NT1210 I d i N kiNT1210 Introduction to Networking - · PDF fileNT1210 I d i N kiNT1210 Introduction to Networking ... systems , televisions ... Modern business telephones and mobile

NT1210 I d i N kiNT1210 Introduction to Networking

Unit 2:Chapter 2, Introduction toChapter 2, Introduction to

Computer Networking

1

ObjectivesObjectives

Identify the major needs and stakeholders for computer networks and network applications.

Identify the classifications of networks and how they are li d t i t f t iapplied 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.

2

ObjectivesObjectives

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.

3

Computer NetworkingUse large variety of components that must work g y ptogether.

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 etcsystems, watches, etc.

4

Defining a Network with User Applications

E l Di it l d ti i li / id t tExamples: Digital advertising, online/video games, text messages, websites, social media, and email.

Network diagrams often use cloud to identify what partNetwork diagrams often use cloud to identify what part of network to ignore for a particular discussion.

LAN vs WAN

5

Defining a Network with User Applications

Figure 2-1Computer Networks: Cloud Representing Hidden Parts of the Network6

An Informal General Definition of aAn Informal General Definition of a Computer Network

T l Sh t f t l h i tiTelecom: Short for telephone communicationsPrimarily focuses on role of traditional telephone companies.

D t Sh t f d t i tiDatacom: Short for data communicationsOlder synonym for computer networking.

7

User Actions and the User Devices

U t k d i i li ti ( )Users use network devices via applications (apps).

Application: Why we use networks.Example: Would you use a phone that did not allow phone calls? Maybe, but what if it also did not allow texting? Or email? Or posting to social media? Or web surfing? Or anything that

d t k?used a network?

Key common feature for many apps: Need to send bits.

F f thi h t E il i ll d idFocus of this chapter: Email, voice calls, and video downloads.

8

Email

El t i M il O f ld t t ki li tiElectronic Mail: One of oldest networking applications.Sends mail electronically with bits.

Write (type) emailWrite (type) email.Identify (type) sender’s and receiver’s email addresses.Give messages to email service.Email service delivers email to destination email address.

9

Email

U t i ll il i il ft bUsers typically access email using email software or web browser.Email software apps gives users way to create sendEmail software apps gives users way to create, send, and receive email.Common email apps:

Microsoft Outlook Microsoft Windows MailMozilla ThunderbirdMozilla ThunderbirdApple MailMany built-in mail apps on phone/tablet

10

Email

E l A l ’Example: Apple’s Mail application

Figure 2-2Sample Window on Email Software: Barney Types Email to Fred11

Sending Email: Sender’s ComputerSending Email: Sender s Computer Perspective

St 1 St t il li ti d li k iStep 1: Start email application and click icon or menu item to cause “create message” window to open.Step 2: Type destination’s email address and messageStep 2: Type destination s email address and message.Step 3: Behind the scenes:1. Application stores and processes bits and bytes of message and

addresses in RAM and (sometimes) on hard disk.2. Application uses some kind of character set to represent text.3. Application uses email addresses to identify sender and pp y

recipient of email.4. Application works with other parts of computing device to send

email.

12

Email

Th O ti S t (OS) thThe Operating System (OS) on the computer typically plays a big role, because every modern OS includes lots of networking features and thelots of networking features, and the applications rely on the OS to do part of the work. The email client essentially asks the OS to send theessentially asks the OS to send the email. However, the OS, being software, cannot physically send the bits. So the OS asks for help pfrom the NIC. Figure 2-3 shows the general idea.

Figure 2-3General Process of Sending an Email on Barney’s Computer13

Sending Email: Network’s PerspectiveNetwork sits between user devices and physically moves p y ybits between devices.Networks must provide services that help clients(d i th t t k) t d t k th t t d(devices that use network) to do tasks they want to do.Example: using “snail mail”:

To send mail could go to different post office or dropTo send mail, could go to different post office or drop.When receiving mail, must go to particular place to pick it up. (e.g., box by house door, common area in apartment complex)

E h ili dd t b k b b th t ffiEach mailing address must be known by both post office and people who live at address.

14

Sending Email: Network’s Perspective

E l B d l tt t F d’ t l dd B dExample: Barney sends a letter to Fred’s postal address. Barney drops the letter in the mailbox for outgoing mail at his apartment complex (step 1). The postal service moves the letter towards Fred (step 2), and eventually the postal service leaves the letter in Fred’s mailbox (stepeventually, the postal service leaves the letter in Fred s mailbox (step 3). Then the letter sits in Fred’s mailbox until he next checks his mail.

Figure 2-4Using an Outgoing Mail Drop/Box, and an Incoming Mail Box15


W k i il t il il b t ilWorks similar to snail mail but uses email servers.Email servers (software running on computer in network) must be ready to receive process and hold emails formust 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 itsTo receive mail: Email client must get mail from its incoming mail server also using POP3.

Email application must know location of incoming mail server.

16


Step 1: Barney sends an email to his outgoing email server.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] 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.

Figure 2-5Using Outgoing and Incoming Email Services17

Voice Telephone Calls

M d t l h t k bit t d t l hModern telephony networks use bits to send telephone calls (voice calls).Modern networks need to be ready to send bits noModern networks need to be ready to send bits, no matter whether those bits make up email or represent voice traffic.

18

Early Analog Voice Calls

M j it f t l h i i USA f fi t 100Majority 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 eachLocal 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 Example

B i k h h i N Y k d di lBarney picks up home phone in New York and dials Fred’s phone number in California.To make Barney’s call work Telco has to know all phoneTo make Barney s call work, Telco has to know all phone numbers and their matching phone lines.Telco keeps a list of all phone numbers and knows which phone line connects to which phone using that phone number.When new call occurs Telco knows exactly where callWhen new call occurs, Telco knows exactly where call physically needs to go.

20

Early Analog Voice Calls

T t th ll th T l t l t i l i it ll th fTo 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 Call21

Early Analog Voice Calls, Part 1

1 Telco creates electrical circuit between phones1. Telco creates electrical circuit between phones.2. Barney speaks, creating sound waves in air.

– When graphed over time, sound waves go up and down just like waves in the ocean.

3. Microphone near mouth of speaker takes in sound waves and outputs electrical signal that looks verywaves and outputs electrical signal that looks very similar to graph of caller’s sound waves.

(continued on next slide)

22

Early Analog Voice Calls, Part 2

4 Fred’s phone converts analog electrical signal back to4. Fred s phone converts analog electrical signal back to sound waves using speaker in part of phone near his ear. – Speaker takes in analog electrical signal and vibrates air,

creating sound waves that look like analog electrical signal. – Result: What Barney speaks, Fred hears.

23

Digital Voice Calls, Part 1

Telco had large networks to support analog voice callsTelco had large networks to support analog voice calls long before computers became commonplace in businesses.To take advantage of computers and related technology, Telco replaced analog telephone networks with digital onesones.Telco developed analog to digital (A to D—A/D) process to take electrical signal they already worked with (the analog signal) and convert it to digital signal (bits).A/D paved way for VoIP (Voice over IP): Way to send digital voice signal over IP networkdigital voice signal over IP network.

24

Digital Voice Calls, Part 2

Part of A/D process breaks voice into very small timePart of A/D process breaks voice into very small time intervals.

Voice in calls sampled voice 8000 times per second so each sound sample was .125 milliseconds long

Another part of A/D process assigns binary value to each unique short sound (similar to character map process)unique short sound (similar to character map process).

Original AT&T A/D conversion process used 8-bit code.

To make use of networks for more efficient, lower cost, and better calls, Telcos added equipment to do A/D conversion process on each end of each call.

25

Th t h h t l t i l i it i t th T l b t th

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.

Figure 2-8Analog to the Phones, Digital in the Telco26

Digital Voice Calls1. Barney speaks, creating sound waves. y p , g2. Phone creates analog signal representing voice and

sends into Telco network.3. Telco uses A/D device to convert analog voice to bits.4. Telco sends bits across its network.5 Telco con erts bits back to analog electrical signal for5. Telco converts bits back to analog electrical signal for

transmission to Fred’s home phone.6. Fred’s home phone uses speaker to convert electrical p p

signal into sound waves.NOTE: Devices that perform A/D conversion called codecs (coders/

decoders) G 711—original AT&T codec—used 8 000 8-bitdecoders). G.711—original AT&T codec—used 8,000 8-bit samples per second to create 64Kbps voice calls.

27

End-to-End Digital Voice with Business andEnd to End Digital Voice with Business and Mobile Phones

Modern business telephones and mobile phones onlyModern business telephones and mobile phones only use digital voice.Phone can connect to same network as PCs.Send and receive digital signals (bits) directly; A/D converter built into phone.Phones often have computer-like features built-in.

Display with simple web browser.

Some phones essentially have built-in tablet computersSome phones essentially have built-in tablet computers so they are mobile.

Look more like small computers with phone attached; voice lli f t j t f f tcalling feature just one of many features.

28

End-to-End Digital Voice with Business andEnd to End Digital Voice with Business and Mobile Phones

M bil h h f f t b iMobile phones have some of same features as business phones, but no cables.Mobile phones (cell phone) use wireless technologiesMobile phones (cell phone) use wireless technologies to send and receive bits for voice calls and data applications (like text messaging).

Summary: Voice traffic exists as common type of traffic in networks today. Networks typically support voice traffic as just one of

li timany applications.

29

Recorded Video

N t k d t t li d d d idNetworks may need to support live and recorded video.Focus: Recorded video

Digital Video RecordingsDigital Video RecordingsVideo FilesVideo Compression

30

Recorded Video

Modern video cameras make digital recordings

d t th bitand store them as bits.Camera also has processors to takeprocessors to take input and convert light and sound into bits to store as file on permanent storagestore as file on permanent storage.Later, user can copy video to PC.

Figure 2-9Video Camera Components and Moving the Video Files to a PC31

Video Files

Digital video revolves around concept of single videoDigital video revolves around concept of single video frame (think animation cells).

Rectangle (width by height) of individual points of light of each id i till ivideo image as still image.

When played back, video player software shows one frame after another.Computers cannot store video as points of light or as motions on screen, but as bits.Computer thinks of video frame as pixel grid.To represent color of pixel, computer uses table that lists all colors and matching binary codeall colors and matching binary code.

32

Video Files

Vid fil b lVideos files can become very large.Example: High definition video with these specifications:

3-byte code to represent color of each pixel3-byte code to represent color of each pixelFrame size 1920 (wide) by 1080 (high)Records 30 frames per second for smooth video

Figure 2-10A Somewhat Extreme Example of Uncompressed Video33

Video Compression

Large video files cause problems: Take long time toLarge video files cause problems: Take long time to download over network.Compression: Stores video file as smaller file.Compressed video file often looks just as good as original (depends on compression ratio used).

Example: Video originally recorded with frame size of 1920 xExample: Video originally recorded with frame size of 1920 x 1080 could be compressed by shortening width and height to 25% original size (480 by 270); only requires 1/16th original number of pixelsnumber of pixels.

NOTE: To learn many aspects of video and video compression, use tools built into PC. Check out Real World Video Compression, by Andy BeachAndy Beach.

34

Video Compression

E l f th ll fl Th id d th hExample of the overall flow: The video producer – the person who recorded the video and decided what compressions to use –compressed and posted the file on a video server on the Internet (steps 1 through 3) Later at step 4 video users might actually watch the1 through 3). Later, at step 4, video users might actually watch the video because it downloads in a reasonable amount of time.

Figure 2-11Producing and Posting Smaller Compressed Video Files35

Break

Take 10

36

A Deeper Look at One Application: WorldA Deeper Look at One Application: World Wide Web

W ld Wid W b (th W b) W b b ftWorld Wide Web (the Web): Web browser software which allows users access to Web may be single most commonly used application in world.y ppWeb 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 webservice from another device (information from web server).

37

World Wide Web

Th b b ( li t) d b t th t th bThe 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 thebrowser 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 Server38

Web Browsers (Web Clients)

Web browser (first oneWeb browser (first one came out in early 1990s): Software that allows user to get and display copy of web page from web server.Once web server sendsOnce web server sends content back to browser, it displays information. Example: Apple’s Safari browser.

Figure 2-13Window Created by Apple Safari Web Browser39

Components on the Client Computer

W b b t f ll t f l th t t llWeb browsers must follow same set of rules that tell browser how to request web page from server.Browsers generally work same way in how they divideBrowsers generally work same way in how they divide work: browser does some work but also relies on computer OS for some parts.1. Client computer requires way to physically connect to network so

bits that make up web page can move from server to client.2. Client typically uses hardware called Network Interface Card

(NIC) for network access.

Figure 2-14Photo of Network Interface Card (NIC)40

Components on the Client Computer: NIC

Each NIC has a circuit board with microchips and circuits (main part ofEach NIC has a circuit board with microchips and circuits (main part of the board) that is inside the computer case, as well as a port for the cable to connect to it on the outside of the case.

Figure 2-14Photo of Network Interface Card (NIC)41

Components on the Client Computer

S NIC i t t t i dSome NICs exist as separate computer expansion cards.Other devices put NIC functions onto some other part of devicedevice.

Tablet: Has wireless NIC function but doesn’t have NIC as separate physical card.

OS t l CPU RAM t t d thOS controls CPU, RAM, permanent storage, and other hardware, including NIC.

OS also manages all applications and provides services to them.g pp p

When user clicks or types something to load new web page, browser, OS, and NIC all play roles.

42

Components on the Client ComputerSteps when user decides to load web page from p p gwww.example.com web server:1. Browser creates message to request web page from server and gives

request to OS for helprequest to OS for help.2. OS does some work on request, including adding web server’s network

address, then asks NIC to send request.3 NIC h i ll d t bit i t t k3. NIC physically sends request as bits into network.

Figure 2-15Three Major Steps on Client Computer after the User Requests a Web43

Using Web Addresses (URLs)

Web address: Identifies specific web page to displayWeb address: Identifies specific web page to display.Formal name: Universal Resource Locator (URL).Identifies web server and specific web page (file) on p p g ( )server:

Server name: Name listed between // and /Web page: Name after /Web page: Name after /Example: http://www.itt-tech.edu/information-technology

Web ServerProtocol Web Page

Figure 2-16Example of Identifying a Web Page Using a Web Address (URL)44

Using Web Addresses (URLs)

C l b i h li kCan also access web pages via hyperlinks.Hyperlinks hide web addresses.When hyperlinked item on web page is clicked theWhen hyperlinked item on web page is clicked, the browser loads web page for web address linked via that hyperlink.

Note: When using web browsers to see hidden web address associated with hyperlink, hover over link, and right click mouse yp , , gbutton. Browser will list menu that typically shows options to either display linked web address or copy.

45

Web Servers (Hardware and Software)

Store information (text graphics video and audio) thatStore information (text, graphics, video, and audio) that users see and hear.Waits to receive requests for web pages, and sends page back to browser when requested.Is software so must run on computer hardware which can support many kinds of applicationscan support many kinds of applications.

46


Web server software allow web services to happen (e gWeb server software allow web services to happen (e.g., storing web pages, listening for requests, and sending web pages in response to requests).Hardware can be almost any computer that has OS that supports web server software.Businesses must consider:Businesses must consider:

Number of users requesting same web page at same time.Number of pages server must supply per second.Speed of connection to network.And many other factors.

47


Many businesses buildMany businesses build or lease space for their physical servers in a special type of room: Data Center (DC).Server hardware sits inServer hardware sits in racks (see graphic).DC also typically connects each server to network using cables.cables.

Figure 2-17Data Center with Servers in Racks48


What happens inside the server once it has decided to send a webWhat happens inside the server once it has decided to send a web page out into the network?1. Server takes the web page in storage and asks the OS to send it

out (via the network) to the web browser that requested the page.out (via the network) to the web browser that requested the page.2. The OS does some work (not shown) and asks the NIC for help.3. The NIC sends the request physically into the network.

Figure 2-18Three Steps: Web Server Sends Web Page into Network49

Web Sites, Pages, and ObjectsWeb page: Collection of content (text, images, video, p g ( , g , ,audio) that server supplies to web browsers.Web objects: Parts of Web page stored as separate filfiles.Web page includes links to objects’ locations on server.

Text in one Web object (file) and each graphic in as differentText in one Web object (file), and each graphic in as different object (file).

Figure 2-19Conceptual View: Web Site, Web Page, Web Object50

The Process to Get One Web Page

HTTP (HyperText Transfer Protocol): Defines rulesHTTP (HyperText Transfer Protocol): Defines rules that web browsers use to ask for web pages from web servers and that web servers use to send web pages b k t bback to browsers.GET request/response

Allows Web browser to get web object (GET request)Allows Web browser to get web object (GET request).Allows Web server to supply web object (GET response).

Web pages often contain more than 1 object.To get entire Web page, browser may have to do multiple HTTP GET requests and look for more instructions in each object it receivesinstructions in each object it receives.

51

The Process to Get One Web Page, Part 1

1.The Web client issues an1.The Web client issues an HTTP GET request for the original object (Main1.html), based on what the user clicked or typed.

2.The Web server supplies the Web object in the HTTP GET Reply.

3.The Web browser reads the Main1.html file and sees directions that tell it to get three other objects on the Web page.

Figure 2-21Using Four HTTP GET Requests for One Web Page52

The Process to Get One Web Page, Part 2

4.The Web browser issues an4.The Web browser issues an HTTP GET request for the first extra object (Object1.jpg).

5.The Web browser issues an HTTP GET request for the second extra object (Object2.jpg).

6.The Web browser issues an HTTP GET request for the third extra object (Object3.jpg).

Figure 2-21Using Four HTTP GET Requests for One Web Page53

Refining the Definition of a Network

Revised definition of computer networking could be:Revised definition of computer networking could be: Software on client computers (e.g., Web browsers).Software on server computers (e.g., Web server software).OS on those computers.Some hardware to connect computers to network (e.g., NIC).Network able to deliver bits from one computer to another.Complete set of protocols (rules) that allow devices to work together to send bits from one computer to another.

54

Refining the Definition of a Network, Part 1

1.The Web browser thinks about the user’s action (a click of a hyperlink),1.The Web browser thinks about the user s action (a click of a hyperlink), and creates an HTTP GET request for the Web address.

2.The OS performs some networking tasks that the browser cannot do, like identifying the correct Web server’s address. The OS then asks thelike identifying the correct Web server s address. The OS then asks the NIC to transmit the bits.

3.The NIC physically transmits the bits representing the HTTP GET request into the networkrequest into the network.

Figure 2-22A Demonstration of Web Components Working Together55

Refining the Definition of a Network, Part 2

4.The network delivers the bits that contain the HTTP GET request to the4.The network delivers the bits that contain the HTTP GET request to the server.

5.The server’s NIC receives the bits and gives them to the OS.6 The OS processes the data mainly deciding which application should6.The OS processes the data, mainly deciding which application should

be given the received data. 7.The Web server thinks about the HTTP GET request and prepares to

respondrespond.

Figure 2-22A Demonstration of Web Components Working Together56

Uncovering the Network Between theUncovering the Network Between the Application Endpoints

Compare Computer Networks to Road SystemsCompare Computer Networks to Road SystemsCreate a road (link) between 2 places (devices): Cables, radio waves, etc.

Figure 2-23A Road Between Two Houses (and the Network Equivalent)57


Comparing Computer Networks to Road Systems:Comparing Computer Networks to Road Systems: Sharing roads (links) between towns (sites)

Would there be a d di tl froad directly from

each house in the first town to each house in the otherhouse in the other town?No, they would build one roadbuild one road between the two towns and share the roadthe road.

Figure 2-24Sharing a Road Between Towns (and the Network Equivalent)58


N t k t l ShNetwork topology: Shows each device and each cable between pairs of devices pwith little or no detail.Cables used to transmit data

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6789/ps7290/ps10589/images/data_sheet_c78-598389-2.jpg

data.If connected to multiple cables, networking device can receive http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps64

06/images/product data sheet0900aecd806b0bd8-2.jpgbits over one cable and send them out again over another.

Two very common devices:

06/images/product_data_sheet0900aecd806b0bd8 2.jpg

http://us.fotolia.com/id/692608yswitches, routers.

Figure 2-25Photos of Routers, Switches, and a LAN Networking Cable59


Links and NodesLinks and Nodes Link: Any cable between two devices.Node: Any device.

Link acts like road between two towns; node acts like intersection.

Figure 2-26Network Nodes (Like Intersections) and Links (Like Roads)60


You arrive at node 1 with “Node 10” on your signYou arrive at node 1 with Node 10 on your sign.The policeman for node 1 tells you to take the lower path.You travel over the link to node 4.The node 4 policeman tells you to take the link towards node 7.You travel over theYou travel over the link to node 7.

Figure 2-27Road Network with Policemen at Every Intersection (Node)61


Small Lab Networks: Devices typically all sit in the same room. TheSmall 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.

Figure 2-28A Simple Lab Network: One Cable62


A more convenient way to connect multiple devices into the same smallA 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.

Figure 2-29A Simple Lab Network: All Computers Connect to One Switch (Node)63


Wireless networking: Uses radio waves to communicate.Example: Home-based network with multiple devicesmultiple devices.

Each device creates link to switch using cables (wires) or radio frequency (wireless)or radio frequency (wireless) to send bits to each other.Bits first go to switch, then toreceiving devicereceiving device.

Figure 2-30A Home Network Using Wired (Cabled) and Wireless64


E t i N t kEnterprise Networks Small/Medium Business (SMB)Enterprise: Businesses largerEnterprise: Businesses larger than SMBs

Example: physical topology for multi floor businessmulti-floor business.

Figure 2-31A Single Site in an Enterprise with LAN Switches65


Enterprise Networks: Use Wide Area Networks (WANs)Enterprise Networks: Use Wide Area Networks (WANs) to connect various remote sites together.Network designers prefer routers to connect sites using WAN links, as routersusing 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 ro ter then o er the short LAN link to the first floor s itch and so on

Figure 2-32Multiple Sites in an Enterprise with Routers

router, then over the short LAN link to the first floor switch, and so on.

66


I t t I t t d N t kInternet: Interconnected NetworksInternet core looks like one big network but isone big network, but is many networks.Internet Service Providers (ISPs) build networks that combine to create Internet core.

Figure 2-33All Who Care to Use the Internet Connect to the Internet67


Internet Core is hugeInternet Core is huge.Some ISPs have thousands of sites with many network devices at each site.at each site.Worldwide, thousands of ISPs exist with millions of business

t d billi f i di id lcustomers and billions of individuals.

Figure 2-34Internet Core: Three ISPs and One Mobile Service Provider68

Summary: This chapterSummary: This chapter…Began by focusing on the parts of networking that the average person uses: apps on typical consumeraverage person uses: apps on typical consumer electronics and computing devices.Introduced the hidden concepts and terms of networking p gwhile 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 WebWeb browser requests a Web page, and how the Web server responds to supply that Web page.Explained how Web server software, running on some p , gcomputer hardware, uses the network between the computers to send a Web page to a user’s computer.

69

S Thi h tSummary: This chapter…Used a “road” scenario to compare the functions in aUsed a road scenario to compare the functions in a computer network to transportation systems (roads and intersections).Used common terms to describe networks of different sizes, from small home networks to the worldwide Internet.Internet.Described network topology as a set of nodes and links.

70

Q ti ? C t ?Questions? Comments?

71

Documents

NT1210 I d i N kiNT1210 Introduction to Networking - · PDF fileNT1210 I d i N kiNT1210 Introduction to Networking ... systems , televisions ... Modern business telephones and mobile