[Ns-bugs] [Bug 968] Beacon generation does not use CSMA deferral

Tue Aug 3 23:54:48 PDT 2010

http://www.nsnam.org/bugzilla/show_bug.cgi?id=968

Kirill Andreev <andreev at iitp.ru> changed:

           What    |Removed                     |Added
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                 CC|                            |andreev at iitp.ru

--- Comment #2 from Kirill Andreev <andreev at iitp.ru>  2010-08-04 02:54:48 EDT ---
(In reply to comment #0)
Hi!
I did not find any information about backoff procedures for beacons. If medium
is defined busy, beacon will be sent after the medium has been idle a PIFS
(9.3.2.1) interval.

The following note "NOTE—Though the transmission of a Beacon frame may be
delayed because of CSMA deferrals, subsequent Beacon
frames shall be scheduled at the undelayed nominal beacon interval. This is
shown in Figure 11-1." in section 11.1.2.1 does not mean a backoff procedure.
It says, that beacon shall be generated after data frame + PIFS deffereal.

Also in your example you have started both APs simultaneously, so (because
there are no random start and there is no model of processing delay), beacons
are generated exactly simultanuoisly, and CSMA can't resolve this problem.

In dot11s module beacons are strictly periodical, and when we have removed
random start for beaconing generation, nothing works properly.

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