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Change or document the 100% reliability of control (0-length) packets #2517

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stevenengler opened this issue Nov 2, 2022 · 1 comment
Open

Change or document the 100% reliability of control (0-length) packets #2517

stevenengler opened this issue Nov 2, 2022 · 1 comment
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Component: Documentation In-repository documentation, under docs/ Type: Enhancement New functionality or improved design
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Validate and impr...

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@stevenengler
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stevenengler commented Nov 2, 2022 •
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I know this is just ported over from the C code, but I wonder if we should do something about this at some point. For someone using Shadow to model a lossy network, having 0-length-payload packets be 100% reliable doesn't seem right.

Maybe open an issue to revisit and leave a link here? Or update the comment to be more clear about whether this is/isn't actually a bug in shadow?

Originally posted by @sporksmith in #2516 (comment)

  1. What's the reason for having 100% reliability of control packets?
  2. What happens if we don't include this code?
  3. This is also affecting 0-length UDP packets. Should we change this?
@stevenengler stevenengler mentioned this issue Nov 2, 2022
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@robgjansen
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Note that the 100% reliability of control packets only applies to network graphs links that set a positive packet loss rate. In other words, no matter what you set as the packet loss rate, control packets are not dropped at the packet loss application step. This was added because I don't think we are correctly retransmitting control packets (I think maybe because the retransmission algorithm works on sequence numbers and control packets don't have sequence numbers).

HOWEVER, the router+CoDel algorithm step does drop packets independent of their length or packet type.

Ideally we should remove these hacky work-arounds and fix the underlying retransmission bugs.

@stevenengler stevenengler added Type: Enhancement New functionality or improved design Component: Documentation In-repository documentation, under docs/ labels Feb 22, 2023
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Component: Documentation In-repository documentation, under docs/ Type: Enhancement New functionality or improved design
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Validate and improve TCP simulation a...
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