POWDER indoor OTA OAI deployment: 5G-oai-indoor-ota_basic_deploy profile

[Ghinwa]

Hi everyone,

I am debugging a POWDER indoor OTA OAI deployment and I reached a state where the control plane works, but the dataplane appears one-way. I would appreciate any guidance in case this is a known issue or a known profile/version mismatch.

Setup and the link is:

https://www.powderwireless.net/instantiate.php?profile=9b9417b5-9429-11ed-b318-e4434b2381fc&rerun_instance=90cc0d45-abbc-4039-a07b-2fe0ca78c8e7

I am using the POWDER OAI indoor OTA setup with:

• cn5g-docker-host
• ota-x310-3-gnb-comp
• ota-nuc1-cots-ue / ota-nuc2-cots-ue

Core changes I had to make first

The original core stack did not come up correctly with the images referenced by the profile, so I switched to:

• oaisoftwarealliance/oai-amf:v1.4.0
• oaisoftwarealliance/oai-smf:v1.4.0
• oaisoftwarealliance/oai-spgwu-tiny:v1.4.0

and I used the non-NRF compose file with FQDN disabled.

After that:

• the core containers became healthy,
• the gNB connected to the AMF,
• the UE attached successfully in 5G SA,
• and the UE obtained an IP address (e.g. 12.1.1.129, 12.1.1.130).

Current problem

The UE attaches successfully, but end-to-end traffic still fails.

For example:

• UE gets IP on qwwan0
• ping -I qwwan0 192.168.70.135 fails
• oai-ext-dn -> UE ping also fails

I captured traffic and the behavior is consistent across runs:

1. UE attach / session establishment succeeds
   • SIM_READY
   • PS: Attached, DataCap: 5G_SA
   • DHCP lease obtained on qwwan0
2. gNB and AMF are connected
   • AMF shows the gNB as connected
3. Uplink traffic reaches ext-dn
   On the CN side, I can see:
   • UE ICMP request arrives encapsulated in GTP-U
   • UPF decapsulates it and forwards it to oai-ext-dn
   • oai-ext-dn sends an ICMP reply back to the UPF

4. But no downlink GTP-U is sent back to the gNB
   On the outer N3 capture, I consistently see only:

   • 192.168.1.2:2152 -> 192.168.70.134:2152

   i.e. gNB -> UPF uplink GTP-U

   I do not see the reverse direction:

   • 192.168.70.134:2152 -> 192.168.1.2:2152

So the current state looks like:

• control plane: OK
• uplink dataplane: OK
• downlink dataplane: broken / absent

One suspicious SMF log line

Earlier during session setup I also saw:

• Could not get local_up_fteid from created_pdr

I am not sure whether this is expected noise or directly related to the missing downlink GTP-U.

My question

Has anyone seen this behavior before in this POWDER OTA OAI setup?

More specifically:

1. Is this a known issue with using v1.4.0 / non-NRF / FQDN-disabled core images with this profile?
2. Does this symptom usually point to a PFCP/PDR/FAR downlink programming issue in SMF/UPF?
3. Is there a known “correct” image/compose combination for this OTA profile that avoids this one-way dataplane behavior?

I am trying to stay conservative with modifications and avoid invasive changes unless I know they are safe for the profile.

Thanks a lot.

Ghinwa

[Dustin Maas]

Hi Ghinwa,

Thank you for the detailed problem description!

Do have an experiment running now that I can have a look at?

Thanks,
Dustin

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[Ghinwa]

Hi Dustin,

Thank for your reply, I found the real cause of that problem.

Actually it was a configuration mismatch between the UE/SMF session parameters and the UPF configuration in the active compose file.

Since the session used

DNN=oai

and

S-NSSAI SST=1, SD=1

, while the UPF was configured with

DNN=default

and

NSSAI 222/123

.

After aligning the UPF configuration to

DNN_0=oai

,

NSSAI_SST_0=1

, and

NSSAI_SD_0=1

, downlink GTP-U appeared correctly and end-to-end connectivity succeeded.

Thank you again.
Ghinwa

[Dustin Maas]

Ah.. that makes sense given that you used a different configuration.

Thanks,
Dustin

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