1. A New Retrieval Strategy for P2PA New Retrieval Strategy for P2P
Video-On-Demand SystemsVideo-On-Demand Systems
Presented By…
Ashwini Ramesh More
Mounika Eluri
CS 696 – Advanced Distributed System
San Diego State University

2. AGENDA
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3. INTRODUCTION
 VoD (Video on Demand) - allows users to select and
watch/listen to video content whenever they want.
 Necessity to provide instantaneous response to end-users.
 Delivering the media content over the network with best
response time has been a popular topic of many
discussions.
 Our objective is to design a retrieval strategy to achieve
minimum response time and maximize the overall
throughput of the system. 3

4. DRAWBACK OF LEAST LOAD FIRST
 It selects a serving peer having the least load for
delivering the media content.
 Since only one peer is responsible for servicing the
request, it takes more time to respond to the request
thereby affecting response time.
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5. MOTIVATION
 Least Load First strategy is time consuming.
 Can we develop an algorithm which can reduce the mean
response time ?
 We propose an algorithm called CollaborativeRetrieval
(CoRe) algorithm which aims in minimizing the mean
response time.
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6. CORE MODEL
10 40
3020
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7. CORE MODEL
10
30%
40
3020
40%
20%
10%
C
B
A
D
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Collaborative Retrieval

8. CORE ALGORITHM
Input: Batch of movie requests, list of available peers, list of movie replicas distributed
across multiple peers.
Output: response time for each request
1. for each request ri do
2. size = getSize(ri)
3. Get list of available peers containing the movie and store in list Lp
4. Total = count (Lp)
5. for each peer pi in list Lp do
6. Set distance with respect to the request source
7. end for
8. Sort the list Lp according to the distance factor in ascending order
9. for each peer pi in list Lp do
10. Calculate the cost, cost [pi] = distance [pi]/Total
11. Request_service_time = size * cost [pi]/transfer_rate (31Kbps assumed)
12. end for
13. Record start time and end time for request ri
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9. EXPERIMENTAL PARAMETERS
Parameter Values
Number of requests 2000-15000
Number of peers 100
Number of movies 500
Skew 50-50, 60-40, 70-30
Aggregate access rate (1/s) 50, 100, 150, 200, 250, 300
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10. 10
MEAN RESPONSE TIME (SKEW 70-30)

11. MEAN RESPONSE TIME (SKEW 60-40)
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12. 12
MEAN RESPONSE TIME (SKEW 50-50)

13. RESPONSE IMPROVEMENT (SKEW 70-
30)
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14. RESPONSE IMPROVEMENT (SKEW 60-
40)
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15. RESPONSE IMPROVEMENT (SKEW 50-
50)
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16. CONCLUSION
 We proposed an efficient CoRe strategy for retrieving the
videos.
 Our experimental results showed that CoRe performs
significantly better than existing Least Load First algorithm
even in the case of heavy workload.
 Simulations performed for skew distribution of 70-30
showed that CoRe algorithm achieved the maximum
improvement of 36 percent over Least Load First.
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17. FUTURE WORK
Further studies in this research can be performed by
taking into consideration the issues like,
 Data corruption
 Peer or network failure and recovery
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18. Thank You !!!
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