netsukuku/doc/main_doc/ntk_rfc/Ntk_viphilama

== NTK_RFC 0010 ==

Subject: Viphilama - Virtual to Physical Layer Mapper

----
This text describes a change to the Npv7.
It will be included in the final documentation, so feel free to correct it.
But if you want to change the system here described, please contact us first.
----


=== Viphilama ===

Viphilama will permit to Netsukuku to expand itself over the Internet and then
switching automatically to the physical layer without interfering with the
stability of the Net.
The theory of Viphilama isn't complete yet. This document, right now, is just
a description of what it would be.

=== Layer ===

Netsukuku will be split in two layer: the virtual layer and the physical one.

==== The physical layer ====

This is the original Netsukuku layer: every node is linked to other nodes by
physical links (wifi, cables, ...).
The physical layer is prioritised over the virtual one.

==== The virtual layer ====

The virtual layer is built upon the Internet or any other existing network.
The Netsukuku nodes, in this layer, are linked each other by tunnels.

A node, in order to join in the virtual layer, has to know its physical
coordinates. 
The use of geographical coordinates is required for Viphilama, because it has
to map the virtual layer to the physical one and it needs a way to measure
the effective distance between two virtual nodes.

The coordinates can be retrieved using an online map service like
http://maps.google.com or with a GPS.

The coordinates are stored in the internal, external and bnode maps. 
In the internal map there are the coordinates of each single node.
In the external maps, the coordinates which locate a gnode are set to its
barycenter: it is the average of the coordinates of all its internal nodes.

==== Gate node ====

The two layers are joined by the gate nodes. They are nodes which belong to
both layers.
This means that the two layer form a unique network.


=== Virtual to Physical mapper ===

The mapper does a basic job: whenever it finds that a virtual link can be
replaced by a physical one, it removes the virtual link.

Assume this scenario:

{{{
	Tokyo      Moscow          Rome      London
	  |	     |               |	       |
	  |	     |               |	       |
	  |__________|Internet tunnel|_________|
}}}

Only one link exists, and it is a virtual one.
Only Tokyo and London are linked, all the other cities are alone.

When Tokyo and Moscow will be linked by a series of physical nodes, the mapper
will change the net in this way:

{{{
	Tokyo<--ntk nodes-->Moscow     Rome          London
	                     |		|		|
		   	     |______ Internet tunnel ___|
}}}


When even Moscow and Rome will be linked by physical nodes:

{{{
	Tokyo<--ntk nodes-->Moscow<--ntk nodes-->Rome          London
	                                   	  |		   |
		   	                          |__ Inet tunnel _|
}}}

And so on.

Basically when there are two nodes linked physically, one of them can cut
its virtual link which connects it to the virtual layer.

Let's go into the details.

==== Virtual hooking ====

A node, which hasn't any physical neighbours, resides in a black zone and, for
this reason, it can't hook to the physical layer. It will hook directly to
a vnode (virtual node), joining the virtual layer.
Let this hooking node be X.

The first part of the Virtual Hooking is the creation of the virtual links
(ip tunnels).

X chooses, at first, a random vnode which can be located anywhere in the
globe. If it is its first hook to the virtual layer, it will get the IP of
the vnode from a small public list available on the Internet, otherwise it
will consult its saved virtual maps.
Let the chosen vnode be Y.

X sends to Y a packet containing its coordinates. This pkt will be forwarded
with a greedy technique: 
Y looks up its maps and forwards the pkt to the vnode which is the nearest to X.
If this latter vnode knows another vnode which is nearer to X, it forwards
again the packet. Finally, the pkt will arrive to the node Z, which is a node
very near to X.

Let d(A, B) be the physical distance between the node A and B.

The node Z appends its Internet IP to the received packet and forwards it
again to a node T, so that d(X,T) ~= d(X,Z).
The node T will do the same (adds its IP and forwards the pkt).
When the packet will be forwarded for the 16th time or when it can't be
forwarded anymore, it is sent back to the node X.

The node X collects this last packet and creates a virtual link (tunnel) to
each Internet IP which has been stored in the packet itself. 
These linked nodes are the new rnodes of the node X.


At this point the node X will hook to each linked node. This procedure is
called v-linking:

Let "L" be the generic linked node.

X sends the I_AM_VHOOKING request to L.

L analyses its virtual rnodes and compares d(L,vR) to d(X,vR), where vR is a
vrnode. If d(X,vR) < d(L,vR), L adds the Internet IP of the vR in the reply
packet. This means that if L finds out that X is nearer to one of its
vrnodes, it tells X to create a link to it and deletes its link to the vrnode.

X receives the reply packet of L and tries to create a virtual link to each
vR listed in the same packet.
X writes the list of all the vR nodes which has been successfully linked to X
itself. This list is sent back to L.

L reads this latter list and delete all its links to the vR nodes, which has
been successfully linked to X.

X repeats this same hooking procedure for each L.

In the end, X chooses one of its vrnodes and hooks with the classical method
to it.

==== Gate hooking ====

A node can hook to the physical layer as a normal node or as gate node.

A normal node is the old plain node of Netsukuku, it doesn't have to specify
its coordinates and doesn't need any other prerequisites.

The gate-node has an Internet connection that it uses to connect to
the virtual layer, it is also connected to physical nodes.

There are two cases:

 * When the node is from the start a gate node
 * When it is first a vnode and then becomes a gate node

In the first case it hooks directly to a physical node. If one of its rnodes
is a gate node too, it will start the v-linking procedure with it. 
In this way, the new gate-node will be linked to its nearer vrnodes.
The old gate-node will delete all the links to the vrnodes which have been
linked by the new gate-node.

In the second case, the node directly v-links to the new gate node which is
connected to.

When a gate-node can reach one of it vrnodes using both a virtual and a
physical link, it will delete the virtual one.

== TODO ==

 * Is it possible to avoid using the coordinates?
 * What does happen when a (v)node dies?

---- 

Feel free to help the development of Viphilama.