dialog Update README with explanation of in-dialog request behaviour

modules/dialog/README

@@ -1149,6 +1149,11 @@ modparam("dialog", "ka_timer", 10)
    dialog setup or previous keep-alive. The value represents the number of
    seconds.
 
+   If the requests times out (generating a 408) or if the UA responds with
+   481 the lifetime is set to 10 seconds. When lifetime expires the dialog
+   will be terminated. Any other response (including error responses) will
+   reset the timers.
+
    Default value is "0" (no keep alive). The lowest settable interval is
    30 seconds.
 

modules/dialog/doc/dialog_admin.xml

@@ -1247,6 +1247,13 @@ modparam("dialog", "ka_timer", 10)
 			the ka_interval elapsed from dialog setup or previous keep-alive.
 			The value represents the number of seconds.
 		</para>
+		<para>
+			If the requests times out (generating a 408) or if the
+			UA responds with 481 the lifetime is set to 10 seconds.
+			When lifetime expires the dialog will be terminated.
+			Any other response (including error responses) will
+			reset the timers.
+		</para>
 		<para>
 		<emphasis>
 			Default value is <quote>0</quote> (no keep alive). The lowest