Network Emulation for Researching Long-Fat Networks, Delay Tolerant Networks and Grid Environments

1. Network Emulation for Researching Long-Fat Networks, Delay TolerantNetworks and Grid Environments Presented by: Eric Coe Computer Systems Research Department, M1–102The Aerospace Corporation www.aero.org ecoe@aero.org(310) 336-1911 February 9, 2005

2. Outline • Aerolab: Aerospace Testbed based on EMULAB • What it is, how it works, why we need it • Define the following and motivate why network emulation is appropriate • Long Fat Network (aka High-Speed Bandits) • Delay or Disruption Tolerant Networks • Grid Environments • Demo: So how easy is it? • Future Directions 2

3. What is Aerolab? • Time- and Space-Shared Network Emulation System • Construction of Complex Topologies • Emulation of Link Conditions—Delay, Loss and Bandwidth (dynamic) • Boot Multiple Operating Systems—FreeBSD, Linux, and U of Utah’s OS-Kit (real-time Linux, Windows on the Way) • Runs on Commodity Hardware—PCs and Cisco Switch • Scales to Hundreds of Physical Nodes and supports Multiple Logical Nodes per Physical Nodes • Easy-To-Use Front-End • Automates Configuration of OS, Topology and Links • Supports both ns2 style scripting and Web-based GUI • Originally developed by University of Utah under a National Science Foundation Grant 3

4. Aerolab Architecture 4

5. programmable switch physical nodes control nodes Utah’s Emulab 5

6. Why Network Emulation (Utah) • “We evaluated our system on five nodes.” -job talk from university with 300-node cluster • “We evaluated our Web proxy design with 10 clients on 100Mbit ethernet.” • “Simulation results indicate ...” • “Memory and CPU demands on the individual nodes were not measured, but we believe will be modest.” • “The authors ignore interrupt handling overhead in their evaluation, which likely dominates all other costs.” • “Resource control remains an open problem.” 6

7. Why Network Emulation (Aerospace) • “Different projects need to evaluate/operate different networks” • “Network set-up and running cables is costly and open to configuration errors (HW/SW)” • “Aerolab should hide the networking “magic” so that researchers can experiment at the application or protocol level” • “In theory simulation and the real-world are the same but in practice they are different” • “Repeatability, Repeatability, Repeatability and archiving. Old demos can be run w/ little overhead.” 7

8. Why Network Emulation (more..) • “You have to know the right people to get access to the cluster or real network.” • “The cluster or real network is hard to use.” • “<Experimental network X> runs FreeBSD 2.2.x.” • “October’s schedule for <experimental network Y> is…” • “<Experimental network Z> is tunneled through the Internet” 8

9. Aerolab’s Value to Aerospace • Enhances Networking Capabilities • Large Scale Experiments • Complex Topologies • Hardware and Software “In The Loop” • Automates Laboratory Operations • Reduces Labor and Complexity • Improves Repeatability and Allows “Archiving” Experiments • Facilitates Resource Sharing Emulab is not just the latest cool thing, it’s the right way to run a networking lab. 9

10. Outline • Aerolab: Aerospace Testbed based on EMULAB • What it is, how it works, why we need it • Define the following and motivate why network emulation is appropriate • Long Fat Network (aka High-Speed Bandits) • Delay or Disruption Tolerant Networks • Grid Environments • Demo: So how easy is it? • Future Directions • Potential Collaboration 10

11. Long Fat Networks (LFN) • What they are: • Characterized as networks with large bandwidth-delay products • Typically gigabit speeds and have delays larger than 70 msec • Examples: networks of compute-clusters; satellite networks; transcontinental or transoceanic high-speed links. • Network where standard TCP has poor performance 11

12. Long Fat Networks (LFN) • What an Aerolab like system provides: • Install custom kernel images that contain various transport protocols (HS-TCP, BIC, CUBIC, WEB100, XCP) • Total control of the networking environment • Run what-if scenario’s • Guarantee no other traffic on the network or only “known” traffic • Packet loss can be attribute to “WHO”. • Dynamic Link Characteristics (satellite) • Varying bandwidth • Varying error rates, probability of packet loss • Repeatability: When results from this week do not match last weeks. . 12

13. Delay Tolerant Networks (DTN) • What they are: • Characterized as networks with no contemporaneous end to end path • Occur due to intermittent connectivity which is caused by • large propagation delays • nodes going up and down frequently • with highly mobile nodes in sparse network • Networks where standard TCP has no performance due to the lack of an end to end path 13

14. Delay Tolerant Networks (DTN) 14

15. Delay Tolerant Networks (DTN) • How we classify: • Application basis • Interplanetary Network (networking the solar system) • Sensor networks • Static nodes (due to nodes choosing their on and off periods • Mobile nodes (mobility process dictates links presence or absence) • Hybrid case • Link types • Deterministic: Contacts can be scheduled • Probabilistic: Contacts happen based on some distribution • Dynamic: Contacts happen in a purely opportunistic way 15

16. Delay Tolerant Networks (DTN) • What an Aerolab like system provides: • Dynamic link conditions for delay, bandwidth, and even link availability • Ability to run Bundling Protocol on top of a topology and over different topologies • Ability to evaluate routing protocols across the variety of networks discussed earlier • A common facility for other researchers to conduct experiments Avoids everyone having their own “version/vision” of what constitutes a DTN 16

17. Grid Environments • What they are: • Networks of loosely coupled computational resources • Heterogeneous by nature in both capacity and availability • Basic grid services and applications must inhabit a dynamic, heterogeneous, distributed environment • Issue: How to quantitatively evaluate grid services and applications in such an environment? 17

18. Quantitative Evaluation of Grids • What an Aerolab-like system could support for grid research: • Playback mechanism for network behavior, cross traffic • Injecting errors for testing fault tolerance, robustness • Testing autonomic computing methods (AC control cycle: monitor, analyze, plan, execute) • Remove a link or halt processes on a host • Evaluate response of autonomic control system • Testing information or resource discovery on larger networks • Quantitatively evaluate scalability in larger topologies • Quantitative evaluation wrt topology structure and connectedness • Tools needed to provide these capabilities in a general way 18

19. APSimScript Globus APSim USC discover APSim APSim HLA/RTI ISI HLA/RTI HLA/RTI overlay request start overlay config MDS-2 Aerospace ATMD ATMD XBone Manager overlay register Example: Evaluation of Grid Application Performance • DARPA Active Networks Project • Exploit application topology to compute lower-bound timestamp in distributed simulations • Globus used to manage Xbone and start HLA-compliant simulation • Very hard to run large test cases HLA Time Mgmt done “in the network” by overlay of active time mgmt daemons 19

20. Example: Evaluation of Grid Application Performance • Solution: Emulate larger topologies on Utah EmuLab • Set of quasi-random, tree topologies generated • 4, 8, 16, 32, 64 end-hosts • 9, 15, 22, 29, 34 interior service hosts • Tree topologies constrained to have average 2.5 degree of connectedness • 550 Lower Bound Timestamp (DRN) calculations done for each topology Example: topology w/ 32 end-hosts 20

21. Optimistic Mesh Generation on the Grid • Optimistic Delauney Mesh Generation • Optimism controlled by number of cavity expansion msgs – affects BW demand, latency • Already run on clusters and TeraGrid • Work in Progress: run on AeroLab to do repeatable parametric tests controlling available bandwidth Nave, Chrisochoides, Lee, Deerfield, International Meshing Roundtable, Sept. 2004 21

22. Aerolab • #1. Create a topology • #2. Do something useful Demo: So how easy is it? 22

23. Future Directions • Different OSes, namely Solaris, real-time Linux and Windows • Incorporate Hardware emulators (IXP,SPIRNET) • Incorporate passive network sniffers (layer 1) • Wireless nodes, possible mobile campus nodes • Merge with the Aerospace cluster (more nodes) • Integrate 10 Gigabit capability • Federate with other testbeds • More nodes...more nodes...more nodes 23

24. Aerolab • Thank You! • Questions? 24