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Digital Fountains: Understanding the Ideal Data Transmission Paradigm and Related Advances, Slides of Business Administration

An overview of digital fountains, an ideal paradigm for data transmission that yields an infinite data stream from a finite file. It covers the history, construction, and applications of digital fountains, including reliable multicast, parallel downloads, long-distance transmission, and content distribution. It also discusses challenges and potential solutions, such as patent issues and the need for a simple, easy-to-use implementation.

Typology: Slides

2012/2013

Uploaded on 07/29/2013

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Digital Fountains:
Applications and Related Issues
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Download Digital Fountains: Understanding the Ideal Data Transmission Paradigm and Related Advances and more Slides Business Administration in PDF only on Docsity!

Digital Fountains:

Applications and Related Issues

Goals

  • Explain the digital fountain paradigm for network

communication.

  • Examine related advances in coding.
  • Summarize work on applications.
  • Speculate on what comes next.

How Do We Build

a Digital Fountain?

  • We can construct (approximate) digital

fountains using erasure codes.

  • Including Reed-Solomon, Tornado, LT, fountain codes.
  • Generally, we only come close to the ideal

of the paradigm.

  • Streams not truly infinite; encoding or decoding times; coding overhead.

History

  • Reed-Solomon codes
  • Tornado Codes
  • Luby Transform
  • Rateless/Raptor codes

Applications

  • Reliable multicast
  • Parallel downloads
  • Long-distance transmission (avoiding TCP)
  • One-to-many TCP
  • Content distribution on overlay networks
  • Streaming video

Reliable Multicast

  • Many potential problems when multicasting

to large audience.

  • Feedback explosion of lost packets.
  • Start time heterogeneity.
  • Loss/bandwidth heterogeneity.
  • A digital fountain solves these problems.
  • Each user gets what they can, and stops when they have enough.

Point-to-Point Data Transmission

  • TCP has problems over long-distance connections.
    • Packets must be acknowledged to increase sending window (packets in flight).
    • Long round-trip time leads to slow acks, bounding transmission window.
    • Any loss increases the problem.
  • Using digital fountain + TCP-friendly congestion control can greatly speed up connections.
  • Separates the “what you send” from “how much” you send. - Do not need to buffer for retransmission.

One-to-Many TCP

  • Setting: Web server with popular files, may have many open connections serving same file. - Problem: has to have a separate buffer, state for each connection to handle retransmissions. - Limits number of connections per server.
  • Instead, use a digital fountain to generate packets useful for all connections for that file.
  • Separates the “what you send” from “how much” you send. - Do not need to buffer for retransmission.
  • Keeps TCP semantics, congestion control.

Video Streaming

  • For “near-real-time” video:
    • Latency issue.
  • Solution: break into smaller blocks, and encode

over these blocks.

  • Equal-size blocks.
  • Blocks increases in size geometrically, for only logarithmically many blocks.
  • Engineering to get right latency, ensure blocks

arrive on time for display.

Other Applications

  • Other possible applications outside of

networking

  • Storage systems
  • Digital fountain codes for errors
  • Others???

Patent Issues

  • Several patents / patents pending on irregular LDPC codes, LT codes, Raptor codes by Digital Fountain, Inc.
  • Supposition: the theory/practice of digital fountains was greatly developed by the company and its employees.
  • Supposition: but this stifles external innovation.
    • Potential threat of being sued.
    • Potential lack of commercial outlet for research.
  • Suggestion: need unpatented alternative that approximate a digital fountain. - There is work going on in this area, but more is needed to keep up with recent developments in rateless codes.

Perceived Complexity

  • Digital fountains are now not that hard…
  • …but networking people do not want to deal with developing codes.
  • A research need:
    • A publicly available, easy to use, reasonably good black box digital fountain implementation that can be plugged in to research prototypes.
  • Issue: patents.
    • Legal risk suggests such a black box would need to be based on unpatented codes.

Conclusions

  • Digital fountain paradigm and enabling codes have significant potential. - Many proposed applications. - More to come.
  • Applications helped push forward the technology.
    • Codes with better and better properties.
  • Challenge in moving from a “technology” to use in the real-world. - A simple, easy-to-use implementation based on non- proprietary might spur research community. - Need more potential killer apps to spur business community.