8-route-53

R53 Public Hosted Zones §

A R53 Hosted Zone is a DNS database for domain

• Globally resilient (multiple DNS Servers)
• Created with domain registration via R53 - created separately
• Host DNS records (A, AAAA, MX)
• Hosted Zones - what DNS system references - Authoritative for domain

Public hosted zone:

• DNS Database (zone file) hosted by R53 (public name servers)
• Accessible from public internet and VPCs
• Hosted on “4” R53 Name Servers (NS) specific for the zone
  • Use NS records to point at these NS
• Resource records created within hosted zone
• Externally registered domain can point at R53 public zone

Private hosted zone:

• Associated and only accessible through VPCs
  • Using different account supported via CLI/ API
• Split-view (overlapping public and private) for public and internal use with same zone name

CNAME vs R53 Alias §

• “A” maps a Name to IP address
  • catagram.io => 1.3.3.7
• CNAME maps name to another name
  • www.catagram.io => catagram.io
• Problem: CNAME is invalid for naked/ apex (catagram.io)
  • Many AWS services use DNS name (ELBs)
  • With just CNAME, catagram.io => ELB is invalid

Alias use case:

• ALIAS record map NAME to AWS resource
• Can be used for both naked/apex and normal records
• For non apex/naked, functions like CNAME
• No charge for ALIAS => AWS
• Default to pick ALIAS for AWS service
• Should use same “Type” for whatever the record is pointing

Simple routing

• Supports 1 record per name
• Each record can have multiple values
• Client chooses and uses 1 of the randomly returned value
• Does not support health check when queried

R53 Health Checks §

Health checks - separate from but used by records

• Located globally
• Checks every 30s (every 10s costs extra)
• TCP, HTTP/HTTPS, HTTP/HTTPS with string matching
  • Need to return 2XX/3XX within 2s
• Based on checks, endpoint can be healthy or unhealthy
• What to monitor: Endpoint, CloudWatch alarm, check of checks (calculated)
  • Calculated check - check app wide including every single component

R53 Failover Routing §

R53 Failover routing - if the target of health check is unhealthy, any queries return the secondary record

• Common architecture - use failover for “out of band” failure page for a service (EC2, S3)
• Used to configure active passive failover

R53 Multi value routing §

Multivalue routing - mix between simple and failover routing

• Create many records all with same name
• Each record can have associated healthy check
• Multi value improves availability, but not replacement for load balancing
  • Load balancer - handle connection request to server so it’s used equally

R53 Weighted Routing §

Weighted routing - simple load balancing or testing new software versions

• Specify weight for each record
  • ‘0’ weight means never returns, unless all are considered
• Each record is returned based on its record weight vs total weight

R53 Latency-Based Routing §

Latency-based routing - optimize for performance and user experience

• supports one record with same name in each AWS region (WWW, us-east-1, A, 1.2.3.3)
• AWS maintains database of latency between users general location and latency tagged in records (Source, Dest, Latency)
• record returned is one with lowest etimated latency and healthy

R53 Geolocation routing §

Geolocation routing - similar to latency but using location of resources and customers

• records tagged with location (“US State”)
• IP check verifies location of user
• Geolocation
• Checks for records
  1. State
  2. Country
  3. Continent
  4. Optionally, most specific record or no answer
• Routing policy type not about closest record, but relevant locations

R53 Geoproximity Routing §

Geoproximity routing - provides record a closest as possible

• Records tagged with AWS region or lat and long coordinates
• Routing is distance based (including bias)
• ”+” or ”-” bias can be added to increase region or decreases neighbouring regions

R53 Interoperability §

R53 Interoperability - Using route53 to register domains or host zone files when other part with not route 53

R53 functions:

• Do both, or either domain registrar or domain hosting
• Accepts money (domain registration fee)
• Allocated 4 name servers (NS) (domain hosting)
  • Creates zone file (domain hosting) above Name servers
• Communicates with registry of TLD (domain registrar)
  • Sets NS record for domain to point at 4 Nameserver above

Both roles:

Registrar only (rarer):

Hosting only (more often):