CCS 101 Session 6 Lecture Notes PDF

CCS 101 SESSION 6 Presented by: Dr Mohamed Badawy  Overview Internet IP URL DNS HTML Recap Question and Motivation How do computers communicate across different networks?  Internet A network of interconnected networks. Requirements of Internet ⚬ Device...

CCS 101 SESSION 6 Presented by: Dr Mohamed Badawy  Overview Internet IP URL DNS HTML Recap Question and Motivation How do computers communicate across different networks?  Internet A network of interconnected networks. Requirements of Internet ⚬ Device (computer) ⚬ Router ⚬ Internet Service Provider (ISP) ⚬ Web Browser ⚬ Connection Line  IP Internet Protocols that define communication rules over internet. IPv4 ⚬ 32-bits split to 4 groups ⚬ Bit Groups determine network and host ids. ￭ e.g. 190.15.25.240 ￭ Yellow -> Network ID, Purple -> host id.  IPv6 IPv4 gives limited numbers of hosts. IPv6 ⚬ uses 128 bits broken to 16 parts (uses hexa-decimal) ￭ e.g. A8FB:7A88:FFF0:0FFF:3D21:2085:66FB:F0FA ⚬ Benefits ￭ Has built-in authentication. ￭ Allows for efficient routing. ￭ Allows a wider range of IP addresses.  Subnetting Divide a network to smaller networks ⚬ e.g. divide network to different university departments. We apply a subnet mask to get the host/network id by the following: ⚬ Convert the IP to Binary. ⚬ Apply AND mask with 1s equal to the number of net bits and 0s equal to the host bits. ⚬ The result is the net id. ⚬ Applying not to the mask and redoing the same operation again gives you the host id. Subnetting Example 1- given the IP address 10.128.240.50, and given that the net id is 29 bits long. Find the host and the net ids. Solution IP in binary: 00001010.10000000.11110000.00110010 Net Mask: 1111 1111.1111 1111.1111 1111.1111 1000 (29 1s and 3 0s) IP & Net Mask = 00001010.10000000.11110000.00110000 = Net ID Host Mask = ~Net Mask = 0000 0000.0000 0000.0000 0000. 0000 0111 IP & Host Mask = 00000000.00000000.00000000.00000010 = Host ID  Private and Public IPs To reduce the need for many IPs, we divide the internet to a series of private networks. Every network does not have direct access to the internet. Every computer in a private network has a private IP address known only for the private network (can be duplicated across different networks) Computers connect to Router (which has a public IP address) Public IP addresses cannot be duplicated.  URL They provide an easy way to access pages (instead of using IP addresses directly) They take this form: ⚬ protocol://webaddress/path/filename ￭ https ￭ www.something.com ￭ user/first year/ ￭ Student name  DNS Maps domain names (e.g., must.edu.eg) to IP addresses. Contain database of URLs and their matching IP addresses. When the user enters a url: ⚬ The DNS searches the database for the URL and translated it to IP. ⚬ It then communicates with the internet to fetch the page requested (if found) ⚬ The browser displays the retrieved information. Time for HTML!