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Performance of Xen’s Secured Virtual Networks

Performance of Xen’s Secured Virtual Networks. Emanuele Cesena <cesena@mat.uniroma3.it> Paolo Carlo Pomi <paolo.pomi@polito.it> Gianluca Ramunno <ramunno@polito.it> Davide Vernizzi <davide.vernizzi@polito.it>. Outline. Introduction

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Performance of Xen’s Secured Virtual Networks

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  1. Performance of Xen’s Secured Virtual Networks Emanuele Cesena <cesena@mat.uniroma3.it> Paolo Carlo Pomi <paolo.pomi@polito.it> Gianluca Ramunno <ramunno@polito.it> Davide Vernizzi <davide.vernizzi@polito.it>

  2. Outline • Introduction • Experiments • Model • Security mechanism • Conclusion

  3. Introduction

  4. Motivations • Server consolidation • Planning • Model of virtual network • Emulation • Comparison

  5. Virtualization • “Technique for dividing the resources of a computer into multiple execution environments called virtual machines (VMs)” (A. Singh) • Full virtualization • Complete emulation of the underlying hardware • Unmodified operating system in the VM • Paravirtualization • VM needs a modified OS • Best performance, close to native

  6. Virtualization: XEN • XEN is a free Virtual Machines Monitor (hypervisor) • x86, Intel Itanium, PowerPC platforms • Paravirtualization, full virtualization (hw support) • Very low overhead when paravirtualized: average 3-5% • Virtual machines • Domain-0: privileged VM • Direct access to hardware • Direct interface to the hypervisor • Guest domains

  7. Domain 0 Guest 1 Guest 2 vif1.0 vif2.0 eth0 eth0 XEN hypervisor Virtual Network in XEN • Network interfaces • Front-end within VM: eth0 • Back-end in Domain-0: virtual interface (vif) • Connection between netfront and netback provided by the hypervisor

  8. Domain 0 physical world switch peth0 br0 eth0 Dom-0 vif0.0 vif1.0 Guest 1 vif2.0 Guest 2 XEN hypervisor Virtual Network in XEN • Virtual Network • Domain-0 manages all the netbacks • Bridge as “L2-switch”

  9. Guest 1 Guest 2 Domain 0 br0 eth0 eth0 vif1.0 vif2.0 Virtual Network in XEN • Example: Guest 1 sends a packet to Guest 2 • packet created within Guest 1 stack • copied from FE to BE via page flipping • forwarded through the bridge • copied from BE to FE, then received by Guest 2 • we call this a virtual link

  10. Experiments

  11. Experiments • HP Compaq dc7700 • Intel Core2 Duo 2.13 GHz • RAM: 2GB • XEN 3.0.4 • Linux kernel 2.6.20 • 10 Virtual Machines (guests) • RAM: 128 MB • Linux kernel 2.6.20 • minimal Debian installation • IPerf to test network bandwidth

  12. Client Guest 1 bridge Server Guest 1 Client Guest 2 Server Guest 2 Client Guest 3 Server Guest 3 Client Guest 4 Server Guest 4 Client Guest 5 Server Guest 5 Experiments: Virtual Network • Simple topology • All VMs connected to the same bridge

  13. Client Guest 1 bridge Server Guest 1 Client Guest 2 Server Guest 2 Client Guest 3 Server Guest 3 Client Guest 4 Server Guest 4 Client Guest 5 Server Guest 5 Experiments: Virtual Network • Simple topology • All VMs connected to the same bridge • Up to 16 virtual links • IPerf TCP channels • Example with 7 links

  14. Experiments: tests • SMP disabled • SMP enabled • Static domain scheduling • 10 iterations for each experiment • 1 minute per link • Samples every 5 sec • Average value

  15. Experiments: Results • NoSMP vs. SMP

  16. Experiments: Results • Dynamic scheduling vs Static scheduling

  17. Model

  18. Model: assumptions • Simple resource model • Single type of resource • Resources completely separated in system and network • Network described by the number of virtual links • Bandwidth equally distributed among links

  19. Bandwidth Network resources System resources F M Total resources K n links Model • M: maximal total bandwidth • M – K: minimal total bandwidth • F(n): total bandwidth

  20. Model • Model curve vs. experimental data: error less than 2%

  21. Security mechanisms

  22. Security mechanisms • Adding security brings • More workload • More networking • We focused on increase of number of links (eg. firewalls)

  23. Security mechanisms • Number of links increases by a factor s • Depending on topology • Depending on the security mechanism • The model allows prediction on the loss of bandwidth

  24. Model application 1/2 • Scenario: server consolidation • Computation power available • The virtual network must supply the physical interface • If the virtual network is well-designed, the virtual network supports the transaction

  25. Model application 2/2 • What happens if we introduce a firewall? • Applying the model we can esteem the resulting bandwidth

  26. Conclusions

  27. Future works • Improve the model • Relax assumptions • Forecast parameters without experiments • Validate the model • Other architecture • Other security solutions • Improve Xen • D2D communication • Optimization

  28. Conclusions • We developed a simple (but still effective) model • Explain how virtual network works in Xen • Foresee performance of the virtual network • Planning • Impact of security solutions • We show the limits of current Xen’s implementation and suggested improvements

  29. Thank youAny question?

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