.TH "n2n_v2" 7 "Sep 21, 2009" "revision 3909" "Background"
.SH NAME
N2n Version 2 \- version 2 of the n2n decentralised peer-to-peer network overlay
VPN.
.SH DESCRIPTION
N2n is a peer-to-peer network overlay or VPN system that provides layer 2 over
layer 3 encapsulation with data transform capabilities such as encryption and
compression. This guide discusses the differences of version 2 or n2n from
version 1.
.SH PROTOCOLS
N2n-2 uses a different set of messages to communicate with edges and
supernodes. The n2n-2 messages are not compatible with n2n-1. There is no
backward compatibility for n2n-1.
.SH ENCRYPTION
N2n-2 offers a new way of handling encryption compared to n2n-1. N2n-1 provided
facility for a single community password with no expiration. In n2n-2 this
method is preserved but a new mechanism has been added using a key schedule
file.
.TP
Key Schedule
A key schedule file lists a number of keys with the period for which each is
valid along with the encryption type identifier and the actual key value. This
allows the user to define up to 32 keys in advance with a pre-set time at which
they keys will change. The key schedule file can be reloaded while the edge is
running to allow new keys to be loaded and unused keys expunged.
.TP
Timing Requirements When a key rolls over to the next in the schedule, the new
key is used for all transmitted packets; however any packets received using an
older key can still be decoded as the keys from the key schedule are still
known. As a result edges do not need to have accurate time synchronisation. The
accuracy of required synchronisation depends to a large degree on the key
schedule. Rapid key roll-overs requires more accurate time synchronisation.
.P
N2n-2 provides the following encryption ciphers; more can be added as required:
.TP
.B (1) NULL
Data is encapsulated unchanged. Useful for testing and high-performance, low
sensitivity applications.
.TP
.B (2) TF
Twofish AES candidate.
.P
The following additional ciphers are specified but not yet implemented:
.TP
.B (3) AES-CBC
AES in CBC mode with 256-bit key.
.TP
.B (4) LZO
LZO compression of data (no encryption).
.TP
.B (5) TF-LZO
TF cipher with LZO compression of data prior to encryption.
.TP
.B (6) AES-CBC-LZO
AES-CBC ciper with LZO compression of data prior to encryption.

.SH EXTENSIBILITY
N2n-2 decouples the data transform system from the core of the edge
operation. This allows for easier addition of new data transform
operations. N2n-2 reserves 64 standard transform identifiers (such as TwoFish
encryption) but allocates transform identifiers 64 - 65536 for user-defined
transforms. This allows anyone to add to n2n new private transforms without
breaking compatibility with the standard offering.

.SH MULTIPLE SUPERNODES
N2n-2 introduces the capability of multiple supernodes to be used by an
edge. N2n-2 offers supernode in several flavours:
.TP
Stand-alone supernode

This is the same concept as from n2n-1. Supernode is a small efficient C program
which operates in isolation.
.TP
Federated supernodes

This is a cluster of supernodes which share information. Edges registered to any
of the cooperating supernodes can relay packets through the supernode federation
and switch supernodes if required. Supernodes can send PACKET or REGISTER
messages to other supernodes to try and find the destination edge.

.P
The n2n-2 edge implementation allows multiple supernodes to be specified on the
command line. Edges monitor the current supernode for responses to
REGISTER_SUPER messages. If 3 responses are missed then the edge starts looking
for a new supernode. It cycles through the list of supernodes specified until it
finds a working one.

.SH EFFICIENCY
The n2n-2 message formats have been made more efficient. The amount of data
overhead has been reduced by ensuring the messages contain only the data fields
required. Some optional fields do not consume data if they are not present.

.SH DAEMON OPERATION
The supernode and edge use daemon mode of operation by default. This sense is
inverted from n2n-1 where they ran in the foreground by default. They can be
made to run in the foreground so tools such a DJB's daemontools can work with
them. See the 
.B -f
option

.SH MANAGEMENT CONSOLE
Edge and supernode in n2n-2 provide a UDP-based management console. Both listen
on the localhost address 127.0.0.1. Commands can be sent to the programs by
sending to the UDP socket. Responses are returned to the socket from which
commands were issued. This only works from the computer on which the programs
are running. Statistics can be retrieved and commands issued. The netcat utility
is all that is required; but more sophisticated tools could be built on the
interface.

.SH SUPERNODE AUTHENTICATION
.B (To be implemented)
Space has been reserved in the supernode registration messages for an
authentication mechanism.

.SH MESSAGE SUMMARY
The following message types work within n2n-2.
.TP
REGISTER_SUPER
Sent from an edge to its local supernode to register its MAC with the community.
.TP
REGISTER_SUPER_ACK
Sent from a supernode to an edge to confirm registration. This also carries the
definition of the edge socket as seen at the supernode so NAT can be detected
and described.
.TP
REGISTER_SUPER_NAK
Supernode refusing to register an edge.
.TP
PACKET
Encapsulated ethernet packets sent between edges. Supernodes forward or
broadcast these and edges send them direct in peer-to-peer mode.
.TP
REGISTER
A peer-to-peer mode registration request from one edge to another. Supernodes
forward these to facilitate NAT crossing introductions.
.TP
REGISTER_ACK
Complete peer-to-peer mode setup between two edges. These messages need to
travel direct between edges.
.TP
FEDERATION
Federated supernodes exchanging community information.

.SH OTHER DIFFERENCES
.TP 
HTTP Tunneling
This experimental feature (-t option in n2n_v1) of n2n_v1 has been removed
entirely from n2n_v2.
.SH AUTHORS
.TP
Richard Andrews andrews (at) ntop.org - main author of n2n-2
.TP
Luca Deri
deri (at) ntop.org - code inherited from n2n-1
.SH SEE ALSO
ifconfig(8) edge(8) supernode(1)