EDNS Client Subnet

<p>EDNS Client Subnet (ECS) is an option in the <a href="/facts/Extension_Mechanisms_for_DNS/KUKTkVtx">Extension Mechanisms for DNS</a> that allows a <a href="/facts/Recursive_DNS_resolver/rfxdWFsj">recursive DNS resolver</a> to specify the <a href="/facts/Subnetwork/s1rQsNDv">subnetwork</a> for the <a href="/facts/Client_(computing)/u0wlVsWI">host or client</a> on whose behalf it is making a <a href="/facts/Domain_Name_System/rfxdWFsj">DNS</a> query. This is generally intended to help speed up the delivery of data from <a href="/facts/Content_delivery_network/SVuID7jd">content delivery networks</a> (CDNs), by allowing better use of DNS-based <a href="/facts/Load_balancing_(computing)/jddk6ang">load balancing</a> to select a service address near the client when the client computer is not necessarily near the recursive resolver. 
</p><p>When an <a href="/facts/Name_server/pUgmBMNW">authoritative name server</a> receives a DNS query, it takes advantage of ECS DNS extension to resolve the <a href="/facts/Hostname/WcLyMFKA">hostname</a> to a CDN which is <a href="/facts/Internet_geolocation/CAS3a4tv">geolocationally</a> near to the client <a href="/facts/Internet_Protocol/Qq6VeEal">IP</a>'s <a href="/facts/Subnetwork/s1rQsNDv">subnet</a>, hence the client makes further requests to a nearby CDN, thereby reducing latency.
The EDNS client subnet mechanism is specified in <a href="/facts/RFC_(identifier)/esftTvE7">RFC</a> <a href="https://www.rfc-editor.org/rfc/rfc7871">7871</a>.
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EDNS Client Subnet open-in-new

EDNS Client Subnet