Security at Multiple Layers

Layer

Example

Application

Application-specific (for instance, passwords for a

database program); Application (Proxy) Firewalls

Transport

SSL (TLS), Packet Filter Firewalls

Internet

IPsec, Packet Filter Firewalls

Data Link

Point-to-Point Tunneling Protocol (PPTP), Layer 2

Tunneling Protocol (L2TP)

Physical

Physical locks on computers, Notebook Encryption