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What is PPTP Protocol?

Monday, January 7th, 2013

What is PPTP? How do I use it? How is it different from other protocols?

PPTP stands for “Point to Point Tunneling Protocol” and utilizes a control channel over TCP and GRE tunnels that operate encapsulate PPP packets. It is a common VPN technology, and was the first VPN protocol to be supported by the Microsoft Dial-up Networking protocol. Ever since the release of Windows 95, all operating systems have been bundled with a PPTP client. So what does this mean to the everyday consumer? Well, it means that it is compatible with a majority of the Microsoft Windows product families. Definitely a very good thing. PPTP is also one of the most popular methods used for VPN providers.

Point-to-Point Tunneling Protocol (PPTP) is a simple protocol used to implement virtual private networks (VPN). It is one of the oldest protocols available to deploy VPNs and works via tunneling of point-to-point protocol (PPP) packets over the network. In this article, we look at the origins of the PPTP protocol and check out its pros and cons.

History – The first implementation of PPTP was conceptualized and developed in 1999 by a group of companies that included Microsoft, Ascend Communications, 3Com, among several others. The basic idea was to develop a protocol that provided remote access and security features similar to virtual private networks. It is worthwhile to note that the PPTP specification itself doesn’t specify authentication or security features; instead it relies on tunneling of PPP packets through Transmission Control protocol (TCP) or Generic Routing Encapsulation (GRE) for its operation. Even though PPTP is a major VPN protocol, it has not been ratified by Internet Engineering Task Force (IETF).

System Support – Every major operating system, including most mobile platforms, offers support for Point-to-Point Tunneling Protocol. PPTP was one the first VPN protocols to be supported by Microsoft Dialup Networking and it has been a part of Windows operating system family since the launch of Windows 95 OSR2. The latest versions of Windows support Protected Extensible Authentication Protocol (PEAP) along with PPTP. Other major operating systems like Mac iOS and OSX, Linux as well as mobile operating systems such as Windows Mobile, Android and Palm also come bundled with a PPTP client. In addition, PPTP also supports devices that can connect to DD-WRT router which is a major plus point over other VPN protocols.

Encryption – PPTP uses Microsoft Point-to-Point Encryption protocol (MPPE) to encrypt PPP packets. The protocol uses 128 bit encryption to encrypt its data which is considered less secure than other protocols offering 256 bit or even higher encryption.

Configuration – PPTP is one of the easiest protocols to set up and configure since it requires bare minimum details such as a username, password and the server IP address for configuration.

Speed – Since PPTP uses 128 bit encryption, it has less encryption overhead when compared to other VPN protocols. This makes PPTP based VPN systems a little faster although the speed difference isn’t really noticeable.

Port – PPTP uses fixed ports for its operation. The tunneling happens through port number 1723 for TCP and protocol 47 for GRE. Due to use of fixed ports, it is easy to restrict PPTP just by blocking access to the above port numbers.

Stability – The PPTP protocol is considered less stable and reliable when compared to other VPN protocols such as OpenVPN. Also, PPTP often has compatibility issues with GRE protocol and is slow to recover from failures.

Security Issues – PPTP is vulnerable to security flaws and several security issues have been discovered in the protocol. The security issues mainly relate to the underlying encryption and authentication technologies as well as the interaction between them. In particular, the MSCHAP-v2 issue and the use of RC4 algorithm make the protocol open to dictionary and bit-flipping attacks.

Conclusion – Point-to-Point Tunneling Protocol is not really the best choice as far as security and privacy issues are concerned. The protocol has several security flaws and is considered less stable and reliable than its competitors. The only instance where PPTP might be useful is when you want to setup a VPN on a device that does not support OpenVPN or L2TP/IPSec protocols.

January 7, 2013

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