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An Introduction to the Internet and the Web Frank McCown COMP 250 – Internet Development Harding University Photos were obtained from the Web, and copyright.

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Presentation on theme: "An Introduction to the Internet and the Web Frank McCown COMP 250 – Internet Development Harding University Photos were obtained from the Web, and copyright."— Presentation transcript:

1 An Introduction to the Internet and the Web Frank McCown COMP 250 – Internet Development Harding University Photos were obtained from the Web, and copyright is held by the respective owners. Short History of Computing by Frank McCown is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported LicenseCreative Commons Attribution-NonCommercial 3.0 Unported License

2 http://www.opte.org/maps/

3 http://internet-map.net/

4 The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide. http://en.wikipedia.org/wiki/Internetcomputer networksInternet Protocol Suite http://en.wikipedia.org/wiki/Internet Internet Computer 1Computer 2 255.254.253.2521.2.3.4

5 Internet Protocol Suite Internet Protocol (IP): directs packets to a specific computer using an IP address Transmission Control Protocol (TCP): directs packets to a specific application on a computer using a port number. – Common port numbers: Common port numbers 22 – ssh 23 – telnet 25 – email 80 – Web

6

7 Web VoIP email IM Streaming video Internet != Web The Internet File transfer

8 Overview of the Web Internet Client – Web BrowserWeb Server 255.254.253.2521.2.3.4 World Wide Web: The system of interlinked hypertext documents accessed over the Internet using the HTTP protocol

9 http://gs.statcounter.com/?#browser-ww-monthly-200807-201308 Web Browser Software that runs on the client used to access and display web content

10 http://gs.statcounter.com#mobile_browser-ww-monthly-200807-201308 Mobile Web Browser Mobile browsers account for 18% of web access in Aug 2013

11 Web Server A computer (or software running on a computer) on the Internet that listens for HTTP requests, typically on port 80, and responds with HTTP responses Apache : 52.2% Microsoft IIS: 19.7% ngnix: 13.6% Google: 3.9% Market Share for Top Servers Across All Domains, Aug 1995 – July 2013 http://news.netcraft.com/archives/category/web-server-survey/

12 Hypertext Transfer Protocol (HTTP) Protocol that runs over TCP/IP and governs communication between web browsers and web servers Client Request GET /comp/ HTTP/1.1 Host: www.harding.edu Server Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Example request for http://www.harding.edu/comp/ http://www.harding.edu/comp/

13 Uniform Resource Locator (URL) A URL identifies the location of a resource on the Web. http://www.foo.org/abc/bar.html schemehostnamepath local hostname domain name TLD

14 Domain Name System (DNS) DNSDNS is a hierarchical look-up service that converts a given hostname into its equivalent IP address www.google.comwww.google.com 1.4.5.8 www.cnn.comwww.cnn.com 4.6.2.8 www.hulu.comwww.hulu.com 6.7.8.9 Etc... DNS Server www.harding.edu 128.82.4.20 DNS servers contact parent servers for missing entries Authoritative name servers are responsible for specific domains Warning: DNS cache poisoningDNS cache poisoning

15 Example: Web Page Request http://foo.org/bar.html Client (Web Browser)Web Server (4) HTTP GET bar.html (1) Enter URL (6) HTTP Response (5) Locate the resource (7) Parse HTML & display (8) HTTP GET image1 (N) HTTP GET imageX Potentially many requests & responses DNS (2) foo.org (3) 1.2.3.4

16 Dissecting the Request GET /comp/ HTTP/1.1 Host: www.harding.edu User-Agent: Mozilla/5.0 Firefox/3.6.8 Request type

17 Dissecting the Request GET /comp/ HTTP/1.1 Host: www.harding.edu User-Agent: Mozilla/5.0 Firefox/3.6.8 Relative URL

18 Dissecting the Request GET /comp/ HTTP/1.1 Host: www.harding.edu User-Agent: Mozilla/5.0 Firefox/3.6.8 HTTP version

19 Dissecting the Request GET /comp/ HTTP/1.1 Host: www.harding.edu User-Agent: Mozilla/5.0 Firefox/3.6.8 Hostname

20 Dissecting the Request GET /comp/ HTTP/1.1 Host: www.harding.edu User-Agent: Mozilla/5.0 Firefox/3.6.8 Identify client

21 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body HTTP version Status code & phrase

22 Status Line HTTP/1.1 200 OK Popular status codesPopular status codes: 200Successful 301 Moved permanently 302 Found under different temporary URI 304Not modified 403Forbidden 404Not found 500Internal server error HTTP version Status code & phrase

23 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body Number of bytes in response

24 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body MIME type

25 Popular MIME types text/html text/plain image/jpeg image/gif image/png application/pdf application/msword application/vnd.ms-excel video/quicktime IANA list of MIME types

26 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body URI for resource

27 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body When the file was last modified on the server

28 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body Web server software

29 Dissecting the Response HTTP/1.1 200 OK Content-Length: 6018 Content-Type: text/html Content-Location: http://www.harding.edu/comp/ Last-Modified: Mon, 05 Jul 2010 18:49:40 GMT Server: Microsoft-IIS/6.0 Harding University - Computer Science Etc... Header Message body HTML displayed in the browser

30 How can I see the HTTP headers? Chrome – Ctrl-Shift-I Developer Tools – Network button Firefox – Ctrl-Shift-K Web Console – Net button should be down Internet Explorer – F12 Developer Tools – Network tab

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