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By Bradley Mitchell, About.com Guide

VPN TunnelingVirtual Private Networks Tutorial

vpn network protocols

Virtual private network technology is based on the idea of tunneling. VPN tunneling involves es tablishing and maintaining a logical network

connection (that may contain intermediate hops). On this connection, packets constructed in a specific VPN protocol format are encapsulated w ith

some other base or carrier protocol, then transmitted between VPN client and se rver, and finally de-encapsulated on the receiving side.

For Internet-based VPNs, packets in one of several VPN protocols are encapsulated within Internet Protocol (IP) packets. VPN protocols also

support authentication and encryption to keep the tunnels secure.

Types of VP N Tunneling

VPN supports two types o f tunneling - voluntary and compulsory. Both types of tunneling are commonly used.

In voluntary tunneling, the VPN client manages connection setup. The client first makes a connection to the carrier netwo rk provider (an ISP in th

case o f Internet VPNs). Then, the VPN client application creates the tunne l to a VPN server over this live connection.

In compulsory tunneling, the carrier network provider manages VPN connection setup. When the client first makes an ordinary connection to the

carrier, the carrier in turn immediately brokers a VPN connection between that client and a VPN server. From the client po int of view, VPN

connections are set up in just one s tep compared to the two-step procedure required for voluntary tunnels.

Compulsory VPN tunneling authenticates clients and associates them with specific VPN servers using logic built into the broker device. This netwo

device is sometimes called the VPN Front End P rocessor (FEP), Network Access Server (NAS) or Point of Presence Server (POS). Compulsory

tunneling hides the details of VPN se rver connectivity from the VPN clients and e ffectively transfers management control over the tunne ls from

clients to the ISP. In return, service providers must take on the additional burden of installing and maintaining FEP devices.

VPN Tunneling Protocols

Several computer network protocols have been implemented specifically for use w ith VPN tunnels. The three most popular VPN tunneling protoco

listed below continue to compete with each other for acceptance in the industry. These protocols are generally incompatible w ith each other.

Point-to-Point Tunneling Protocol (PP TP)

Several corporations wo rked together to create the PPTP specification. People generally associate PPTP with Microsoft because nearly all flavors

Windows include built-in client support for this protocol. The initial releases of PPTP for W indows by Microsoft contained security features that som

experts claimed were too weak for serious use. Microsoft continues to improve its PPTP support, though.

More - About PPTP

Layer Two Tunneling Protocol (L 2TP )

The original competitor to PPTP for VPN tunneling was L2F, a protocol implemented primarily in Cisco products. In an attempt to improve on L2F, t

best features of it and PPTP were combined to create a new standard called L2TP. Like PPTP, L2TP exists at the data link layer (Layer Two) in the

OSI model -- thus the origin of its name.

Internet Protocol Security (IP sec)

IPsec is actually a collection of multiple related protocols. It can be used as a complete VPN protocol solution or simply as the encryption scheme

within L2TP or PPTP. IPsec exists at the network layer (Layer Three) of the OSI model.

Next page > About PPTP > Page 1, 2, 3, 4, 5, 6

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