add an Inform Message Type

README.md

@@ -76,6 +76,8 @@ The following special netids are defined:
 This message is the introductory message that a new node sends to any node of the network it can reach and which identifies the new one.
 It has no payload.
 
+Any node which receives a *Hello* message SHOULD add the sending node to it's local neighbor table and associate the src IP address of the packet with that sending node.
+
 #### Message Type *Goodbye*
 
 - Message Type: `0x02`
@@ -98,6 +100,34 @@ It has no payload.
 A message which MUST ONLY be originated by a node in response to a previous *Ping* message.
 It has no payload.
 
+#### Message Type *Inform*
+
+- Message Type `0x05`
+
+This message may be sent by a node to inform it's neighbors about other neighbors.
+
+For example, if Node A is a local neighbor of Node B, Node B could use this message to signal a third Node C that Node A exists.
+Node C could then try to reach Node A on it's own and/or add it to it's remote neighbor table.
+
+It has the following payload:
+```
+0          7 8        15 16       23 24        31 
++-----------+-----------+-----------+------------+
+|                subject netid                   |
+|                                                |
++-----------+-----------+-----------+------------+
+|             subject ip address                 |
+|                                                |
++-----------+-----------+-----------+------------+
+|      subject port     |
+|                       |
++-----------+-----------+
+```
+
+- *subject netid*: The netid of the third node which is being informed about (Node A in the example above).
+- *subject ip address*: The IP Address at which the third node was reachable for the node which originated this message.
+- *subject port*: The port at which the third node was reachable for the node with originated this message.
+
 #### Message Type *Data*
 
 - Message Type `0x10`