Another example could be to provide additional security
to a smaller division of users that need a higher level of security provided in an
L2TP/IPSec VPN, such as users with elevated privileges or human resources employees.
This would result in a reduction in costs because the higher cost of purchasing and maintaining
certificates, required for L2TP/IPSec, would be limited to fewer users.
Both the PPTP and L2TP protocols are based on the Point-to-Point Protocol (PPP). The
technology works by encapsulating IP packets within PPP frames to transmit them
securely across a link. If the packets are intercepted, the contents of the frames are unreadable
and garbled, making them useless to unauthorized users. Both PPTP and L2TP
perform the same basic tunneling functionality by wrapping the PPP frame with additional
information required to route the data across the Internet to the remote VPN server.
The remote VPN server receives the packet, removes the wrapper, and delivers the packet
to the destination, essentially creating a virtual tunnel, such as the one shown in
223 Examining ISA Server 2006 VPN Capabilities and Requirements
9
Figure 9.
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