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EDNS Client Subnet (ECS) support for ALIAS records

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Back in March of this year, the DNSimple team started working on a feature many of you have asked for. Today, we're pleased to announce EDNS Client Subnet (ECS) support for our ALIAS records.

We've had a lot of requests for this feature from customers who want to optimize their response times when their web resources are delivered by Content Delivery Networks (CDNs). It helps improve the overall user experience for their own customers.

Throughout April and May, we did rigorous testing to confirm compliance to defined standards, and inter-compatibility with most major CDN providers. We released this feature in mid-May, and we've made it available across all subscriptions.

How it works

The EDNS (extension mechanisms for DNS) Client Subnet is a mechanism defined in RFC7871 for recursive resolvers to send partial client IP address information to authoritative DNS nameservers. It allows the recursive DNS resolver to carry information about the network that originated a DNS query. We pass this information along to the authoritative nameservers to tailor their responses.

Latency-sensitive services, like CDNs, use this information to provide accurate geo-location-aware responses when answering name lookups coming from the recursive resolvers based at your Internet Service Provider (ISP), from or public resolvers, like Google's Public DNS ( service.

DNSimple implemented an RFC7871-compliant solution to support this type of DNS query at our authoritative DNS servers for customers using ALIAS records.

If your ALIAS records point to a Content Delivery Network (CDN), or other latency-sensitive service that supports ECS, our systems will pass this information along, returning the geo-location-aware responses back to the end users.

How does it benefit my services?

By having EDNS Client Subnet support enabled along the path of DNS queries, your customers will get the closest edge node provided by your CDN of choice. This reduces the average time required to load your web page in your customers' browsers, and can improve the overall latency of the network services that you provide.

Which CDNs do you support?

In our research and testing for the current EDNS Client Subnet support among the CDN providers, we only picked CDN providers that confirmed full compliance with the RFC7871 standard. That way we could make sure our customers weren't affected by non-adherence to the above standard, and avoid suboptimal operations.

We've enabled full EDNS Client Subnet (ECS) support for Netlify CDN, and plan to expand the service to even more Content Delivery Network providers. If you operate a CDN, or use a CDN we don't support yet, please contact us so we can determine compatibility.

More information

You can find a more detailed explanation of what an ALIAS record is, and how you can use it with our systems, in our support documentation.

If you want to read more about EDNS Client Subnet support for our ALIAS records, take a look at this article. And as always, get in touch with any questions you might have. We're happy to help.

At DNSimple, we're constantly working to improve DNS automation. When you're ready to experience best-in-class DNS management, give us a try free for 30 days.

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Atanas Argirov

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