VOLTE – Core Network Performance Monitoring and Troubleshooting

Available Tools

Monitoring:TPIM, Liberty Server, IRIS

Troubleshooting:nSI, Vantage, IRIS, Netscout

Monitoring TPIM (S&PGW User plane Payload) http://tpimnational.t-mobile.com/tpimportal/cacheServlet In TPIM, S1_U and QC1 payload is monitored. If there is a dip or degradation in the payload then

it’s investigated.

Liberty Server (MME) http://ers.internal.t-mobile.com/Reports/Pages/Report.aspx?ItemPath=%

2fNational+Performance%2fLTE+CORE%2fMME+KPIs-Daily Following MME KPIs are monitored for VOLTE:

Liberty Server (S&PGW) http://ers.internal.t-mobile.com/Reports/Pages/Report.aspx?ItemPath=%2fNational+Perfor

mance%2fVoLTE%2fCISCO+P-GW+VoLTE+KPIs Following S&PGW KPIs are monitored for VOLTE:

Liberty Server (SBG) http://ers.internal.t-mobile.com/Reports/Pages/Report.aspx?ItemPath=%

2fNational+Performance%2fVoLTE%2fERI+SBG+KPIs Following SBG KPIs are monitored for VOLTE:

Liberty Server (TAS) http://ers.internal.t-mobile.com/Reports/Pages/Report.aspx?ItemPath=%2fNation

al+Performance%2fVoLTE%2fTAS+VoLTE+DROP+CALL Following TAS KPIs are monitored for VOLTE: Drop calls can also be monitored per Internal Cause Code (for e.g. CC 1024, 1806 etc)

Liberty Server (PCRF) Following PCRF KPIs are monitored for VOLTE:

Liberty Server (BGF – Breakout GW) Following BGF KPIs are monitored for VOLTE:

Troubleshooting Troubleshooting Using nSI

(Subscriber/MME) https://

10.46.23.155:8443/ResourceManager/en_US/login.jsp?InvalidText=IDS_SESSION_IS_INVALID Using nSI, both subscriber level and MME level complaints can be investigated. For example, there was one subscriber in Virginia which caused lots of Network failures during

VOLTE PDN connectivity procedure. After investigating the issue using Vantage, it was apparent that the subscriber was requesting IMS with IPv4 instead of IPv6.

Resolution: Tier-2 Packet Core changed the HLR profile to IPv6 for this sub and the issue resolved.IMSI: 310260982437458TAC: 21505 (Virginia)

Vantage UsingVantage, Dedicated Bearer setup for VOLTE call can be seen. If the Dedicated Bearer is

failed then it can be found out which node sent the failure (MME or eNB or PGW etc). Since IRIS won’t show the eNB part, its always good to open Vantage trace ON while IRIS is capturing the CORE part of the call.

• For e.g.: This VOLTE call below shows Dedicated bearer setup, E-Rab setup and Context request b/w eNB and MME.

IRIS (Session Analyzer) https://ipisnq01.internal.t-mobile.com:8543/

Using IRIS, the VOLTE call flow through the entire core network can be seen and the issues such as Call drop, Call setup failure, SIP error codes and Bad call quality could be investigated. It includes the following CORE nodes: CSCF, PCRF, PGW, P-CSCF, MME, SBG.

For example, the drive testing team captured VOLTE call drops during setup. The issue was investigated using IRIS and it was found out that SBG (NVATF001) was releasing the call with SIP error code 504. The issue was then further investigated by the Vendor and the emergency patch was released to fix the issue.

TEMS Trace

IRIS Trace

IRIS (Performance Intelligence) Using PI, we can pull Cause code distribution per node on various

Services/Interfaces/Protocols/Types and investigate the issue accordingly: