1. DNS Domain Name System By Alexandros Zampas B101 Coursework The Technology Context

2. Domain Name System was Introduced in 1984 and made the use of the Internet really practical. DNS in general the backbone of the Internet and tells your computer for example that www.google.com is attached to the IP Address 209.85.147.147 so that there is no need to remember the IP address but just the Domain Name (www.google.com). It is like an Internet Phonebook where your computer requests the IP address for a Domain Name.www.google.com In the DNS database all the devices connected to the Internet have a unique IP Address and each one of those addresses have their own Domain Name assigned to it. So every time you write an address in your browser and you press enter automatically you search for the IP Address for the Domain Name entered. What is the Domain Name System? (DNS)

3. How does DNS work?  The DNS works in a tree structure  First of all we have the root zone and it consists from the Top Level Domain. The Top Level Domain identifies if the Domain Name is about an organisation for example.org, or for a country for example.uk and.com which is commonly used for business.  After that we have the second level Doman Names which corresponds to the organisation or company etc. For example toshiba.co.uk  Then we have the sub domains which is created from the second-level domain name for example laptops.toshiba.co.uk (which is also registered to the company).  And then we have the host name that identifies the resource (server) on the network, for example offers.laptops.toshiba.co.uk.com.uk root.org.net.eu.info.co.ac.toshiba.laptops.printers.performance.offers.new.home.televisions This part is controlled by Internet Authority This part is controlled by Toshiba Company

4. III Most important components With the significant increase of Internet use the DNS came up dividing the information into smaller parts being stored in different servers. The three main components of DNS are:  The Domain Name Space, for example laptops.toshiba.co.uk which is separated in 4 parts  The Domain Name Servers which hold the information about the tree structure.  The Resolvers  Iterative Resolution: When the resolver asks the closest server for the answer, if the server doesn’t have the answer then it sends back the IP Address of the server that might have the correct answer.  Recursive Resolution: It asks the server for the final IP Address about the requested Domain Name. If the server is not authorized for the specific Domain Name then it searches through other servers until the correct IP Address for that Domain Name is found, and the answer is then sent to the original server. Fourth-Level Domain Third-Level Domain Second-Level Domain T0P-Level Domain

5. DNS, UK and the law One of the UK legislations about the DNS is about protecting Domain Names. There are people who keep buying Domain Names which are famous or in the future a company might need them, so they would sell them in the future making big profits. The possession of the Domain Name from the wrong person or business could lead into a fraud and damage the genuine business by selling things that have nothing to do with the original business. So if the owner of a business owns a registered trademark then has the legal right for that Domain Name. The legislation on child pornography. The Internet Watch Foundation in UK alert the Internet Providers for child pornography and they take the right actions.

6. About DNS size: DNS servers is a group of physically connected servers that all together hold the Domain Name Space. I believe that the entire size of the Domain Name System is unlimited based on the fact that by increasing the number of the Domain Names Servers that store the databases, it has very small effect on the DNS performance. So by increasing the DNS servers we get more space. But since the Domain Names point to IP Addresses, we get the limitation of those Addresses. Until now IPv4 was used where approximately 4.3 Million Addresses where available. This year this number was exceeded and this is why IPv6 was invented, where trillions of Addresses are available. Off course it is almost impossible to run out of these IPv6 Addresses.

7. Issues A big limitation of the DNS it is it’s age. Nobody ever thought that Internet would be used from all of us so much in our everyday life. Due to this expansion security issues and lack o efficiency are a fact. The concern is that just one breach of security would compromise the entire system. Another limitation is the speed of resolving IP Addresses. Requests for Domain Names are stored in many servers until the server that can best handle that query is found. The speed would increase significantly if the DNS had the answer in it’s cache memory. Internet Service Provides, virus protection companies and many owners of websites work together to prevent cache poisoning which is the main thread of the DNS, mitigation and amplification attacks.

8. Conclusion After all this research I strongly believe that DNS is the backbone of the Internet. It is the solution which made the use of the Internet easy and capable for all of us. Most people don’t even know it’s existence but everybody should since everybody use it everyday. I conclude that by increasing the number of the Top Level Domains and the physical servers that would increase the DNS size, so by expanding all of these we don’t have any definitive size.

9. References:  Donald E. (1998). Bigger Domain Name System UDP Replies. Retrieved from : http://www.ietf.org/proceedings/42/I-D/draft-ietf-dnsind-udp-size-02.txt  P. Mockapetris. (1987). DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION Retrieved from : http://tools.ietf.org/html/rfc1035  From Wikipedia, the free encyclopedia. (30 November 2011). Domain Name System. Retrieved from : http://en.wikipedia.org/wiki/Domain_Name_System.html  Alvin.(2006).DNS Components. Retrieved from : http://www.accuwebhosting.com/Articles/DNS_COMPONENTS.html  An illustration of the tree-like DNS structure. Retrieved from : http://baraknaamafinal.appspot.com/dns.jsp  DNS Architecture. (2011). Retrieved from :http://technet.microsoft.com/en-us/library/dd197427(WS.10).aspx  Brain, M. & Crawford, S. 2000, April 1. "How Domain Name Servers Work" Retrieved from : http://www.howstuffworks.com/dns.htm  From Wikipedia, the free encyclopedia. (2011, December 2). IPv4 address exhaustion.. Retrieved from : http://en.wikipedia.org/wiki/IPv4_address_exhaustion  Jonietz E (2009). Internet Domain Names Go International. Retrieved from : http://www.technologyreview.com/blog/editors/24309/  Ward M. (2010). Internet approaches addressing limit. Retrieved from http://www.bbc.co.uk/news/10105978