Social Networks and Peer to Peer

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Social Networks and Peer to Peer

• As Presented by Jeremy Robinson
• 3/22/2007

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What is a social network?

• A social network is a social structure of nodes
  tied together by one or more specific types of
  relations.
• Examples
• Classmates.com
• Friendster
• Myspace
• Facebook

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SPROUTIntroduction

• Why do we need it?
• P2P vulnerable to routing Denial of Service
  Attacks
• Misrouting attacks
• What is misrouting?
• Any failure by a node to forward a message to the
  appropriate peer according to the correct routing
  algorithm.

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SPROUTIntroduction

• Malicious users
• Masquerade as index owner of keys
• Can acquire several valid network identifiers to
  control multiple nodes Sybil attack.
• Can avoid this by sending messages only to
  trusted nodes like people we know personally
  perhaps in a real life social context.
• They propose to use existing social network
  services to build P2P Networks to add highly
  trusted links at little additional cost.

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SPROUTTrust Model

• Big Assumption
• Friends are not likely to be selfish or
  malicious.
• Also, friends of friends are also unlikely to be
  malicious.
• Also assume that likelihood that B purposefully
  misroutes As message is proportional to distance
  between As owner and Bs owner.

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SPROUTTrust Function

• T ( A, B) is the trust A has in B
• Probability f 0.95 that friends will route
  correctly, 0.90 that friends friends route
  correctly, 0.85 that friends friends friends
  route correctly and so on.
• Probability r 0.6 that any random node will
  route correctly.
• This means 40 of randoms are malicious

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SPROUTPath Rating

• Path trust rating, P, found by multiplying
  separate node trust ratings for each node.
• Source node S, Destination D
• P T(S,A) T(S,B) T(S,C) T(S,D)

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SPROUTSocial Path Routing Algorithm

• Build a DHT routing algorithm built on basic
  Chord algorithm.
• Can be applied to other DHT designs like CAN or
  Pastry.
• Like in Chord, user joins, gets randomly assigned
  a network identifier. Establishes links to
  sequential neighbors, but THEN add additional
  links to any friends that are online.
• Most popular instant messenger services keep user
  aware of when friends enter or leave network.

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SPROUTSocial Path Routing Algorithm
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SPROUTOptimization

• Lookahead
• Can see friends friends
• Minimum Hop Distance MHD
• May have friend at each sequential neighbor,
  gives worst case routing O(n).
• Use MHD of 0.25 then next friend must be at least
  a quarter away, or we use Chord.

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SPROUTSimulations

• Used data from Club Nexus community website at
  Stanford University.
• About 2200 users, on average each node had about
  8 links.
• Also ran experiments on 130,000 AOL Instant
  Messenger users.
• Used f 0.95 and r 0.6.

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SPROUT VS. CHORD
Avg. Path Length Avg. Reliability
Regular Chord 5.343 0.3080
Augmented Chord 4.532 0.3649
SPROUT(1,0.5) 4.569 0.4661
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Evaluating Lookahead and MHD
MHD Lookahead Lookahead Lookahead Lookahead Lookahead Lookahead
MHD None None 1 - level 1 - level 2 - level 2 - level
MHD Length Rating Length Rating Length Rating
0 4.875 0.4068 5.101 0.4420 5.378 0.4421
0.125 4.805 0.4070 5.003 0.4464 5.258 0.4478
0.25 4.765 0.4068 4.872 0.4525 5.114 0.4551
0.5 4.656 0.4033 4.569 0.4661 4.757 0.4730
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Performance of SPROUT and AC
Fig. 1. Performance of SPROUT and AC in different
size Small World networks. The third curve shows
the relative performance of SPROUT with respect
to AC, plotted on the right-hand y-axis. Note
that the x-axis is logscale.
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SPROUTCalculating Trust
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SPROUTMessage Load

• Biggest problem for SPROUT
• Uneven distribution. Load bigger than AC.
• Can use as advantage,
• One highly connected large capacity node
  increases reliability and decreases load on other
  nodes.

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Searching Social Networks

• Only small bit pertains to P2P
• P2P uses brute force to find things, they propose
  a referral agent system.
• Most P2P algorithms dont fit social networks
  because they cannot be partitioned by IP address.
  Also P2P have fixed routing tables for each node
  so network is not reconfigurable.

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The End

• Questions??