There are THREE key differences between PPTP and L2TP/IPSec. FIRST, encryption process in PPTP begins after the PPP process is completed. This means the PPP authentication is used for this protocol. In L2TP/IPSec, encryption begins before the PPP process begins.

Second, PPTP uses a stream cipher called Microsoft Point to Point Encryption (MPPE) that uses 40, 56, or 128-bit encryption keys. This stream cipher encrypts DATA as a bit stream. L2TP/IPSec, on the other hand, uses Data Encryption Standard (DES), a block cipher that encrypts data in discrete blocks.

LASTLY, PPTP requires only user-level authentication whereas L2TP/IPSec requires both user-level and system-level authentication.

There are three key differences between PPTP and L2TP/IPSec. First, encryption process in PPTP begins after the PPP process is completed. This means the PPP authentication is used for this protocol. In L2TP/IPSec, encryption begins before the PPP process begins.

Second, PPTP uses a stream cipher called Microsoft Point to Point Encryption (MPPE) that uses 40, 56, or 128-bit encryption keys. This stream cipher encrypts data as a bit stream. L2TP/IPSec, on the other hand, uses Data Encryption Standard (DES), a block cipher that encrypts data in discrete blocks.

Lastly, PPTP requires only user-level authentication whereas L2TP/IPSec requires both user-level and system-level authentication.