Content for TR 29.811 Word version: 13.0.0
2 References
3 Definitions, symbols and abbreviations
4 EPC race conditions scenarios and scenarios with hanging session/bearer contexts
5 Possible solutions for effective handling of EPC race conditions scenarios and scenarios with hanging session/bearer contexts
6 Conclusions and recommendations
$ Change History
2 References p. 5
3 Definitions, symbols and abbreviations p. 6
3.1 Definitions p. 6
3.2 Abbreviations p. 6
4 EPC race conditions scenarios and scenarios with hanging session/bearer contexts p. 6
4.1 Introduction p. 6
4.2 Scenario 1 - Create Session Request at SGW colliding with an existing PDN connection context p. 6
4.3 Scenario 2 - Hanging IP-CAN session context in PCRF p. 7
4.4 Scenario 3 - Overlapping transactions in the network p. 9
4.4.1 Scenario description p. 9
4.4.1.1 Introduction p. 9
4.4.1.2 MME/SGSN reselecting an alternative PGW during a PDN connection establishment - overlapping transactions over Gx p. 9
4.4.1.3 TWAN/ePDG reselecting an alternative PGW during a PDN connection establishment - overlapping transactions over Gx p. 11
4.4.1.4 TWAN/ePDG reselecting an alternative PGW during a PDN connection establishment - overlapping transactions over S6b p. 11
4.4.1.5 PDN connection re-establishment via an alternative serving node - overlapping transactions over Gx p. 11
4.4.1.6 MME/SGSN reselecting an alternative SGW during a PDN connection establishment - overlapping transactions over S5/S8 p. 12
4.4.2 Summary of identified problems p. 12
4.5 Scenario 4 - Hanging session context in 3GPP AAA Server p. 13
5 Possible solutions for effective handling of EPC race conditions scenarios and scenarios with hanging session/bearer contexts p. 14
5.1 Introduction p. 14
5.2 Solutions for scenario 1 - Create Session Request at SGW colliding with an existing PDN connection context p. 14
5.3 Solutions for scenario 2 - Hanging IP-CAN session context in PCRF p. 17
5.4 Solutions for scenario 3 - Overlapping transactions in the network p. 17
5.4.1 Solution 1 - Guard timer at PGW to control the maximum time to respond to a Create Session Request p. 17
5.4.1.1 Solution description p. 17
5.4.1.2 Impacts on existing nodes and functionality p. 18
5.4.1.3 Evaluation of the solution p. 18
5.4.2 Solution 2 - Longer T3 timer for the last GTP-C repetition p. 18
5.4.2.1 Solution description p. 18
5.4.2.2 Impacts on existing nodes and functionality p. 18
5.4.2.3 Evaluation of the solution p. 18
5.4.3 Solution 3 - PCRF accepting the new IP-CAN session and tearing down the Gx session towards the previous PGW p. 19
5.4.3.1 Solution description p. 19
5.4.3.2 Impacts on existing nodes and functionality p. 19
5.4.3.3 Evaluation of the solution p. 19
5.4.4 Solution 4 - Including a Timestamp in the session request p. 19
5.4.4.1 Solution description p. 19
5.4.4.2 Impacts on existing nodes and functionality p. 22
5.4.4.3 Evaluation of the solution p. 22
5.4.5 Solution 5 - Including a Timestamp and Maximum Wait Time in the session request p. 23
5.4.5.1 Solution description p. 23
5.4.5.2 Impacts on existing nodes and functionality p. 26
5.4.5.3 Evaluation of the solution p. 26
5.4.6 Solution 6 - Introducing "Resend Indicator" in Create Session Request p. 27
5.5 Solutions for scenario 4 - Hanging session context in 3GPP AAA Server p. 28
6 Conclusions and recommendations p. 29
6.1 Introduction p. 29
6.2 Conclusion for scenario 1 - Create Session Request at SGW colliding with an existing PDN connection context p. 29
6.3 Conclusion for scenario 2 - Hanging IP-CAN session context in PCRF p. 30
6.4 Conclusion for scenario 3 - Overlapping transactions in the network p. 30
6.5 Conclusion for scenario 4 - Hanging session context in 3GPP AAA Server p. 32
$ Change History p. 33
