'abnormal BSN' handling in M2PA

Hi,

I need some clarification regarding 'abnormal BSN' handling in M2PA.

According to ITU-T specification Q.703, if two out of three received message

have wrong BSN, the message signal unit or fill in signal unit should be
discarded. Also level 3 is informed that the link is faulty (section 5.3.1).


Question 1:
-----------------
This is contradicting with the test case 3.8.10 specified in
draft-bidulock-sigtran-m2pa-test-08.

Test Description:
(1)   The test begins with the link in the "In Service" state.
(2)   Send a Data message to the IUT with an abnormal Backward
         Sequence Number.
(3)   Check that the IUT acknowledges the Data message delivers an
         MSU to Level 3 at the IUT.
(4)   Send a Data message to the IUT with an normal Backward Sequence
         Number.
(5)   Check that the IUT acknowledges the Data message delivers an
         MSU to Level 3 at the IUT.
(6)   Check that the IUT maintains the "In Service" state.

In step 3 M2PA should not deliver the data to level 3 and should not
acknowledge the data. It should silently discard it.

Question 2:
-----------------
In test case 3.8.11 of draft-bidulock-sigtran-m2pa-test-08, out of service
message
is send from IUT after a DATA_ACK message with normal BSN when two DATA_ACK
message is received with abnormal BSN previously.

   ___________________________________________________________________

|
|
  |   VAT:
PT                                    IUT                      |

|
|
  |              DATA-ACK  --FFFFFF,
7FFFFF->                                                      |
  |              DATA-ACK  --FFFFFF,
7FFFFF->                                                      |
  |              DATA-ACK  --FFFFFF,
FFFFFF->                                                      |
  |
<-----------------  OUT-OF-SERVICE         |

|
!out of service                |

|
|
  |___________________________________________________________________|

When two DATA_ACK has been received with wrong BSN value, why should we wait

for next DATA_ACK (with or without correct BSN value) to indicate the link
as a
fauly link?
Rather, OOS message can be trasmitted to peer along with proper link status
indication
to level 3 just after reception of 2 consecutive wrong BSN reception.

Please let me know if my understanding is correct.
Thanks for your time to read this query.

Regards,
Debasri

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