Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher...
Transcript of Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher...
![Page 1: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/1.jpg)
Lecture 13Internet & Internet ServicesCSCS100 - Spring 2008 – Forman Christian CollegeAsher ImtiazWajeeha Akram
*Several of these slides have been adapted and modified from VU CS101 slides (Dr. Altaf A. Khan) and Peter Norton’s supplementary material.
![Page 2: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/2.jpg)
Today’s Goal• Internet Architecture• Addressing scheme used on the Internet• To look at several services provided by
the Internet• Web• eMail• Instant messaging• VoIP
![Page 3: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/3.jpg)
What Does the Internet Enable?• Enables users located at far-way locations
to easily share information with others located all over the world
• Enables users to easily and inexpensively communicate with others located all over the world
• Enables the users to operate and run programs on computers located all over the world
![Page 4: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/4.jpg)
The Internet is unlike any previous human invention. It is a world-wide resource, accessible to all of the humankind.
![Page 5: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/5.jpg)
“Cool” internet appliances
World’s smallest web serverhttp://www-ccs.cs.umass.edu/~shri/iPic.html
IP picture framehttp://www.ceiva.com/
Web-enabled toaster +weather forecaster
Internet phones
![Page 6: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/6.jpg)
Internet Users Worldwide
673M in 2002
1B+ in 2005(48% wireless)
![Page 7: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/7.jpg)
Key Characteristics (1)
Geographic Distribution
Global - reaches around the world
Robust Architecture
Adapts to damage and error
Speed
Data can travels at near ‘c’ on copper, fiber, airwaves
![Page 8: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/8.jpg)
Key Characteristics (2)Universal Access
Same functionality to everyone
Growth RateThe fastest growing technology ever
Freedom of SpeechPromotes freedom of speech
The Digital AdvantageIs digital: can correct errors
![Page 9: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/9.jpg)
Internet: Network of Networks
• A large number of networks, interconnected physically
• Capable of communicating and sharing data with each other
• From the user’s point view, Internet – a collection of interconnected networks – looks like a single, unified network
![Page 10: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/10.jpg)
Internet ---- Web?
![Page 11: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/11.jpg)
Internet ---- Intranet?
![Page 12: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/12.jpg)
Internet Networking Protocols
Communications on the Internet is controlled by a set of two protocols: TCP and IP
![Page 13: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/13.jpg)
TCP/IP (1)Transmission Control Protocol/Internet Protocol
• Networking protocol used by all computers and networks on the Internet
• Originally developed by the US DoD for Unix, but now available for most other OSes
![Page 14: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/14.jpg)
TCP/IP (2)Transmission Control Protocol/Internet Protocol• TCP breaks down the message to be sent
over the Internet into packets
• IP routes these packets through the Internet to get them to their destination
• When the packets reach the destination computer, TCP reassembles them into the original message
![Page 15: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/15.jpg)
Internet Addressing• Regular post cannot be delivered unless
we write a destination address on the envelope
• Same is true for the Internet
• Regular post can be delivered at the intended address even if the given address is not precise. That is not the case for Internet addressing
![Page 16: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/16.jpg)
216.122.128.109
www.fccollege.edu.pk
IP addressDNS address
![Page 17: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/17.jpg)
IP Address (1)
• A unique identifier for a computer on a TCP/IP network
• Format: four 8-bit numbers separated by periods. Each 8-bit number can be 0 to 255
• Example:• 216.122.128.109 (IP address of the FCC Web
server)
![Page 18: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/18.jpg)
IP Address (2)
• Networks using TCP/IP route messages based on the IP address of the destination
• Any IP addresses (as long as they are unique) can be assigned within a PN
• However, connecting a PN to the Internet requires using unique, registered IP addresses
![Page 19: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/19.jpg)
Domain Names• IP addresses are fine for computers, but
difficult to recognize and remember for humans
• A domain name is a meaningful, easy-to-remember ‘label’ for an IP address
• Examples:216.122.128.109
www.fccollege.edu.pk216.239.33.101 www.google.com
![Page 20: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/20.jpg)
DNS: Domain Name System (1)
• DNS is the way that Internet domain names are located & translated into IP addresses
• Maintaining a single, central table of domain name/IP address relationships is impractical• Billions of DNS-IP translations take place
every day• The DNS-IP tables get updated continuously
![Page 21: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/21.jpg)
DNS: Domain Name System (2)
• Tables of DNs & IP addresses are distributed throughout the Internet on numerous servers
• There is a DNS server at most ISPs. It converts the domain names in our Internet requests to actual IP addresses
• In case it does not have a particular domain name in its table, it makes a request to another DNS server on the Internet
![Page 22: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/22.jpg)
TCP/IP Settings in a Computer
![Page 23: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/23.jpg)
Internet Services
There are many, but we will look at only the following:
• Web• eMail• Instant messaging• VoIP
![Page 24: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/24.jpg)
The Web
• The greatest, shared resource of information created by humankind
• A user may access any item on the Web through a URL, e.g.
http://www.fccollege.edu.pk/cs/index.html
• Before, going any further, let us dissect this URL
![Page 25: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/25.jpg)
http://www.fcc.edu.pk/cs/index.html
ProtocolIdentifier
ServerAddress
Directory & File Name
![Page 26: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/26.jpg)
How does the Web work?
![Page 27: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/27.jpg)
User’sComputer
User launches the browser on his/her computer
Browser
![Page 28: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/28.jpg)
User’sComputer
User types in the URL into the browser
![Page 29: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/29.jpg)
User’sComputer
The browser breaks down the URL
http://www.fcc.edu.pk/cs/index.html
httpProtocolIdentifier
www.fcc.edu.pkServer’s Name
cs/index.htmlDirectory &File Name
![Page 30: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/30.jpg)
User’sComputer
DNSServer
Browser sends server’s name to the DNS server
Domain Name
IP Address
![Page 31: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/31.jpg)
User’sComputer
WebServer
Internet
Browser establishes a connection with the server
![Page 32: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/32.jpg)
User’sComputer
WebServer
Browser sends a ‘GET’ request for cs/index.html
![Page 33: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/33.jpg)
User’sComputer
WebServer
Server sends the requested file to the browser
![Page 34: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/34.jpg)
User’sComputer
Browser displays index.html
X
![Page 35: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/35.jpg)
eMail• Computer-to-computer messaging
• Inexpensive, and quite quick, but not instant!
• The most popular service on the Internet, even more than surfing, but soon to be overtaken by instant messaging
• Billions are sent every day
![Page 36: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/36.jpg)
The Trouble with eMail• Slow response times
• No way of knowing if the person we are sending eMail to is there to read it
• The process of having a conversation through eMail by exchanging several short messages is too cumbersome
Instant messaging (IM) solves these problems
![Page 37: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/37.jpg)
Instant Messaging
• The IM services available on the Internet (e.g. ICQ, GoogleTalk, MSN Messenger, Yahoo! Messenger and Skype) allow us to maintain a list of people (contacts) that we interact with regularly
• We can send an instant messages to any of the contacts in our list as long as that contact is online
![Page 38: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/38.jpg)
Using Instant Messaging (1)
• Whenever a contact in our list comes online, the IM client informs us through an alert message and by playing a sound
• To send an instant message to a contact, just click on the contact in the IM client, and start typing the message
• The selected contact will receive that message almost immediately after you press ‘Enter’
![Page 39: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/39.jpg)
Using Instant Messaging (2)
• When the contact’s IM client receives the message, it alerts the contact with a blinking message and by playing a sound
• That contact then can type a response to the received message, and send it instantly
• Several such conversations can be carried out simultaneously, each occupying a separate IM windows
![Page 40: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/40.jpg)
Key Point
• Once the IM server provides the communication info to the user and his/her contact’s IM client, the two are able to communicate with each other without the IM server’s assistance
• This server-less connection is termed as a P2P connection
![Page 41: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/41.jpg)
Question
• Why do we require the server in the first place?
• Why doesn’t my IM client look for the user’s contact’s IM client without the IM server’s help?
![Page 42: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/42.jpg)
Answer• Many users (including almost all home
users) do not have permanent IP addresses. They are assigned temporary IP addresses by their ISP each time they connect to the Internet
• The server-based IM scheme removes the need of having permanent IP numbers
• It also gives IM users true mobility, allowing them the use of IM from any Internet-connected computer
![Page 43: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/43.jpg)
VoIP: Voice over IP• Voice delivered from one device to another
using the Internet Protocol
• Voice is first converted into a digital form, is broken down into packets, and then transmitted over a TCP/IP network (e.g. Internet)
• Four modes:• C2C• C2T• T2C• T2T (with a TCP/IP net somewhere in between)
![Page 44: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/44.jpg)
Pro
Much cheaper than traditional phone service
ConNoticeably poor quality of voice as
compared with land-line phone service, but not much worse than cell phone
service
![Page 45: Lecture 13 Internet & Internet Services CSCS100 - Spring 2008 – Forman Christian College Asher Imtiaz Wajeeha Akram *Several of these slides have been.](https://reader035.fdocuments.us/reader035/viewer/2022070409/56649e905503460f94b955a5/html5/thumbnails/45.jpg)
Who runs the InternetWho runs the Internet??
Who owns itWho owns it??