traffic across N2N VPN

traffic across N2N communities. Packet forwarding through N2N is disabled by default, as this can be a security flaw. N2N users can enable it if necessary but doing so requires explicit user awareness.The need to cross NAT and firewall devices motivated the use of P2P principles for interconnecting N2N nodes. During the design phase, the authors analysed several popular P2P protocols [14] ranging from proprietary (e.g. Skype SDK) to open (e.g. BitTorrent [15]) protocols. Unfortunately most protocols have been created for file sharing and are not suitable for N2N because PDUs (Protocol Data Units) have been designed to carry file information (e.g. name, length, type, attributes such as MP3 tags) and perform distributed file searches. Even though existing P2P protocols were not immediately usable for N2N without modification, some concepts already present in other P2P architectures [16] have been utilised as is explained in the following chapter. In addition to the properties listed so far, N2N presents further differences from other approaches [28] [29] [30]:• Unlike most P2P overlay networks such as Chord [25] and Pastry [26] that are affected by the problem or locating objects/peers in a limited number of overlay hops, in N2N this is not a problem as, by design, peers are reachable either directly or in one hop when passing through the N2N community. This design choice has dramatically simplified peer lookup and membership information without requiring complex algorithms for information bookkeeping [27].