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NT1210 Introduction to Networking
Unit 2:
Chapter 2, Introduction to
Computer Networking
1
Objectives
 Identify the major needs and stakeholders for computer
networks and network applications.
 Identify the classifications of networks and how they are
applied to various types of enterprises.
 Explain the functionality and use of typical network protocols.
 Use preferred techniques and necessary tools to troubleshoot
common network problems.
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Objectives
 Define a computer network.
 Identify the primary needs for computer networks and
network applications.
 Draw the four major physical network topologies: bus, star,
ring, and mesh.
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Computer Networking
 Use large variety of components that must work
together.
 Move bits from one device to another.
 Bit: Smallest unit of data, binary 1 or 0.
 Focuses on copying bits on one device to another.
 Computing devices include computers, gaming
systems, televisions, phones, tablets, GPS navigation
systems, watches, etc.
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An Informal General Definition of a
Computer Network
 Telecom: Short for telephone communications
 Primarily focuses on role of traditional telephone companies.
 Datacom: Short for data communications
 Older synonym for computer networking.
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Data Communication System
Network Definition
• A network is a set of devices connected by
communication link to share resources
• The devices are often referred as node.
• Node can be a computer, printer or any
other devices capable of sending and
receiving data.
• A link can be a cable, air, optical fiber, or
any medium which can transport a signal
carrying information
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Overview of Network Components
Figure 1-1 Sample Computer Network
Defining a Network with User Applications
Computer Networks: Cloud Representing Hidden Parts of the Network
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Purpose of a Network
 It can serve a variety of purposes including:
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File sharing between two computers
Video chatting across different parts of the world
Surfing the Web
Instant messaging (IM) between computer with
IM software installed.
 E-mail
 Voice over IP (VoIP)
 A converged network is one that transports
multiple forms of traffic (video, voice, and
data)
Network Defined by Geography
 Local-area network (LAN)
 Wide-area network (WAN)
 Metropolitan-area network (MAN)
 Personal-area network (PAN)
Network Defined by Resource Location
 Yet another way to categorize networks is
based on where network resources reside.
 Network that have all the resources
residing in a server are called client –
server networks.
 Network that have their resources on
several clients and no server is called a
peer-to-peer network
Client-Server Network
Figure 1-13 Client-Server Network Example
Peer-to-Peer Network
Figure 1-14 Peer-to-Peer Network Example
Network Defined by Topology
A bus topology connecting three stations
A ring topology connecting six stations
A star topology connecting four stations
A fully connected mesh topology (five devices)
A hybrid topology: a star backbone with three
bus networks
Network Criteria
• Performance
– Depends on Network Elements
– Measured in terms of Delay and Throughput
• Reliability
– Failure rate of network components
– Measured in terms of availability/robustness
• Security
– Data protection against corruption/loss of data due
to: 1.Errors 2. Malicious users
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Email
 Electronic Mail: One of oldest networking applications.
 Sends mail electronically with bits.
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Write (type) email.
Identify (type) sender’s and receiver’s email addresses.
Give messages to email service.
Email service delivers email to destination email address.
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Sending Email: Network’s Perspective
 Email servers (software running on computer in network)
must be ready to receive, process, and hold emails for
clients using SMTP (Simple Mail Transfer Protocol).
 To send email: Email application sends mail to outgoing
mail server using POP3 (Post Office Protocol, ver. 3).
 Client must know location of outgoing mail server.
 To receive mail: Email client must get mail from its
incoming mail server also using POP3.
 Email application must know location of incoming mail server.
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Sending Email: Network’s Perspective
Step 1: Barney sends an email to his outgoing email server.
Step 2: Barney’s outgoing email server must know how to find the
incoming email server used by Fred – more specifically, the incoming
email server used by email address [email protected].
Step 3: Fred’s incoming email server holds the email for Fred, waiting
until he next checks his email.
Using Outgoing and Incoming Email Services
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Figure 2-5
Early Analog Voice Calls
 Majority of telephone services in USA for first 100 years
grew from Bell’s original work and business ventures.
 Local telephone company (Telco) ran cable to each
home.
 Inside Telco network, lots of other equipment connect to
create telephone network.
Big Picture View, Two Home Phones and the Telco
Figure 2-6
Early Analog Voice Calls
To create the call, the Telco creates an electrical circuit all the way from
one phone to the other. Once the Telco creates the call by creating an
electrical circuit, the two people can talk.
Electrical Circuit Between Two Phones to Carry the Voice Call
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Figure 2-7
Digital Voice Calls
The two home phones create an electrical circuit into the Telco, but the
analog circuit does not extend from phone-to-phone.
Analog to the Phones, Digital in the Telco
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Figure 2-8
Break
Take 10
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A Deeper Look at One Application: World
Wide Web
 World Wide Web (the Web): Web browser software
which allows users access to Web may be single most
commonly used application in world.
 Web works well for learning networking because uses
basic client-server model.
 User sits at computer and uses web browser (Web client).
 “Client” indicates this software receives some type of
service from another device (information from web
server).
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World Wide Web
The web browser (client) and web server cooperate so that the web
browser can get a copy of the information from a web server. The
server organizes information into pages called web pages. The web
browser asks the web server for a web page, and the server sends the
web page back to the web browser.
Web Browser Requesting and Receiving a Web Page from a Web Server
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Figure 2-12
Web Servers (Hardware and Software)
Three Steps: Web Server Sends Web Page into Network
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Figure 2-18
Uncovering the Network Between the
Application Endpoints
Small Lab Networks: Devices typically all sit in the same room. The
network does not need to be sophisticated at all. In fact, with just two
computers, just connect the two computers by connecting a cable to
the NIC in each computer.
A Simple Lab Network: One Cable
Figure 2-28
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Local Area Network (LAN)
A more convenient way to connect multiple devices into the same small
network uses a device called a Local Area Network (LAN) switch.
The term Local Area Network simply refers to the idea that the
computers sit near each other (local). To create this kind of small
network, connect each computer’s NIC to a cable, and connect the
other end of the cable to the LAN switch.
A Simple Lab Network: All Computers Connect to One Switch (Node)
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Figure 2-29
Wireless Networking
 Wireless networking: Uses radio waves to communicate.
 Example: Home-based network with
multiple devices.
 Each device creates link to
switch using cables (wires)
or radio frequency (wireless)
to send bits to each other.
 Bits first go to switch, then to
receiving device.
A Home Network Using Wired (Cabled) and Wireless
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Figure 2-30
Uncovering the Network Between the
Application Endpoints
 Enterprise Networks: Use Wide Area Networks (WANs)
to connect various remote
sites together.
 Network designers prefer
routers to connect sites
using WAN links, as routers
can connect to both WAN
links and LAN switches.
Bits that represent the customer account number
flow over the LAN link to the Boston switch, then over the
LAN link to the Boston router, then over the WAN link to the headquarters
router, then over the short LAN link to the first floor switch, and so on.
Multiple Sites in an Enterprise with Routers
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Figure 2-32
Summary: This chapter…
 Began by focusing on the parts of networking that the
average person uses: apps on typical consumer
electronics and computing devices.
 Introduced the hidden concepts and terms of networking
while using those familiar topics to ease the process.
 Sketched out how web protocols work so that a user’s
Web browser requests a Web page, and how the Web
server responds to supply that Web page.
 Explained how Web server software, running on some
computer hardware, uses the network between the
computers to send a Web page to a user’s computer.
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Lab Activities
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Complete lab activities on Chapter 2
Lab 2.1: Connecting Computers
Lab 2.2: Network Drivers
Lab 2.3: Network Types and Topologies
Lab 2.4: Command line interface