Introduction – ComputerNetwork Part 1 Jayaseelan Vejayon
Internet• Interconnection of networks worldwide• Allows communication and sharing of information between connected systems• Uses Internet Protocol• Popular applications – World Wide Web – E-mail – File transfer & sharing – Voice and video streaming
Any difference between‘Internet’ and ‘internet’?• YES!• internet is interconnection of networks• Internet with capital I refers to the internet as in the world wide web• Confused? Read again!
What is needed to visit awebsite in the Internet?• A machine installed with TCP/IP protocol• Gateway / Router / Proxy server• DNS server• A browser program• The URL / IP address of the website
TCP/IP• TCP and IP are communication protocols for the Internet• Try this – Check the network properties of your machine to find out whether your machine has TCP/IP installed. Write the IP address of your machine. You can use ‘ipconfig’ command to find your machine’s IP address. – Use the ‘ping’ command to check whether you have connectivity with your friends’ machines. – Type ‘ping/?’ in the command prompt to view the options of this command. If you want to continuously ping, what option will you use?
Internet Protocol• Every computer that communicates on a network needs its own IP address• Static and Dynamic – Static addresses are permanently configured for a machine – Dynamic addresses are given by DHCP servers – Question: When you are connected to Internet through your home Streamyx, what type of IP are you getting: static or dynamic? Why?• Public and private – Public IPs can be seen on the Internet – Private IPs can only be used within a broadcast domain • ranges associated with addresses 10.0.0.0, 126.96.36.199, and 192.168.0.0 through 192.168.255.0. • Question: what type of IP is your machine’s? Private or public? Is it static or dynamic?
IPv4 and IPv6• Two standards of IP addresses being used today• IPv4 – has 4 billion addresses but they are not enough for the growing number of machines connected to the Internet• IPv6 – has 2128 addresses=3.4x1038 addresses – ISPs are moving into implementing IPv6 addresses because of its many advantageous features• Fact finding: Find the role of National Advanced IPv6 Center in the implementation of IPv6 technology in Malaysia. Why need a National organisation to implement IPv6 addresses? Visit http://www.nav6.org to find your answers. (15 minutes)
Domain name• The name of a computer on the Internet• The domain name service (DNS) converts domain names to IP addresses• Who runs the DNS? – Millions and millions of servers – DNS database is the biggest database in the world• Some Top Level Domains - .com, .org, .net• nslookup is a command that you can use to check whether a domain name and its IP are available in a DNS server
• Try this – Find whether the domain name nav6.org is available in OpenDNS and 188.8.131.52 servers – How to do this? • Search the OpenDNS IP from the Internet and use command nslookup – OpenDNS-IP nav6.org • Now try the same command again with DNS IP 184.108.40.206 • See the results. Is the name found in the DNS servers?
URL• Uniform Resource Locator – the global address of documents and other resources on the World Wide Web – The first part of the address is called a protocol identifier and it indicates what protocol to use – The second part is called a resource name and it specifies the IP address or the domain name where the resource is located – For example, the two URLs below point to two different files at the domain nav6.org. The first specifies an executable file that should be fetched using the FTP protocol; the second specifies a Web page that should be fetched using the HTTP protocol: » ftp://www.nav6.org/sample.exe » http://www.nav6.org/v3/index.html
Internet Browser• A program used to view web pages• Question: Can you name some popular internet browsers?
A web page•Is created using HTML tags.Try this: Open Notepad and type the tags and statementsbelow.Save it with extension .htm or .html. Then open it with anInternet browser.<html><head></head><title>This is my title</title><body><H1>Hello world</H1><H2>Hello world</H2><H3>Hello world</H3></body></html>
Creating a web page using Microsoft Word• You can create a web page easily using Microsoft Word.• You can create a page by just creating a document and saving it as a web page.• If you have never tried it, try it!
Protecting your PC• What should you do? – Install antivirus – Try this by downloading a free antivirus like AVG or Avira antivirus and installing them in your PC – Enable your PC firewall – Try this – Update your operating system regularly – Try this by using Windows Update – Install a reliable anti-spyware – Try this by installing Windows Defender. You can also download and install Search & Destroy Spybot• What else should you do? – Don’t accept applications from the websites if you not sure of their contents – Don’t open attachments from your emails if they look suspicious