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Cisco Bug: CSCuo94822 - Configurable MME timer - 4G-3G PS-HO Forw_rel_req and Release-resource

Last Modified

May 27, 2019

Products (1)

  • Cisco ASR 5000 Series

Known Affected Releases

14.0(51)

Description (partial)

Symptom:
When performing a PS-Handover 4G to 3G as detailed in 3GPP 23.401 Annex D3.3, the SGSN sends in step 15 a Forward-Relocation-complete to the MME. Based on the reception, the MME starts a timer and at expiration of this timer, the MME sends to the SGW a Delete-session-request in step 18 and release-resource to eNB (18b).

The eNb starts on its side TS1RelocaOverall timer when receiving the Handover Command (step 8) (see 3GPP 36.413 section 8.4.1) and will locally release resource at expiration timer.

The MME timer is fixed to 5 sec and is not configurable

Conditions:
When the eNB (such as E// eNB) has also a non-configurable timer of 5sec, the eNB timer will always clear resources locally and MME release will come later. This causes eNB to treat such PS-HO as failures and affects KPI
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