How many security protocols available and how the works

There is nothing like security protocol. apply security using the routing protocols. access-lists is the main feature or you can say technology that is used to permit/deny the traffic in/out of the network..
Firewall (pix/asa) is configured for security purpose. companies prefer to do the nat/pat on firewall it has diff domains of higher security (inside) and lower security (anything outside)we can do uncountable things to protect our network on firewall. IPsec is used for secure ip routing,it uses tunnels to carry the traffic. AAA is another feature for security,you can test it o your own pc in "network connections".. as VPNs is the need of ,todays networking culture,security policies also enhanced with it.