1. Korea Advanced Institute of Science and Technology Active Sensor Networks(Mate) (Published by Philip Levis, David Gay, and David Culler in NSDI 2005) 11/11/09 Internet System technology Kim Young-Sun, Choi Sun-Tae Internet system technology

2. Table of Content  Introduction  Background  Design  Evaluation  Pros and Cons 2 Internet system technology

3. 3 Introduction  Wireless sensor networks have limited resources and tight energy budgets.  These constraints make in-network processing a prerequisite for scalable and long-lived applications.  as sensor networks are embedded in uncontrolled environments, a user often does not know exactly what the sensor data will look like, and so must be able to reprogram sensor network nodes after deployment. ※ This paper propose using application specific virtual machines (ASVMs) to reprogram deployed wireless sensor networks Internet system technology

4. Background(Requirement)  Requirement extraction from Maté v1.0  Flexibility : Mat é VM : Very concise programs, but is designed for a single application domain. To provide support for in- network processing, a runtime must be flexible enough to be customized to a wide range of application domains.  Concurrency : Limited resources and a constrained application domain allowed Mate to address the corresponding synchronization and atomicity issues by only having a single shared variable. This restriction is not suitable for all VMs. 4 Internet system technology

5. Background(Requirement)  Propagation : As every handler could fit in a single packet, these instructions were just a simple broadcast. it requires every program to include propagation algorithms. As not all programming models can fit their programs in a single packet, a runtime needs to be able to handle larger data images and should provide an efficient but rapid propagation service.  To provide useful systems support for a wide range of programming models, a runtime must meet these three requirements without imposing a large energy burden. 5 Internet system technology

6. Background(Mate)  Maté v1.0 - Architecture 6 Internet system technology

7. Background(Mate)  Maté v1.0 - instructions  0 OPhalt 0x00 00000000  1 OPreset 0x01 00000001 clear stack  2 OPand 0x02 00000010 push($0 & $1), 3 OPor 0x03 00000011 push($0 | $1) … SCLASS  72 OPgetmb 0x48-4f 01001xxx push(byte xxx from msg header)  108 OPsetfs 0x70-77 01110xxx short xxx of frame = $0 … XCLASS  128 OPpushc 0x80-bf 10xxxxxx push(xxxxxx) (unsigned)  192 OPblez 0xC0-ff 11xxxxxx if ($0 <= 0) jump xxxxxx 7 Internet system technology

8. Design  ASVMs have three major abstractions.  Handlers : Code routines that run in response to system events  Operations : The units of execution functionality  Capsules : The units of code propagation 8 Internet system technology

9. Design  The components of an ASVM.  Template : Which every ASVM includes - Scheduler : executes runnable threads in a FIFO round-robin fashion - Concurrency manager : controls what Threads are runnable, ensuring race-free and deadlock-free handler execution - Capsule store : manages code storage and loading, propagating code capsules and notifying the ASVM when new code arrives  Extensions : The application-specific components that define a particular ASVM 9 Internet system technology

10. Design  Scheduler : Execution  The core of an ASVM : a simple FIFO thread scheduler.  Maintains a run queue.  Interleaves execution at a very fine granularity.  Executes a thread by fetching its next bytecode from the capsule store.  Dispatching to the corresponding operation component through a nesC parameterized interface. 10 Internet system technology

11. Design  Concurrency Manager : Parallelism  The concurrency manager of the ASVM template supports race free execution through implicit synchronization based on a handler’s operation.  When a handler event occurs, the handler’s implementation submits a run request to the concurrency manager.  The concurrency manager only allows a handler to run if it can exclusively access all of the shared resources it needs. 11 Internet system technology

12. Design  Capsule Store: Propagation  ASVM template’s capsule store follows a policy of propagating new code to every node. (Rather than selective propagation) but only some nodes execute it.  To propagate code,capsule store maintains three network trickles - Version packets, which contain the 32-bit version numbers of all installed capsules, - Capsule status packets, which describe what fragments a mote needs (essentially, a bitmask) - Capsule fragments, which are pieces of a capsule. 12 Internet system technology

13. Design  Building an ASVM 13 Internet system technology

14. Evaluation  Concurrency  Propagation  Flexibility: Languages  Flexibility: Applications  Efficiency: Microbenchmarks  Efficiency: Application  Efficiency: Interpretation 14 Internet system technology

15. Evaluation  Concurrency  measured the overhead of ASVM concurrency control, using the cycle counter of a mica mote. 15 Internet system technology

16. Evaluation  Propagation 16 Internet system technology

17. Evaluation  Flexibility: Languages  Support three languages TinyScript Mottle TinySQL 17 Internet system technology

18. Evaluation  Flexibility: Applications  Specific sample ASVMs RegionsVM QueryVM 18 Internet system technology

19. Evaluation  Efficiency: Microbenchmarks  Tradeoff between including functions and writing operations in script code… operations are powerful but what about energy efficient? 19 Internet system technology

20. Evaluation  Efficiency: Application  QueryVM motlle-based ASVM execution of TinySQL data collection queries. 20 Internet system technology

21. Evaluation  Efficiency: Application 21 Internet system technology

22. Evaluation  Efficiency: Interpretation 22 Internet system technology

23. Evaluation(Pros)  Performance  Low power consumption very efficient propagation can be optimized in specific condition  Developer's view  an ASVM would be a component in TinyOS When a developer has to choose an OS for WSN… Choose TinyOS and utilize an ASVM for functions need to be update frequently 23 Internet system technology

24. Evaluation(Cons)  Approach  Extend and generalize prior work (Maté) Maintain basic characteristics of prior work Impact and influence could be restricted  Performance  High-level abstraction might not be helpful to implement complex algorithms  Would be appropriated for specific situations Updates occur frequently Long term, low-duty-cycle data collection 24 Internet system technology

25. Evaluation(Cons)  Flexibility  Application level propagation is very concise. But, we cannot update low level binaries such as an interpreter Flexible enough? 25 Internet system technology