1. Mobile P2P Data Retrieval and Caching
Dewan Tanvir Ahmed
Abdelfettah Diabi

2. P2P System A distributed System Each member (peer) is Applications
Autonomous
Share information or data
Loosely coupled with others
Play a equal role in the system
Applications
Grid Computing
File Sharing
Digital Library

3. P2P Challenges
britney.mpg
Yes, I have

4. P2P Challenges I am not smart as I asked everybody.
britney.mpg
Blind flooding!
I am not smart as I asked everybody.
How can I be a smart guy?
Ask only one peer

5. P2P Challenges
Participation
I have nothing
britney.mpg

6. P2P Challenges Correctness What if I share a corrupted file?
How do we prevent wicked people from hurting others?

7. P2P: Napster Search Request Search Response Download 1000100110100

8. P2P: Gnutella Search Request client Search Relay client
Search Response
client
client
Download
client
client
client
client
client
client
client
client

9. P2P Overlay
End to End
Communication

10. MP2P
This much more challenging as compared to traditional P2P because of
Low bandwidth
Mobility of the peers
Power constraint due to energized by battery

11. M-CAN: Super node
Node SN
Node

12. M-CAN: Hierarchy 36 27 0-9 30-49 10-29 32 25 5 30 2 4 22 9 19 20 12 SN
Node 32 25 5 30
Node 2
Node 4 22
Node 9
Node 19 20 12

13. M-CAN: Whole Peer Community
GROUP 1
Node SN
0-39
40-99
Node SN
0-29
30-55
56-99
GROUP 2 SN
Node
0-99
GROUP 3

14. M-CAN: A Lookup Protocol
GROUP 1
Node SN
0-39
40-99
Node
GROUP 2
Node
0-29
Node SN
Node
0-99
GROUP 3 SN
30-55
Node SN 88
Node
Node
Node SN
56-99
Node
Node
Node

15. M-CAN: Analysis Advantages Disadvantages Decreases the requirements ofBW
Device storage capacity
Grouping overcomes unreliable communication of MP2P
Disadvantages
File ID must be known before making the request
Not scalable – Large searching latency

16. MP2P: Indices Resource discovery and locating is a difficult task
Indices accelerates search
Local Index [Yang and Garcia-Molina]
Each node maintains a local index
If failed to locate then flood that request
Routing Index [Crespo and Garcia-Molina]
Indices are not the location, it is the direction of the resource
Forward request in that direction
Central Index
A central index node
Keep tracks of whole system
But bottleneck of the system

17. MP2P: Dynamic Indices Motivation
Cost of wrong reference is higher than no reference
Each node has R hop neighbors information
To guarantee the correctness
change scope according to the mobility of nodes N
Change of Index Scope

18. Data Structure of GET Req
MP2P: Dynamic Indices
Owner
File name
Next Hop B 1 2 C D 3 E 4 F … K 10 B F G E K I L C D J
Data Structure of GET Req D 3
No Broadcast
CMD
TTL
SRC
GET 7 A F 3 C A 3

19. MP2P: Dynamic Indices F C A E D B
What is the way to change the Radius?
Each node refresh its index in every T time unit
Determine the change in the local index table

20. MP2P: Analysis of Dynamic Indices
Advantages
Reduce number of requests
Accelerates searching
Considers the mobility of the nodes in the algorithm
Disadvantages
Periodic refresh message increases control overhead
Linear searching approach, no hashing techniques were mentioned in the protocol
Ignores power constraint of the mobile devices

21. MP2P: PReCinCt (Locating & Caching)
Item is not in that region?
Broadcast request to gather data
A node is looking for data
Each region is responsible for a set of keys
Network is divided in geographical regions
Should we cached the data?
Caching Policy
A Hash function

22. MP2P: PReCinCt (Dealing Mobility)
Peer Mobility Handling
Inter region
Intra region
Actually no overhead
Distribute his keys to Peers
Low mobility
Close to center
Have enough cache space

23. MP2P: PReCinCt (Data consistency)
It uses Push with Adaptive Pull technique
Push
A peer pushes an updated a data item
Reflected at the home and replica region instead of the whole network
Pull
Individual peer checks validity/freshness of the cached items

24. Thank you!