FSM for lchan release handling -- release indication after SACCH deactivation timeout

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Holger Freyther holger at freyther.de
Sun Apr 23 18:38:28 UTC 2017


Good Evening,


this is a bit of speculation but Keith showed me a trace with some network delay that makes a case for using FSM for the lchan itself.

It seems the following can happen:

* LU REJECT
* Start Channel Release
** Send RR Release to the MS
** Deactivate SACCH
** Start Timer

... network transmission issues... at least 5s

* SACCH deactivate timeout
** Start error release procedure..

...

* LATE RELEASE INDICATION arrives triggering other release procedure?


So with a proper FSM we would have transitioned into the error path and would just ignore the RELEASE INDICATION. The question is if someone has budget to do a FSM transition here? I will try to build a simulated testcase for that.



The other part that seems to happen (and I don't understand yet):

* Allocating a lchan before it is fully freed?!
* The BTS sending us RF Channel Releasse ACK twice


cheers
	holger


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