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Route 53

DNS

Domain Nam System which translates the human friendly hostnames into the machine IP addresses (google.com -> 172.217.18.36)

DNS Terminologies

  • Domain Registrar: Amazon Route 53, GoDaddy...
  • DNS Record: A, AAAA, CNAME, NS...
  • Zone File: Contains DNS records
  • Name Server: resolves DNS queries
  • Top Level Domain (TLD): .com, .us, .vn,...
  • Second Level Domain (SLD): amazon.com, google.com,...

How DNS works?

Amazon Route 53

Amazon Route 53 is a highly available and scalable Domain Name System (DNS) web service. Route 53 connects user requests to internet applications running on AWS or on-premises.

Route 53 - Records

Each record contains:

  • Domain/ subdomain Name - eg: example.com
  • Record Type - eg: A, AAAA...
  • Value - eg: 12.12.23.34
  • Routing policy: how route 53 responds to queries
  • TTL: amount of time the record cached at DNS Resolvers

Route 53 - Record Types

  • A: maps a hostname to IPv4
  • AAAA: maps a hostname to IPv6

  • CNAME: maps a hostname to another hostname

  • The target is a domain name which must have an A or AAAA record

  • Can't create CNAME record for the top node of a DNS namespace (Zone Apex). Eg: You can not create for example.com but you can create for xxx.example.com

  • NS - Name Servers for the Hosted Zone

  • Control how traffic is routed for a domain

Route 53 - Hosted Zones

A hosted zone is a container for records, and records contain information about how you want to route traffic for a specific domain, such as example.com, and its subdomains (acme.example.com, zenith.example.com). A hosted zone and the corresponding domain have the same name. There are two types of hosted zones:

  • Public hosted zones contain records that specify how you want to route traffic on the internet.
  • Private hosted zones contain records that specify how you want to route traffic in an Amazon VPC

CNAME vs Alias

CNAME

  • Point a hostname to any other hostname (app.mydomain.com -> blabla.anything.com)
  • Only for non root domain

Alias

  • Point a hostname to an AWS Resource (app.mydomain.com -> blabla.amazonaws.co)
  • Works for root domain and non root domain
  • Free of charge
  • Native health check
  • Can not set the TTL
  • Can not set an alias record for an EC2 DNS name

Route 53 - Routing Policies

Routing Policies defines how Route 53 responds to DNS queries. Route 53 provides following policies:

Simple

  • Typical route traffic to a single resource
  • Can specify multiple values in the same record (a random one is chosen by the client)
  • Can not be associated with Health Checks

Weight

  • Control % of the requests that go to each specific resource.
  • Can be associated with Health Checks
  • Use case: load balancing between regions, testing new application version...

Latency based

  • Redirect to the resource that has least latency close to us
  • Can be associated with Health Checks

Failover

Geolocation

  • This routing is based on user location
  • Specify location by continent, country
  • Should create Default record (in case there is no match on location)
  • Can be associated with Health Checks

Geoproximity

  • Route traffic to your resources based on the geographic location of users and resources

Multi-Value Answer

  • Use when routing traffic to multiple resources
  • Up to 8 healthy records are returned for each Multi-Value query
  • Can be associated with Health Checks (returns only values for healthy resources)

Route 53 - Health Checks

  • HTTP Health Checks are only for public resources
  • About 15 global health checkers will check the endpoint health
  • Route 53 health checker are outside the VPC -> they can not access private endpoints (You can create CloudWatch Metric and associate a CloudWatch Alarm, then create a Health Check that checks the alarm itself)