Internet Propagation
What information do the Name Servers have?
The information inside of the name servers is referred to as the “Zone File”. It contains a number of different pieces of information which are classified into different sections called records.
1) NS Record – This record is just an internal record that points back to the Name Server it resides inside of. (example: inside of the name server “ns1.site.com” is an NS Record that points back to “ns1.site.com”.
2) MX Records – This controls where an incoming email should be sent to. MX stands for the term “Mail Exchange”.
3) A Records – This is the entry that controls what IP address to point to. There are usually a few different Address Records being used at one time:
example.com A 209.25.195.50
www.example.com A 209.25.195.50
ftp.example.com A 209.25.195.50
mail.example.com A 209.25.195.36
Each of these A Records can go to a different IP address if you wish. You may have the A Record of (mail.example.com) point to the IP address of your email server and then you can set your MX Record to be: (mail.example.com). This lets email come in to the correct server for your domain.
4) CNAME Records – This stands for Canonical Name which is just too hard to say so people just call it CNAME. This is an entry that just points to another name, not an IP address. As an example you may point your domain name (example.com) to the IP address but then setup a CNAME for (www.example.com) to point to the name (example.com):
www.example.com CNAME example.com
When someone looks for the name of (www.example.com), the CNAME say to go to (example.com). Since the entry for (example.com) is an A Record that points to the IP Address, the persons web browser goes to the correct website in the end.
Internet Propagation
What exactly is “propagation”? Why is it important? Basically the term propagation is used to talk about the amount of time it takes for the entire Internet to learn of a change with the name servers. There are a few types of changes where this can become important.
The most common type of change is to change the Name Servers your domain name is using. This is usually done when you already have registered a domain name with a company such as www.GoDaddy.com but you decide to get web hosting at another company such as 1&1 Web Hosting. The advantage to this is their name servers usually are already pointing everything correctly for your account with them. You don’t need to make any further changes to get it to work from that point on.
Another type of change you make is to keep your current Name Servers and just change one of the records inside them to point to a new location. This could be a new IP address for an “A record” or a new mail server for an “MX record”.
The time period for this change to take effect on the Internet can range from just a few minutes up till 72 hours. This depends on the speed of update getting put into the Name Servers as well as how long the rest of the Internet uses the old information before looking up new records.
Once a lookup for a domain names website or email server is done that information is kept and reused for a period of time before a new lookup is done. For example; someone using their cable modem in Australia sends you an email. The company that provides the internet connection in Australia for that user will look up your domain name and find the MX record so they can send that email to your domain.
Once that MX record lookup happens the company in Australia will keep using that same information for a period of time, maybe 12 – 24 hours, and not look it up each time someone sends an email. If you changed your Name Servers right after they did a lookup on your domain they will not learn of the new information till they do a new lookup in 12 – 24 hours. They will keep sending information to the first MX record they found.
Why is this important to you and your site? If you plan on making changes to your Name Servers on your domain keep in mind that the entire Internet will not learn about the change at the same time and it can take 24 – 72 hours for this “propagation” period to complete.
I hope I didn’t get into too much detail, I tend to get carried away at times. It’s not really important to understand everything I covered in the article but the main important facts are the Name Servers are what control all the pointing of traffic for your website. If you wish to make a change to point to a new location for website or email, expect a 24 - 72 hour delay to get completed.
Thanks,
Jim
How does the Internet work?
DNS - How sites are found on the Internet
Every day there are billions of emails and website requests making its way across the Internet, it’s almost surprising things work as well as they do. What I’m going to talk about today is the basic process of how these connections are made and allow the Internet work. It’s all thanks to “DNS”.
DNS stands for Domain Name System, it’s basically the “phone book” of the Internet. It helps turn a domain name that‘s easy for a human to remember into the IP address which computers love using.
“Please understand that my explanation of DNS will be a very simple overview because this can be a very in-depth and detailed topic. I don’t feel like boring you (or myself) with a detailed explanation of the subject. If you are interested in the very fine points of DNS I strongly suggest checking out the book DNS and BIND if you wish to “geek it up”.
if you wish to “geek it up”.Simple illustration of how the Internet works:
The process starts by first connecting to the Internet through your ISP (Internet Service Provider) and opening your web browser. When you enter a website address, such as http://web-hosting-basics.com, you are asking your ISP to first find that location on the Internet and then send you that web server to see the site.
If your ISP does not have information showing what IP address to connect you to, they first need to find out what Name Servers are assigned to that websites domain name. This information is controlled by the company you registered your domain name through. This websites domain was registered through [GoDaddy Link] and I changed my name servers to those of my web hosting company.
This information is able to be seen in what’s called the “Whois” record which is basically like a public record of the domain name:
Registrar: GODADDY.COM, INC.
Whois Server: whois.godaddy.com
Referral URL: http://registrar.godaddy.com
Name Server: DNS1.SUPREMEDNS.COM
Name Server: DNS2.SUPREMEDNS.COM
Since your ISP didn’t know the where on the Internet to send you they found the name servers and request that information from them.
The Name Servers pull that information up and then reply back to the ISP with the answer. Now that the IP address has been learned, your ISP sends you to the site you want to see.
I’m going to stop at this point and in my next update I’m going to cover the information inside of these Name Servers as well as the most frustrating part of working with Name Servers and making changes to them = Propagation. What it is and how to deal with it.
If you are interested in learning more about this as well as other areas of how the Internet works yet you want something written for regular people (aka - non geeks) then you should check out How the Internet Works by Preston Gralla.
This is a great book that is filled with clear and easy to understand explanations as well as great graphics that help to better explain the subject matter being discussed.
Thanks,
Jim.