[AWS] Route 53

Route 53 configures and manages domains: domain registration, DNS (Domain Name System) service, and health checking. – DNS uses port 53. That is how the name comes from.

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Concepts

• DNS (Domain Name Service)
  • maps human-friendly domain names into IP addresses.
• TTL (Time to Live)
  • the amount of time that the DNS resolver will cache the record.

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Features

• Route 53 is commonly used with ELB (Elastic Load Balancer) and CloudFront.
• When creating an A record, you need to specify TTL, a routing policy, and IP values.

Hosted Zones

A hosted zone is a container that holds information about how you want to route traffic for a domain, such as example.com, and its subdomains.

• Split-View DNS option (Hosted zones) allows maintaining both private and public hosted zones with the same domain name.
  • The private hosted zones are allowed within VPCs. Associated VPCs can see the internal version of a website by using the private zone’s A record.
  • A public hosted zone holds the information about how to route the public domain name. The host (www) portion is not included in a public zone’s naming convention.

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Records

• A Record defines how to route traffic.
• A record has:
  • Domain Name, Subdomain Name: ex) example.com
  • Record Type: ex) A or AAAA, CNAME, NS …
  • Value: ex) 24.22.33.44
  • Routing Policy
  • TTL

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Routing (Traffic) Policies

• Simple routing
  • It uses a single record with one or multiple IPs within a hosted zone.
    • Typically, it routes traffic to a single resources. (1 IP)
  • When queried, all registered IPs are returned in a random order. A client needs to choose one.
    • It evenly spreads requests but no performance control (no LB)
  • Simple and default.
  • Limitations: No granular health checks; No performance control; The alias option can only provide a single AWS resource, not multiple.
• Weighted routing
  • It controls (splits) the amount of traffic based on the ratio (percentage) of the weight of each record to the total weight of associated records.
  • Can be associated with health checks
  • Weighted routing can be used to test new features of an application by allowing users a gradual introduction to the features.
• Failover routing: active/passive set up
  • It uses two record sets with the same name (the primary when healthy, the secondary when unhealthy). Route 53 monitors the health of the primary site.
  • The primary instance requires the health check.
    • The health check of the secondary instance is optional.
• Latency-based routing
  • Route53 consults a latency database and resolves the host with the lowest latency.
  • For each record for latency-based routing, you need to specify a region.
  • It is not based on the distance or geolocation. It is based on the network performance.
• Geolocation routing
  • It serves the traffic based on the geographic region of the request .
    • You can map the record to a continent or a country.
  • If a request IP is not placed in the specified region, the traffic is routed to the default record.
    • The default record must be defined.
  • If locations are overlapped, the most specific location is used.
• Geoproximity routing
  • It must use Route 53 Traffic flow – geographic location of resources.
  • Bias: A geographic region can be expanded (1 to 99) or shrunk (-1 to -99).
• Multivalue Answer routing
  • Used when routing traffic to multiple resources.
  • It may return multiple values.
  • It returns only healthy endpoints.
    • It does not replace the load balancer.
    • Sending multiple healthy IPs can improve the availability and load balancing.
• IP-based routing
  • based on client’s IP address (CIDR range)
  • You can route users from a particular ISP to a specific end point.

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Route 53 Health Checks

• You can set health checks on individual record sets. A failed record set will be removed from Route 53 until it passes the health check.
• Types of health checks
  • End Point Checking – agreed way with an agreed frequency (HTTP, HTTPS, TCP – 10 or 30 seconds)
  • Calculated health checks – monitoring various checks and combine them
  • CloudWatch alarms – monitoring CloudWatch alarms from a large range of geographical servers.
• It provides a summarized report from multiple health checks.
• Health checks are charged based on the number of checks within the month. (per month base)

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Limits

• Route 53 has a default limit of 50 domain names.
• The limit can be increased by contacting AWS support.