= OLSR P2PD plugin =

This README file is the main documentation source for the OLSR P2PD plugin

Last update 01/03/2010

== Description ==

This plugin goal is the distribution of Peer to Peer Discovery messages over an
OLSR Wireless Mesh Network.

In a wireless mesh network, the usage of wireless interfaces in ad-hoc mode and
the OLSR routing protocol prevent UDP messages to be distributed all over the
network.

We are especially interested in the distribution of UDP messages, used for host-
based service discovery, over the networks that do not directly participate in
the OLSR mesh cloud.

This task is achieved in the following way: 
 1. the local router picks up from the local non-OLSR (HNA) network UDP messages
    and encapsulates them in a new type of OLSR messages,
 2. the OLSR infrastructure is exploited for the transport of these messages,
 3. remote routers decapsulate UDP messages from received OLSR messages and send
    them over their attached non-OLSR networks.

The work could have its practical and immediate application in wireless network
communities that employ the OLSR protocol.

The plugin captures the traffic (only IPv4 if OLSR is running IPv4 and only IPv6
if OLSR is running IPv6) and encapsulates this traffic in OLSR messages that are
forwarded to all the other nodes in the mesh.

Other nodes running the plugin will decapsulate the packets and will send them
to the interfaces specified in the configuration file

Let's get this example topology

pc1->eth0 ----- eth0<-r1->ath0 -------ath0<-r2->eth0 ---------eth0<-pc2

r1 and r2 are OLSR routers with p2pd plugin enabled. pc1 will be able to receive
UDP traffic generated at pc2 and vice versa

The most interesting feature is that messages are forwarded also by OLSR routers
without the plugin. For example:

pc1->eth0 ----- eth0<-r1->ath0 ---r3----ath0<-r2->eth0 ---------eth0<-pc2

also in this topology UDP traffic between pc1 and pc2 is possible because r3
forwards UDP plugin OLSR packets even if it is not aware of the new application.

== Configuration ==

To enable the Plugin use the following syntax

LoadPlugin "olsrd_p2pd.so.0.1.0"
{
# Specify interfaces where the hosts running Peer to Peer applications are
# attached
PlParam     "NonOlsrIf"   "eth0"
PlParam     "NonOlsrIf"   "eth1"
# P2pdTtl is the time to live given to the P2PD OLSR messages
PlParam     "P2pdTtl"     "5"
# Specify the UDP destination address/port for P2P node discovery
# Allowed: IPv4 broadcast and multicast, IPv6 multicast only
#   MS Groove
PlParam     "UdpDestPort" "255.255.255.255 1211"
#   MDNS multicast (draft-cheshire-dnsext-multicastdns)
PlParam     "UdpDestPort" "224.0.0.251 5353"
# Set to 1 to decrement the TTL on the packet going into the OLSR network (default 0)
#PlParam     "UseTTLDecrement" "0"
}

Where eth0 and eth1 are the names of the interfaces where you want to capture
traffic (and decapsulate incoming traffic).

Note that this interfaces must not talk OLSR and also the subnets on this
interfaces must be announced with an appropriate HNA entry.
This version of the plugin will not chech this stuff to be properly configured!

P2pdTtl is the time to live given to the P2PD OLSR messages. It makes no sense
to announce your services to hosts that are too many hops away, because they
will experience a very bad unicast connection.
With this TTL setting we can tune how far we announce our services and we make
the protocol scale much better

=== References ===

 * OLSR Optimized Link State Routing:
     [http://tools.ietf.org/html/rfc3626 IETF RFC 3626]

=== Contact ===
 * Caspar van Zon CHW.van.Zon@mindef.nl

Revision history
================

01/03/2010 - Changes relative to olsr_mdns plug-in which was used as a base
 * A new plug-in called olsrd_p2pd has been created based on the olsrd_mdns
   plug-in.
 * The initial version number for this plug-in has been set to v 0.1.0
 * A parameter 'UdpDestPort' was added to allow for specification of a UDP IP
   address/port pair.
 * A number of obsolete functions have been removed from the source to decrease
   the plug-in footprint.
 * A mechanism has been added to check whether duplicate messages are received
   and to allow them to be filtered out of the message stream. This is a new
   mechanism and not the one provided within OLSR because the old mechanism
   seems to hold a single list and this should not be contaminated. At this time
   the list holds tuples with information conforming draft-ietf-manet-olsrv2-10.
   Older non-duplicate messages are forwarded to NonOlsrIf interfaces.
 * Some of the return values in the olsr_parser function (p2pdc) have been
   changed so the related messages will not be forwarded if that is not
   desired.
 * Fragmented packets not supported.
 * TTL for outgoing packets are not modified.
 * Parameter 'UdpDestPort' is checked so only IPv4 broadcast and multicast and
   IPv6 multicast values are allowed as the destination address.