The validity time for NF Instances obtained through NF Discovery was
not properly implemented. Since the validity was 3600 seconds(1 hour),
which caused 5G Core to not work properly after 3600 seconds(1 hour).
There was an issue where an NF Instance should be deleted
when its validity time expired, but it was not working correctly
due to incorrect use of reference count.
Therefore, I have modified the Validity of NF Instances obtained
through NF Discovery to work properly.
I also changed the default value of valdityPeriod to 30 seconds.
Fixed not using Reference Count for adding/deleting NF Instances.
Up until now, NF Instances have been managed by referencing the Reference Count.
Initially, when an NF Instance is added, the Reference Count is incremented and
when it is deleted, the Reference Count is decremented.
If a UE discovers another NF Instance through the NF Discovery function,
the Reference Count is incremented. And if a UE de-registers,
the Reference Count of the discovered NF is decremented.
However, there's a problem with this approach.
When other NF is de-registered,
there is no guarantee that it will be 100% notified.
For example, if a UDM is de-registered, but an SCP is de-registered before it,
the AMF will not be notified that the UDM has been de-registered.
In situations where this is not clear, Reference Count cannot be used.
Therefore, we have modified it to not use the Reference Count method.
Also, when a UE connects, it is modified to always search
whether an NF Instance exists by NF Instance ID whenever it is discovered.
To do this, we modified lib/sbi/path.c as shown below.
```diff
@@ -281,13 +281,15 @@ int ogs_sbi_discover_and_send(ogs_sbi_xact_t *xact)
}
/* Target NF-Instance */
- nf_instance = sbi_object->service_type_array[service_type].nf_instance;
+ nf_instance = ogs_sbi_nf_instance_find(
+ sbi_object->service_type_array[service_type].nf_instance_id);
if (!nf_instance) {
nf_instance = ogs_sbi_nf_instance_find_by_discovery_param(
target_nf_type, requester_nf_type, discovery_option);
- if (nf_instance)
- OGS_SBI_SETUP_NF_INSTANCE(
- sbi_object->service_type_array[service_type], nf_instance);
+ if (nf_instance) {
+ OGS_SBI_SETUP_NF_INSTANCE_ID(
+ sbi_object->service_type_array[service_type], nf_instance->id);
+ }
}
```
While they were continuing their fuzzy testing and developing PacketRusher, an unusual issue with the AMF was observed. The problem arises when a single Ethernet frame containing three bundled SCTP chunks is sent. This behavior is reproduced with PacketRusher when attempting to concurrently register two UEs with the same MSIN.
The expected behavior is that the PDU Session Establishment Accept is sent inside a DownlinkNASTransport to RAN UE NGAP ID 1. However, it is actually sent inside an InitialContextSetupRequest to RAN UE NGAP ID 2. The MAC of this NAS message is invalid for the Security Context of RAN UE NGAP ID 2 (probably valid for RAN UE NGAP ID 1)
== Known limitation ==
Placing npcf-smpolicycontrol and pcf-policyauthorization
in different NFs is not supported. Both npcf-smpolicycontrol
and pcf-policyauthorization should be placed in the same NF.
1. UE registered and PDU established.
2. PCF does not receive Heartbeat.
- PCF De-registered state.
- Since PDU is established, SMF should not remove NF instance
3. PCF re-registered.
- HERE, WE NEED TO INCREASE NF REFERENCE COUNT.
Otherwise, NF instance will be removed if PCF is de-registered state
4. UE sends PDU release request.
5. Because SMF knows PCF NF instance, SMF can send PCF delete
TS24.501
8.2.11 DL NAS transport
8.2.11.4 5GMM cause
The AMF shall include this IE when the Payload container IE
contains an uplink payload which was not forwarded and
the Payload container type IE is not set to "Multiple payloads".
-0-
As such, this function 'nas_5gs_send_gsm_reject()' must be used
only when an N1 SM message has been forwarded to the SMF.
All process will be forcely exited if it failed to encode the S1AP/NGAP/GTP/PFCP message. It is to make sure there was no problem with the encoding of open5gs.
- Set the number of UEs in units of AMF/MME instead of gNB/eNB.
- See default value as shown below
Number of UEs per AMF/MME : 4,096
Number of gNB/eNB per AMF/MME : 32
Sukchan Lee
Lester