows down
as more people use it
T-1 to T-4
1.544 Mbps–274
Mbps
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Leased lines used for
commercial
telecommunications
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LOCAL AREA NETWORKS
• Local area network (LAN): a network
connected over a small geographic area
• LANs are popular for
o Sharing
information
o Sharing resources
o Sharing software
o Sharing hardware
• Most LANs are client/server networks
• LANs can also be implemented through
peer-to-peer networks
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LAN TERMINOLOGY
• Ethernet protocol is the technology
standards for connecting computers into
a LAN.
• A bus network uses a main cable, called
a bus, to connect all clients and servers
on the network.
• A gateway is the combination of
hardware and software that connects two
dissimilar computer networks.
• A bridge connects two similar networks.
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WIRELESS LANS
Wireless LANs (WLANs) replace cabling
with wireless transmissions that use radio
frequencies to transmit information between
individual computers.
 The individual computers do not communicate
directly with each other, but instead through a
wireless network hub or router.
 Wi-Fi (wireless fidelity), also called IEEE
802.11b standard, the current popular standard
for wireless networking, supports data rate of 11
megabits/second, with a typical range through
open air of about 200–1000 metres.

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LAPTOPS CONNECTED
TO A WIRELESS LAN
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BLUETOOTH AND PANS
• Personal area network (PAN) is a
technology that enables wireless devices to
communicate over a short distance—less
than 10 metres.
• Bluetooth embeds a low-cost transceiver
chip in each device, making it possible for
wireless devices to be totally synchronized
without the user having to initiate any
operation.
• The overall goal of Bluetooth is to enable
pervasive connectivity between personal
technology devices without the use of
cabling.
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THE INTERNET: A NETWORK
OF NETWORKS
• Originally developed in the 1960s and 1970s as a way of
sharing information and resources among universities and
research institutions, the Internet began its dramatic
growth in 1991.
• No one can say exactly how many people are using it,
with estimates ranging as high as over 1.10 billion in 2005,
and by March 2011, 2.09 billion people were online,
representing over 30 percent of the world’s population.*
• A primary reason for the explosive growth of the
Internet is the tremendous amount of data, information,
and resources that people can access.
*Internet World Stats, “Internet Usage Statistics,” www.internetworldstats.com/stats.htm , retrieved November 15, 2011.
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WHAT IS THE INTERNET?
• The Internet is a network of networks.
• To connect to the Internet, your computer
will usually first connect to a LAN through a
network interface card (NIC) or to an
ISP through a modem and telephone line.
• The LAN, mainframe, or ISP is connected
to a regional network via a high-speed (T-1)
telephone line. The regional network links
into the backbone of the Internet.
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WHAT IS THE INTERNET?
• With each network, there is at least one
host computer that is connected to the
Internet with full two-way access to other
computers on the Internet and with a
unique Internet address.
• Each host computer that connects to the
Internet uses the TCP/IP protocol for
assigning addresses and uses packet
switching for exchanging information.
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CONNECTING TO
THE INTERNET
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E-MAIL ADDRESSES
• An e-mail address is composed of two parts:
the user name and the server address.
• The user name is assigned to a person or
organization that is connected to a server, and
it is separated from the server address by the
“at” symbol @.
• The server address (a.k.a. domain name) is
the IP address of the e-mail host and serves as
an easy-to-remember version of the IP
address.
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INTERNET OPERATIONS
Internet
Operations
Purpose
E-mail
Asynchronously exchange electronic messages
with other Internet users
FTP
Download files (software, documents, or data)
from or upload files to a server located on the
Internet
Newsgroups
Participate in a wide variety of online discussion
groups
Telnet
Work on a computer elsewhere on the Internet
Internet relay chat Synchronously exchange electronic messages with
other Internet users
World Wide Web
Transfer text, images, video, and sound to your
computer; search for information on the Internet
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USE OF AN FTP CLIENT
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THE WORLD WIDE WEB
• The Web is a special type of client/server network.
• The Web is a body of software and a set of
protocols and conventions based on hypertext and
multimedia that make the Internet easy to use and
browse.
• Hypertext is a method of linking related
information in which there is no hierarchy or
menu system.
• Multimedia is an interactive combination of text,
graphics, animation, images, audio, and video
displayed by and under the control of a computer.
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USING A BROWSER
• To access the Web, the client computer uses
software called a browser that initiates activity by
sending a request to a Web server for certain
information. The Web server responds by
retrieving the information from its disk and then
transmitting it to the client.
• Browser: application layer software used for
sending requests and displaying the results
• Hypertext markup language (HTML): tags in
World Wide Web documents that are part of a
special publishing language
• Documents on the Web are referred to as web
pages, and their location is a website
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A WEB PAGE AND
SOURCE CODE
The web page’s
appearance…
… is determined
by the HTML code
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WEB ADDRESSES
There are three parts to a URL (uniform
resource locator), which is the standard means of
consistently locating web pages or other
resources on the Internet.
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INTERNET PROTOCOLS
Protocol
Purpose
http
Retrieve web pages
File
Retrieve files from local hard disk
Telnet
Log on to a remote computer
connected to the Internet
FTP
Download or upload files from an
Internet FTP server
mailto
Send outgoing e-mail
News
Display newsgroup
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WIRELESS NETWORKS
 The fastest-growing trend in networks is wireless
networks, both WANs and LANs, because it
enables devices connected to the network to go
virtually anywhere.
 In the case of wireless WANs, a mobile
telephone client is the most popular method of
connecting to the Internet and Web.
 A number of mobile telephone companies have
collaborated to create a special protocol, called
wireless application protocol (WAP), just
so their telephones can connect to the Internet.
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WIRELESS NETWORKS
Short message service (SMS) is a
service for sending text messages up to
160 characters long to mobile telephones
 Global system for mobile
communication (GSM) protocol is
the most widely used standard mobile
telephone protocol in the world.

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RECAP
1.
2.
3.
4.
5.
What is client/server architecture, and
how does it work?
How does the network layer model
describe a wide area network?
How are local area networks
configured?
How does the Internet work?
What makes the World Wide Web
valuable to business professionals?
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