WHAT IS DNS?
The Domain Name System is a hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities
The Domain Name System (DNS) is the phonebook of the Internet. Humans access information online through domain names, like nytimes.com or espn.com. Web browsers interact through Internet Protocol (IP) addresses. DNS translates domain names to IP Addresses so browsers can load Internet resources.
Each device connected to the Internet has a unique IP address which other machines use to find the device. DNS servers eliminate the need for humans to memorize IP addresses such as 192.168.1.1 (in IPv4), or more complex newer alphanumeric IP addresses such as 2400:cb00:2048:1::c629:d7a2 (in IPv6).
What is DNS and its purpose?
The Domain Name System (DNS) is a central part of the internet, providing a way to match names (a website that you are looking for) to numbers (the address for the website). Anything connected to the internet – laptops, tablets, mobile phones, websites – has an Internet Protocol (IP) address made up of numbers.
How does DNS work?
The process of DNS resolution involves converting a hostname (such as www.example.com) into a computer-friendly IP address (such as 192.168.1.1). An IP address is given to each device on the Internet, and that address is necessary to find the appropriate Internet device – like a street address is used to find a particular home. When a user wants to load a webpage, a translation must occur between what a user types into their web browser (example.com) and the machine-friendly address necessary to locate the example.com webpage.
In order to understand the process behind the DNS resolution, it’s important to learn about the different hardware components a DNS query must pass between. For the web browser, the DNS lookup occurs “ behind the scenes” and requires no interaction from the user’s computer apart from the initial request.
What’s the difference between an authoritative DNS server and a recursive DNS resolver?
Both concepts refer to servers (groups of servers) that are integral to the DNS infrastructure, but each performs a different role and lives in different locations inside the pipeline of a DNS query. One way to think about the difference is the recursive resolver is at the beginning of the DNS query and the authoritative nameserver is at the end.
What are the steps in a DNS lookup?
For most situations, DNS is concerned with a domain name being translated into the appropriate IP address. To learn how this process works, it helps to follow the path of a DNS lookup as it travels from a web browser, through the DNS lookup process, and back again. Let’s take a look at the steps.
Note: Often DNS lookup information will be cached either locally inside the querying computer or remotely in the DNS infrastructure. There are typically 8 steps in a DNS lookup. When DNS information is cached, steps are skipped from the DNS lookup process which makes it quicker. The example below outlines all 8 steps when nothing is cached.
The steps in a DNS lookup:
- A user types ‘example.com’ into a web browser and the query travels into the Internet and is received by a DNS recursive resolver.
- The resolver then queries a DNS root nameserver (.).
- The root server then responds to the resolver with the address of a Top Level Domain (TLD) DNS server (such as .com or .net), which stores the information for its domains. When searching for example.com, our request is pointed toward the .com TLD.
- The resolver then makes a request to the .com TLD.
- The TLD server then responds with the IP address of the domain’s nameserver, example.com.
- Lastly, the recursive resolver sends a query to the domain’s nameserver.
- The IP address for example.com is then returned to the resolver from the nameserver.
- The DNS resolver then responds to the web browser with the IP address of the domain requested initially.
- The browser makes a HTTP request to the IP address.
- The server at that IP returns the webpage to be rendered in the browser (step 10).
WHAT IS DNS CLIENT SERVICE?
The DNS Client (Dnscache) service resolves and caches Domain Name System (DNS) names for the computer. The DNS Client service must run on every computer that performs DNS name resolution. DNS name resolution is needed to locate domain controllers in AD DS domains. The DNS Client service is also needed to enable the location of the devices that are identified through DNS name resolution. Windows 7 includes both Internet Protocol version 4 (IPv4) and Internet Protocol version 6 (IPv6) protocol stacks that are installed and enabled by default. DNS name queries and registrations can involve IPv4 address records (A records) and IPv6 address records (AAAA records).
If the DNS Client service stops, the computer cannot resolve DNS names or locate Active Directory domain controllers, and users cannot log on to the computer.
Computers must perform both A and AAAA queries to determine the best method of connectivity to the endpoint that is wanted. By obtaining IPv4 and IPv6 addresses, there is an increased chance of access to the wanted endpoint if one of the addresses is unreachable. The DNS Client service minimizes the impact on DNS servers when performing DNS name queries through the following behavior:
- If the host has only link-local or Teredo IPv6 addresses assigned, the DNS Client service sends a single query for A records. For more information, see the Teredo Overview on Microsoft TechNet.
- If the host has at least one IPv6 address assigned that is not a link-local or Teredo address, the DNS Client service sends a DNS query for A records and then a separate DNS query to the same DNS server for AAAA records. If an A record query times out or has an error (other than name not found), the corresponding AAAA record query is not sent.
This service is installed by default and it startup type is Automatic. When the DNS Service is started in its default configuration, it logs on by using the Network Service account.
The DNS Client service is dependent upon the following system components:
- NetIO Legacy TDI Support Driver
- TCP/IP Protocol Driver
- Network Store Interface Service
- NSI proxy service driver
Advantages of DNS
1. Internet Dependency Internet has become an important aspect of our daily life such that people and companies cannot carry out their works without internet. DNS makes it easier to use the internet by remembering all the IP addresses. In fact without DNS, internet would simply not exist. 2. Internet Speed One of the key features in DNS is that it can offer high speed connections. Individuals and organizations mostly take use of this speed. 3. Security Some DNS servers are specifically designed for security purposes such that it has become an important component for your home or work connections. Whenever hackers try to hack the servers, their attempts are prevented gaining access into your systems. However if it is a large organization with lots of sensitive informations, you need other security measures as well. 4. IP Address Conversion DNS allows users to categorize and archive search terms without needing to remember IP addresses. All the domains are converted into IP addresses when the name is given to the search engines. Therefore, you don’t need to memorize IP address for each and every site that you access frequently. 5. Stability For some reasons the IP address of websites may change. So users are in need to keep up to date of this information too. This can be very laborious task. But for facilitating this, DNS system constantly updates IP address so that users can avoid important efforts.
Disadvantages of DNS
1. Registry Control Registry control of DNS is under ICANN. Which means that no other organizations will be able to control them. Hence, the concept of net neutrality is questioned here. ICANN is known as a non-profit organization which originates from one single country. 2. Client Informations Informations about the client who started the name resolution do not normally get carried by the DNS queries. Due to this the server side will be able to know the IP address of DNS servers. It can be manipulated by hackers. 3. Server Breakdown When the DNS server gets broken down, the World Wide Web would crash too. Al though in the presence of back up servers and root servers. This is because once the server crashes the connection to the local network will get disconnected not allowing the clients to reach them. 4. DNS Attacks One of the major problems that DNS undergoes is the DNS attack. In here the original DNS address is replaced with a fake one so that users are redirected into fraudulent websites. From this attackers can gather sensitive informations such as band account details. 5. Troubleshooting DNS issues are generally difficult to troubleshoot. This is due to its distributed nature and geographical locations.