[35925] add more EDNS EXPIRE doc, clarify CHANGES note 3911

CHANGES

@@ -1,4 +1,7 @@
-3911.	[func]		Implement EDNS EXPIRE option client side. [RT #35925]
+3911.	[func]		Implement EDNS EXPIRE option client side, allowing
+                        a slave server to set the expiration timer correctly
+                        when transferring zone data from another slave
+                        server. [RT #35925]
 
 3910.	[bug]		Fix races to free event during shutdown. [RT#36720]
 

README

@@ -56,6 +56,10 @@ BIND 9.11.0
 	BIND 9.11.0 includes a number of changes from BIND 9.10 and earlier
 	releases.  New features include:
 
+	- The EDNS EXPIRE option has been implemented on the client
+	  side, allowing a slave server to set the expiration timer
+	  correctly when transferring zone data from another slave
+	  server.
 	- A new "masterfile-style" zone option controls the formatting
 	  of text zone files:  When set to "full", a zone file is dumped
 	  in single-line-per-record format.

doc/arm/Bv9ARM-book.xml

@@ -10509,8 +10509,15 @@ rate-limit {
 
 	  <para>
 	    The <command>request-expire</command> clause determines
-	    whether the local server, acting as a slave, will request
+            whether the local server, when acting as a slave, will
-	    the EDNS EXPIRE value.
+            request the EDNS EXPIRE value.  The EDNS EXPIRE value
+            indicates the remaining time before the zone data will
+            expire and need to be be refreshed.  This is used
+            when a secondary server transfers a zone from another
+            secondary server; when transferring from the primary, the
+            expiration timer is set from the EXPIRE field of the SOA
+            record instead. 
+            The default is <command>yes</command>.
 	  </para>
 
 	  <para>