VPNs at different OSI layers
The layer where VPN is constructed affects its functionality.
Example: In encrypted VPNs, the layer where encryption occurs determines
how much traffic gets encrypted
the level of transparency for the end users
Data link layer VPNs (Layer-2)
Example protocols: Frame Relay, ATM
Expensive - Requires dedicated Layer 2 pathways
may not have complete security – mainly segregation of the traffic, based on types of Layer 2 connection
Q: Is L2TP a layer 2 VPN?