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Domain Name System (DNS)

  • What does Domain Name System (dns) mean?
  • DNS (Domain Name System) is a hierarchically distributed naming system for computers, services, the Internet, or any resource connected to a private network, for partitioning internet space, naming partitions, and organizing communications between departments.
  • Each unit that makes up the Internet network only has its own IP address. These IP addresses are reduced for easy-to-remember addresses such as www.site_name.com for use by users. DNS servers keep the IP addresses of Internet addresses registered.


  • Domain names assigned to each participating organization associate various information. Most notably, it turns (translates) domain names that are easily memorable by humans into the numeric IP addresses required for computer services and devices worldwide. DNS is a basic component for the functionality of most internet services, because it is the basic administrative service of the Internet.


  • Domain Name System DNS assigns responsibility for mapping domains to their IP addresses by assigning authoritative name servers for each domain. Authoritative name servers are responsible for the supported domains and can give authority to the subdomains instead of the alias servers. This mechanism provides distributed and fault tolerant service and is designed to prevent the need for a single centralized database.


  • DNS also specifies the technical functionality of the underlying database service (core). DNS protocol – defines the detailed description of the data structures used in the DNS and exchange of data communication (exchange) – as part of the Internet Protocol Suite. Historically, previous administrators’ services such as DNS were not scalable to large or global administrators because they were originally based on text files and notably the HOSTS.TXT resolver. DNS has been widely used since the 1980s.


  • It provides two main namespaces, the Internet hierarchy domain name and the Internet Protocol (IP) address space. The DNS system provides the domain name hierarchy and provides translation service between it and the address space. Internet name servers and the communication protocol enable the Domain Name System. A DNS name server is a server that stores domain DNS records for its domain name; The DNS name server responds to queries against the database.


  • The most common types of records stored in the DNS database are; DNS zone authority (SOA), IP addresses (A and AAAA), SMTP mail exchangers (MX), nameservers (NS), pointers for reverse DNS lookups (PTR), and domain aliases (CNAME).


  • Although not designed to be a general purpose database, DNS can also store human queries such as automatic machine searches for things like DNSSEC records or records of Personnel (RP) records for other types of data. For a complete list of DNS record types, see the list of DNS record types. As a general purpose database, DNS can also be seen in spam using spam using real time black hole list stored in DNS database. For Internet naming, or for general purposes, the DNS database is traditionally stored in the configured zone file.


  • Dns Objectives
  • Every object on the Internet must have an internet address, every server that interacts with it, and an internet address. This address is 32 bits or 128 bits long depending on whether the protocol level is IPv4 or IPv6. The field name allows the use of names that people can identify with, identify with, corporate identity, and brand, rather than the 32 or 128 bit length. For example, y.x.com provides the Domain Name System with the domain name in conjunction with the IP address. In order; Com, x.com, and y.x.com are nested Internet domains or domains.


  • My site, which provides a phone book service for the Internet by translating human friendly computer system names to IP addresses, is a common analogue for describing DNS. For example, the domain name is translated to addresses www.example.com, (IPv4), and 2606: 2800: 220: 6d: 26bf: 1447: 1097: aa7 (IPv6). Unlike a phone book, DNS can be quickly updated by allowing the location of the service on the network to change without affecting end users who are still using the same host name. Users benefit from a meaningful Uniform Resource Locator (URL) and when they use an email address without knowing how the computer places services.


  • The relationships created by the Domain Name System do not necessarily have to be one-to-one. More than one IP address can be assigned to a domain name. This is the case when there is heavy demand. At addresses like Wikipedia.org, yahoo.com, google.com, this happens a lot. But more widespread, many domain names can be assigned to a single IP. This is called “Virtual Hosting”.


  • The Domain Name System shows a hierarchical structure. Top-level “generics” (gTLD) such as .com, .org, .net, .int, .edu, .info, .biz, .aero, .travel, .jobs, .gov, (CcTLD) such as .us, .de, .uk, .jp, .az. Finally, several top-level regional names such as .eu and .asia have been added.


  • The history of DNS
  • The naming problem on computer networks first appeared in Arpanet, the father of the Internet. In the 1970s, ArpaNet was small enough to be comparable to today’s networks, and served only a few hundred expressible systems. At that time, a single file for naming was found, and all other systems solved the problem of naming this file periodically on its own.


  • The HOSTS.TXT file containing address-name definitions was stored by SRI on a computer called the SRI-NIC (Stanford Research Institute – Network Information Center). This file has been edited so that each name corresponds to a name. The new name definitions and changes on the Arpanet were made via e-mail sent to SRI, and the copy of HOSTS.TXT was taken with the File Transfer Protocol.
  • The connection bang on Arpanet paralleling the use of TCP / IP had problems in assigning an original name to many servers and each computer for name resolution. In addition, only a very high amount of bandwidth was spent for name resolution. Nevertheless, it was not always possible for the names databases used to be compatible.


  • After that, Arpanet started to search for a more scalable name resolution structure. Paul Mockapetris was assigned to do this. In 1984, Mockapetris published RFC 882 and RFC 883, which describe the Domain Name System (DNS). These were later updated by the current RFC 1034 and RFC 1035.


  • Structure of DNS
  • The DNS system consists of name servers and resolvers. Computers configured as name servers maintain IP address information that corresponds to host names. The resolvers are DNS clients. DNS clients have the addresses of DNS servers or servers.


  • When a DNS client wants to find the IP address for a computer’s name, it contacts the name server. If the name server, or DNS server, has such a name in its database, the name will send the corresponding IP address to the client. Records in the DNS database must be entered manually, one at a time.


  • Internet addresses are first allocated according to the countries. Addresses such as tr, de, uk at the end of the addresses indicate the country where the address is located. For example, it shows Germany, UK UK. A country map is not used for US addresses because the country that created DNS and similar applications is the US. On the other hand, a US extension has been created for private organizations in the United States. Internet addresses are allocated to the lower segments such as com, edu, gov after leaving the countries. These expressions correspond to top-level domains in DNS. Top-level domains are as follows.


  • Resolving – Finding a requested record
  • For example, there is an IPv4 address corresponding to http://google.com. Analyzing software performs two types of processes; Recursive and nonrecursive. The type of the query is determined according to the RD (recursion required) bits sent in the queries. Servers responding to non-recursive queries give consecutive name servers in response. If the resulting query is not recurring, you may be given an IP directly or a “machine not found” reply for http://google.com. But in a recursive query, you can give the IP of another name server to find the answer.


  • Authoritive Nameserving
  • It is a server that keeps information about an area. For example, it is the name server that records the MX (Mail eXchanger), NS (Name Server), and A (Address) records of the yildiz.edu.tr field (known as Resource Record – Resource Record).


  • DNS Query
  • DNS; Mail servers are hierarchical structures that hold information such as domain names and IP addresses. A DNS client queries DNS servers for name resolution. DNS services; It resolves a DNS name that the user enters and creates the information associated with that name, such as the IP address.
  • As a result of a scan before making a DNS query, the DNS information is seen as ‘name servers (NS)‘ or ‘domain servers‘. After accessing this information, more information is available through the DNS query.
  • As a result of a misconfigured DNS server, an attack known as ‘Zone Transfer’ can be made. With the transfer of the zone, a lot of information about the target of the DNS query can be reached. Regional transfer; It contains all the data about the domain the DNS server is running. This important information includes the name, IP address, and operating system of the e-mail server.
  • As a precaution against zone transfers, the TCP port number 53 in the firewall (firewall) or in the routers in the gateways should be kept closed against any incoming unauthorized connections.
  • As a protection method from the DNS query, if the domain is not a domain, it does not end with the extension -tr. In domain names that are private domain, personal information is ‘Private’. So the real information is hidden. But, the private domain is not available in every domain provider.


  • Precautions against DNS Policies
  • DNS information is important information. When setting up DNS servers, little information about the system should be given. When a name is given to the server, no name should be given to invoke the operating system. In addition, the space for the operating system used must be left blank.


  • Firewalls must be used or attention must be paid to the ports in the routers in the gateways to prevent unauthorized connections. DNS, port 53 with UDP; Zone Transfer uses TCP port 53, so this must be taken care of. These ports must be closed against unauthorized connections.


  • Use a separate DNS server for the internal network, separate for the internet. If the user wants to exit internete, the internal DNS server receives this request and acts as a proxy server to forward the request to the external DNS server. So someone outside the network will only access the name in the external DNS.
  • Com: Represents commercial organizations.
  • Edu: It shows education institutions.
  • Org: indicates non-commercial, non-governmental institutions.
  • Net: Shows the networks that are responsible for the Internet backbone.
  • Gov: Government shows affiliated institutions.
  • Mile: Military institutions are shown.
  • Num: Shows places where you can find phone numbers.
  • ARPA: Indicates places where reverse DNS query can be performed.


  • This post has recently been added to extensions like us. Field names are used in a structure called a tree structure and branched according to a certain rule. Outside the United States, addresses in all countries connected to the Internet end with the country of ISO 3166 in that country.
Domain Name System (DNS)
Author: wik Date: 8:13 pm

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