virtual private network

1 definition found

virtual private network - Free On-line Dictionary of Computing (26 May 2007) :

  Virtual Private Network
  VPN
  
     <networking, security> (VPN) The use of encryption in the
     lower protocol layers to provide a secure connection through
     an otherwise insecure network, typically the Internet.  VPNs
     are generally cheaper than real private networks using private
     lines but rely on having the same encryption system at both
     ends.  The encryption may be performed by firewall software
     or possibly by routers.
  
     Link-level (layer 2 and 3) encryption provides extra
     protection by encrypting all of each datagram except the
     link-level information.  This prevents a listener from
     obtaining information about network structure.  While
     link-level encryption prevents traffic analysis (a form of
     attack), it must encrypt/decrypt on every hop and every
     path.
  
     Protocol-level encryption (layer 3 and 4) encryption encrypts
     protocol data but leaves protocol and link headers clear.
     While protocol-level encryption requires you to
     encrypt/decrypt data only once, and it encrypts/decrypts only
     those sessions that need it, headers are sent as clear text,
     allowing traffic analysis.
  
     Application (layer 5 up) encryption is based on a particular
     application and requires that the application be modified to
     incorporate encryption.
  
     Cisco  (http://cisco.com/univercd/cc/td/doc/product/lan/cat5000/cnfg_nts/rsm/rsm_pa/4801encr.htm)
      .
  
     (1999-11-15)