APPENDIX 2 : VPN mechanism overview
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User manual ref. 9017009-02
3G-GPRS-EDGE router IPL-G12
Confidentiality
A VPN protects the privacy of information being exchanged between
communicating parties.
3 Operation
Authentication phase
The first operation the end-points carry out is authentication.
2 levels of authentication can be performed using a VPN :
Device level authentication
A code is stored in each end-point (i.e. router or PC); it can be a Key
or a certificate delivered by a certification authority.
During the initial phase, the two end-point exchange their codes; each
party checks that the other party code is valid.
User level authentication
The IPL-G12 router holds a user list; once a VPN has been set with
the remote user PC, the remote user identification code and password
is checked.
Encrypted tunnel transmission phase
Once the end-points have exchanged and checked each other identity
code, they set the VPN tunnel.
It is an Ip frames exchange; the source and destination IP addresses are
the end-points.
That tunnel encapsulates the encrypted IP data flow transmitted between
any of the devices connected to each end-point.
VPN clearing
Periodically, each router (or at least the VPN server router) sends to the
other one a control message to check the VPN must remain established.
If no response is received from the other party, the VPN is cleared.