DNS Service - Route53

DNS stands for domain name system, which is used to convert domain names into respective IP addresses (either IPv4 or IPv6).
A domain name could be suffixed with a top level domain name (and an additional second level domain name, usually the country domain). These top level domain names are controlled by IANA (Internet Assigned Numbers Authority).
All domains can be obtained through domain registrars, which are then registered into InterNIC (a service of ICANN) and store in a database called WhoIS.
The query of each DNS request comes through: root record, name server (NS) record, start of authority (SOA) record.
There are different types of DNS records, including:
- A record: A stands for "address", the fundamental type, directly translates a domain name to the IP address;
- CNAME record: C stands for "canonical", translates one domain name to another, cannot be used on naked domain names (zone apex record);
- Alias record: map one domain name to another;
- MX record: for "mail exchange" only;
- PTR record: pointer records, for reverse DNS lookup.
ELBs (elastic load balancers) do not have pre-defined IP addresses.

Routing Policy

Simple routing policy: can create only 1 basic record of each name and type, but can route traffic to a single record with multiple values (such as an A record with multiple IP addresses), in which case the multiple values are returned in random order.
Weighted routing policy: allows to split traffic based on different weights assigned, which can be used together with health check. Route53 will remove those whose health check has failed.
Latency routing policy: allows to route traffic based on the lowest network latency for the end user.
Failover routing policy: used to create active/passive setup. Route53 uses a health check to monitor the primary site, and switches to the DR site if the primary site is down.
Geo-location routing policy: allows to route traffic based on the geographic location of the end user.
Geoproximity routing policy (traffic flow only): route traffic based on the geographic location of the resources and the end user, can adjust the routing by providing a bias.
Multi-value answer routing policy: can create multiple records of the same name and type, and also able to associate health check with records. When a client makes a DNS request with multi-value routing policy, Route53 will randomly select up to 8 healthy records at a random order.