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SIGCOMM 2008 © 2008 Andreas Haeberlen, MPI-SWS 1 SatelliteLab: Adding Heterogeneity to Planetary-Scale Network Testbeds Andreas Haeberlen MPI-SWS / Rice.

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Presentation on theme: "SIGCOMM 2008 © 2008 Andreas Haeberlen, MPI-SWS 1 SatelliteLab: Adding Heterogeneity to Planetary-Scale Network Testbeds Andreas Haeberlen MPI-SWS / Rice."— Presentation transcript:

1 SIGCOMM 2008 © 2008 Andreas Haeberlen, MPI-SWS 1 SatelliteLab: Adding Heterogeneity to Planetary-Scale Network Testbeds Andreas Haeberlen MPI-SWS / Rice University Marcel Dischinger MPI-SWS Ivan Beschastnikh University of Washington Krishna P. Gummadi MPI-SWS Stefan Saroiu University of Toronto

2 SIGCOMM 2008 2 © 2008 Andreas Haeberlen, MPI-SWS Why are testbeds so popular? Testbeds provide wide-area network paths Realistic network paths are crucial for evaluating the performance of distributed systems Your cluster Testbeds PLANETLAB vs.

3 SIGCOMM 2008 3 © 2008 Andreas Haeberlen, MPI-SWS Access networks and heterogeneity Internet bottlenecks are in access networks Studies show that most queueing, loss etc. happens there Access networks have high heterogeneity Cable, DSL, GPRS, UMTS, EVDO, 802.11, Satellite, Dial-up... Not represented in existing testbeds Internet Backbone Access networks

4 SIGCOMM 2008 4 © 2008 Andreas Haeberlen, MPI-SWS Growing the testbed is not enough Can we simply add more nodes? More nodes from acad. networks do not improve heterogeneity Nodes from the commercial Internet are much more effective Need nodes from the commercial Internet 280 PlanetLab nodes in U.S. and Europe 27 end nodes in U.S. and Europe Inter-AS links covered Node index

5 SIGCOMM 2008 5 © 2008 Andreas Haeberlen, MPI-SWS Challenges 1) Make it easy for volunteers to contribute Will not allow arbitrary code to run on their machines Do not want to spend time managing software Do not want to deal with complaints 2) Keep testbed easy to use for experimenters Resources may vary widely (cell phone vs. workstation) Nodes may have different OSes, hardware, software... Nodes may be behind middleboxes (NATs, firewalls,...)

6 SIGCOMM 2008 6 © 2008 Andreas Haeberlen, MPI-SWS A new testbed architecture Idea: Separate computation and communication Tier 1: Powerful, well-connected nodes (from existing testbed) Contribute computation power, memory, storage... Tier 2: Light-weight nodes Contribute "just their access-network links" Tier 1 Tier 2 "Planets" "Satellites"

7 SIGCOMM 2008 7 © 2008 Andreas Haeberlen, MPI-SWS Outline Motivation SatelliteLab Evaluation Applications Conclusion

8 SIGCOMM 2008 8 © 2008 Andreas Haeberlen, MPI-SWS Delegation Delegate code execution to the planets Problem: Changes the network path Misses the access links Solution: Send traffic through the satellites Planet A Planet B Satellite A Satellite B Application Network path Adds some latency

9 SIGCOMM 2008 9 © 2008 Andreas Haeberlen, MPI-SWS Detour routing Two challenges remain: Satellites are sending traffic that may trigger complaints NATs and firewalls may prevent connectivity Solution: Detour traffic through the planets Planet A Planet B Satellite A Satellite B Firewall

10 SIGCOMM 2008 10 © 2008 Andreas Haeberlen, MPI-SWS The SatelliteLab detour path To send a packet from planet A to planet B: 1. A intercepts the data packet 2. A exchanges a probe packet with its satellite 3. A sends the data packet to B 4. B exchanges a probe packet with its satellite 5. B delivers the data packet Planet A Planet B Satellite A Satellite B Actual path "Ideal" path

11 SIGCOMM 2008 11 © 2008 Andreas Haeberlen, MPI-SWS Challenges revisited 1) Make it easy for volunteers to contribute No complaints: Satellites only communicate with their planet No hassle: Sufficient to install the satellite helper once No CPU slowdown: Planets do all the heavy lifting No security risk: Satellite is just 118 lines of Java code 2) Keep testbed easy to use for experimenters All application code runs on the planets No need to deal with middleboxes No resource limitations due to satellites Works with unmodified binaries

12 SIGCOMM 2008 12 © 2008 Andreas Haeberlen, MPI-SWS Outline Motivation SatelliteLab Evaluation Applications Conclusion

13 SIGCOMM 2008 13 © 2008 Andreas Haeberlen, MPI-SWS Evaluation Is it feasible to recruit edge nodes? Is the availability sufficient for experiments? Can satellites find a nearby planet? Does SatelliteLab preserve... the path capacity? the queueing delay? the jitter? the packet loss rates? Yes.

14 SIGCOMM 2008 14 © 2008 Andreas Haeberlen, MPI-SWS Is it feasible to recruit edge nodes? Built a prototype testbed Asked friends and family to install satellite software Increased heterogeneity with very little effort Ten U.S. states, six countries, 15 commercial ISPs Technologies: Cable, DSL, Ethernet, Wi-Fi, ISDN, BT, EVDO 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Canada Germany Hungary Portugal UK Cable DSL Uni+Wi-Fi Cable+Wi-Fi DSL+Wi-Fi Cable DSL DSL+Wi-Fi Cable+Wi-Fi DSL DSL+Wi-Fi ISDN+BT DSL Cable DSL no yes no yes no yes no Desktop Laptop PDA Laptop Desktop Laptop Desktop Laptop no yes no yes no yes no yes 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 CA, USA CO, USA IL, USA LA, USA MA, USA MD, USA NJ, USA TX, USA WA, USA DSL+Wi-Fi EVDO Cable+Wi-Fi Cable DSL Cable+Wi-Fi Uni Cable+Wi-Fi DSL+Wi-Fi Cable+Wi-Fi Cable Cable+Wi-Fi DSL yes no yes no yes Laptop Desktop Laptop Desktop Laptop Desktop Laptop Desktop no yes no yes no yes no # Location Access link NAT Type Mob.

15 SIGCOMM 2008 15 © 2008 Andreas Haeberlen, MPI-SWS SatelliteLab preserves path capacity Direct path vs. interplanetary path Large difference because bottlenecks are in access networks Detour routing preserves the path capacity Direct path SatelliteLab path PAPA PBPB SASA SBSB Interplanetary path

16 SIGCOMM 2008 16 © 2008 Andreas Haeberlen, MPI-SWS SatelliteLab preserves queueing delay Same comparison for queueing delay Almost all the queueing is in the access networks Detour routing preserves the queueing delay Interplanetary path PAPA PBPB SASA SBSB Direct path SatelliteLab path

17 SIGCOMM 2008 17 © 2008 Andreas Haeberlen, MPI-SWS Outline Motivation SatelliteLab Evaluation Applications Network coordinate system Overlay multicast TCP throughput over cellular links Conclusion

18 SIGCOMM 2008 18 © 2008 Andreas Haeberlen, MPI-SWS Application: Network coordinates Need to measure RTT between nodes Surprising observation (in previous work): Discarding outliers improves network coordinates on PlanetLab [NSDI'06] but not when deployed with Azureus BitTorrent client [NSDI'07] Reason: Huge RTT variance PlanetLab did not predict this observation Could SatelliteLab have predicted it? Figures taken from [NSDI'07]

19 SIGCOMM 2008 19 © 2008 Andreas Haeberlen, MPI-SWS Application: Network coordinates We ran an experiment with several Azureus nodes on SatelliteLab We observed same effect as in [NSDI'07] SatelliteLab could have predicted this outcome! Can we also use SatelliteLab to explain it? Yes - Measurements revealed extremely long queues on the broadband access links Azureus downloads fill up the queues  high RTT variance!

20 SIGCOMM 2008 20 © 2008 Andreas Haeberlen, MPI-SWS Summary Existing testbeds lack heterogeneity SatelliteLab: A new testbed architecture for heterogeneous testbeds Introduces satellites, a new class of light-weight nodes Enables experimenters to improve heterogenity by recruiting end nodes as satellites Builds on existing testbeds and preserves many of their useful properties: Ease of use, ease of management...

21 SIGCOMM 2008 21 © 2008 Andreas Haeberlen, MPI-SWS SatelliteLab is for YOU! We have a new testbed that you can use for your experiments To run an experiment, you need: some planets (e.g., nodes from PlanetLab) some satellites (e.g., nodes from friends or colleagues) the SatelliteLab software http://satellitelab.mpi-sws.org/


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