5G SA End-To-End with ZeroMQ sometimes fails after a while

[TallGuy74]

Issue Description

I have used the 5G SA End-to-End appnote to set up a 5G Core network + srsenb + srsue on a machine with an i9 12 core CPU (gen 12). I am sometimes unable to use the network connection between UE and gNB, resulting in errors.

Setup Details

• A Dell machine with an i9 12900K CPU
• srsRAN 22.04, compiled with UHD, BladeRF, SoapySDR and ZeroMQ RF frontends
• Open5GS configured according to the 5G SA E2E appnote
• Using the configuration files from the 5G SA E2E appnote
• iperf3 -s running in the normal network context
• sudo ip netns exec ue1 iperf3 -c 10.45.0.1 running in the ue1 network context.

Expected Behavior

The iperf3 client is able to communicate with the gNB endpoint running the iperf3 server.

Actual Behaviour

If the connection has been idle for a while, I am sometimes no longer able to contact the gNB's IP address from the ue1 network context.

I see the following errors on the console:

RRC NR reconfiguration successful.                                                             [9/660]│Current sample rate is 11.52 MHz with a base rate of 11.52 MHz (x1 decimation)              [34/1976]
PDU Session Establishment successful. IP: 10.45.0.2                                                   │Setting frequency: DL=1842.5 Mhz, UL=1747.5 MHz for cc_idx=0 nof_prb=52
RRC NR reconfiguration successful.                                                                    │RACH:  slot=171, cc=0, preamble=0, offset=0, temp_crnti=0x4601                                       
Scheduling request failed: releasing RRC connection...                                                │Disconnecting rnti=0x4601.                                                                           
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=7531                 │RACH:  slot=7531, cc=0, preamble=0, offset=0, temp_crnti=0x4602                                      
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=7691                 │Disconnecting rnti=0x4602.                                                                           
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=7851                 │RACH:  slot=7691, cc=0, preamble=0, offset=0, temp_crnti=0x4603                                      
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=8011                 │Disconnecting rnti=0x4603.                                                                           
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=8171                 │RACH:  slot=7851, cc=0, preamble=0, offset=0, temp_crnti=0x4604                                      
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=8331                 │Disconnecting rnti=0x4604.                                                                           
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=8491                 │RACH:  slot=8011, cc=0, preamble=0, offset=0, temp_crnti=0x4605
Scheduling request failed: releasing RRC connection...                                                │Disconnecting rnti=0x4605.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=171                  │RACH:  slot=8171, cc=0, preamble=0, offset=0, temp_crnti=0x4606
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=331                  │Disconnecting rnti=0x4606.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=491                  │RACH:  slot=8331, cc=0, preamble=0, offset=0, temp_crnti=0x4607
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=651                  │Disconnecting rnti=0x4607.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=811                  │RACH:  slot=8491, cc=0, preamble=0, offset=0, temp_crnti=0x4608
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=971                  │Disconnecting rnti=0x4608.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=1131                 │RACH:  slot=171, cc=0, preamble=0, offset=0, temp_crnti=0x4609
Scheduling request failed: releasing RRC connection...                                                │Disconnecting rnti=0x4609.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4011                 │RACH:  slot=331, cc=0, preamble=0, offset=0, temp_crnti=0x460a
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4171                 │Disconnecting rnti=0x460a.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4331                 │RACH:  slot=491, cc=0, preamble=0, offset=0, temp_crnti=0x460b
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4491                 │Disconnecting rnti=0x460b.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4651                 │RACH:  slot=651, cc=0, preamble=0, offset=0, temp_crnti=0x460c
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4811                 │Disconnecting rnti=0x460c.
Random Access Transmission: prach_occasion=0, preamble_index=0, ra-rnti=0xf, tti=4971                 │RACH:  slot=811, cc=0, preamble=0, offset=0, temp_crnti=0x460d

Steps to reproduce the problem

Run the iperf3 client, wait a while, and try again.

Additional Information

[Any additional information, configuration or data that might be necessary to reproduce the issue]

[mariatsampazi]

Have you managed to figure it out?

[andrepuschmann]

Hey, the issue comes from the UE not handling RRC idle mode correctly. It's a limitation that renders the UE failing to connect again after it was put in RRC idle (after RRC Release). Currently the best way to circumvent this is to use a larger RRC inactivity timer in the eNB.