1. Domain Name & Domain Name Server (DNS) IP = a string of numbers –Computers can work on them efficiently –But meaningless and difficult to remember for human –  Domain Name Give to each host (with IP) for easy identification (by human) Easier to remember

2. www.yahoo.com Better than 66.218.71.112

3. Domain Name www.yahoo.com.hk www.info.gov.hk intranet.kcc.edu.hk pta.mst.edu.hk intranet.kcc.edu.hk

4. Host Name Sub-domain (Name of server) 2 nd level domain (Name of org) Generic Code (top-level domain) Country code (top-level domain)

5. Top-level Domain –Country Code Indicate the geographical location of the host computer (server).ca /.cn /.hk /.jp /.uk /.us –Generic Code Indicate the type of organization.com /.edu /.net /.org /.idv /.mil

6. 2 nd -level Domain –Represent the name of the organization Sub-Domain –Represent the host (server) of the domain –One domain can has many sub-domain –Most common : www –Map to its IP E.g. 218.188.3.5 = aero.kcc.edu.hk

7. Domain Name Server Since –IP is used by computer –Domain Name is more convenient to human A specialized host –Domain Name Server –Used to translate the domain names into the corresponding IP address –Or vice versa