[LMS-2267] minor: documentation for "ftp.server.passivemode.port.range"

SVN: 21618

datastore_server/dist/etc/service.properties

@@ -365,9 +365,15 @@ dss-rpc.put-default = main-thread
 # port where the FTP event connections will be opened. Optional parameter, default value is 2121.
 #ftp.server.port=2121
 #
+# Specifies a range of ports to be used when working in passive mode. The default value is "2130-2140",
+# meaning only 11 ports will be provide to connecting clients. If there are more than 11 concurrent 
+# users the configuration will have to be adjusted accordingly.  
+#ftp.server.passivemode.port.range=2130-2140
+#
 # when set to true enables the FTP server to run in "active mode". This means data connections
 # will always go to a single pre-configured port on the server. Such a configuration can ease the 
-# server firewall administration (only one additional port should be opened).
+# server firewall administration (only one additional port should be opened). However it requires 
+# the client machines to be directly visible from the server.
 #ftp.server.activemode.enable=true
 #
 # the active mode port number configuration. Default value is 2122.