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Transcript of CIT 1100. In this chapter you will learn how to: Describe the hardware used to connect to the...
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