1. Large-scale Virtualization in the Emulab Network Testbed Mike Hibler, Robert Ricci, Leigh Stoller Jonathon Duerig Shashi Guruprasad, Tim Stack, Kirk Webb, Jay Lepreau Proc. Of the 2008 USENIX Annual Technical Conference Hoon-gyu Choi hgchoi@mmlab.snu.ac.kr 2008.10.27

2. Contents Introduction Motivation Key techniques Results Conclusion 2015-12-04 MMLAB 2

3. Introduction Testbed is more realistic than simulation –Experimenters can use real OS, other software, and obtain actual performance measures Emulab: Network Testbed –Provide time- and space-shared public facility 2015-12-04 MMLAB 3

4. Motivation Emulab is not scale –Too small –Inefficient Original Emulab maps virtual network nodes and links one- to-one onto dedicated PCs and switched Ethernet link Solution –Multiplex logical nodes and networks onto the physical infrastructure –Use Virtualization to perform network experiments using fewer physical resources –Should be transparent to applications and should preserves experiment fidelity 2015-12-04 MMLAB 4

5. Three Goals Application transparency –Real application on virtual machines –Keep most semantics of unshared machines Application fidelity –Physical results ≈ Virtual results –Avoid virtual node interference System capacity –Low overhead –Don’t prolong experiments 2015-12-04 MMLAB 5

6. Key techniques Virtualization technology –Host and network Resource mapping Feedback-directed emulation 2015-12-04 MMLAB 6

7. Virtualization Extending FreeBSD jail –Namespace isolation –Virtual disks –Network virtualization Ability to bind to multiple interfaces New virtual network device (veth) Separate routing tables 2015-12-04 MMLAB 7

8. Virtualization 2015-12-04 MMLAB 8

9. Mapping Map the virtual topology to a physical topology Good mapping –Pack using resources efficiently Packs virtual hosts, routers, and links on to a minimum number of physical nodes without overloading the physical nodes –Do it quickly Use assign –A solver for the Network Testbed Mapping Problem –Pack both nodes and link –Use Resource-based Packing Avoid scarce resources Works well for heterogenious virtual and physical nodes 2015-12-04 MMLAB 9

10. Mapping quickly Apply a heuristic pre-pass to the virtual graph before running assign –Exploit the structure of the input topology –Two coarsening algorithms Combine all leaf nodes from the same LAN Graph partionining 2015-12-04 MMLAB 10

11. Mapping quickly 2015-12-04 MMLAB 11 200

12. Mapping quality 2015-12-04 MMLAB 12

13. Feedback Do I know how tightly I can pack my virtual nodes? –No, But we have a closed, repeatable world Process 1.Pick a packing 2.Run experiment 3.Monitor for artifacts CPU near 100%, significant paging activity, disk utilization 4.Re-pack & Repeat Measure resource use Feed into resource-based packing 2015-12-04 MMLAB 13

14. Results Application fidelity Adaptation Application transparency 2015-12-04 MMLAB 14

15. Application Fidelity Setup –All results gathered on Emulab’s low-end “pc850” machines 850 MHz PCs with 512MB RAM and four 100Mb Ethernet interfaces –Uses Pathrate bandwidth measurement tool –Running p2p file sharing application, Kindex Total 60 clients Each client –Uploads a single file’s index, and random searches for other files –generates 20-40 request per minute –Network topology consists of six 10Mbps campus LANs Each LAN is connected to a router via a 3Mbps 2015-12-04 MMLAB 15

16. Application Fidelity 2015-12-04 MMLAB 16

17. Adaptation Results Setup –Java-based web server on one host with 69 clients Each clients continually download a 64KB file Three different types –9 clients were evenly spread across 3 links on a single router using 2MB LANs (to emulate cable modems) –40 clients were directly connected to a single router using 2MB multiplexed link (to emulate DSL modems) –20 clients were directly connected to a single router using 56Kb multiplexed link (to emulate phone modems) 2015-12-04 MMLAB 17

18. Adaptation results Feedback case study 2015-12-04 MMLAB 18

19. Conclusion Virtualization increase Emulab’s capacity –Transparently –Preserves fidelity Requires solving several challenging problems But, can be useful 2015-12-04 MMLAB 19