AWS Route 53 Basics

Amazon Route 53 is a highly available and scalable cloud Domain Name System (DNS) web service. It is designed to give developers and businesses an extremely reliable and cost effective way to route end users to Internet applications by translating names like www.medium.com into the numeric IP addresses like 192.0.2.1 that computers use to connect to each other. Amazon Route 53 is fully compliant with both IPv4 and IPv6.

AWS named it Route 53 as DNS operates on port 53. It provide following list of features to AWS customers:

1. Domain Registration : Amazon Route 53 offers domain name registration services, where you can search for and register available domain names. It is same as other Domain Registration service line Godaddy.
2. Transfer Domain : Route 53 also provides the functionality of transferring domain from some other registrar to AWS, like you have purchased domain from Godaddy but now you want to migrate it to AWS, you can do this via Route 53 Transfer domain functionality.
3. Health checks and monitoring : With the help of Route 53 DNS failover routing policy, it also take care of making your servers available all the time. If any of your primary webservers are not responding, it take care of directing traffic to other working primary or secondary servers.
4. Traffic flow : It routes end users to the best endpoint for your application. This best endpoint is calculated based on routing policy you have set on your hosted zone.

Suppose you have purchased a domain called medium.com from Godaddy and now you want to link this domain with your webserver. From linking we mean whenever user enters medium.com on browser, it needs your webserver IP address to redirect the request to your webserver. Route 53 helps us to create this mapping. Your webserver can be hosted via any hosted platform like EC2, ECS etc.

First you have to create a Hosted zone in Route 53 to configure this mapping. Hosted zone is basically a Route 53 concept. It is equivalent to traditional mapping file which had set of resource names belong to same parent domain and their IP addresses.

Similary Hosted zone would have record sets belong to same parent domain. For example if your domain name is medium.com, you could have recordsets with domain names “medium.com”, “support.medium.com”, “hr.medium.com” etc and their IP address mapping. If you have noticed all these “support.medium.com”, “hr.medium.com” etc have common parent domain “medium.com” . These are called subdomains of parent domain. This hosted zone cannot have any recordset with name internal.medium.in as our parent domain is “medium.com” and subdomain cannot have different suffix i.e “.in”.

This Hosted zone name would be same as your domain name. If you are buying a domain from AWS only, It will by-default create a Hosted zone with same name as domain name inside Route 53. Like S3, AWS Route 53 service is also a global service in your AWS account and not specific to a region.

All Hosted zone by default have 2 record sets. First record is related to NameServer(NS) and other would be related to Start of Authority (SOA). Let’s talk about What is NA and SOA.

Hosted Zone name - exampletest.com with NS and SOA default record sets

Whenever you enter medium.com on web browser, first it checks if browser have cached IP corresponding to medium.com. If it does not find there, it checks whether ISP(Internet Service Provider) DNS have cached IP for medium.com. If it finds, it would return to browser and you will land to medium.com website. If it does not found in ISP DNS, Request go to RD(Root Domain).

Root Domain is the highest hierarchical level of a site and is separated from the Top Level Domain by a dot

Root domain look at the domain name and check what is its TLD(Top Level Domain) and based on that it will forward the request to respective TLD. In this example our Top Level Domain is “.com”. TLD points to all its subdomains.

Name server (NS) record has the same name as your hosted zone. It lists the four name servers that are the authoritative name servers for your hosted zone. From the authoritative name servers we mean servers which have webserver address of your domain. It by-default creates 4 name servers to increase its availability level so that if one name server is down or not responding, it can send request to other name server to fetch the address of your webserver.

The State of Authority or SOA is a mandatory record in all zone file. It basically contains administrative information about zone.

Other than NS and SOA, Hosted Zone can contains records of following type as well :

A Record : A stands for Address here, it mean it is address type record. In this record you can add a domain/subdomain and its IP address. IP address here would have IPv4 address(4 bytes)

AAAA Record : This is same as A record but it is used for IPV6 type records.

CNAME Record : CName stands for Canonical records. This is used when you want to give another name to your domain. For example your domain name is medium.com but you want even if the customer is entering story.medium.com, you want to redirect her to medium.com. In that case you can create a CNAME type recordset inside your medium.com hosted zone and build this mapping.

There are multiple other type of records supported by Route 53, these were the few popular ones.

Now lets talk about the Route 53 routing policies.When you create a record, you choose a routing policy, which determines how Amazon Route 53 responds to queries:

• Simple routing policy — Use for a single resource that performs a given function for your domain, for example, a web server that serves content for the example.com website.
• Failover routing policy — Use when you want to configure active-passive failover. Here you have to associate health check with your routing policy which will monitor performance of your webserver, if it is down it will redirect the traffic to secondary servers.
• Geolocation routing policy — Use when you want to route traffic based on the location of your users. It can be used for cases where your webserver is rendering local content. For example your website is rendering content in Hindi if request is coming from India and it is in English when request is coming from US. In that case you can configure the routing based on the location from where request is coming.
• Geoproximity routing policy — Use when you want to route traffic based on the location of your resources and, optionally, shift traffic from resources in one location to resources in another.
• Latency routing policy — Use when you have resources in multiple AWS Regions and you want to route traffic to the region that provides the best latency.
• Multivalue answer routing policy — Use when you want Route 53 to respond to DNS queries with up to eight healthy records selected at random.
• Weighted routing policy — Use to route traffic to multiple resources in proportions that you specify. Here you can configure weight to each entry, Suppose you want to render 80% traffic to webserver A and 20% to webserver B.