The InternetThe Basics

Outline

• Client/server model• Internet Protocols• IP numbers• Domain Name Service • ISPs and the infrastructure

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Client/Server Interaction

• Server is the computer that stores information• Web server, file server, mail server

• Client is the computer that wants the information

• When you click a Web link, your computer (the client) enters into a client/server relationship with a web server

• Once the page is sent to you, the client/server relationship ends

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Client/Server Interaction

• These relationships are brief, so a server can serve many clients “at the same time”• Ask, receive, done

• One server can provide information to many clients• Yahoo, Google, eBay… a web site can be used by many different people

at once, and they all get service

• One client computer can ask for services from many servers• A web page may have many links, each to a different web server

Direction matters!

• When you request information from a server and it is delivered, that is a download• When you send information (as small as clicking on a link to request a

Web page, or as large as a video file) to a server, that is an upload

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Internet Protocols

• TCP and IP serve as the primary protocols responsible for message transmission on the Internet

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Following Protocol

• A protocol describes the specific technical steps involved in how information is actually transmitted,

It is a set of rules on how a conversation happens

• TCP/IP (Transmission Control Protocol/Internet Protocol)• Information is broken into a sequence of small fixed-size units called IP packets

• Each packet has space for a chunk of data (e.g., piece of the novel), the IP addresses of the source and destination computers, and a sequence number

• The packets are sent over the Internet one at a time using whatever route is available

• Each packet can take a different route, so congestion and service interruptions do not delay transmissions

IP protocol

• The Internet Protocol was designed to work with POOR connections • It is very difficult (and expensive) to keep a good quality connection

between two points working long enough to send a huge file• BUT it is not hard to keep a good connection for a few seconds - long

enough to send a few packets (cheaper)

IP Addresses

• IP addresses are addresses that identify computers on the Internet• Static IP address• Dynamic IP address• Try 72.21.210.250 – where is it?

Problem with IP numbers

• When they created the Internet protocol they never anticipated the size the Net has grown to!• The range of possible IP numbers is being exhausted.• IPv6 is a new version of the protocol with a much larger range of IP

numbers (they are longer!) it is being introduced right now.• Dynamic IP numbers is a short-term fix until IPv6 gets widespread

IPv6 numbers

• Internet Protocol version 6 will solve the problem of “not enough numbers for all the devices”• Example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334• 8 groups of 4 hexadecimal digits with colons between

Dynamic vs. Static IP numbers

• Static IP number is permanently assigned to a machine• Dynamic IP number (DHCP) only a temporary fix until IPv6 is

widespread• DHCP = Your machine gets an IP number assigned every time it logs

into the ISP, only for the duration of the connection• When you log out, someone else can reuse that IP number

Domain Names

• Easy-to-remember names for Internet servers• Ends with an extension that indicates its top-level domain

• Every domain name corresponds to a unique IP address• Domain Name System• cybersquatting

• ICANN (Internet Committee for Assigned Names and Numbers) coordinates technical management of the Internet’s Domain Name System

Domain Names

• Most specific information on the LEFT• Top Level Domain Names• .gov .com .edu .net

• Subnets and Sub Domains• uky.edu• cs.uky.edu• www.cs.uky.edu• ftp.cs.uky.edu

Current Top-Level Domains.aero Members of the air transport industry.biz Businesses.com Can be used by anyone.coop Cooperative associations.edu Degree granting institutions.gov United States government.info Information service providers.mil United States military.museum Museums.name Individuals.net Networking organizations.org Organizations (often nonprofits).pro Credentialed professionals

Top Level Domains - Country Codes

Cybersquatting

• when Internet was young, it used only ONE company as registrar, "Network Solutions"• NS handled domain name requests on first come, first served basis -

you paid the fee, you had the name for a year or two• Clever people registered domains that would be in high demand, like

"apple.com"• Then demanded payment “blackmail” to release them

ICANN

• Internet Corporation for Assigned Names and Numbers • makes rules about domain names• certifies companies to serve as registrars for adding new domain names to

DNS system• recently (2008) decided to allow new TLDs to be formed - applicant has to pay

a hefty fee and agree to act as registrar and DNS for the new TLD (www.accounts.bofa, pay.bill.visa)

URL

Uniform Resource Locator• Unique Internet address

• Protocol could be http, mailto, ftp, news, …• NOTE difference between http and https

URL http://

Protocol identifies the

means of access

www.nytimes.com/

Domain name contains the host and

top-level domain

Pages/cartoons/

Path identifies the subdirectories

within the Web site

Navigating the Web: Web Browsers

• Software running locally on your machine • Graphical• Enables Web navigation• Popular browsers:• Internet Explorer• Firefox• Camino (Mac OSX)• Chrome (Google)

The Internet and Copyright

• All original material on the Net is copyrighted, © or not• Copyright is violated when you get economic benefit from using the

material• Exception of "academic fair use"

• Plagiarism is different from copyright violation – it is presenting someone else's work as your own• Credit your sources!

ISP Infrastructure

Choosing an ISP

Factors to consider:• Cost• Local access numbers• Services Offered – email, web page hosting, news reading• Reliability• Speed• Support and Customer Service

Internet Structure