GeoDNS is easily the most powerful set of tools on the DNS level. These services can be used to improve the performance of your domains on a global scale, build your own CDN, and deliver unique content based on qualities of your end-users.
Before we get into how each service works, let's do a 10 second recap of how DNS works.
Every time you type a domain into your browser, you are performing a query. This query is looking for the IP address that maps to the your domain. We are going to look at the path your query takes to find that answer, so that we can better understand how DNS and GeoDNS work.
Click the diagram on the right to see DNS in action. For a more detailed explanation please view the video explanation at LearnDNS.
An end-user or querying client is perceived as the resolving name server. The resolving name server is specific to the the end user trying to access the domain.
Every client that accesses the Internet will go thorugh a resolving name server to resolve an FQDN (fully qualified domain names) to an IP address.
When you add GeoDNS into the mix, things get a little more complicated. GeoDNS services allow you to make routing decisions based on the location of your end-users.
For the next two illustrations, we will be using an IP Filter to make routing decisions. We'll talk more about IP Filters in just a minute.
Do you see the problem? Routing decisions aren't specific to the end-user's true location. Instead, decisions are made based on the location of the resolving name server, which could be close by or a Public DNS server.
But things are changing! Recently there has been a big push to have more resolving name servers support RFC 7871 which is the EDNS client subnet. This means that actual clients' IP addresses are making the original query.
The resolving name server actually says “I am asking this information on behalf of xx.xx.xx.xx/24”. This is very important to understand because the response provided by the authoritative name server can be much more specific than if the normal IP of the resolving name server is used.
When you use an EDNS client subnet with GeoDNS, the response to the querying client would look like this.
Now that we have a basic understanding of how queries can be answered with GeoDNS and EDNS client subnet, we can start looking at more advanced configurations.
Decisions are made based on the location or specific attributes of the querying client. Geo IP services can be applied to A, AAAA, CNAME, and ANAME records.
GTD uses zone-based routing to direct end-users to name servers within their current region: US East, US West, Asia-Pacific, Europe, or Oceania.
Allows you to make very specific rules and configurations based on the querying client. Very granular responses regions, and networks.
Very accurate in determining which zone configuration will be used with the use of the IP Anycast+ network. Proven to be the most reliable GeoDNS solution in the world.
Constellix is the only service that is able to overcome the disadvantages of both of these services. You can combine the Global Traffic Director with GeoIP services to effectively fix incorrectly mappings. Simply create unique GeoIP rules and filters within your GTD enabled domain to fix any incorrectly geo-targeted IP address.
You can use filters to send end-users to a specific IP or hostname; or restrict access. Users can be filtered based on their network, ASN, IP address, or location. The diagram illustrates the four different types of IP Filters you can create with Constellix.
GeoProximity uses our GeoIP engine to automatically calculate which of your predefined servers is closest to your end-users. If you have multiple web or application servers in a high traffic region, this is a great way to slash resolution times and deliver location-specific content.
Constellix’s Global Traffic Director (GTD) uses our powerful IP Anycast+ network to identify the geographical location of the querying client. When GTD is enabled for a domain, you can create regionally defined rules for answering queries.
When you combine the GTD with GeoIP services (IP Filters and GeoProximity) you can correct any errors caused by incorrect IP to Location mapping databases; as well as incorrect lookups by poor peering practices.
The illustrations shows how GTD is able to detect the true location of a user with a European IP address and accurately route them to a nearby server in US East.
Constellix is the only platform that offers these two services together, giving you the most accurate configurations in the industry. (Patent pending)