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Cisco Bug: CSCua94728 - 622386385 Improper use of EMM Cause#8 by MME on Attach_Reject

Last Modified

Dec 25, 2016

Products (1)

  • Cisco ASR 5000 Series

Known Affected Releases

12.2(19) 12.2(32)

Description (partial)

Symptom:
In Release 12.2 (43211) Improper Use of EMM Cause#8 (EPS Services and non-EPS Services Not
Allowed) by MME on Attach_Reject due to Attach_Accept with no Complete

Conditions:
There has been several reports from customers and vendors indicating that LTE devices are going into No Service Condition.

Analyzing UE screenshots and UE logs collected, it appears that the UE is receiving
EMM Reject Cause of #8 (EPS Services and non-EPS Services Not Allowed) which is sending
them into SOS

Analysis of packet captures to indicate scenarios where the MME is
abnormally sending Cause#8 as follows:

During  Attach_Request procedure:
If Attach_Accept is Successful, but Attach_Complete is ever received by MME, MME is sending out Attach_Reject w/EMM_Cause=#8

When Attach_Complete is not received by MME because UE moves to another eNodeb:
MME repeats Attach_Accept 2x before failing

When MME gives up (likely due to T3450 timer expiry):
MME performs S1AP UE ContextRelease w/Cause=Detached (which is OK) but also sends Attach_Reject w/Cause=#8 (which is NOT OK).

When T3450 timer expires, MME should ABORT the Attach procedure (ie: not send Attach_Reject at all).
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