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CONNECTIVITY

CONNECTIVITY 2.0 KB
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  1. This document describes how nodes in a VPN find and connect to eachother and
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  2. maintain a stable network.
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  3. 

  4.    Copyright 2001-2006 Guus Sliepen <guus@tinc-vpn.org>
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  5. 

  6.    Permission is granted to make and distribute verbatim copies of
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  7.    this documentation provided the copyright notice and this
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  8.    permission notice are preserved on all copies.
    9. 

  9. 

  10.    Permission is granted to copy and distribute modified versions of
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  11.    this documentation under the conditions for verbatim copying,
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  12.    provided that the entire resulting derived work is distributed
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  13.    under the terms of a permission notice identical to this one.
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  14. 

  15. 1. Synchronisation
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  16. ==================
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  18. Each tinc daemon has zero or more connections to other tinc daemons. It will
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  19. try to keep its own information synchronised with the other tinc daemons. If
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  20. one of its peers sends information, the tinc daemon will check if it is new
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  21. information. If so, it will update its own information and forward the new
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  22. information to all the other peers.
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  23. 

  24. This scheme will make sure that after a short amount of time all tinc daemons
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  25. share the same information. It will also almost completely prevent information
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  26. from looping, because "new" information that is already known is ignored and
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  27. not forwarded any further. However, since information can also be deleted
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  28. there's the possibility of a looping sequence of add/delete messages. This is
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  29. resolved by additionaly adding a unique identifier to each broadcasted message.
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  30. Messages are dropped if the same message with that identifier has already been
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  31. seen.
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  32. 

  33. 2. Routing
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  34. ==========
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  35. 

  36. Every node tells its peers to which other peers it is connected. This way
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  37. every node will eventually know every connection every node has on the VPN.
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  38. Each node will use graph algorithms to determine if other nodes are reachable or not and
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  39. what the best route is to other nodes.
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  40. 

  41. Because all nodes share the same information, using a deterministic algorithm
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  42. each node will calculate the same minimum spanning tree for the entire VPN.
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  43. The MST will be used to send broadcast VPN packets.
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