1. Internet Applications INTERNET & INTERNET APPLICATIONS

2. Internet The Internet is a global system of interconnected computer networks that interchange data by packet switching using the standardized Internet Protocol Suite (TCP/IP). It is a "network of networks" that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by copper wires, fiber-optic cables, wireless connections, and other technologies. The Internet carries various information resources and services, such as electronic mail, online chat, file transfer and file sharing, online gaming, and the inter-linked hypertext documents and other resources of the World Wide Web (WWW). Internet

3. Internet Connections Internet Customers connect to an ISP ISPs connect to backbone Backbone networks ISP networ k Customer Networks Bandwidth-limited links

4. Internet Connections Internet

5. Service Provider Networks: Reliance Enterprise Network

6. Service Provider Networks: Reliance Reliance Data Centers, are connected to 132 countries across 4 continents spanning US, UK, Mid-east and Asia-Pac through Flag Telecom backbone (Reliance Infocomm 's group company) and other undersea cable systems like Se-Me-Wea-3 and i2i and are having public / private peering relationship with large Tier 1 ISPs and content providers at more than 15 Internet Exchange points across the globe. There also exists peering relationship with other popular domestic ISPs on STM-1 bandwidth levels. The data centers further are connected to Reliance's country wide optic fiber based IP network with terabytes of capacity having points of presence at more than 1100 cities. Customers' can access the Internet by connecting to any of these 1100 PoPs using multiple means like local dedicated leased lines, PSTN -ISDN dialup links OR simply by using Reliance's 3G CDMA mobile services. The Reliance Data Centers at various locations are also interconnected through redundant fiber ring with bandwidth capacity of STM-4 for data replication purposes for providing Disaster Recovery services. Enterprise Network

7. Service Provider Networks: Reliance Enterprise Network

8. How Web Works? Let's say you want to visit the google website. First you enter the address or URL of the website in your web browser. Then your browser requests the DNS Server to get the IP address of the web server WWW

9. How Web Works? Then your machine sends an HTTP request to the web server that hosts the google site. The server sends the data over the Internet to your computer. Your web browser interprets the data, displaying it on your computer screen. WWW

10. QUESTIONS?

11. DNS

12. Internet Naming Hierarchy DNS The silent dot at the end of all addresses.com.net.org.in.tcd www.ac.co.iitk www

13. DNS Operation DNS Setup A DNS server maintains the name to IP address mapping of the domain for which it is the name server. The DNS server for a domain is registered with the domain registrar and the entry is maintained by the Internet Root-Servers (13) or Country Level Root- Servers. Whenever a server is queried, if doesn’t have the answer, the root servers are contacted. The root servers refer to the DNS server for that domain (in case the domain is a top level domain) or the Country Root Server (in case the domain is country level domain).

14. Load Balancing DNS DNS supports Load Balancing: The same name resolves to multiple IP Addresses (IP addresses of different Mirrored servers). Companies like google, akamai, yahoo use "Enhanced DNS" services: Different DNS results based on source IP. Web browser could automatically be directed to the closest web server thus reducing the download time Companies like google, akamai, yahoo etc. maintain mirror sites of many organizations on their server and direct request for these sites to the nearest server.

15. DNS Setup DNS CONFIGURATION

16. DNS Configuration DNS Setup named daemon is used A DNS Server may be caching/master/slave server The named.ca file has information of all Root Servers. There is a Forward Zone file and a Reverse Zone file for every domain. Configuration file: /var/named/chroot/etc/named.conf Forward Zone File: /var/named/chroot/var/named/ Reverse Zone File: /var/named/chroot/var/named/

17. Sample Master named.conf DNS Setup zone "." { type hint; file "named.ca"; }; zone "0.0.127.in-addr.arpa" { type master; file "named.local"; allow-query {any;}; }; zone "iitk.ac.in" { type master; file "hosts.db"; allow-query {any;}; }; zone "95.200.203.IN-ADDR.ARPA" { type master; file "hosts.rev.203.200.95"; allow-query {any;}; }; zone "iitk.ernet.in" { type slave; file "hosts.iitk.ernet.in"; masters { 202.141.40.10; }; allow-query {any;};

18. Sample Forward Zone File DNS Setup $TTL 86400 @ IN SOA ns1.iitk.ac.in. root.ns1.iitk.ac.in. ( 200605091 ; Serial 10800 ; Refresh - 3 hours 3600 ; Retry - 1 hour 1209600 ;Expire - 1 week 43200 ) ; Minimum TTL for negative answers - 12 hours IN NS ns1.iitk.ac.in. IN NS ns2.iitk.ac.in. IN MX 5 mail0.iitk.ac.in. IN MX 10 mail1.iitk.ac.in. IN MX 20 mail2.iitk.ac.in. $ORIGIN iitk.ac.in. ns1 IN A 203.200.95.142 mail0 IN A 203.200.95.144 proxy IN CNAME mail0

19. Sample Reverse Zone File DNS Setup $TTL 86400 $ORIGIN 200.203.in-addr.arpa. 95 IN SOA ns1.iitk.ac.in. root.ns1.iitk.ac.in. ( 200605091 ; Serial 10800 ; Refresh - 5 minutes 3600 ; Retry - 1 minute 1209600 ; Expire - 1 weeks 43200 ) ; Minimum TTL for negative answers - 12 hours IN NS ns1.iitk.ac.in. IN NS ns2.iitk.ac.in. $ORIGIN 95.200.203.in-addr.arpa. ; 142 IN PTR ns1.iitk.ac.in. 144 IN PTR mail0.iitk.ac.in.

20. Configuring Local Resolver DNS Setup /etc/resolv.conf server 127.0.0.1

21. Test DNS DNS Setup nslookup host dig Test your DNS with the following DNS diagnostics web site: dnsstuff.comdnsstuff.com

22. QUESTIONS?

23. Web Server WEB SERVER

24. Web Server HTTP (Hyper Text Transfer Protocol) is used to transfer web pages from a Web Server to Web Client (Browser) Web Pages are arranged in a directory structure in the Web Server HTTP supports CGI (Common Gateway interface) and application languages like Java, PHP etc. HTTP supports Virtual Hosting (Hosting multiple sites on the same server) Popular Web Servers Apache Windows IIS IBM Websphere Web Server

25. Apache Setup APACHE SETUP

26. Web Server Web Server Setup Apache Web Server is used Daemon is httpd (service httpd start/stop/restart)

27. Files used by Apache Web Server Setup Configuration file: /etc/httpd/conf/httpd.conf Log files: /var/log/httpd/access_log and /var/log/httpd/error_log Modules /etc/httpd/modules Default Document Root /var/www/html

28. Apache Configuration Directives Web Server Setup Server Name Min and Max Servers Document Root CGI Enable/Disable User Directory Directory Index Mime Types Modules Access Restrictions Secure Server Virtual Hosting

29. Basic Settings Web Server Setup Change the default value for ServerName www. in httpd.conf and put the website content in /var/www/html Additionally you can configure Name based Virtual Hosting (allow more than one websites to run on the same server)

30. Virtual Hosting Web Server Setup NameVirtualHost *:80 ServerName server-name DocumentRoot path-to-virtual-document-root ServerName server-name DocumentRoot path-to-virtual-document-root

31. QUESTIONS?