How GeoDNS Works

The most powerful DNS-level routing techniques.

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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.

Basic DNS Lookup

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.

basic DNS lookup

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Terms You Need to Know

A

The 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.

basic GeoDNS lookup

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Standard GeoDNS Lookup

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.

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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.

GeoDNS with EDNS

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.

basic DNS lookup

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Before we dive into how GeoDNS queries are answered, let's do a quick recap of the different GeoDNS services Constellix offers.

Types of GeoDNS Services

GeoIP Services

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.

Global Traffic Director

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.

IP Filters

Answers are based on the country, state, geographical coordinates, ASN (network), IP address, or subnet of incoming queries.

GeoProximity

Uses the GeoIP engine to automatically calculate which servers are closest to your end-users for the fastest response.

GeoIP Services

Global Traffic Director

Pro's

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.

Con's

GeoIP routes the querying client using an IP to Location database (ie. Maxmind, etc.). Occasionally, the querying client’s IP address may be incorrectly mapped as the network could have recently moved. This could result in an incorrect GeoDNS lookup.

Limited to regional routing.

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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.

GeoIP Configurations

IP Filters

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.

If you want to set up this configuration for your own domains, you can follow the tutorial or watch this video.

basic DNS lookup

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basic DNS lookup

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GeoProximity

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.

If you want to set up this configuration for your own domains, you can follow the tutorial or watch this video.

GeoProximity + IP Filters

You can combine GeoProximity rules with IP Filters for even more granularity. Queries will first be answered based on IP Filter rules(s). If there is no matching rule, then the query will be answered based on the GeoProximity rule(s).

basic DNS lookup

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Global Traffic Director

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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.

global traffic director lookup

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You can create a different version of your domain for each of the five GTD regions. GTD effectively decreases resolution times and offers the most accurate location-based routing.

If you want to set up this configuration for your own domains, you can follow the tutorial or watch this video.

GTD + GeoIP Services

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)

GTD and GeoIP lookup

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