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Virtual Private Network and OpenVPN

Feb 27, 2009, 23:04 (2 Talkback[s])

[ Thanks to linuxconfig for this link. ]

"VPN tunnels are generally considered as something mysterious and everybody who mentions them, is "cool" :-) However, there is nothing to be afraid about, in the fact principle of Virtual Private Network is very simple.

"Data in IP networks are exchanged in packets. Information about destination and a source of the packet can be found in the packet's header. The actual user data are carried as a payload. Let's imagine that ssh client wants to talk to ssh server over the Virtual Private Network. Packets leaving a host's network interface located on the local network are sent with a destination port number 22. When this packet reaches a VPN tunnel it is encapsulated into the VPN packet where original packet is now treated as a payload. If the VPN server listens on the port 443, the VPN packet will carry a destination port 443.

"When looking at the previous figure it is apparent that this kind of network data transfer over the VPN is a waste of transfer rate because original packet has a smaller payload space just because it needs to fit into the VPN tunnel packet. In VPN analogical sense this can be considered as a drawback."

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