๐Ÿชด Quartz 4.0

Amazon Route 53

6 min read

DNS ๋ž€

DNS Terminologies

  • Domain Register: Amazone Route 53, GoDaddy, โ€ฆ
  • DNS Records: A, AAAA, CNAME, NS, โ€ฆ
  • Zone File: Contains DNS records
  • Name Server: Resolves DNS queries (Authoritative or Non-Authoritative)
  • Top Level Domain (TLD): .com, .gov, .org, โ€ฆ
  • Second Level Domain (SLD): amazon.com, google.com, โ€ฆ

How DNS works

Amazon Route 53

  • A HA, scalable, fully managed, and Authoritative DNS
    • Authoritative: Customer can update the DNS records
  • R53 is also a Domain Register
  • Health-check available
  • The only AWS service that provides 100% availability SLA

Records

  • How you want to route traffic for a domain
  • Each record contains:
    • Domain/Subdomain Name: e.g. example.com
    • Record Type: e.g. A or AAAA
    • Value: e.g. 123.456.789.123
    • Routing Policy: How R53 responds to queries
    • TTL: Amount of time the record cached at DNS Resolvers
  • R53 supports the following DNS record types:
    • A / AAAA / CNAME / NS
    • (Advanced) CAA / DS / MX / NAPTR / PTR / SOA / TXT / SPF / SRV

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
    • Cannot create a CNAME record for the top node of a DNS namespace (Zone Apex)
  • NS: Name Servers for the Hosted Zone
    • Control how traffic is routed for a domain

CNAME vs Alias

  • AWS Resources (LB, CloudFront, โ€ฆ) expose an AWS hostname
  • CNAME
    • Points a hostname to any other hostname (app.domain.com โ‡’ any.thing.com)
    • Only for non-root domain (sub.domain.com)
  • Alias
    • Points a hostname to an AWS Resources (app.domain.com โ‡’ any.amazonaws.com)
    • Works for the root domain and non-root domain (domain.com)
    • Free of charge
    • Native health-check

Alias Records

  • Maps a hostname to an AWS resource
  • An extension to DNS functionality
  • Automatically recognizes changes in the resourceโ€™s IP addresses
  • Unlike CNAME, it can be used for the top node of a DNS namespace (Zone Apex)
    • e.g. example.com
  • Alias Record is always of type A/AAAA for AWS resources (IPv4/IPv6)
  • Cannot set TTL
  • Alias Records Targets
    • ELB
    • CloudFront Distributions
    • API Gateway
    • EB Environments
    • S3 Websites
    • VPC Interface Endpoints
    • Global Acceleratorโ€™s Accelerator
    • R53 Record in the same hosted zone
    • But cannot set for EC2 DNS name

Hosted Zones

  • A container for records that define how to route traffic to a domain and its subdomains
  • Public Hosted Zones - contains records that specify how to route traffic on the internet (public domain names)
  • Private Hosted Zones - contains records that specify how you route traffic within one or more VPCs (private domain names)
  • $0.5 per month per hosted zone

Resolver Endpoints

  • Inbound Endpoint
    • On-premises ๋„คํŠธ์›Œํฌ์—์„œ ๋“ค์–ด์˜ค๋Š” DNS ์ฟผ๋ฆฌ๋ฅผ ์ฒ˜๋ฆฌํ•˜๋Š” VPC ์˜ ์—”๋“œํฌ์ธํŠธ
    • VPC ๋‚ด์˜ ๋„๋ฉ”์ธ ์ด๋ฆ„์— ๋Œ€ํ•œ DNS ์ฟผ๋ฆฌ๋ฅผ ์ฒ˜๋ฆฌํ•˜๋Š” ๋ฐ ์‚ฌ์šฉ
    • On-premises DNS Resolver ๊ฐ€ DNS ์ฟผ๋ฆฌ๋ฅผ R53 Resolver ๋กœ ์ „๋‹ฌ ๊ฐ€๋Šฅ
    • On-premises DNS Resolver ๊ฐ€ R53 Private Hosted Zone ์—์„œ AWS ๋ฆฌ์†Œ์Šค ๋ฐ ๋ ˆ์ฝ”๋“œ์— ๋Œ€ํ•œ ๋„๋ฉ”์ธ ์ด๋ฆ„ ํ™•์ธ ๊ฐ€๋Šฅ
  • Outbound Endpoint
    • VPC ์—์„œ On-premises ๋„คํŠธ์›Œํฌ๋กœ DNS ์ฟผ๋ฆฌ๋ฅผ ์ „๋‹ฌํ•˜๋Š” VPC ์˜ ์—”๋“œํฌ์ธํŠธ

Health Checks

  • HTTP Health Checks are only for Public Resources
  • Health Check โ†’ Automated DNS Failover:
    • Health Checks that monitor an endpoint (application, server, other AWS resources)
      • About 15 global Health Checkers will check the endpoint health
      • Health Checks pass only when the endpoint responds with the 2xx or 3xx
      • Health Checks can be set up to pass/fail based on the text in the first 5120 bytes of the response
    • Health Checks that monitor other health checks (Calculated Health Checks)
      • Combine the results of multiple Health Checkers into a single Health Check
      • Used to perform maintenance to a website without causing all health checks to fail
    • Health Checks that monitor CloudWatch Alarms
      • R53 Health Checkers are outside the VPC
      • CW metric and associate CW alarm to Health Check the alarm
  • Health Checks are integrated with CloudWatch metrics

Routing Policies

  • Define how R53 responds to DNS queries
  • R53 supports the following Routing Policies
    • Simple
    • Weighted
    • Failover
    • Latency-based
    • Geolocation
    • Multi-Value Answer
    • Geoproximity (using R53 Traffic Flow feature)

Simple

  • Typically, route traffic to a single resource
  • Can specify multiple values in the same record
    • A random one is chosen by the client
  • When Alias is enabled, specify only 1 AWS resource
  • Canโ€™t be associated with Health Checks

Weighted

  • Control the % of the requests that go to each specific resource
  • Assign each record a relative weight
  • DNS records must have the same name and type
  • Can be associated with Health Checks
  • Assign a weight of 0 to a record to stop sending traffic
  • If all records have weight of 0, then all records will be returned equally

Failover

Latency-based

  • Redirect to the resource that has the least latency close to the user
  • Latency is based on traffic between users and AWS Regions
  • Can be associated with Health Checks

Geolocation

  • Different from Latency-based
  • This routing is based on user location
  • Specify location by Continent, Country or by US State
  • Should create a โ€œDefaultโ€ record (in case thereโ€™s no match on location)
  • Use cases: website localization, restrict content distribution, โ€ฆ
  • Can be associated with Health Checks

Geoproximity

  • Route traffic to resources based on the geographic location of users and resources
  • Ability to shift more traffic to resources based on the defined bias
  • To change the size of the geographic region, specify bias values:
    • To expand (1 to 99) - more traffic to the resource
    • To shrink (-1 to -99) - less traffic to the resource
  • Must use R53 Traffic Flow (advanced) to use this feature

IP-based Routing

  • Routing based on clientsโ€™ IP addresses
  • Provide a list of CIDRs for clients and the corresponding endpoints/locations
  • Use cases: Optimize performance, reduce network costs, โ€ฆ
  • e.g. Route end users from a particular ISP to a specific endpoint

Multi-Value

  • User when routing traffic to multiple resources
  • R53 returns multiple resources
  • Can be associated with Health Checks
  • Up to 8 healthy records are returned for each Multi-Value query
  • Multi-Value is not a substitute for having an ELB

References

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