Remote Access Solutions

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VPN stands for Virtual Private Network. VPN is the term used to refer to any device that is capable of creating a semi-permanent encrypted tunnel over the public network between two private machines or networks to pass non-protocol specific, or arbitrary, traffic. This tunnel can carry all forms of traffic between these two machines meaning it is encrypting on a link basis, not on a per application basis. VPNs are useful in situations where an entity is paying for dedicated leased lines due to security concerns or the need to provide layer two communications over a WAN link via transparent bridging, WINS servers, or other broadcast repeaters (Snyder, 2004).

The VPN allows the end points to connect to the Internet and have this same functionality without the need for expensive leased lines. The other common use for VPNs is to provide dial-up access or network extension for remote employees. Instead of making expensive calls and maintaining access servers with modem banks, a remote user can dial up and connect to the Internet locally, then use the VPN to access the main site securely over the Internet. This allows for reduction in phone bills and elimination of expensive and hard to secure modem banks and access servers. One of the key elements of VPNs is encryption. To protect sensitive or non-routable data as it passes over the public Internet, we need to create a virtual private tunnel (Snyder, 2004). This tunnel is built by encrypting the packets or frames and then encapsulating these in regular IP traffic between the two hosts or networks. The protection and encapsulation of these packets is vital to the function of a VPN and one of the most complex pieces to get right (Schneier and Ferguson, 2006). VPNs work by creating a virtual tunnel over the public Internet. In order to create this tunnel, symmetric encryption is used. Both sides of the tunnel share common encryption and decryption keys and use them to encrypt all traffic in both directions. Symmetric encryption is very fast and there are many solid algorithms available to implement this (Blowfish, AES, 3DES) (Dumon, 2006). There are two problems with symmetric encryption. To get these common keys to both sides of the tunnel is called key exchange or key agreement. To know we are exchanging keys with the correct entity is called authentication (Dumon, 2006). There are many ways to exchange keys.

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