What is the DNS? System converts domain names to IP (Internet Protocol) addresses URL (Uniform Resource Locator) → IP address DNS Problems Limitations in IP addresses available Reducing availability of specific domain names

Size of the Domain Name System IPv4 (Internet Protocol version 4) 32 bit numerical code eg Over 4 billion unique IPv4 addresses mathematically available 2 32 = IPv6 (Internet Protocol version 6) Quadruple amount of bits (128 bits) in Hexadecimal eg. 3ffe:1900:4545:3:200:f8ff:fe21:67cf Around sixty thousand trillion trillion addresses available URL Address includes the domain name of a website. Text in domain name syntax usually associated with content or institution of website. Ends with generic TLD (Top Level Domain) representing type of institution

Components for DNS operations Database Contains Domain Name Space which maps out domain names and separates name syntax strings from the TLD and SLD (Second Level Domain) using a tree diagram Name Server Database of URLs and corresponding IP address, also used to help clients find information in the DNS tree. Contains information required to translate domain name into an IP address in its database that is saved in its local disk Client Requests specific information from the DNS tree. Deals with sending and receiving database records

Domain Name – University of Portsmouth World Wide Web prefix SLD (Second Level Domain) - Academic TLD (Top Level Domain) – UK Country Specific Domain Name Syntax (string) - University of Portsmouth IP address for

Function of the Domain Name System Makes it easier for users to remember addresses of websites while making it easier for computer databases to store addresses Introduced so that users do not have to remember a string of numbers Invented in 1984 Replaced the HOSTS.TXT file made in the 1970s Contained the name to address mapping for a few hundred hosts

DNS Legislations in the UK.gov.uk Second level domain Only available for government bodies, certain departments and agencies. Only available upon request & approval by UKERNA on behalf of Cabinet Office Domain name syntax must not contain promotional material unless approved.uk Top Level Domain Not available for public use as a SLD must be used (eg..co.uk,.org.uk etc.) Country Specific TLD Represents the name of a country Examples:.au,.mx,.sy,.fr,.de,.es No restriction on the use of other countries' TLDs in the UK Blocking access to certain websites Redirects traffic going to a specific IP address to different one Mainly used by governments to block access to specific websites In the UK there not many websites which are not available for public viewing Domain name syntax Must not infringe anyone else's trademark rights

Total Sites Across All Domains, August 1995 – December 2011

Limitations to continued DNS operation Restriction of IPv4 addresses Exponential growth of new websites and amount of devices using the Internet provides an uncertain future for the current DNS with more IP addresses IPv4 was designed in the 1970's (UAE - Arabic) (Syria - Arabic) (India - Hindi) Domain Name Syntax Limited names available can make it hard for companies to choose a domain name Growing number of TLDs means more domain names are becoming available on other TLDs and country specific TLDs Domain names in other languages such as Arabic provides more availability Examples: امارات. سوريا.. भारत

IPv6 (Internet Protocol version 6) IPv6 Feasibility Supports much more unique addresses Networking compatibility already supported and built in to Microsoft Windows, MacOSX and Linux "The switchover will result in roughly 5,000 addresses for every square micrometer of the Earth's surface", Simson Garfinkel, Technology Review Magazine Disadvantages: Slower, less secure and even easier to perform peer-to-peer sharing Transition to version 6 means that every program, application and modem router will have to be able to handle 128 bit hexadecimal addresses Eastern Asian countries such as China and Korea Republic Most enthusiastic about the transition to version 6. Only have 62.1 million allocated IPv4 addresses compared to the USA which has 3 billion out of the 4 billion addresses Everlasting Solution? Number of IP addresses will have increased by a factor of 7.9x10 28

References: Liu, C., Albitz, P., (2006). DNS and BIND, 5th Edition. United States of America: O'Reilly Media. Dostálek, L., Kabelová, A., (2006). DNS in action. Olton Birmingham, GBR: Packt Publishing Ltd. Davidowicz, D., (1999). Domain Name System (DNS) Security. Retrieved from Garfinkel, S., (2004, January). Internet 6.0. Technology Review. Netcraft. (2011, 9 th December). December 2011 web server survey. Retrieved from