Transcript The Internet - University of Kentucky

The Internet
The Basics
Outline
• Client/server model
• Internet Protocols
• IP numbers
• Domain Name Service
• ISPs and the infrastructure
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
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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
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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
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uky.edu
cs.uky.edu
www.cs.uky.edu
ftp.cs.uky.edu
Current Top-Level Domains
.aero
.biz
.com
.coop
.edu
.gov
.info
.mil
.museum
.name
.net
.org
.pro
Members of the air transport industry
Businesses
Can be used by anyone
Cooperative associations
Degree granting institutions
United States government
Information service providers
United States military
Museums
Individuals
Networking organizations
Organizations (often nonprofits)
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
Protocol
identifies the
means of
access
URL
http://
Domain name
contains the host and
top-level domain
www.nytimes.com/
Path identifies the
subdirectories
within the Web site
Pages/cartoons/
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:
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Cost
Local access numbers
Services Offered – email, web page hosting, news reading
Reliability
Speed
Support and Customer Service
Internet Structure