Saturday, November 9, 2013

CRC and Checksum Tutorial Webinar

I've completed my FAA-sponsored look at CRC and Checksum performance for aviation systems. While some of the material is aircraft-specific, it is all relevant to safety critical systems and contains quite a bit of information about CRC vs. checksum performance.

I'm pleased to be able to share a two-hour Webinar recording describing all the work, as well as the slides and draft report. There is a guide to the material below that you may find useful if you are looking for a specific topic.

The general flow of the presentation is as follows, by slide number:
  • 6 - CRC and checksum background and terminology
  • 10 - Why picking the right CRC isn't as easy as you might think
  • 20 - Summary of project technical approach
  • 21 - Project results overview
  • 24 - Checksum results (Checksum, Fletcher Checksum, ATN-32)
  • 30 - CRC-32 compared to checksums
  • 31 - It's all about the Hamming Distance
  • 33 - Table of checksum compared to CRC-32
  • 35 - Good CRC choices (8 & 16 bits)
  • 36 - Good CRC choices (24 & 32 bits)
  • 37 - Aviation industry results (might be enlightening for everyone)
  • 43 - Multiple CRC & memory-specific CRC results
  • 46 - System level effects and cross-layer interactions (e.g., unprotected length field, bit encoding)
  • 48 - ARINC-825 / CAN issues
  • 52 - 8b10b encoding Gbit Ethernet issue
  • 53 - Mapping to criticality levels (how do you know your CRC/checksum is good enough?)
  • 64 - Determining Bit Error Ratio (BER)
  • 71 - Error detection mechanism failure and scrubbing
  • 74 - A simple recipe for how to determine how big and capable a CRC/checksum you need
  • 76 - CRC/Checksum seven deadline sins (bad ideas)
  • 79 - Review of the study project subtasks (most readers can skip this part)

I owe significant thanks to my Co-Investigators Kevin Driscoll and Brendan Hall at Honeywell labs, without whom this work could not have been done. And also a warm and sincere thanks to our FAA contacts, and especially to Chuck Kilgore for his good spirits, kind words, and unfailing support.

NOTES:

"The provided links will give you the option of downloading the video file or view it through your web browser.   Some people have reported problems viewing the video with their web browser due to the 2 hour length.  Others have been able to view the video in a browser without any problems.   If you encounter problems, we recommend that you download the file for offline viewing if possible to avoid any streaming issues."

"This work was supported by the Federal Aviation Administration, Aircraft Certification Service, and Assistant Administration for NextGen, William J. Hughes Technical Center, Aviation Research Division, Atlantic City International Airport, New Jersey 08405. The findings and conclusions in this presentation are those of the author(s) and do not necessarily represent the views of the funding agency.  This presentation does not constitute FAA policy."

The Webinar was scheduled Oct 1, 2013, but was delayed due to the government shutdown. The webinar was actually held on Oct 29, 2013.

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