Sudden Remove of all PFCP sessions resulting in losing connection

Q/A
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#1

We have a simple setup:

  1. A Free5GC core network (one UPF, one SMF, one AMF, etc.) deployed on two VMs. One VM hosting the control plane functions and another VM hosting the user plane functions (only one UPF in this case)
  2. The UPF supports only one DNN (that supports internet access) with a cidr 60.61.0.0/16
  3. Boths VMs are connected to a gNB (Amarisoft) through a VPN tunnel
  4. There is only one slice configured in the network.
  5. A 5G mobile phone is used as a user terminal that connects to the gNB.

Once we launch the network, the user is well connected to the 5G network and receives an IP address in the range 60.61.0.0./16 and has internet access. However, after some time, the user loses the internet access. We don’t know why yet.

When the user loses its internet connection, it cannot ping to the gNB nor to the core network.

From the PFCP log (below), we did not understand why there is the msg: Remove Request Transaction

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After the above messages, we lose the connection for good with no attempt for re-connection.

From the SMF log, from time to time we have the following error message :

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From the UPF log, we also have from time to time the pool is full error and the below error:

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Finally, on the free5gc log we have a lot of SCTP timeout between the AMF and the NGAP protocol

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We are using go version 1.14.4 and free5GC version: v3.0.5-10-gc19c1bb

We would like to know if the problem comes from the UPF, SMF or the PFCP protocol or is it a network configuration problem maybe due to the VPN. Is there a limit on the amount of PFCP sessions ? After all, we have only one user connected.

Thank you in advance !

#3

Update:
I installed the latest version of Free 5G Core v3.2.1.
I was able to get a 5G connection but without internet access. I can not even ping from the phone to the core network or the gNB (similar with the previous problem).

There are no errors in the logs. Everything looks normal. But I don’t have access to my DNN that I have configured.

Any help ?

#4

Hello, julien. I have reviewd your question. There are many possible reasons resulting in the disconnection of internet(N6). I suggest that you can activate free5GC by run sudo ./run.sh -dp -cp. It will produce log of free5GC , -dp means data plane and -cp means control plane. The log file in free5gc/log/{date-time}/free5gc.pcap. You can open in readble form by opening it in Wireshark. First you can check whether your UE data flow have throughed by RAN、UPF、Internet, then figure out what’s your problem is.

BRs, Ben

#5

Thank you for your reply. However, when adding -dp -cp I did not get the pcap log files. I only got the log files from free5GC in .log format.

#6

@julien hello, I’m sorry for my suggestion is not suitable for your condition. Becase the bash script named run.sh which support the recording of pcap file is implemented in version v3.1.0 and higher of free5gc. I recommented for you to use one of these version of free5gc, or you can just use v3.0.5 but you need to record the network event using wireshark during your problem happening. Thanks.

#9