A method and apparatus for enabling enterprise customers to detect VPN
protocol blocking by access network providers and provides client VPN
software with instructions to activate another VPN protocol such as
Secure Socket Layer (SSL) that is less likely to be blocked by their
provider are disclosed. For instance, if the access network provider
blocks the IPSec VPN protocol, the client VPN software will switch to an
alternative VPN protocol, such as Secure Socket Layer (SSL) protocol,
Layer 2 Tunneling Protocol (L2TP), or Point-to-Point Tunneling Protocol
(PPTP), to connect to the VoIP network. The SSL, L2TP, and PPTP protocols
are all VPN protocols designed to enable encrypted and authenticated
communications across the public Internet.