SMF consuming all VM memory

Q/A
#1

Hi All,

I am facing an issue while sending heavy downlink traffic.

Scenario: A CPE is connected to the 5G Core and accessing data. After sometime UE lost the network and UE context release is received by the AMF.

At this moment I am generating downlink traffic for that UE. AMF is sending Paging Request to the UE and there is no response from UE.

If I increase the load, I see lot of 409 Conflict messages in SMF.

2024-10-17T12:07:24.173185192Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.178098681Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.183516753Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.188245270Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.193165088Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.198838158Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.204284772Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict
2024-10-17T12:07:24.208340081Z [WARN][SMF][PFCP] Send N1N2Transfer failed: 409 Conflict

Once I started to see this log, SMF keeps on consuming memory and VM gets stuck.

The only way to come out of this situation is to kill smf process.

Does anyone observed similar issue or have any suggestions ?

#2

Hello @aleemgsl , thank you for raising the issue.
Please allow me to ask the following questions first:

  1. What is the version of free5GC you are using?
  2. Is the CPE using UERANSIM?
  3. Can you provide a detailed step-by-step description of the problem you encountered?
  4. If possible, could you provide the full pcap file?

Tks

#3

Hello @aleemgsl, Here are some suggestions that might help you

When traffic passes through the SMF, the SMF records traffic information to facilitate subsequent tracking. Therefore, if there is a large amount of traffic, the SMF’s memory usage will increase.

To address this issue without killing the SMF process, here are two possible solutions:

  1. After the transmission ends, send a PDU Session Release Request to release the resources occupied by the PDU session (this is the recommended method).
  2. After the transmission ends, perform DeRegistration on the UE. (ref here)
    llllll
    llllll644×637 20.9 KB

If you have any confusion about the solution, please let me know.