VPNs - PowerPoint PPT Presentation

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VPNs

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  1. VPNs • Virtual Private Networks • Use the Internet for transmission instead of a PSDN • Sometimes called VPNs if use Frame Relay or ATM with added security Internet

  2. VPNs • Why use the Internet? • Inexpensive • Business partners are already connected to the same network (the Internet) • May use different PSDNs, but everybody is connected to the Internet

  3. VPNs • Problems with the Internet • Congestion: slows transmissions • Reliability: cannot always connect, sometimes fails during transmissions • Lack of security

  4. VPNs • IETF developing IPsec security standards • IP security • At the internet layer • Protects all messages at the transport and application layers E-Mail, WWW, Database, etc. TCP UDP IPsec

  5. VPNs • IPsec Transport Mode • End-to-end security for hosts Local Network Internet Local Network Secure Communication

  6. VPNs • IPsec Tunnel Mode • IPsec server at each site • Secure communication between sites Local Network Internet Local Network IPsec Server Secure Communication

  7. VPNs • IPsec Modes Can be Combined • End-to-end transport mode connection • Within site-to-site tunnel connection Local Network Internet Local Network Tunnel Mode Transport Mode

  8. VPNs • Another Security System for VPNs is the Point-to-Point Tunneling Protocol (PPTP) • For dial-up connections, based on PPP • Connects user with securely to a remote access server at a site Dial-Up Connection Local Network Internet PPTP Connection Remote Access Server

  9. Virtual Private Networks • Other Problems Remain • Internet Congestion is Still a Problem • Internet throughput tends to be low • Internet Reliability is Low • Cannot get connections • Backbone fails occasionally

  10. Virtual Private Networks • Alternative • Avoid the congested and unreliable backbone! • Use one ISP that serves all sites • Should offer QoS service level agreement (SLAs) for latency and reliability Site 1 ISP Site 2

  11. Virtual Private Networks • Alternative • Avoid the congested backbone • Use ISPs that “peer” with one another: connect with one another not through the Internet backbone • May offer end-to-end SLAs Site 1 ISP A ISP B Site 2 Peering

  12. WANs in Perspective • Both Leased Line Networks and PSDNs are widely used and will be for several years to come • Leased Line Networking is shrinking while PSDN networking is growing rapidly • VPN technology and standards are still immature and use will be very low for several years to come