presented by: su yingbin. outline introduction socialswam design notations algorithms evaluation...

SocialSwarm: Exploiting Distance in Social Networks for Collaborative Flash

File Distribution

Presented by: Su Yingbin

Outline

Introduction

SocialSwam Design

Notations

Algorithms

Evaluation

Conclusion

Tit-for-tat as incentive to uploadWant to encourage all peers to contributePeer A said to choke peer B if it (A)

decides not to upload to BEach peer (say A) unchokes at most 4

interested peers at any timeThe three with the largest upload rates to A

Where the tit-for-tat comes inAnother randomly chosen (Optimistic Unchoke)

To periodically look for better choices

Typical BitTorrent incentives create inefficienciesClients typically avoid increasing the number

of unchoke slotsBandwidth reserved to peers won’t actually

be used totally.Social hubs can’t receive the highest priority

in receiving file

Karame et al. show that combining locally optimal solutions of the smaller social teams would give a globally optimal solution for the entire social network.

Just work as a team!

SocialSwam Design Goal

Maximize collaboration between social peers

Maintain game-based techniques to encourage the cooperation of non-social peers

SocialSwarm Interaction Overview1. Retrieve social peers

and non-social peers from tracker

2. Identifies Bob’s social peers

3. Coordinates chunk collection with them

4. Altruistically shares bandwidth with them

5. Interact with each other as well as standard BitTorrent clients

How ?How to identify social peers and non-social

peers ?Social Distance

How to collaborate with each other among a social group as well as non-social peers ?Adaptive Bandwidth AllocationChunk PrioritizationOptimistic Unchoke Candidate Selection

Notations

Altruism Between Direct Social Peers

•I(a, b) is the number of reciprocal interactions a has had within a given time window with b •I(a, all) is the number of reciprocal interactions a has had with all of its peers duringthe same window of time. •A(a, b) represents the proportional willingness that a peer a has to share resources with each of its direct peers

Approximating SocialDistance Between Indirect Peers

-------- direct peers

Peers beyond this value are

considered as non-social

Notations

Overall Rarity for Each Given Chunk

Social Rarity for Each Given Chunk

Non-social Rarity for Each Given Chunk

The “gather-and-share” TechniqueFrom the social group perspective

When the average social rarity for all chunks is high, allocate more bandwidth for non-social peers.

As the average social rarity for all chunks decreasing, allocate more bandwidth for social peers.

Average social rarity for all chunks:

Maximum percentage of bandwidth allocated to social peers:

The “gather-and-share” TechniqueFrom the social individual perspective

Chunk prioritization

Optimistic Unchoke Candidate Selection

combines the social, non-social, and overall rarities to form a combined weighted rarity for each given chunk

target a peer with the largest group of rare chunks at each time interval ti

SocialSwarm in a Nutshell

Social Network Data Set500 nodes with their interactions – Wall

Postings – extracted from Facebook

Each pair of reciprocal postings is considered a single interaction.

Interactions are used to determine the direct level of altruism between Facebook users.

Beyond MaxSocialDistance are considered as non-social peers

Baseline Test Parameters

Comparison of Basic Download Time

Client Download Rate Comparison

Chunk Rarity Reduction Comparison

Effect of File Size on Peer Throughput

Effect of Maximum SocialDistance on Peer Throughput

Effect of Additional Seed Capacity

Bandwidth Contribution and Unchoke Slot Allocation

ConclusionTypical incentives create inefficiencies

SocialSwarm exploits SocialDistance to reduce this inefficiencies

The “gather-and-share” technique achieve better performance