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  1. Course Matters

  2. Recent Papers from journals

  3. Good PostersBad Posters

  4. Improving I/O Performance of Intermediate Multimedia Storage Node Pal Halvorsen Thomas Plagemann Vera Goebel Multimedia Systems 03

  5. Problem • Improve the performance of I/O in integrated multimedia storage node • 3 areas of improvement are identified • reduce memory copy • checksum computation • FEC computation

  6. Reduce Memory Copy • File system maintain pointer to an area in memory • Communication system maintain pointer to same area in memory • Memory copy avoided!

  7. Network Level Framing • Packet payloads are stored with checksum • When packets are retrieved for sending, destination address in header is updated • Checksum is updated with new destination • No need to recompute checksum for payload

  8. Integrated Error Management • Data are stored on RAID-4 (single parity checks) • Use the same error correcting code for RAID and packets • Avoid multiple computation of error correcting code

  9. Experiment: Memory Copy • Read 28662512B file 38 times in a loop • The time to transmit data through the storage node is reduced by 45-50% when there is no CPU load, and by 70-73% when CPU load is high

  10. Experiment: Network Level Framing • Transmit 255MB file • Time to calculate checksum is reduced by 95-99% • Time spent in kernel is reduced by 51-61%

  11. Experiment: Integrated Error Management • With encoding FEC, the maximum throughput is 22-24 Mbps. • Without encoding FEC, the maximum throughput is 1Gbps

  12. Let’s try again..

  13. Improving I/O Performance of Intermediate Media Storage Node Pal Halvorsen Thomas Plagemann Vera Goebel

  14. Contributions • Improve performance by • reducing memory copy • reducing checksum computation • reducing ECC computation

  15. Reduce Memory Copy • One shared copy of data for different OS component Memory Network System File System data

  16. Network Level Framing store payload with payload’s checksum • Reduce time to packetize data and compute checksum for data 1 3 update header and checksum 2 read payload with checksum

  17. Integrated Error Management • Avoid multiple computation of error correcting code reuse RAID ECC as ECC packet RAID ECC data data data ECC

  18. Results: Zero Copy

  19. Results: Network Level Framing Accumulated UDP Protocol Execution Time for sending 225MB file

  20. Results: Integrated Error Management Maximum Throughput with/without Encoding using Cauchy-based Reed Solomon Erasure Code

  21. Ad Hoc Networks Session 1

  22. Mobile Ad Hoc Network Radio Router Host

  23. Animation • http://www-i4.informatik.rwth-aachen.de/~mesut/manet/manet_en.html

  24. Radio Radio Radio Radio Router Router Router Router Host Host Host Host Mobile Ad Hoc Network

  25. Examples • Battlefield • Highway • Disaster Zone

  26. Challenges • All the difficulties of wireless LAN • Plus • Nodes can move • Connections can go up/down • No fix route

  27. Two Papers • IEEE JSAC • Special Issues in Wireless Multimedia • Baochun Li from U. of Toronto • Shiwen Mao from Polytechnic U.

  28. NonStop: Continuous Streaming Service on MANET Baochun Li IEEE JSAC 2004

  29. Streaming over MANET

  30. Network Partition Problem

  31. Only Solution .. • Predict Partition • Replicate Service

  32. Partition Prediction

  33. Network Partition Problem

  34. How to Predict Partition? • given velocity of each node • cluster nodes into “mobile groups” • find mean group velocity

  35. Clustering Algorithm

  36. Clustering Algorithm

  37. Clustering Algorithm

  38. Clustering Algorithm

  39. Choosing Server ?

  40. How to Choose Server? • find “stable group” • choose server within stable group with the most similar velocity

  41. Stable Group probability A B distance mean <= radio range and variance is not too large

  42. Stable Group B A C H D G E F

  43. Stable Group BCD are in my group AGH are in my group B A C H D G E F

  44. Stable Group BCDGH are in my group ABDGH are in my group B A C H D G E F

  45. How to Choose Server? • find “stable group” • choose server within stable group with the most similar velocity

  46. Summary • Server construct mobile group by clustering nodes using velocity • Use mean mobile group velocity to predict network partition • Replicate service before partition to ensure continuous service

  47. Summary • Node construct stable group by comparing distance over time • Choose server within stable group with most similar velocity

  48. Multipath Transport and Multistream Coding for MANET Shiwen Mao et. al. IEEE JSAC

  49. Single Path Transport

  50. Multipath Transport