L2TP vs PPTP
L2TP/IPSec and PPTP are similar in the following ways:
provide a logical transport mechanism to send PPP payloads;
provide tunneling or encapsulation so that PPP payloads based on any protocol can be sent across an IP network; rely on the PPP connection process to perform user authentication and protocol configuration.
Some facts about PPTP:
+ PPTP easy to deploy
+ PPTP use TCP, this reliable solution allow to retransmit lost packets
+ PPTP support
– PPTP less secure with MPPE(up to 128 bit)
– data encryption begins after the PPP connection process (and, therefore, PPP authentication) is completed
– PPTP connections require only user-level authentication through a PPP-based authentication protocol
Some facts about L2TP(over PPTP):
+ L2TP/IPSec data encryption begins before the PPP connection process
+ L2TP/IPSec connections use the AES(up to 256bit) or DESUup to three 56-bit keys)
+ L2TP/IPSec connections provide stronger authentication by requiring both computer-level authentication through certificates and user-level authentication through a PPP authentication protocol
+ L2TP use UDP. It is a faster, but less reliable, because it does not retransmit lost packets, is commonly used in real-time Internet communications
+ L2TP more “firewall friendly” than PPTP — a crucial advantage for an extranet protocol due to most firewalls do not support GRE
– L2TP require certificate infrastructure for issuing computer certificates
There’s no clear winner, but PPTP is older, more light-weight, works in most cases and clients are readily pre-installed, giving it an advantage in normally being very easy to deploy and configure (without EAP).
But for most of countries like UAE, Oman, Pakistan, Yemen, Saudi Arabia, Turkey, China, Singapore, Lebanon PPTP blocked by ISP or government so they need L2TP or SSL VPN
Reference : http://vpnblog.info/pptp-vs-l2tp.html
IPSec VS L2TP/IPSec
The reason people use L2TP is due to the need to provide login mechanism
to users. IPSec by itself is meant to by a tunneling protocol in a
gateway-to-gateway scenario (there are still two modes, tunnel mode &
transport mode). So vendors use L2TP to allow people to use their
products in client-to-network scenario. So, they use L2TP only for
logging and the rest of the session would be using IPSec. You have to
take in consideration two other modes; pre-shared-keys vs. certificates.
Reference : http://seclists.org/basics/2005/Apr/139
IPsec tunnel mode
When Internet Protocol security (IPsec) is used in tunnel mode, IPsec itself provides encapsulation for IP traffic only. The primary reason for using IPsec tunnel mode is interoperability with other routers, gateways, or end systems that do not support L2TP over IPsec or PPTP VPN tunneling. Interoperability information is provided at the Virtual Private Network Consortium Web site.
Reference : http://forums.isaserver.org/m_2002098668/mpage_1/key_/tm.htm#2002098668