Used to convert human friendly domain names into an IP address, like a yellow phone book
IPv4 space is a 32 bit has over 4 billion different address
IPv6 was created to solve this depletion and has an address space of 128 bits
Last word in domain name: .com, .edu
The second word is second level domain name (optional, depends on the domain name): .co.uk, .gov.uk
These top level domain names are controlled by Internet Assigned Numbers Authority (IANA) in a root zone database
Can view this database by visit:
https://www.iana.org/domains/root/db
Because all domain name have to be unique, there needs to be a way to make sure this is not duplicated.
→ Domain registrars
A registrar is an authority that can assign domain names directly under one ore more top-level domain
These domains are registered with InterNIC, a service of ICANN, which enforces uniqueness of domain name across the Internet
Each domain name becomes registered in a central database known as WhoIS database
Popular domain registrar: Amazon, GoDaddy, ..
After bought a domain name, every DNS address begin with a start of SOA record.
Stores information about
- The name of the server that supplied the data for the zone
- The admin of the zone
- Current version of data file
- Default number of seconds for the TTL file on resource records
Name Server Records
This record indicates which DNS server is authoritative for that domain (which server contain the actual DNS records)
Top Level Domain servers uses NS records to direct traffic to Content DNS server which contains the authoritative DNS records
- type address into browser
- browser doesn't know IP address for that domain
- browser go to Top Level Domain (TLD) server and query for authoritative DNS records:
- browser: "I got this domain, I need to know the IP address of it"
- TLD server doesn't contain the IP address: has something similar to this:
- domainxxx.com. 123123123 IN NS ns.awsdns.com
- ns.awsdns.com: NS Records
- Go to NS Records, give Start Of Authority
- SOA contains DNS records
How a DNS Server works - https://www.youtube.com/watch?v=mpQZVYPuDGU
(?) ☝️How did the TLD server know which authoratative Name Server to use?
- → Domain Registrar
- Domain Registrar has right and authority to assign which Name Server they should use ns1.exampleserver.com, ns2.exampleserver.com, ...
- Registrar tell the Registry to update the TLD Name Servers
A for Address, used to translate the name of the domain to an IP address.
For example: example.com → 123.10.10.10
Length that DNS record is cached on either Resolving Server of the user local PC, in seconds
Default: 48 hrs
A Canonical Name (CName) is used to resolve one domain name to another
For eg: m.example.com is used for when user browser to domain name on their mobile devices
Instead of 2 separate IP addresses, we map one pointing to another
Map resource record sets in your hosted zone to ELB, CloudFront distributions or S3 buckets that are configured as website
Works like a CNAME record in that you can map one DNS name (www.example.com) to another 'target' DNS name elb1234.elb.amazonaws.com)
Key difference: A CNAME can't be used for naked domain names (zone apex record, domain without www)
Can't have a CNAME for http://example.com, it must be either an A record or an Alias
It can take up to 3 days to register depending on the circumstances
ELBs do not have pre-defined IPv4 addresses, you resolve to them using a DNS name
Route53 returns all values to the user in a random order
Can only have one record with multiple IP addresses
Split traffic based on weight
Tips
Health Checks
- Can set health checks on individual record sets
- If a record set fails a health check it will be removed from Route53 unit till passes the health check
- Can set notifications to alert if a health check is failed
Route traffic based on the lowest network latency
Send request to EU-WEST-2 since it has a much lower latency
Used when you want to create an active/passive setup
Normally, traffics are sent to primary site
Eg: set primary site to be in EU-WEST-2 and secondary DR Site in AP-SOUTHEAST-2
Route 53 will monitor the health of primary site using a health check
A health check monitors the health of your end points
Traffic will be sent based on the geographic location of your users
Lets Amazon Route 53 route traffic to your resources based on the geographic location of your users and your resources.
Can choose to route more traffic or less to a given resource by specifying a value - bias
A bias expands or shrinks the size of the geographic region from which traffic is routed to a resource.
Must use Route 53 traffic flow
Return multiple values, such as IP addresses for your web servers, in response to DNS queries
Route53 returns only values for healthy resources
Similar to simple routing however it allows you to put health checks on each record set
QA:
True or False: There is a limit to the number of domain names that you can manage using Route 53.
- True and False. With Route 53, there is a default limit of 50 domain names. However, this limit can be increased by contacting AWS support.
