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tinc Connectivity
This document describes how nodes in a VPNVirtual Private Network find and connect to eachother and
maintain a stable network.
1. Synchronisation
Each tinc daemon has zero or more connections to other tinc daemons. It will
try to keep its own information synchronised with the other tinc daemons. If
one of its peers sends information, the tinc daemon will check if it is new
information. If so, it will update its own information and forward the new
information to all the other peers.
This scheme will make sure that after a short amount of time all tinc daemons
share the same information. It will also almost completely prevent information
from looping, because "new" information that is already known is ignored and
not forwarded any further. However, since information can also be deleted
there's the possibility of a looping sequence of add/delete messages. This is
resolved by additionaly adding a unique identifier to each broadcasted message.
Messages are dropped if the same message with that identifier has already been
seen.
2. Routing
Every node tells its peers to which other peers it is connected. This way
every node will eventually know every connection every node has on the VPN.
Each node will use graph algorithms to determine if other nodes are reachable or not and
what the best route is to other nodes.
Because all nodes share the same information, using a deterministic algorithm
each node will calculate the same minimum spanning tree for the entire VPN.
The MST will be used to send broadcast VPNVirtual Private Network packets.