1. Virtual Private Networks: An Overview with Performance Evaluation Shashank Khanvilkar and Ashfaq Khokhar, University of Illinois at Chicago Presented by: Abe Murray CS577: Advanced Computer Networks

2. Outline Abstract / Intro VPN Basics VPN Software Architecture VPN Characterization –Network Performance –Features and Functionality –Operational Concerns Experiments Results –Network Performance –Features and Functionality –Operational Concerns Closing CS577: Advanced Computer Networks

3. Abstract Virtual Private Network (VPN) –Have become popular –Multitude of Proprietary, and Open-Source solutions –Authors compared a number of open-source linux- based VPN solutions (OSLVs) UDP tunnels have 50% less overhead, 80% greater bandwidth utilization, and 40-60% less latency CS577: Advanced Computer Networks

4. VPN Basics A VPN is a TCP/IP stack modification –Adds a VPN daemon, and a Virtual Network Interface (VNI) –Control plane (TCP): Peer authentication Session keys IP mapping to subnetworks –Data plane (TCP or UDP): Serial pipeline with encryption Authentication, compression CS577: Advanced Computer Networks

5. VPN Software Architecture 1.VPN packet arrives at eth1, routed to VNI 2.VPN packet arrives at VNI, handed to VPN daemon 3.VPN packet is compressed/encrypted, then handed to transport layer Subsequently, handled and routed like any other packet, with the exception that its contents are encrypted with the session key CS577: Advanced Computer Networks

6. VPN Characterization: Network Performance Overhead –75% header/trailers, compressible –25% encryption, padding, not compressible Bandwidth Utilization –Overhead reduces goodput –Latency makes default TCP window insufficient –TCP stacking results in degradation Latency/Jitter –Longer packet data path –Additional processing due to encryption –Additional data copies due to user-space VPN CS577: Advanced Computer Networks

7. VPN Characterization: Features and Functionality Code Modularity –Flexibility of OSLV regarding plugins Cryptos Routing Security updates Routing –Required for transport among VPN participants, must be shared among VPN participants. –Manual? Automated? CS577: Advanced Computer Networks

8. VPN Characterization: Operational Concerns Security (relative, subjective) –Proprietary? (security through obscurity) –Open Standard Protocol? (published) –Open Non-Standard Protocol? (published but obscure) Scalability –Memory utilization per VPN tunnel –Processor utilization per VPN tunnel –Configuration and management (order of magnitude) CS577: Advanced Computer Networks

9. Experiments All links 100 Mbps Test Tools: –ethereal - overhead –iperf – bandwidth and jitter –ping – latency CS577: Advanced Computer Networks Private Net 1Private Net 2 RedHat 9 Server P4 2 GHz 512 MB RAM RedHat 8 Workstation PII 400 MHz 128 MB RAM Private Network PC Network Experiments Private Network PC Network Experiments VPN Tunnel Assorted OSLV types

10. Results: Network Performance CS577: Advanced Computer Networks

11. Results: Features and Functionality CS577: Advanced Computer Networks

12. Results: Operational Concerns - Security CS577: Advanced Computer Networks

13. Results: Operational Concerns - Scalability CS577: Advanced Computer Networks

14. Conclusions CS577: Advanced Computer Networks Tunnel over UDP! Where did they present the memory/CPU utilization results? OSLVs are present and useable