There are three main forms of VPN protocol currently in use, these are:
PPTP (Point to Point Tunnelling Protocol)
PPTP was designed in a consortium led by Microsoft, which included an implementation of the protocol as a standard component of Windows NT 4. Microsoft also released PPTP as a free add-on to Windows 95 and Windows 98, allowing users of (at the time) the most popular version of Windows to access corporate networks.
PPTP enables the secure transfer of data from a remote computer to a private server by creating a VPN connection across IP-based data networks. PPTP supports on-demand, multiprotocol, virtual private networking over public networks, such as the Internet.
PPTP proved unsuited to large companies (being limited to 255 connections per server), but more seriously, the PPTP standard did not settle on a single form of user authentication or encryption; therefore two companies could offer software supporting PPTP, yet each product would be incompatible with the other! From Windows 2000 onwards, Microsoft replaced PPTP with L2TP (see below). Continue reading “VPN protocols”