1. 1 Dong Lu, Peter A. Dinda Prescience Laboratory Department of Computer Science Northwestern University Evanston, IL 60201 GridG: Synthesizing Realistic Computational Grids

2. 2 Outline Why GridG? What is GridG? Topology generation –Hierarchical vs. degree based? –What are the relationships among the power laws of Internet topology? Annotation –What are the intra- and inter- correlations among the hosts and within a host? –How to build the correlations into GridG? Conclusions and future work

3. 3 Why GridG? Synthetic Grids needed to evaluate Middleware Existing physical grids too small Can’t control parameters Example: Evaluation of our RGIS system Example: Grid simulation projects –GridSim and SimGrid Example: overlay network simulations –Application level multicast

4. 4 GridG: A Synthetic Grid Generator Output: Network topology annotated with the hardware and software available on each node and link. –Layer 3 network: hosts, routers, links –Hosts: memory, architecture, number of CPUs, disk, operating system, vendor, clock rate –Routers: switching capacity –Links: bandwidth and Latency

5. 5 Example 1 Router (switching capacity) Host (arch, numcpu, clock rate, os vendor, mem, disk,) Link (bw, latency)

6. 6 Requirements Realistic topologies –Connected –Hierarchical topology –Power laws of Internet topology Realistic annotations –Distributions of attributes –Correlations of attributes Intra-host Inter-host

7. 7 GridG architecture A sequence of transformations on a text- based representation of an annotated graph.

8. 8 Outline Why GridG? What is GridG? Topology generation –Hierarchical vs. degree based? –What are the relationships among the power laws of Internet topology? Annotation –What are the intra- and inter- correlations among the hosts and within a host? –How to build the correlations into GridG? Conclusions and future work

9. 9 Quick review of the Power laws of Internet topology Power LawsExpression Rank exponent Outdegree exponent Eigen exponent Hop-plot exponent

10. 10 Current Graph generators Random (Waxman) Hierarchical : Tiers, Transit-Stub, etc. have clear network hierarchy, but don’t follow power laws Degree based : Inet, Brite, PLRG, etc. follow power laws, but don’t have clear network hierarchy

11. 11 Topology Generation in GridG (1/2) 1.Generate a basic graph without any redundant links using Tiers This is a hierarchical graph 2.Assign each node an outdegree randomly using the outdegree exponent power law as the distribution This enforces all the power laws! Scale-free 3.Determine the remaining outdegree of each node by taking original hierarchical links into consideration

12. 12 4.Add redundant links between randomly chosen pairs of nodes with sufficient remaining outdegree Nodes at higher levels (e.g., WAN) are given priority over nodes at lower levels (e.g., MAN) 5.Repeat 4 until there is no pair of nodes with positive remaining outdegree Topology Generation in GridG (2/2)

13. 13 Evaluation: Topology Obeys Rank Exponent Law

14. 14 Evaluation: Topology Obeys Outdegree Exponent Law

15. 15 Evaluation : Topology Obeys Hop-plot Law

16. 16 Evaluation : Topology Obeys Eigenvalue Exponent Law

17. 17 Comparing To The Internet Power Law Internet Routers GridG Tiers Rank -0.49 -0.51 -0.18 R 2 0.94 0.89 Outdegree -2.49 -2.63 -3.4 R 2 0.97 0.55 Eigen -0.18 -0.24 -0.23 R 2 0.97 0.97 Hop-plot 2.84 2.88 1.64 R 2 0.99 0.99 Notice Close Match

18. 18 Relationship among power laws (0) An interesting phenomenon: GridG and several other graph generators generate graphs according to the outdegree law only. But the generated graphs follow all four power laws! How is this possible? The power laws are closely related Can we deduce other power laws from the outdegree power law?

19. 19 Relationship among power laws (1) Eigenvalue law follows from the outdegree law [Mihail and Papadimitriou] Hop-plot and Eigenvalue power laws are followed by many topologies [Medina, et al] Outdegree law follows from the rank law Rank law does not follow from outdegree law Alternative rank law follows from outdegree law and fits data better Our Results

20. 20 Relationship among power laws (2) Rank law Outdegree law This is a power law

21. 21 Relationship among power laws (3) Log-log plot of the derived Outdegree law. Perfect power law fit. So we can do Rank law Outdegree law.

22. 22 Relationship among power laws (4) Outdegree law Rank law This is NOT a power law

23. 23 Relationship among power laws (5) Log-log plot of the derived Rank law. Not power law! So we can NOT do Outdegree law Rank law. Corresponds well to the Faloutsos Internet data

24. 24 Relationship among power laws (6) Log-log plot of derived Outdegree law using the new Rank law. It is perfect power law.

25. 25 Relationship among power laws (7) We propose the following as the relationships among Internet topology power laws New rank lawOutdegree power law Eigenvalue law

26. 26 Outline Why GridG? What is GridG? Topology generation –Hierarchical vs. degree based? –What are the relationships among the power laws of Internet topology? Annotation –What are the intra- and inter- correlations among the hosts and within a host? –How to build the correlations into GridG? Conclusions and future work

27. 27 Annotation Generator Distributions for attributes –Example: Smith MDS trace for memory Intra-host correlation of attributes –Example: Memory and CPU Inter- host correlations of attributes –Example: cluster of identical machines

28. 28 Intra-host correlations The Memory size, Architecture, CPU clock rate, Number of CPUs, Disk size, etc, all have certain distributions. These distributions are not independent, however –Example: a host with 64 CPUs is likely to have very big memory. Similarly, a host with a 3Ghz processor is likely to have bigger memory than a host with 1Ghz processor Many Intra-host correlations are unknown GridG has heuristic rules and can be extended by the user

29. 29 Heuristic Intra-host rules One processor will have memory between 64M and 4G More CPUs, more likely to have bigger memory and disk More memory, more likely to have bigger disk, and vice versa Windows machines won’t have more than 4 processors Machines with different architectures have different distributions of CPU clock rate Host load is not correlated to other attributes.

30. 30 Assumed Dependence Tree

31. 31 Inter-host correlations Hosts that are close to each other are likely to share some attributes. For example: OS concentration –Every IP subnet we probed had a dominant OS OS concentration rule built into GridG –User can disable

32. 32 Annotation Algorithm : Basic Based on the dependence tree, make grid conform to correlations by applying conditional probability –Choosing the distribution of an attribute based on attribute picked before it. For example: first choose architecture according to a distribution, then choose the number of CPUs based on it, finally, choose the size of memory based on the previous two choices.

33. 33 Annotation Algorithm: user rules User can add rules to GridG: for example, “all the hosts with N or above processors will have memory bigger than N*1024 MB”, etc. User rules appear as perl functions. User can also configure the distribution of host attributes in the config file.

34. 34 Examples: Silly hosts HostNum CPU Clock rate Mem (MB) Disk (GB) ArchOSOS vendor 1512120025640IA32DUXSun 2161000512800PARISCNetBSDMicrosoft 341600512160SPARC32DUXRedHat 41180065536400IA32SolarisMicrosoft Hosts generated without considering Intra-host correlation, each attribute follows its own distribution.

35. 35 Examples: Sensible hosts HostNum CPU Clock rate Mem (MB) Disk (GB) ArchOSOS vendor 151212006553610240MIPSFreeBSD 21610008192800PARISCNetBSD 3416001024160SPARC32SolarisSun 41180051280IA32Win2kMicrosoft Hosts generated with considering Intra-host correlations.

36. 36 Open questions What are the real distributions of host attributes? What are the real intra- and inter-host correlations? Difficult to answer without measurement data Difficult to acquire measurement data (see paper) We would appreciate your help!

37. 37 Conclusions 1.We have presented GridG, a tool kit for generating synthetic computational grids. 2.The topology generation component can produce structured network topologies that obey the power laws of Internet topology. 3.The annotation generation component of GridG is built upon Internet measurements and a set of heuristic rules.

38. 38 Conclusions 4.While developing GridG’s topology generator, we discovered an interesting relationship among the power laws, and proposed a new one that better fits the data. 5.While measuring the Internet, we found the OS concentration phenomenon and built it into GridG as an user option.

39. 39 For More Information GridG is released online at: http://www.cs.northwestern.edu/~urgis/GridG http://www.cs.northwestern.edu/~urgis Related RGIS project papers: “Nondeterministic queries in a Relational Grid Information Service”, In proceedings of SC03. “Scoped and Approximate queries in a Relational Grid Information Service”, In proceedings of Grid2003.