remove discussion about falling back to plain DNS on timeout

(cherry picked from commit aca78add3a686f7df1053efc3cba3b7df44b7342)

diff --git a/doc/arm/Bv9ARM-book.xml b/doc/arm/Bv9ARM-book.xml
index f65a65cd1e6fea2ecfb7d60f75edbdb9cb4604ba..1009d2035418614331738b83ccd1b489eabc1f93 100644 (file)
--- a/doc/arm/Bv9ARM-book.xml
+++ b/doc/arm/Bv9ARM-book.xml
@@ -9014,18 +9014,7 @@ avoid-v6-udp-ports { 40000; range 50000 60000; };
                  this has the greatest chance of success on the first try.
                </para>
                <para>
-                 If the initial response times out, <command>named</command>
-                 will try again with plain DNS, and if that is successful,
-                 it will be taken as evidence that the server does not
-                 support EDNS. After enough failures using EDNS and
-                 successes using plain DNS, <command>named</command>
-                 will default to plain DNS for future communications
-                 with that server.  (Periodically, <command>named</command>
-                 will send an EDNS query to see if the situation has
-                 improved.)
-               </para>
-               <para>
-                 However, if the initial query is successful with
+                 If the initial query is successful with
                  EDNS advertising a buffer size of 512, then
                  <command>named</command> will advertise progressively
                  larger buffer sizes on successive queries, until