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Ad-hoc Storage Overlay System (ASOS): A Delay-Tolerant Approach in MANETs

Ad-hoc Storage Overlay System (ASOS): A Delay-Tolerant Approach in MANETs. Guang Yang, Ling-Jyh Chen, Tony Sun, Biao Zhou and Mario Gerla Computer Science Department, UCLA Mobile Adhoc and Sensor Systems (MASS), 2006 IEEE International Conference on. Outline. Introduction

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Ad-hoc Storage Overlay System (ASOS): A Delay-Tolerant Approach in MANETs

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  1. Ad-hoc Storage Overlay System (ASOS):A Delay-Tolerant Approach in MANETs Guang Yang, Ling-Jyh Chen, Tony Sun, Biao Zhou and Mario Gerla Computer Science Department, UCLA Mobile Adhoc and Sensor Systems (MASS), 2006 IEEE International Conference on

  2. Outline • Introduction • Application Scenarios and Design Principles • The Ad-hoc Storage Overlay System(ASOS) Architecture • Probabilistic Data Replication • Evaluation • Conclusion

  3. INTRODUCTION • MANETs • set up rapidly without pre-deployed infrastructure • Military battlefields, disaster recovery • tasks must be fulfilled quickly • Nodes may crash, lose power, be blocked, or move out of the communication range of its neighbors

  4. Motivation • End-to-end connectivity is highly susceptible to disruption • Adjusting the motion of existing nodes or deploying additional nodes can improve it • For scenarios where connectivity cannot be immediately improved • Proposed solution: Ad-hoc Storage Overlay System (ASOS)

  5. Assumption • A heterogenous MANET environment • File transfer are considered as delay tolerant • A number of mobile nodes capture useful data and send back to the control center • Part of the data may not be delivered to the control center in time due to connectivity disruptions

  6. Design Principles • Safe and robust storage • Immediate availability • Efficient storage and easy delivery • Friendly interface

  7. ASOS architecture • Initialization and Maintenance of ASOS • Selecting ASOS peers • Peer and file IDs • Initialization • Maintenance • ASOS Interface • Data Management

  8. ASOS architecture disconnect source ASOS destination

  9. Selecting ASOS peers • ASOS is a self-organized P2P overlay of existing nodes • It is desirable to designate a set of powerful nodes • Other regular nodes must understand the ASOS interface to access the storage utility

  10. Peer and file IDs • Every node has a unique ID • Files can be uniquely identified by hashing from source/destination IDs and other information

  11. Initialization • All ASOS peers form a multicast group • Each ASOS peer multicasts periodic HELLO messages to all ASOS peers • Every peer can hear from all other reachable peers and know which files are stored in ASOS and where they are

  12. Format of a HELLO message

  13. Maintenance • Each ASOS peer maintains a lookup table of reachable neighbors • Entries in the table contain similar fields as in the HELLO messages • Each entry is also associated with an expiration timer that is reset when the entry is refreshed

  14. ASOS architecture • Initialization and Maintenance of ASOS • ASOS Interface • Advertising of ASOS peers • Disruption detection and data submission • Data retrieval from ASOS • Data Management

  15. Advertising of ASOS peers • Regular nodes could look at the HELLO messages to learn about the nearby ASOS peers and stored files • Overhead • Introduce a new type of ADVERTISE messages • One node only forwards the first fresh ADVERTISE message it receives

  16. Decouple the task of advertising ADVERTISE message B A D Entries lookup table ASOS G C A 1 10unit (5,10) files F E a A 100k info

  17. Disruption detection and data submission destination ASOS ASOS C disconnected ASOS A B RERR RERR Source Switching end-to-end flow to the ASOS mode

  18. Disruption detection and data submission destination ASOS ASOS C disconnected ASOS A B Source be divided into several chunks

  19. Data retrieval from ASOS: pull model destination ASOS ASOS ADVERTISE C ASOS A B Source

  20. Data retrieval from ASOS: push model destination ASOS ASOS C hello ASOS A B Source

  21. ASOS architecture • Initialization and Maintenance of ASOS • ASOS Interface • Data Management • Probabilistic selection of storage locations • Other data transfer between ASOS peers • Data deletion and replacement

  22. Probabilistic selection of storage locations • To increase storage reliability, data is also replicated to other ASOS peers • Storage locations are selected by probabilistic replication: • A peer closer to the destination node • A peer further away from other ASOS peers • A peer less heavily loaded have a higher probability to be selected

  23. Other data transfer between ASOS peers • An ASOS peer may also dynamically transfer stored data to another peer • running short of power or storage space

  24. Data deletion and replacement • When the data is successfully delivered or has lost its usefulness • The original source or destination message its ASOS agent to delete data • The agent disseminates this message to all ASOS peers

  25. ASOS Peer Deployment and Probabilistic Location selection under the VT Mobility Model • The Virtual Track (VT) mobility model targets the MANET scenario where mobility of the grouped nodes is constrained • Initially, each group contains a certain number of ASOS peers • Due to splitting, a group may temporarily have zero ASOS peers • nodes turn to ASOS peers, or to static/individual peers

  26. The Virtual Track mobility model

  27. Evaluation • Application module: QualNet • Simulation scenario: UCLA campus map • 30 Nodes 1600 m×1600 m square area: 5 static, 5 individual (RWP) and 20 grouped (divided into 4 groups) • Each source generates a periodic constant-bit-rate (CBR) flow, at the rate of 80 Kbps, for 10 seconds every minute • Each simulation runs 20 minutes

  28. Screen snapshot of the simulation topology in QualNet

  29. Simulation parameters are summarized

  30. Simulation parameters are summarized

  31. Instantaneous throughput measured at the destination node

  32. Cumulative amount of data delivered to the destination as time proceeds

  33. Delivery ratios of data generated in each minute static node individual node grouped node

  34. Cumulative distribution function (CDF) of the size of HELLO messages

  35. Delivery ratio vs. number of ASOS peers

  36. Delivery ratio vs. number of replicated data copies

  37. Conclusion • The Ad-hoc Storage Overlay System (ASOS) that extends end-to-end data transport in MANETs when connectivity is disrupted • Storing undeliverable data reliably in an overlay of storage-abundant • Implemented the ASOS in QualNet

  38. Future work • ASOS peers can be dynamically elected • Data encryption, user authentication and intrusion detection are needed • Soft disruptions

  39. Thank you!

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