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meanwhile can be used by unauthorized VPN users so that what VPN users obtained is
only a logistic private network. This public network is regarded as VPN Backbone.
Build a credible and secure link by connecting remote users, company branches, partners to the
network of the headquarters via VPN so as to realize secure transmission of data.
It is shown in the figure below:
Enterprise
Headquarter
Embranchment
Cooperative
Partner
VP
N
VP
N
VPN
Remote Access
Fundamental Principle of VPN
The fundamental principle of VPN indicates to enclose VPN message into tunnel with tunneling
technology and to establish a private data transmission channel utilizing VPN Backbone so as to
realize the transparent message transmission.
Tunneling technology encloses the other protocol message with one protocol. Also,
encapsulation protocol itself can be enclosed or carried by other encapsulation protocols. To the
users, tunnel is logical extension of PSTN/link of ISDN, which is similar to the operation of actual
physical link.
VPN settings include IPSec settings, IPSec tunnels, GRE tunnels, L2TP client, PPTP client,
OpenVPN, OpenVPN Advanced and certificate management.
3.6.1 IPSec Settings
A majority of data contents are Plaintext Transmission on the Internet, which has many potential