[Ns-bugs] [Bug 555] DCF immediate access bug

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=555





--- Comment #13 from TimoB <timo.bingmann at student.kit.edu>  2009-06-25 13:05:09 EDT ---
(In reply to comment #12)
> Would it not be possible to instead fix this bug my adding an end of tx signal
> to MacLow, forward it to DcaTxop, and invoke RequestAccessIfNeeded from there
> at the end of tx for broadcast/multicast messages ?
> 
> This would add yet another event, but, at least, it seems pretty
> straightforward: the way the current patch works makes my brain hurt.

No, it does not change anything about the bug reported.
If you delay RequestAccessIfNeeded() to after the TX the test case changes to:

  // Test case where two packets are queued at DcaTxop, the first send starts
  // immediately and the second is also immediately indicated but has to wait
  // for its backoff.
  //
  //  20          60     66      70   80
  //   | tx        | sifs | aifs  | tx |
  //   |20: request access for first packet
  //               |60: request access for second packet

and we still need to differentate this case from

  //  20          60     66              70      75
  //   | tx        | sifs | aifs+backoff  | idle | tx |
  //   |20: request access for first packet
  //                                             |75: request access for second
packet

I don't see what's wrong with adding a "backoff elapsed" flag to DcaTxop.


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