CIT 1100

Connecting to the Internet

In this chapter you will learn how to: Describe the hardware used to connect to the Internet

Explain protocols and software used with networking and the Internet

Discuss Web content and Web-delivered services

Connecting to the Internet

Millions of smaller networks connected together form the Internet. Like telephone network, the Internet is a "supernetwork" of smaller networks It was designed to make certain that nothing could

stop the flow of communication, not even a nuclear attack, so they specified a highly decentral ized network with multiple connections between the various computers

The heart of the Internet- the backbone - consists of many university, corporate, and government networks, connected together via thick bundles of glass fila ments, called fiber optic

 The Physical Connection

Physical ConnectionPre-Internet communication requires all connections to be made from a central hubRemote sites would have dedicated connections to the central hub

message

messagemessage

messagemessage

If the enemy destroys the central site all communications would be lost

Decentralized Network

Rather than having a centralized hub connection, networks were decentralized

Specialized devices were developed that would automatically route traffic to the proper destination

Decentralized Network

Routers provide multiple paths to multiple end points

Message

Message

Message

Decentralized Network

Message

In the event a cable gets cut, or a router fails the network can continue to route messages, routers can easily find alternate paths

X FAIL

Routers provide connection points between networks and determine the route for a data packet to take from the source network to destination network Routers range from high-end machines that direct

huge amounts of Internet traffic to the little box attached to your cable modem at home

Home routers often offer multiple functions, most have built-in switches and wireless access points

Routers know the destination of data because routers use TCP/IP the common protocol of the Internet

They read network ID of each data packet and send it by the shortest route they know to its destination

Routers

Get ting your computer connected to the Internet requires some sort of intermediary network with a router into which you can tap. This router connects to the In ternet through an Internet service provider (ISP)

Routers

RoutersEstablishing a link between your computer and the ISP requires three things: Some kind of network device on your computer, like a

modem or network card A cable or radio transmitter that enables the network

device to access the world outside your door Programs to make that hardware go, like the built-in

network software in Windows and TCP/IP installed

The least expensive Internet connection is called dial-up networking. It consists of three pieces:◦ A modem◦ A working telephone line◦ An ISP

ISP Connection

Early on, people realized that computer information traveled slowly over regular analog telephone lines. The concept of an Integrated Service Digital Network (ISDN) began in1984 It was supposed to evolve into a completely

digital telephone system so that data would go faster through phone lines.

ISDN never caught on as was expected because other, faster technologies soon came along such as DSL and cable

ISDN supports data transfer rates of 128 Kbps.

ISDN the Other Dial-Up

Broadband connection gives you access to the Internet through a single high-speed connection Always on, as opposed to a dial-up

connection Two technologies dominate the broadband

connection field◦ Cable◦ DSL

Broadband Connections

Cable connections use regular cable TV cables to delivering TV programming and high speed internet access Supports upload speeds of up to 1.5 Mbps and

download speeds from 2 to as high as 24 Mbps Cable connections use a cable modem that

connects to a NIC in your PC via an Ethernet cable

Cable TV companies take advantage of the fact that their cable TV signal occupy only a fraction of the capacity of the cables running into your home leaving room for internet access

Cable

DSL makes use of the fact that standard copper telephone lines can handle a much greater range of frequencies, or bandwidth, than what is needed to transmit voice during phone calls DSL uses this extra bandwidth capacity to

send data over telephone wires without disturbing their ability to carry voice conversations

DSL

Once you have a physical connection to the Internet, your computer, switch, and router all start talking to one another exchanging data. In order to know how to communicate, they

need to use a predetermined lan guage Protocols fill that need 

Protocols and Settings

A major issues for early computer networks have never been which pathway you use to send information. Rather, they're concerned with how you send the information so that it goes to the right place and it is understood This became a big problem for the U.S. military, the

Navy bought their computer equipment from one company, the Army from somebody else, each being proprietary

They couldn't send information back and forth, since these different systems had different ways of treating information

The Department of Defense created a common protocol that would run on any platform TCP/IP

Protocols

Protocols are the ”Rules of the Road” when establishing communications Transmission Control Protocol/Internet

Protocol (TCP/IP) protocol suite does the same thing for networks,

Providing a common set of rules and guidelines for electrical signals, packaging of information, error correction, security, etc.

Protocols

Transmission Control Protocol (TCP) controls the sending and receiving of information Two computers communicating use TCP to

make a con nection and handle flow of data between them

Computers use the Internet Protocol (IP) to determine packaging and labeling of data

When data is sent its neatly cut up and packaged into bits of information that are all the same size

TCP/IP

The Operating System uses IP to determine how to package the data, the operating system on the receiving computer knows how to unpack the information (and how to put it back together) To address the data so it is sent to the correct

endpoint your operating system uses IP to put a numerical destination and source address-called IP addresses-onto the packets

IP addresses follow specific conventions. Most commonly, IP addresses have four sets of numbers ranging from 0 to 255, separated by periods, like this: 192.168.1.52.

TCP/IP

There are two different components to an IP address: The Network ID defines the network The Host ID describes your node-the

computer you use to access the Internet

TCP/IP

This came from a Node on the 192.168.17 network and was sent to the 202.99.19 network

This came is pc .49 on the sending network, Was sent to pc .235 on the receiving network

Special computers, called Domain Name Service (DNS) servers keep databases of IP addresses and their corresponding names For example it may be hard to remember

74.125.65.106 but most people can remember Google.com

When you enter WWW.Google.Com into your browser the DNS server responds with the actual IP address, otherwise your browser would not be able to locate Google

For a small annual fee the ISP will maintain DNS settings allowing users to quickly locate web pages

DNS

DNS lookup

Internet

```

Open a Browser on a PC

www.google.com

The first thing that must happen is the Name www.google.com must be resolved to an IP Address

DNS request

The ISP has a DNS server that will resolve URL to an IP Address

“Hey who is WWW.Google.com?”

That’s 74.125.95.106

DHCP

DHCP Dynamic Host Configuration Protocol enables you to create a pool of IP addresses that are given temporarily to machines

When a PC is first turned on it transmits a request to the DHCP server (built into your home router)

DHCP!

IP Address: 192.168.1.17DNS Server: 14.16.2.2Default Gateway:192.168.1.1

Let me check the pool of IP

addresses and I’ll let you know

Hey, I need an IP Address, also who is the DNS server and the Gateway I’ll use to send stuff to the internet?

The PC now has an IP AddressIt knows the address of the DNS serverIt knows the Default Gateway to send any internet traffic to.

TCP/IP Services

After you've established a connection between the PC and the ISP, you can do nothing on the Internet without applications designed to use one or more TCP/IP services:

◦ The World Wide Web◦ E-mail◦ FTP (File Transfer Protocol)◦ VoiP (Voice over IP)

Each of these services requires a special application each having special settings

The World Wide WebThe Web provides a graphical interface for the Internet Web servers, providing Web sites that you access by using HTTP on port 80 Using Web-browser software, you can click a link on a Web

page and be instantly connected the Web server anywhere in the world

One thing the protocol HTTP lacks is security. When you want to buy something from an online retailer you don't want someone else co vertly capturing your credit card number

Secure Sockets Layer (SSL) security proto col, used to create a secure connection to Web sites which has been incorporated into a secure web browser HTTPS

HTTPS is very similar to HTTP but uses a different port number 443

FTPThe File Transfer Protocol (FTP), using ports 20 and 21, is a protocol used to share files between systems Instead of typing in a Web ad dress and seeing a Web

page, typing an FTP address like ftp://ftp.cise/ufl.edu brings you to a file and folder directory structure

Here, you can upload and download files (if you have permission to do so)

E-Mail Protocols

E-mail clients, such as Microsoft Outlook need to be configured before you can use them to access your e-mail, fill in your e-mail address and password Next you add the names of the Post Office

Protocol ver. 3 (POP3) or Internet Message Access Protocol (IMAP) server and the Simple Mail Transfer Protocol (SMTP) server

POP3 or IMAP server is the computer that handles in -coming (to you) e-mail, SMTP handles outgoing mail

POP3 POP3 is the most widely-used standard, although the latest version of IMAP, IMAP4, supports some newer features POP3 doesn't IMAP4 enables you to search through

messages on the mail server to find specific keywords, then select the mes sages you want to download onto your machine

Even with the advantages of IMAP4 over POP3, the vast majority of incoming mail servers use POP3

VoiPYou can use Voice over IP (VoiP) to make voice calls over your computer network Allowing you to use the extra capacity on the data

network for phone calls VoiP works with every type of high-speed Internet

connection such as DSL and cable Remember when installing VoiP is that low network

latency is more important than high network speed Latency is the amount of time a packet takes to get

to its destination measured in milliseconds