Reliable Multicast Using ReedSolomon and Gossip

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Reliable Multicast Using Reed-Solomon and Gossip

• Continues Project to FEC using RS Project

Daniel Finchelstein and Noam Ivri
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Project Goals

• Search and determine the best approach to add
  reliability and performances to our
  Frame-Distribution system and implement it.
• Analyze the new system results Vs. first
  projects results.

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Recap on FEC using RS

• One lecturer (server) and many students (clients)

Server User Interface
FEC encoder
Server Application
Wireless Network
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Client
from the air
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What happens when we need more packets?

• Need more packets less then K were received
  after N were sent.
• Option1 (naïve) ask the server to send again
• Option2 change the (K,N) values for future
  packets
• Option3 get it from near-by clients!

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Near-by clients?

• Reasonable assumption
• different clients loose different packets
• Physical proximity allows good connection
• The clients have the resources to deal with low
  number of requests.

Using a background mechanism the clients can
exchange needed packets!
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How does it work?

• Fixed redundant information set produced by the
  server (N-K rate)
• Clients join a Group Membership System (GMS)
• Gossip between sets of members
• Exchange needed packets from the redundant set.

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Benefits of our approach

• Immediate correction of fault receives.
• Can work with low values of N,K.
• Does not bother the server.
• Extremely efficient for large number of clients.
  (epidemic rate of progress).
• Cost effective no need for complicated
  calculations.

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The Gossip Stage

• Our work focuses on creating a highly effective
  gossip mechanism
• The selected solution is based on pbcast. (based
  on Cornell's project)

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Gossip, Requirements

• Work independently- regardless of the RS system.
• Exchange needed information only.
• Exchange data MUCH faster than its production.
• Allow clients to join and leave at any stage.

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Gossip, Design

• unsynchronized gossip rounds .
• In each round, 2 phases
• 1.detect message loss .
• 2 .correct such losses (runs only if needed) .

Members randomly choose other members ? send a
summary of their packets history ? ask for
packets they discover themselves to be lacking
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Projects Time Table
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Questions ?

• Thank You.