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Know How DNS Works
Domain name Servers (DNS) are an important but invisible part of the internet, and form one of the largest databases on it. Each machine on an internet is assigned a unique address, called an IP address, which is 32 bit number and is expressed as 4 octets. The method user to represent these IP addresses is known as dotted decimal Notation". A typical address looks like this: 199.249.150.4 It is very difficult to keep in mind the IP addresses of all the websites we visit daily, because it's not easy to remember strings of numbers. However, we do remember words. This is where domain names come into the picture. If you want to connect to a particular site, you need to know its IP address but do need to know its URL. The DNS gets the mappings of the IP addresses and the corresponding names. Names and numbers DNS converts the machine names (such as www.xyz.com) to IP addresses (such as 199.249.150.9). Basically, it translates from a name to an address and from an address to a name. The mapping from the IP address to the machine name is called reverse mapping. When you type http://www.xyz.com into your browser, the browser first needs to get the IP address of www.xyz.com. The machine uses a directory service to look up IP addresses and this service is called DNS. When you type www.xyz.com your machines firsts contacts a DNS server, asking it to find the IP address for www.xyz.com. This DNS server might then contact other DNS servers on the internet. DNS is therefore is considered as the global network of servers. The great advantage of DNS is that no organization is responsible for updating it. It is what is known as distributed database. The three letter codes A DNS server is just a computer that's running the DNS software. The most popular DNS software is BIND (Berkeley Internet Name Domain) DNS is hierarchical, tree-structured system. The top is donated by'.'. And is known as the root of the system. Below the root there are seven immediate sub domain nodes and these are 'com', 'org', 'gov', 'mil', 'net', 'edu', 'Int', etc. DNS consists of two components Nameserver: This performs the task of looking up the names. Usually, there is one nameserver for a cluster of machines. If the nameserver does not contain the requested information, it will contact another nameserver. But it is not required for every server to know how to contact every other server. Every nameserver will know how to contact the root nameserver, and this in turn will know the location of every authoritative nameserver for all the second level domains. Resolver: This runs on a client machine to initiate DNS lookups. It contains a list of nameservers to use. As we have read, the function of each of these nameservers is to resolve name queries. There are three types of nameservers-primary nameserver, secondary nameserver, and caching nameserver. The secondary nameservers are configured for backup purposes. Caching nameservers only resolve name queries but do not maintain any DNS database files. It is important to note here that any change to primary nameservers needs to be propagated to secondary nameservers. This is because primary nameservers own the database records. The changes are propagated via a 'zone transfer'. HOW 'CACHING"WORKS DNS uses principle of 'caching' for its operation. When a nameservers receives Information about a mapping, it caches this information .further queries for the same mapping will use this cached result, thereby reducing the search cost. The nameservers don't cache forever. The caching has a component called time to live (TTL) and the TTL determines how long a server will cache a piece of information. So when the nameservers caches receive an IP address, it receives the TTL with it. The nameserver caches the IP address for the period of time then discards it. When a process needs to determine an IP address given a DNS address, it calls upon the local host to resolve the address. This can be done in variety of ways: Table look up. On UNIX hosts, the table is /etc/hosts. The process communicates with a local nameservers. This is named on a UNIX system. By sending a massage to the remote system that is identified from the information in the file/etc/resolve.conf. When a nameserver receives a query for a domain that is does not serve, it may send back a referral to the client by specifying better nameservers. Typically operate in the recursive manner wherein any DNS server passes requests it cannot handle to higher level server and so on, until either the request can be handled or until the root of the DNS name space is reached. The nameservers contain pointers to other nameserver with the help of which it is possible to traverse the entire domain naming hierarchy. A host with the initial nameserver addresses has to be configured. After this, it is able to use DNS protocols to locate the nameserver responsible for any part or the DNS naming hierarchy. Thus when a nameserver receives a request, it can do one of the following: It can answer the request with an IP address. This method is called iterative. In this, the client simply asks the server to resolve a domain name. The server accesses its database, finds its IP address and sends that back. If the server does not find the address, it sends back an error ;DNS not found'). Contact another nameserver and try to find the IP address for the requested name. Send back a referral to the client specifying the IP address of better nameservers. A popular user interface, called 'nslookup'is available on the UNIX system. With this, you can perform any DNS function. This program also displays the result to the user. Using is nslookup, you can obtain a listing of all the hosts in a zone. In order to do this, you first need to identify the nameserver for the zone. The threats that are associated with the DNS are due to the lack of integrity and authenticity checking of the data held within the DNS. Also, other protocols can use host names as an access control mechanism. The internet engineering task force (IETF) has come up with DNS security (DNSSEC) extensions to DNS protocol. The main objective to DNSSEC is to provide authentication and integrity to the DNS. These are provided through the use of cryptographic' About The Author Pawan Bangar, Visit us at: www.birbals.com, www.ebirbals.com, www.hbirbals.com, www.seobirbals.com
Latest News:Site: Yahoo! News Search Results for news Jeff Ritter: Beware the Tampa QB, more fantasy news, views (Sports Illustrated) We're cruising full speed ahead into Week 2 of the NFL season. It's been a wild week of news, from Tom Brady's ligaments, to Vince Young's grumpiness. There have also been a few new stories that could affect your fantasy lineup this Sunday, such as ... Futures flat; Lehman buyout news, data awaited (Reuters via Yahoo! News) Stock index futures were little changed on Friday as investors awaited news on the fate of Lehman Brothers after a slide in its stock this week heightened fears over whether the investment bank can survive. Myanmar's Suu Kyi to get family letters, news mags (Reuters via Yahoo! News) Detained Myanmar opposition leader Aung San Suu Kyi has managed to wring small concessions from the ruling generals in the form of letters from her family and some international news magazines, her lawyer said on Friday. SEC Looks Into UAL Stock Scare; Implications For Online News? (CBS News) A ton of digits have been devoted to this in other spots but the SEC's decision to investigate takes it to another level. The backstory: a six-year-old news story about UAL declaring bankruptcy made it into the Tribune-owned Sun-Sentinel 's current news flow, was picked up by a Google (NSDQ: GOOG) News bot and, via a reporter for a newsletter, made it onto Bloomberg News. After a lot of buck ... JCDecaux in talks for News Outdoor Group in Russia (AP via Yahoo! News) French outdoor advertising firm JCDecaux SA said Thursday it is negotiating to buy Russian rival News Outdoor Group from global media company News Corp. JCDecaux and News Corp. in talks to combine outdoor ad groups (International Herald Tribune) The News Corp. chief executive, Rupert Murdoch, has recently expressed nervousness about investments in Russia, where News Outdoor generated the bulk of its revenue last year. Help News pick Stadium's greatest moment (New York Daily News) The News is marking the countdown to the final game at The House That Ruth Built by reflecting on Yankee Stadium's greatest moments - and we're asking you - the reader - to help us pick out the best of the best. Get Indexed and Ranked in Google News (Search Engine Journal) Google News can bring tons of traffic and boost your site performance. If you own news site and consider it ?newsworthy?, getting included in Google news is one of the first thing you should do: Make sure your site meets all requirements to be included: Shimon Sandler did a great job listing the factors that will help [...] News Corp tightens grip on Premiere with new CEO (Reuters via Yahoo! News) Rupert Murdoch tightened his grip on German pay-TV broadcaster Premiere by appointing News Corp executive Mark Williams as CEO in a move to get the company back on track. SEC Looks Into UAL Stock Scare; Implications For Online News? (paidContent.org via Yahoo! Finance) A ton of digits have been devoted to this in other spots but the SEC's decision to investigate takes it to another level. The backstory: a six-year-old news story about UAL declaring bankruptcy made it into the Tribune-owned Sun-Sentinel's current news flow, was picked up by a Google News bot and, via a reporter for a newsletter, made it onto Bloomberg News. Site: news - Google News Gas Supplies To Poland Stable, No New Caps Planned - Operator - CNNMoney.com
MORE RESOURCES: Site: Yahoo! News Search Results for domain names "Brews.com," other domain names up for auction through Sedo (Boston Business Journal) Sedo, an online marketplace for buying and selling domain names, has announced a list of domain names that will be up for sale in an upcoming auction. Fake Antispyware Purveyor Doubles as Domain Registrar (Washington Post) A cyber gang known for aggressively spreading fake anti-spyware programs through hijacked and malicious Web sites has become an authorized reseller of domain names. Security Fix has learned that this gang is using its access as a registrar to ease the process of creating new Web sites used to push their invasive software. Klikdomains.com, also known as Vivids Media GMBH, sells Web site names in ... Aggressive Fake Antispyware Seller an Authorized Domain Registrar (CircleID) A group known for aggressive distribution of bogus anti-spyware programs through hijacked and malicious websites is found to be also an authorized reseller of domain names. Vietnamese domain name unmarketable (Vietnam Net) Bridge ? Just 3,800 domain names have been registered in Vietnamese since they were first issued 18 months ago. Most site owners said they registered their domains in Vietnamese to not miss advertising opportunities on search engines like Google or Yahoo. Presented By: BuyDomains.com, get the domain name you want! (Tom's Hardware) Choose the premium domain name for your business from the world?s largest inventory and marketplace for domain names - BuyDomains.com. We?ve helped thousands of businesses get the name they want. Call 866-830-6476 and let our Domain Consultants help you! www.buydomains.com Ads by Pheedo Premium Domain Names Including Love.Me and MovieRentals.com to Be Part of Live, Open Domain Name Auction (PRWeb via Yahoo! News) Buying descriptive and easy to remember domains offers businesses a faster way to generate traffic and build brand awareness Domain Strategies Launches Slideshow.com - From Parked Domain to Thriving Business in 45 Days (PRWeb) Domain Strategies and Gil Benatar (domain owner) partnered to develop a parked domain into a full functioning site that is poised to grow in the secured presentation and image display market. Domain owners looking for a way to derive the full value of a domain name have turned to domain development companies like Domain Strategies to realize the dream. (PRWeb Sep 12, 2008) Read the full story ... September Hosting And Domain Promos (Web Host Industry Review) September 11, 2008 -- ( Sedo, the leading online marketplace for buying and selling domain names, today announced premium domains for its September GreatDomains Auction. 29 names crowd Rosemount ballot (Minneapolis-St. Paul Star Tribune) Interest mushroomed after a mass mailing encouraged residents to run, citing an eminent-domain controversy. Site: domain names - Google News Negotiating the Domain Name Thicket - E-Commerce Times
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