examples:rpl_udp updated README.md on using the build parameters

examples/rpl_udp/README.md

@@ -1,31 +1,71 @@
-#tl;dr
-
-command order:
-
-	init [r|n]
-	server
-	send <node-id> <message>
-
-# setup
-compile the application
+# Setup the build
+First switch to this application directory:
 
 	cd RIOT/examples/rpl_udp
+
+#### Parameterizing the build
+The build system provides two specific parameters for the RPL module.  
+These parameters are:
+ * `RPL_MAX_ROUTING_ENTRIES` sets the desired maximum number of entries for the RPL routing table. _If this parameter is not provided, a [default](https://github.com/RIOT-OS/RIOT/blob/master/sys/net/include/rpl/rpl_config.h#L130) value is used._
+ * `RPL_NODE_IS_ROOT` indicating the build is specifically for a root node. This parameter is **only required** for using [`RPL_NON_STORING_MODE`](https://github.com/RIOT-OS/RIOT/blob/master/sys/net/include/rpl/rpl_config.h#L31) MOP to initialize a RPL routing table. The parameter is ignored in all other cases. _For non-storing MOP a node does not require to provide a routing table._
+
+#### Compiling the executable
+**example for [`RPL_STORING_MODE_NO_MC`](https://github.com/RIOT-OS/RIOT/blob/master/sys/net/include/rpl/rpl_config.h#L139):**
+
 	make
 
-Set up a bridge for *two* tap devices to communicate over
+builds the project and creates `128` entries for the RPL routing table by default.
+
+	make RPL_MAX_ROUTING_ENTRIES=103
+
+builds the project and creates `103` entries for the RPL routing table **overwriting** the default value.
+
+**example for [`RPL_NON_STORING_MODE`](https://github.com/RIOT-OS/RIOT/blob/master/sys/net/include/rpl/rpl_config.h#L133):**
+
+	make RPL_MAX_ROUTING_ENTRIES=103 RPL_NODE_IS_ROOT=1
+
+builds the project and creates `103` entries for the RPL routing table for the root node.
+
+#### _[native only]_ Set up a bridge for *two* tap devices for communication
 
 	../../cpu/native/tapsetup.sh create 2
 
-# rpl init
+The `2` corresponds to the number of _virtual_ nodes to be started.  
+The tap devices are bound to the _virtual_ native node on starting the created executable `rpl_udp.elf`.  
 
+#### _[native only]_ Starting _virtual_ nodes
 Run the first node
 
 	make term
 
+This starts the executable binding a _virtual_ node to the first tap device `tap0`.  
+
+**Further nodes must be bound to tap devices manually.**  
+For the second node it would be:
+
+	make term PORT=tap1
+
+
+# RPL init
 Type ``help`` to see the commands available.
 
-Init your rpl node as either a root or a node router.
+#### Command order:
 
+	init (r|n|h)
+	server
+	send <node-id> <message>
+
+
+Init your RPL node either as root (`r`), as node router (`n`), or as non-routing node (host-mode) (`h`)
+
+	> init r
+	init r
+	INFO: Initialize as root on address 1
+	6LoWPAN and RPL initialized.
+	Channel set to 10
+	Transport layer initialized
+
+or
 	> init n
 	init n
 	INFO: Initialize as node on address 2
@@ -34,11 +74,10 @@ Init your rpl node as either a root or a node router.
 	Transport layer initialized
 
 or
-
-	> init r
-	init r
-	INFO: Initialize as root on address 1
-	6LoWPAN and RPL initialized.
+	> init h
+	init h
+	INFO: Initialize as non-routing node on address 3
+	6LoWPAN initialized.
 	Channel set to 10
 	Transport layer initialized
 
@@ -66,9 +105,9 @@ You can now use the ``dodag`` command to obtain information on the node's rank i
 	fe80:0000:0000:0000:3612:00ff:fe00:0001
 	---------------------------
 
-#sending via UDP
+#Sending via UDP
 
-In order to be able to receive UDP messages from other nodes, we have to start rpl_udp's UDP server:
+In order to be able to receive UDP messages from other nodes, we have to start `rpl_udp`'s UDP server:
 
 	> server
 	server