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Learning Windows Server 2003 by Jonathan Hassell

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Virtual Private Networks

A virtual private network, or VPN, provides a secure connection over the public network infrastructure. VPNs give an organization the same access capabilities for remote connectivity as owned or leased connections, but at a much lower cost. (Of course, leased lines have their own benefits, but as far as private access is concerned, VPNs are a good solution.) Today, companies look to VPNs for extranet and wide-area intranet services.

How It Works

VPNs encrypt data before sending it through the public infrastructure, and then they decrypt the data at the receiving end of the network. For additional security, you can encrypt originating and destination network addresses. The VPN provides a point-to-point connection between the remote user’s computer, the VPN client, and the organization’s server, with data being passed through a “tunnel” that shields the data from the public network. In a sense, the public network’s logistics don’t matter because the data looks as if you sent it across a dedicated private link. Although the pathway doesn’t matter to the VPN user, that pathway’s performance does matter.

VPNs based on Microsoft technology first used the Point-to-Point Tunneling Protocol (PPTP) to create a secure environment in which to tunnel through the network, while VPNs on Cisco equipment used the proprietary Layer 2 Forwarding (L2F) protocol. However, as the popularity of VPNs grew, each company merged the best parts of its standard with the other, and ...

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