Presented by Joe Gigliotti & Ben Lodsin RFC 1034 (November 1987) ◦ Concepts and Facilities Introduction to the system and its components Explains the concepts of the Domain Name Space and Zones RFC 1035 (November 1987) ◦ Implementation and Specification Details of protocols and algorithms Invented in 1983, shortly after TCP/IP Developers: Jon Postel and Paul Mockapetris Replaced the HOSTS.txt deployment system, a Since its original development, there have been multiple revisions DNS, while useful, has major security flaws because of its need for constant record changes and updates. Short for Domain Name System, DNS’s sole purpose is to resolve hostnames (Domain Names) to IP Addresses. Works as a hierarchy system, a system with “chains of command” and resolution procedures. Referred to as the worlds largest distributed database system. While not needed for communication functionality, DNS helps provide resources to services using human readable names. The domain name space consists of a tree of domain names. Top Level Domains (TLD) consist of the following, among many others. ◦ Com. ◦ Org. ◦ Net. ◦ Edu. ◦ Gov. ◦ Mil. Each zone master is responsible for the namespace levels of itself, and all child objects. A system administrator can let another control part of the name space within his zone authority. This splits the zone into two multiple, dependent but independent, zones. A domain name usually consists of two or more labels. For example, example.com. The rightmost label conveys the top-level domain. For example, the address www.example.com has the top level domain com. Each label to the left specifies a subdivision, known as a subdomain. Example.com comprises a subdomain of the com domain, and www.example.com comprises a subdomain of the domain example.com. Subdivisions can theoretically go 127 levels deep. In this example, the DNS recursor consults three name servers to revolved the address www.wikipedia.org A DNS resolver interactively queries a root name server, org. and wikipedia.org. name server in its quest to revolve the IP address associated with the domain name www.wikipedia.org. Device checks its hosts file (if present) then checks its local cache. If the lookup doesn’t exist, the device uses its configured DNS servers to send out a request for a resolution. If the DNS server being asked holds a record for the domain name, it sends it back. If not, it refers to the TLD’s root server. The TLD server provides the address of the name server holding the record for the domain name. The client sends a request to the name server for the desired record of the domain name. The name server responds with the requested record holding the IP Address associated with the domain name. Using the provided resolution, the device access the network service using the discovered IP Address. Reverse lookups are essentially the same as normal query's. Instead of trying to find an IP address associated with a domain, DNS uses PTR records to associate a domain with IP address. This allows for circular references to network resources and also helps validity of the response lookup. TTL is an acronym for Time to Live In order to help elevate stress on the vast amount of lookups of the same domain, domain servers/clients Cache their lookup using the TTL value. This means that once example.com is resolved from a network device, it is locally kept until it is purged. By doing this, the same lookup doesn’t need to be completed again and consume bandwidth and resources. The same technique is used for ARP, RIP, and other network protocols. "Howstuffworks "How Domain Name Servers Work"" HowStuffWorks.Com. 02 May 2008 <http://computer.howstuffworks.com/dns.htm>. "The Lazy Admin: DNS Tips #15 - DNS Resolution Explained." The Lazy Admin. 28 Apr. 2008 <http://thelazyadmin.com/blogs/thelazyadmin/archive/2006/02/2 1/DNS-Tips-_2300_-15-_2D00_-DNS-Resolution-Explained.aspx>. "Understanding DNS." 23 May 1997. 03 May 2008 <http://www.insan.co.id/tutor.eng/dns.html>.
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