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Cisco Bug: CSCvs36965 - [21.5.23] [ASR5000] [MME/SGSN] SRVCC Cancellation - missing NAS Notification with new TAU Request

Last Modified

Oct 10, 2020

Products (2)

  • Cisco MME Mobility Management Entity
  • Cisco MME Mobility Management Entity

Known Affected Releases

21.11.16 21.17.6 21.19.0 21.19.n1 21.20.0 21.5.23 21.5.23.72430 21.5.26

Description (partial)

Symptom:
SRVCC procedure starts from MME as required as seen in frame 1175 of the pcap. HO command is issued to UE however Customer says UE never received this due to radio conditions. 

UE locates LTE again and sends TAU Request with EBI 5,6,7 active but via a different eNB to where they were previously. MME triggers SRVCC cancellation procedure however MME is not sending NAS 
notification to the UE after the new TAU Request indicating SRVCC cancellation ims session re-established required, even when STI flag is set in SRVCC_PS_TO_CS_Cancel_Ack message.

Conditions:
TAU Request is received when SRVCC is ongoing
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Bug Details Include

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