diff --git a/Doc/Sdi/dns.xml b/Doc/Sdi/dns.xml
index e74132e666b6f23c37f298a9bcb26c0383c5bb98..d60ee68cae91efa30f7d1b8ecfd94313a59835ba 100644
--- a/Doc/Sdi/dns.xml
+++ b/Doc/Sdi/dns.xml
@@ -18,6 +18,12 @@
       <title>Documentation links</title>
 
       <itemizedlist>
+        <listitem>
+          <para><link
+          xlink:href="https://www.cloudflare.com/learning/dns/what-is-dns">What
+          Is DNS? | How DNS Works</link></para>
+        </listitem>
+
         <listitem>
           <para><link
           xlink:href="http://www.htmlgoodies.com/beyond/webmaster/article.php/3473261/An-Introduction-to-DNS.htm">An