VPN
Protocols
You
can use virtual private networks (VPNs) to provide remote access
without having to rely on dial-up networking hardware, such as
modems, on the remote access servers. VPNs use an additional
protocol that allows users to connect to LANs over their existing
Internet or dial-up connections. These connections can
be
secure even though the connection may use public Internet hardware.
VPN protocols encapsulate TCP/IP, IPX/SPX, or NetBEUI data packets
inside PPP data packets. The remote access server, with the help of
the client, performs all security checks and validations and enables
data encryption, making it safe to send data over non-secure
networks, such as the Internet. Typically, users connect to the VPN
by first connecting to an Internet service provider (ISP) and then
connecting to the VPN ports through that Internet connection.
VPNs
use either Point-to-Point Tunneling Protocol (PPTP) or Layer Two
Tunneling Protocol (L2TP) to establish connections.
Point-to-Point Tunneling Protocol (PPTP)
Point-to-Point Tunneling Protocol (PPTP) enables the secure transfer
of encapsulated data from a PPTP client to a PPTP server across a
TCP/IP internetwork, such as the Internet. PPTP encapsulates PPP
frames in TCP/IP
packets for transmission over an internetwork. Because of this
encapsulation, you can use all features of PPP, including TCP/IP,
IPX/SPX, NetBEUI, and Microsoft Point-to-Point Encryption (MPPE), in
a PPTP virtual private network. Windows 2003 supports PPTP, which
you can use in private LAN-to-LAN networking.
Layer
Two Tunneling Protocol (L2TP)
Layer Two Tunneling Protocol (L2TP) is an industry standard
tunneling protocol. Like PPTP, L2TP uses the authentication and
compression mechanisms of PPP. Unlike PPTP, L2TP does not utilize
MPPE to encrypt PPP frames. Instead, L2TP relies on Internet
Protocol Security (IPSec) for encryption services. The result is
that L2TP-based virtual private network connections are always a
combination of L2TP and IPSec. For an encrypted L2TP virtual private
network, both the client and the server must support L2TP and IPSec.
L2TP allows any combination of TCP/IP, IPX/SPX, or NetBEUI traffic
to be encrypted and then sent over any medium that supports
point-to-point packet delivery, such as Ethernet, X.25, frame relay,
or asynchronous transfer mode (ATM).
IPSec
Internet Protocol Security (IPSec) ensures data security in
TCP/IP-based communications by providing an additional layer of
network security. IPSec integrates with the security inherent in
Windows 2003 to safeguard intranet and Internet communications. L2TP
can be combined with the security provided by IPSec to provide data
security. IPSec provides data integrity and encryption. It is
superior to PPTP, which uses MPPE encryption. Using IPSec results in
both increased demands on the CPU resources of the client and the
server and an increased network payload
