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DNS Trac Steering The DNS resiliency features discussed in the previous section are built in to DNS and help DNS work effectively in large-scale deploy‐ ments. But there are features that some DNS providers include as add-ons that aren't built in to the DNS protocol. This doesn't mean that these features are any less valuable or important to security. It just means that fewer DNS providers offer them. Most of these enhanced features revolve around traffic steering, the process of redirecting requests between different sites in a multi‐ cloud architecture based on a previously-defined set of rules. DNS sits in a unique position because it is the first step in the process for requesting content from a web application. As a result, DNS is an effective place to implement traffic steering rules. For example, organizations in the process of adding a new site to a multicloud solution might want to ease it into the rotation to ensure that the new site is as resilient as the others. In a case like this, the organization might choose to direct the traffic-steering capable DNS server to send only 20% of the traffic to the new site. A more common approach is to use a DNS provider to perform health checks on your services prior to responding to a DNS request with an answer. In this type of traffic steering set up, the DNS pro‐ vider continuously monitors the health of all web properties, regard‐ less of where they are hosted. If a cloud provider stops responding to requests, the DNS server will no longer direct DNS requests to that cloud provider until it is responding again. Using DNS in this manner is not quite as reliable as using a load bal‐ ancer, but it can be much more cost effective. Customers or end users will be able to access the web applications without interrup‐ tion, even during a major outage at a cloud provider's datacenter. Finally, some DNS providers are able to use traffic steering as a way to maximize the performance of web applications. Performance optimization can take many forms. A common type of performance optimization is redirection of traffic based on geolocation informa‐ tion. In a multicloud environment, organizations might have the same web application running in dozens or even hundreds of loca‐ tions. DNS providers can optimize incoming DNS requests and send visitors to the closest cloud providers. For example, suppose that the multicloud architecture is set up in datacenters in Miami, DNS Resiliency and Trac Steering | 41

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