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Working with AWS's Domain Name System: Amazon Route 53


Route 53 Introduction
Health checks

This course has been replaced with a new course that you can find here


Amazon's Route 53 provides three services: record creation (which registers the human-readable names you'd like associated with your web domains), request handling (to direct web traffic to the right servers), and health checks (to ensure that traffic isn't being directed to servers that can't handle the load).

Very few web-facing AWS deployments can really be considered complete without applying the tools Route 53 makes available, so cloud expert David Robinson will guide you through some of the more common - and useful - domain-related tasks, including:

If you'd rather focus on AWS cloud computing basics, try our AWS introductory courses.

If you have thoughts or suggestions for this course, please contact Cloud Academy at support@cloudacademy.com.


Welcome to AWS 262, Amazon Route 53. This is an intermediate course that will provide in-depth discussions, as well as demonstrations that you can follow along with. Route 53 is Amazon's highly available and scalable domain name system.

During this lesson, we will cover a range of topics from purchasing a domain name to the various types of routing configurations available to support your low latency and fault tolerant architectures. Before we get into Route 53, we will do a quick refresher on what DNS is and the general terminology that will be used throughout this lesson.

The domain name system, DNS is a hierarchical distributed naming system for computers, services or any resource connected to the internet or a private network. It associates various information with domain names assigned to each of the participating entities and is responsible for the translation of domain names to numerical IP addresses. A common analogy used to explain DNS, is that it is the phone book of the internet, as you can look up a human-friendly name. For example, www.CloudAcademy.com, and it will provide the respective IP address.

The domain name space consists of a tree of domain names with each node or leaf of the tree holding one or more resource records which contain information associated with the domain. If we look at a domain, and for the purpose of this, we will use Cloud Academy's domain, which is cloudacademy.com. A key point to remember is that when determining the hierarchy of domains, they descend from right to left, and each label to the left specifies a subdivision or subdomain to the right. So in our example, the route is the uppermost part of the DNS Hierarchy.

And in this case, the top level domain is the last segment dot com, and Cloud Academy represents a subdomain of com. And if it was Apac.CloudAcademy.com, than APAC would be a subdomain of Cloud Academy, and so on.

What is Route 53? Route 53 is Amazon's highly available and scalable domain name system that provides secure and reliable routing of requests, both for services within AWS and infrastructure that is outside of AWS.

Route 53 is able to provide this service through its global network of authoritative DNS servers that reduce latency and can be managed via the management console or API hosted zones. A hosted zone is a container that holds information about how you want to route traffic for a domain such as CloudAcademy.com and its subdomains. This hosted zone contains a collection of resource records which are managed under a single domain name.

Route 53 supports the following type of zones: Number one, a public hosted zone. This zone determines how traffic is routed on the internet, and number two, a private hosted zone. For Amazon VPC, this zone determines how traffic is routed within the Amazon VPC. Your resources are not accessible outside the VPC, and you can use any domain name you wish. Domains supported by Route 53: AWS supports generic top level domains, TLD's and geographic domains, however it is recommended to check that your domain is supported, if it is one of the new and upcoming generic TLD's, in the documentation on AWS supported domains.

Resource record types Route 53 supports the most common resource record types, which will meet the need for the majority of customer DNS requirements as shown in this table.

Routing policy: When you create a resource record set, you must choose a routing policy that will be applied to it, and this then determines how Route 53 will respond to these queries.

The routing policies are: Simple routing policy. This is the default policy, and it is for single resources that perform a given function. For example, a single web server, in this case, all responses to the DNS query are based solely on the values you entered into the resource record when you created it.

Weighted routing policy: This is suitable when you have multiple resource records that perform the same function, such as a website, and you want to route traffic between them based on proportions that you specify. To determine the probability, the formula is the weight of individual resource record divided by the sum of the total value in resource record set. For example, if you have three servers, weights are assigned two, two and six, a sum of 10. The first two are selected 20% of the time, and the last one 60% of the time.

Latency routing policy: This is suitable when you have resources in multiple EC2 data center locations that perform the same function, and you want Route 53 to respond to DNS queries with resources that provide the lowest latency, Failover routing policy: Public hosted zones only. This is when you want to configure an active passive failover in which a single resource takes all the traffic when it's available. And in the event that it fails, the secondary takes the load. Please note that this cannot be configured in a private hosted zone.

Geo-location routing policy: This lets you route traffic based on the geographic location of your users. You can define geographic routing policies based on continent, country or state in the U.S.

For this type of routing, there are a few things that you need to be aware of. Number one: If you have overlapping geographic regions, for example continent and country, it will direct to the smallest denominator, and in this case, that would be country.

Number two: You cannot create two geo-location resource record sets that specify the same geographic location.

Number three: This works by mapping out the addresses to geographic locations, and if you create a geo-location policy and don't create a default resource record set, those IP addresses that can't be mapped to a location, for locations that are specified Route 53, will return a no answer.

Limits on Route 53. This table lists the limits on Route 53 that you need to be aware of when planning your Route 53 implementation, and you will note that many of these limits can be increased, but you will need to raise a support request to AWS for the request, and if you exceed these limits, you should request early to minimize disruption. You can request an increase in the limits from the AWS management console.

Pricing. Pricing for Route 53 is based on hosted zones, the number of queries and the type of these queries. For example, geo-location and latency, health checks configured, and of course, any domain names that you purchase from AWS directly.

The pricing breakdown is: Hosted Zones are billed at $.50 per hosted zone, per month, for the first 25 hosted zones, and $.10 per hosted zone, per month, for additional hosted zones. The monthly hosted zone prices are not pro-rated for partial months. And a hosted zone is charged upon setup, and on the first day of each subsequent month. To facilitate testing, a hosted zone that is deleted within 12 hours of creation, is not charged. However, any queries on that zone will be charged at the defined rates.

Standard Queries. $.40 per million queries for the first billion queries per month, and $.20 per million queries over a billion queries per month.

Latency-based Routing Queries. $.60 per million queries for the first billion queries per month, and $.30 per million queries over one billion queries per month.

Geo-DNS Queries. $.70 per million queries for the first billion queries per month, and $.35 per million queries over a billion queries per month.

All of the above query prices are pro-rated. For any queries to alias records that are mapped to elastic load balancers, Amazon Cloudfront distributions, and Amazon S3 website buckets are free. And these will appear on the Route 53 usage report as Intra-AWS-DNS-Queries, Intra-AWS-LBR-Queries and Intra-AWS-Geo-Queries.

Health Checks. Health checks are based on the type of check, and whether or not this is an AWS or non-AWS endpoint, and the price for this is shown in the table.

Domain Names. If you wish to purchase a domain from Amazon, you should refer to the website for current pricing for TLDs.

Service Level Agreements. AWS has an SLA in place for 100% availability of Route 53. And their definition of 100% is that Amazon Route 53 did not fail to respond to your DNS queries during a monthly billing cycle. In the event of a service outage, AWS works on a service credit model, which are calculated on one day of service credit that is based on the previous monthly billing cycle prior to the outage, which may then be applied to future payments from you. To claim a service credit, you need to open a case in the AWS support center. For more details on the SLA requirements, please review the Route 53 SLA documentation.

About the Author
Learning Paths

David's acknowledged hands on experience in the IT industry has seen him speak at international conferences, operate in presales environments and conduct actual design and delivery services.

David also has extensive experience in delivery operations. David has worked in the financial, mining, state government, federal government and public sectors across Asia Pacific and the US