N2n Version 2 - version 2 of the n2n decentralised peer-to-peer network overlay
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
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.
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
- 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.
- Timing Requirements When a key rolls over to the next in the schedule, the
- 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.
N2n-2 provides the following encryption ciphers; more can be added as required:
- (1) NULL
- Data is encapsulated unchanged. Useful for testing and high-performance,
low sensitivity applications.
- (2) TF
- Twofish AES candidate.
The following additional ciphers are specified but not yet implemented:
- (3) AES-CBC
- AES in CBC mode with 256-bit key.
- (4) LZO
- LZO compression of data (no encryption).
- (5) TF-LZO
- TF cipher with LZO compression of data prior to encryption.
- (6) AES-CBC-LZO
- AES-CBC ciper with LZO compression of data prior to encryption.
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.
N2n-2 introduces the capability of multiple supernodes to be used by an edge.
N2n-2 offers supernode in several flavours:
- Stand-alone supernode
This is the same concept as from n2n-1. Supernode is a small efficient C
program which operates in isolation.
- 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
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.
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
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 -f
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.
(To be implemented)
Space has been reserved in the supernode registration
messages for an authentication mechanism.
The following message types work within n2n-2.
- Sent from an edge to its local supernode to register its MAC with the
- 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.
- Supernode refusing to register an edge.
- Encapsulated ethernet packets sent between edges. Supernodes forward or
broadcast these and edges send them direct in peer-to-peer mode.
- A peer-to-peer mode registration request from one edge to another.
Supernodes forward these to facilitate NAT crossing introductions.
- Complete peer-to-peer mode setup between two edges. These messages need to
travel direct between edges.
- Federated supernodes exchanging community information.
- HTTP Tunneling
- This experimental feature (-t option in n2n_v1) of n2n_v1 has been removed
entirely from n2n_v2.
- Richard Andrews andrews (at) ntop.org - main author of n2n-2
- Luca Deri
- deri (at) ntop.org - code inherited from n2n-1
ifconfig(8) edge(8) supernode(1)