Route53

 

I. What is DNS?

• Domain Name System which translates the human friendly hostnames into the machine IP address
• wwwgoogle.com => 172.217.18.36
• DNS is the backbone of the internet
• DNS uses hierarchical naming structure

DNS Terminologies

• Domain Registrar: Amazon Route53, GoDaddy, ...
• DNS Records: A, AAAA, CNAME, NS, ...
• Zone file: contains DNS records
• Name Server: resolves DNS queries ( Authoritative or Non-Authoritative)
• Top Level Domain (TLD): .com, .us, .in, .gov, .org, ...
• Second Level Domain (SLD): amazon.com, google.com

How DNS Works?

II. Route 53 Overview

Amazon Route 53

• A hightly available, scalable, fully managed and Authoritative DNS
• Authoritative = the customer (you) can update the DNS records
• Route 53 is also a Domain Registrar
• Ability to check the health of your resources
• The only AWS service which provides 100% availability SLA
• Why Route 53? 53 is a reference to the tranditional DNS port

Route 53 - Records

• How you want to route traffic for a domain
• Each record contains:
• Domain/ suddomain Name - e.g., example.com
• Record type - e.g., A or AAAA
• Value - e.g., 12.34.56.78
• Routing policy - how Route 53 responds to queries
• TTL - amount of time the record cached at DNS Resolvers
• Route 53 supports the following DNS record types:
• (must know) A / AAAA / CNAME / NS
• (advanced) CAA / DS / MX / NAPTR / PTR / SOA / TXT / SPF / SRV

Route 53 - Record Types

• A - maps a hostname to IPv4
• AAAA - maps a hostname to IPv6
• CNAME - maps a hostname to another hostname
• The target is domain name which must have an A or AAAA record
• Can't create a CNAME record for the top node of a DNS namespace (Zone Apex)
• Example: you can't create for example.com, but you can create for www.example.com
• NS - Name Servers for the Hosted Zone
• Control how traffic is routed for a domain

Route 53 - 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) application1.mypublicdomain.com
• Private Hosted Zone - contain records that specify how you route traffic within one or more VPCs (private domain names) application1.company.internal
• You pay 0.5$ per month per hosted zone

Route 53 - Public vs Private Hosted Zones

III. Route 53 - Registering a domain

IV. Route 53 - Creating our first records

V. Route 53 - EC2 Setup

VI. Route 53 - Records TTL (Time to Live)

• Hight TTL  - e.g., 24hr 
• Less traffic on Route 53
• Possibly outdated records
• Low TTL - e.g., 60s
• More traffic on Route 53 ($$)
• Records are outdated for less time
• Easy to change records
• Except for Alias records, TTL is mandatory for each DNS records

VI. Route 53 - CNAME vs Alias

CNAME vs Alias

• AWS Resources (Load Balancer, CloudFront...) expose an AWS hostname:
• ib1-1234.us-east-2.elb.amazonaws.com and you want myapp.mydomain.com 
• CNAME:
• Points a hostname to any other hostname (app.mydomain.com => blabla.anything.com)
• ONLY FOR NON ROOT DOMAIN (aka: something.mydomain.com)
• Alias:
• Points a hostname to an AWS resource (app.mydomain.com => blabla.amazonaws.com)
• Works for ROOT DOMAIN and NON ROOT DOMAIN (aka mydomain.com)
• Free of charge
• Native health check

Route 53 - Alias Records

• Maps a hostname to an AWS resource
• An extension to DNS functionality
• Automatically recognizes changes in the resource'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)
• You can't set the TTL

Route 53 - Alias Records Targets

• Elastic Load Balancers
• CloudFront Distributions
• API Gateway
• Elastic Beanstalk environments
• S3 Websites
• VPC Interface Endpoints
• Global Accelerator accelerator 
• Route 53 record in the same hosted zone
• You cannot set an ALIAS for an EC2 DNS name

VII. Routing Policy

Route 53 - Routing Policies

• Define how Route 53 responds to DNS queries
• Don't get confused by word "Routing"
• It's not the same as Load Balancer routing which routes the traffic
• DNS does not route any traffic, it only responds to the DNS queries
• Route 53 supports the following Routing Policies
• Simple
• Weighted
• Latency based
• Failover
• Geolocation
• Mutil-Value Answer
• Geoproximity (using Route 53 Traffic Flow feature)
• IP-based 

1. Routing Policy - Simple

• Typically, route traffic to a single resource
• Can specify multiple values in the same record
• If multiple values are returned, a random one is chosen by the client
• When Alias enabled, specify only one AWS resource
• Can't be associated with Health Checks 

2. Routing Policy - Weighted

• Control the % of the requests that go to each specific resource
• Assign each record a relative weight
• 
  
  
  
• Weights don't need to sum up to 100
• DNS records must have the sam name and type
• Can be associated with Health Checks
• Use cases: load balancing between regions, testing new application versions...
• Assign a weight of 0 to a record to stop sending traffic to a resource
• If all records have weight of 0, then all records will be returned equally

3. Routing Policy - Latency-based

• Redirect to the resource that has the least latency close to user
• Super helpful when latency for users is a priority
• Latency is based on traffic between users and AWS regions
• Germany users may be directed to the US (if that's the lowest latency)
• Can be associated with Health Checks (has a failover capability)

4. Routing Policy - Failover

5. Routing Policy - Geolocation

• Different from Latency-based!
• This routing is based on user location
• Specify location by Continent, Country or by US State (if there's overlapping, most precise location selected)
• Should create a "Default" record (in case there's no match on location)
• Use cases: website localization, restrict content distribution, load balancing, ...
• Can be associated with Health Checks

6. Routing Policy - Geoproximity

• Route traffic to your 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
• Resources can be:
• AWS resources (specify AWS region)
• Non-AWS resources (specify Latitude and Longitude)
• You must use Route 53 Traffic Flow (advanced) to use this feature

Geoproximity Routing Policy

7. IP-based Routing

• Routing is based on client' IP address
• You provide a list of CIDRs for your client and corresponding endpoints/ locations (user-IP-to-endpoint mappings)
• Use cases: Optimize performace, reduce network costs, ...
• Example: route end users from a particular ISP to a specific endpoint

8. Multi-Value

• Use when routing traffic to multiple resources
• Route 53 return multipe values/resources
• Can be associated with Health Checks (return only values for healthy resouces)
• Up to 8 healthy records are returned for each Multi-Value query
• Multi-Value is not a substitute for having an ELB    

VIII. Route 53 - Health Checks

• HTTP Health Checks are only for public resources
• Health Check => Automated DNS Failover:
• Health Checks that monitor an endpoint (application, server, other AWS resource)
• Health Checks  that monitor other health checks (Calculated Health Checks)
• Health Checks tha monitor CloudWatch Alarms (full control!!) - e.g., throttles of DynamoDB, alarms on RDS, custom metrics, ... (helpful for private resources)
• Health Checks are integrated with CW metrics

 Health Checks - Monitor an Endpoint

• About 15 global health checkers will check the endpoin health
• Healthy/ Unhealthy Threshold - 3 (default)
• Interval - 30sec ( can set to 10 sec - higher cost)
• Supported protocol: HTTP, HTTPS and TCP
• if > 18% of health checkers report the endpoint is healthy, Route 53 considers it Healthy. Otherwise, it's Unhealthy.
• Ability to choose which locations you want Route 53 to use
• Health Checks pass only when the endpoint responds with the 2xx or 3xx http status codes
• Health Checks can be setup to pass / fail based on the text in the first 5120bytes of the response
• Config your Router/ firewall to allow incoming requests from Route 53 Health Checker

Route 53 - Calculated Health Checks

• Combine the results of multiple Health Checks into the single Health Check.
• You can use OR, AND, or NOT
• Can monitor upto 256 Child Health Checks
• Specify how many of the health checks need to pass to make the parent pass
• Usage: perform maintenance to your website without causing all health checks to fail

Health Checks - Private Hosted Zones

• Route 53 health checkers are outside the VPC
• They can't access private endpoints (private VPC or on-premises resource)
• You can create a CloudWatch Metric and associate a CloudWatch Alarm, then create a health check that checks the alarm itself

IX. Route 53 - Health Checks hands on

X. Route 53 - Traffic flow

• Simplify process of creating and maintainng records in large and complex configurations
• Visual editor to manage complex routing edcision trees
• Configurations can be save as Traffic Flow Policy
• Can be applied to different Route 53 Hosted Zones ( differen domain names)
• Supports versioning

XI. 3rd Party Domains & Route 53

1. Domain Registar vs DNS service

• You buy or register your domain name with a Domain Registrar typically by paying annual charges (e.g., GoDaddy, Amazon Registrar Inc, ...)
• The Domain Registrar usually provides you with a DNS service to manage your DNS records
• But you can use another DNS service to manage your DNS records
• Example: purchase  the domain from GoDaddy and use Route 53 to manage your DNS records

2. GoDaddy as Registrar & Route 53 as DNS service

3. 3rd party Registrar with Amazon Route 53

• If you buy your domain on a 3rd party registrar, you can still use Route53 as the DNS service provider
• Create Hosted Zone in Route 53
• Update NS Records on 3rd party website to use Route 53 Name Servers
• Domain Registrar != DNS Service
• But every Domain Registrar usually come with some DNS features