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

2. 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

3. 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

4. 4 Aerolab Architecture

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

6. 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.”

7. 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.”

8. 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.” “ runs FreeBSD 2.2.x.” “October’s schedule for is…” “ is tunneled through the Internet”

9. 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.

10. 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

11. 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

12. 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..

13. 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

14. 14 Delay Tolerant Networks (DTN)

15. 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

16. 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

17. 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?

18. 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

19. 19 USC Aerospace ISI APSimScript Globus MDS-2 ATMD overlay APSim HLA/RTI APSim HLA/RTI APSim HLA/RTI start discover register overlay request overlay config XBone Manager 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

20. 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

21. 21 Optimistic Mesh Generation on the Grid Nave, Chrisochoides, Lee, Deerfield, International Meshing Roundtable, Sept. 2004  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

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

23. 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

24. 24 Aerolab Thank You! Questions?