Domain Name Servers - DNS explained : IndicHosts.net
|DNS can be tricky especially when first registering a domain name or transferring your website to a web hosting provider. The strangest things can happen that would lead you to believe that your new web hosting provider is at fault. 99.99% of the time the hosting provider is not to blame and we will show you why. |
There is an easy way to explain DNS and that is the whole purpose of this article. Some things are described in detail as required but keep in mind, that you may choose to re-read this a couple of times to be sure it has been absorbed. You can always come back at another time and do some follow up reading as well.
There are a number of areas involved in DNS that we will familiarize you with.
1. IP Addresses
2. Service Providers
3. Domain Names
4. Domain Name Registrars
6. The Propagation Process
7. Things That Can Go Wrong
The internet is comprised of a number of different layers much like the cable TV service provided to your home. Cable TV companies can provide you with not only television, but telephone and internet access all through one cable.
The internet provides the same functionality and as a result there are a number of different ways to communicate over it. For the purpose of web hosting, we will be discussing matters relating to the TCP/IP layer. This is just one of the many protocols used to communicate over the internet.
TCP/IP = Transfer Control Protocol OVER Internet Protocol.
In English: We Talk To Each Other OVER An Addressing Scheme.
1. IP Addresses
TCP is the language that is spoken over the internet and IP is the addressing system that is used to find each computer. Our computers talk to each other by identifying themselves using numerical addresses much like the address on your home or for your telephone. When one computer wants to speak to another computer, it all boils down to an address or what we call an "IP Address".
Here is an example: 192.168.100.100
Just about every computer, server, router, or gateway on the internet has its own IP address to uniquely identify itself. When computers communicate with each other, they send little messages called "Packets" to each other. Each one of these packets for the most part contains the sending computers IP address and the receiving computers IP address.
Gateways and routers use this information to send the packets across the internet from the origin to the destination. IP addresses are assigned to service providers in blocks of numbers.
An example would be: 192.168.100.1 ~ 192.168.100.100
This would give the service provider a total of 100 IP addresses to use for their network equipment such as servers, routers, gateways and modems. Typically service providers receive thousands of IP addresses to be used on their networks. IP addresses in the United States are assigned by ARIN, the American Registry for Internet Numbers. They are the assigned numbers authority and they control who gets IP addresses in the US .
2. Service Providers
The service providers will use these IP addresses to identify their network equipment so that they can conduct business on the internet. There are many different types of service providers but for the purpose of this article, we will only discuss two of them.
ISP – Internet Service Provider
WHP – Web Hosting Provider
The ISP is the company that provides you with access to the internet. Without them, you would not be able to send email or surf the world wide web . When you connect to your ISP, they will assign your computer one of their IP addresses. This IP address will be used to identify your computer while you are connected to the internet.
The WHP is a company that provides a means for individuals or businesses to publish a website on the internet. When the website is published, it is placed on a special computer known as a server that is connected to the internet via a high-speed connection. The WHP has already assigned this server one of their IP addresses.
Now, let's summarize what we have learned by looking at a typical internet users experience:
Let's say that you want to surf your newly published website. You connect to your ISP and your ISP assigns your computer an IP address automatically. You then open up your web browser and type in your website's domain name: yourdomain.com.
Then you hit enter. In a torrent of un-restricted energy, your computer lashes out a packet containing your request. That request is blasted across the internet jumping through routers and gateways, across wires and beamed to satellites and back down to Earth again. After traveling several thousand miles in just a few milliseconds, it finally arrives at your WHP's web server because it contains the IP address of the computer you are looking for.
The server then responds by sending a copy of the website's home page back to your computer because it knows the IP address of the computer that made the request. You are now looking at your published home page in your PC's web browser in merely a few seconds.
But there is an element that we have not discussed yet. We mentioned it briefly, but intentionally left it out because we wanted you to have a good understanding of the basics of internet communication.
The element we are referring to is known as DNS. But before we can cover DNS we must understand why it is needed and that brings us to domain names.
3. Domain Names
A domain name is what you typically enter into your web browser when you want to visit a website. We also use them when sending email.
Domain names provide a fast and convenient way of reaching our favorite website's and sending email to each other. It is easy to remember the name of a friend's website or a company that you like to shop with rather than trying to remember a number like: 192.168.100.100
So, we use domain names to surf website's. But if computers use IP addresses to talk to each other, then how does a domain name work? Well, this is the whole reason for DNS.
4. Domain Name Registrar
It all starts when you register your domain name with your domain name registrar. We will just call them the "registrar". If you want to have your own domain name you will need to register one through a company called a Domain Name Registrar. Examples of such companies are GoDaddy, Dotster and Register.com. The domain registrar has tools that allow you to search for and register an available domain of your choosing.
The registrar is more or less at the top of the whole DNS chain. When you register a domain name, the domain registrar is the one responsible for publishing your domain name at the root DNS level.
DNS is a software program that runs on a dedicated computer known as a DNS server. DNS serves two primary functions:
1) To translate domain names into IP addresses.
It's much easier to remember a domain like mydomain.com than a sixteen digit number like 192.168.100.1. DNS servers make translating or "Resolving" this information fast and seamless. When your computer needs to know the IP address for yourdomain.com it asks a DNS server (usually the one provided by your ISP.)
2) To act as authority for designated domain names.
Wherever you decide to host your website, the network you are on must have its own DNS servers. In fact, it is an industry-wide standard to have at least two DNS servers or more. These servers will act as the authority for your domain name because your network provider will put a special entry in their DNS server as it relates to your domain name that says: YOU ARE HERE! Technically this is known as an "A" record for "Authority".
There are literally hundreds of thousands of these DNS machines world wide. They ARE the yellow pages of the internet and they contain information about your domain name. Keep in mind that no single DNS server holds all the domain names for the internet; they only hold the names that they are responsible for, and a few pointers to find the rest.
Some DNS servers strictly store names while others are doing the work of providing lookup services for computers that need to look up names. Many DNS servers do both. Technically, the server that is responsible for a particular domain is called the "Authority". Remember the "A" record?
There are a few pieces of crucial information stored in a DNS server with regard to your domain name. This information as a whole is known as your "DNS Record". In it you can find a variety of other pieces of information (or records) about your domain name.
Contents of a DNS record:
Your actual domain name
Indicates which DNS server is the authority
The mail server that accepts mail for your domain
DNS record expiration (in minutes)
For the purposes of this article we will focus on the domain name, the ‘A' record (or your WHP's DNS servers).
6. The Propagation Process
As we said before, your domain registrar is the one responsible for publishing your domain name at the root DNS level. When it is published it is placed into a directory that is broadcast out to primary DNS servers around the world. The primary DNS servers broadcast out to secondary DNS servers and so on and so forth.
This process is known as propagation and it can take upwards of 72 hours to complete. Propagation refers to the amount of time it takes for all the DNS servers everywhere around the world to recognize the fact that either a new domain is being registered, a domain name has been changed, or that the authority for that domain has changed.
Other reasons why it takes so long is obviously the size of our planet and the total number of DNS servers that require updated information. DNS servers are always updating themselves and changing dynamically during the course of any given day. When or why one DNS server will receive updated information before another is a complete mystery and best described as the ebb and flow of DNS propagation.
In most cases, your DNS propagation will complete well within the 72 hour period but you can't be sure that everything is fine until you wait out the 72 hours! Once propagation is complete, anyone, anywhere on the internet should be able to visit your hosted website.
Now, let's summarize what we have learned:
A DNS server is much like a phone book directory with names and addresses of website's When you enter a domain name into your computers web browser, your computer will ask your ISP's DNS servers if they know the IP address of the requested domain. Chances are, if you are looking for a website like google.com, your ISP's DNS servers will already know about it because someone else most likely requested it before.
If they don't know the answer, they will ask other DNS servers until they find the DNS server that is responsible for the domain. When they find an answer, your ISP's DNS server will store the answer its own database for future reference and send the answer back to your computer. Your computer then uses the IP address to directly contact the web server that is hosting the requested website. This all happens very fast.
7. Things That Can Go Wrong
Now that you understand DNS and how it works, let's talk about problems common to DNS. Earlier I mentioned that strange things can happen when it comes to DNS especially when you are registering a new domain name or transferring your website to a new WHP.
Here is an example:
You have just activated a hosting account at a WHP. Once your account is activated (which is right-away) we make an entry in our DNS servers regarding your new domain name and set it as the authority.
We then provide you with information that you use to modify your nameservers at your domain name registrar. Once you have updated the nameservers, the propagation process begins.
During that time you may experience strange occurrences. This is because not every DNS server that needs to know, knows about your domain name. Take your ISP for example. They use two DNS servers, well, 24 hours after making your nameserver changes, only one of your ISP's DNS servers might receive the update regarding your domain name and the other might not.
As you use your ISP's services and browse the web, you will switch back and forth between their DNS servers. You won't even know it is happening , it's all done in the background. You only need one DNS server to resolve domain names into IP addresses, which server you use at any give time is determined by load and demand. If one server is overloaded with requests (demands), you will be directed to the other DNS server for the answer. This is known as load-balancing. The very next time you click a link in your browser, you may be directed to another of your ISP's DNS servers to give you the answer.
If only one of these servers can resolve your domain to an IP address and the other can not, what you will experience would be as though your website was going up and down. One moment it is there, the next it is not. Hey! What the...???
Here is another example:
A friend or associate of yours can somehow see your new website and you can not. This is most likely because his ISP's DNS servers are able to get the information at that time, where your ISP's DNS servers can not. Huh?!?
Here is yet another example:
What if you inadvertently provide the wrong nameserver information to your registrar such as entering one DNS server correctly but the other wrong? In this case, you would have experienced these problems right up to and well beyond the 72 hour propagation period. You'll have to update that information again and wait another 72 hours. Ouch!
Here is a neat one:
You are transferring your hosting to a new WHP. During propagation you are working on development of some pages in your website. But you notice that when trying to view your most recent changes, they appear and then vanish or they don't appear at all.
Think about the load-balancing DNS servers again. One server has information about your OLD WHP and the other has information about your NEW WHP! This can be a weird experience and may take some time to figure out. What you really need to do is WAIT OUT THE 72 HOURS!
You see, if you avoid making changes to your website during a transfer/propagation period, you will always have a consistent functional website available to your visitors. They won't know that you have switched WHP's because as far as they can tell, they are just browsing your website. They won't realize that you are in a state of propagation and that from one minute to the next, they are potentially browsing your site from two different WHP's
How about this one:
What if the WHP enters the wrong information? No doubt, this would cause problems as well. The truth is that it does happen but not very often. Put it this way; at Datavend we have had only a single DNS entry error since we've been in business. This is mostly due to the fact that we use scripts to create our hosting accounts and enter DNS information. This eliminates human intervention, unless of course the customer activating the hosting account misspells their own domain name. Yikes!
All of these occurrences are very common and each one of them will result in a phone call to the WHP asking why the server is going up and down. When in reality the server is fine. The problem is that the domain owner has not let 72 hours pass by, after which these and other similar problems will have vanished.
So as you can see, you must have patience and wait the full three days before you can try to determine if your website is experiencing a problem or not.