NT1210 Introduction to Networking

Unit 2:

Chapter 2, Introduction to Computer Networking

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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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Figure 1-1 Sample Computer Network

Overview of Network Components

Defining a Network with User Applications

Computer Networks: Cloud Representing Hidden Parts of the Network9

Purpose of a Network

It can serve a variety of purposes including: 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.

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 fred@example.com.

Step 3: Fred’s incoming email server holds the email for Fred, waiting until he next checks his email.

Figure 2-5Using Outgoing and Incoming Email Services24

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.

Figure 2-6Big Picture View, Two Home Phones and the Telco

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.

Figure 2-7Electrical Circuit Between Two Phones to Carry the Voice Call26

The two home phones create an electrical circuit into the Telco, but the analog circuit does not extend from phone-to-phone.

Digital Voice Calls

Figure 2-8Analog to the Phones, Digital in the Telco27

Break

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Take 10

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.

Figure 2-12Web Browser Requesting and Receiving a Web Page from a Web Server30

Web Servers (Hardware and Software)

Figure 2-18Three Steps: Web Server Sends Web Page into Network31

Uncovering the Network Between the Application Endpoints

Figure 2-28A Simple Lab Network: One Cable

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.

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Local Area Network (LAN)

Figure 2-29A Simple Lab Network: All Computers Connect to One Switch (Node)

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.

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Wireless Networking

Figure 2-30A Home Network Using Wired (Cabled) and Wireless

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 toreceiving device.

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Uncovering the Network Between the Application Endpoints

Figure 2-32Multiple Sites in an Enterprise with Routers

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.

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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

• 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