Global DNS (Route 53) Advanced Flashcards
What is a Simple Routing Policy?
o A Simple Routing Policy is a single record within a hosted zone that contains one or more values. When queried, a simple routing policy returns all the values, in a random order
o The Client receives the list of IPs and can select the appropriate one and initiate a session with a resource
o Pros: Simple, default, even spread of requests
o Cons: No performance control, no granular health checks, for alias type only a single AWS resource is allowed, no multiple values. The TTL value (forcing clearing the cache and therefore regenerating the random sequence) low enough can help creating a basic load balancing
What is a Failover Routing Policy?
o Failover routing allows you to create 2 records with the same name, one designated as primary, the other as secondary. Queries will resolve to the primary, unless it’s unhealthy, in which case Route 53 will respond with the secondary
o Failover can be combined with other types to allow multiple primary and secondary, and therefore provide emergency resources during failures.
What is a Weighted Routing Policy?
o Weighted routing can be used to control the amount of traffic that reaches specific resources. It can be useful when testing new software or when resources are being added or removed from a configuration that doesn’t use a load balancer (not for load balancing!)
o Records are returned based on a ratio of their weight to the total weight, assuming records are healthy
o Multiple records with the same name have to be created, and Route 53 will return them depending on their relative weight
What is a Latency Routing Policy?
o With Latency Policy, Route 53 consults a latency database each time a request occurs to a given latency-based host in DNS from a resolver server.
o Record sets with the same name are considered part of the same latency-based set; each is allocated to a region. The record set returned is the one with the lowest latency to the resolver server
What is a Geolocation Routing Policy?
o Geolocation routing lets you choose the resources that serve your traffic based on the geographic region from which queries originate
o A record set is configured for a Continent or a Country: that record set is used for queries in that same region, with more specific matches taking priority
o A record set can be set as the Default that gets returned if the IP matching process fails or if no record set is configured for the originating query region
o A no-result is returned if no match exists between a record set and the query location
