HADOOP-13039. Add documentation for configuration property ipc.maximum.data.length (Contributed by Mingliang Liu)

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -1012,6 +1012,17 @@ for ldap providers in the same way as above does.
   </description>
 </property>
 
+<property>
+  <name>ipc.maximum.data.length</name>
+  <value>67108864</value>
+  <description>This indicates the maximum IPC message length (bytes) that can be
+    accepted by the server. Messages larger than this value are rejected by
+    server immediately. This setting should rarely need to be changed. It merits
+    investigating whether the cause of long RPC messages can be fixed instead,
+    e.g. by splitting into smaller messages.
+  </description>
+</property>
+
 <!-- Proxy Configuration -->
 
 <property>