Qos enforcement implemenation in UPF /GTP

Q/A
#1

I have studied source code and so far the qoS enforcement seems to be not in place.

What is the free5gc proposed architecture to implement QoS? Should be done in the GTP tunnel?

The QoS model of the 5G system architecture ETSI TS 123 501 sect. 5.7.1 does not clearly define in which component the QoS is enforced. I find statements:

The QoS profile and the QFI of a QoS Flow shall be provided to the ®AN

Does this mean that the RAN, i.e. the gNB must enforce the rules and there are already RAN implementations in place where nothing in addition needs to be done?

For UL:

UPF and UE perform Session-AMBR enforcement and the UPF performs counting of packets for charging.

Now the UPF and the UE is in duty? How could an UE be trusted to enforce it?

AMBR/MFBR enforcement and rate limitation:

The RAN shall enforce UE-AMBR (see clause 5.7.2.6) in UL and DL per UE for Non-GBR QoS Flows

For 5QI I cannot find where it should be enforced.

Also in the GTP message protocol ETSI TS 129 281 I find not reference of QER, where is the inclusion of it defined by the specifications? Is this a custom approach of free5gc?

#2

Hi @ka-oh

I have studied source code and so far the qoS enforcement seems to be not in place.
What is the free5gc proposed architecture to implement QoS?

Currently, free5GC supports the functionality of QoS in the control plane, it didn’t implement the QoS Enforcement in GTP5G. However, UE and RAN are able to get the correct QoS profile from the 5GC.

You can refer to the following links to understand the actual implementation better.

By the way, the free5GC supports these functions in version 3.3.0.

Should be done in the GTP tunnel?

Yes, but it also needs to be supported by other NFs (e.g. SMF, PCF, UPF…).

The QoS model of the 5G system architecture ETSI TS 123 501 1 sect. 5.7.1 does not clearly define in which component the QoS is enforced. I find statements:

The QoS profile and the QFI of a QoS Flow shall be provided to the ®AN

Does this mean that the RAN, i.e. the gNB must enforce the rules and there are already RAN implementations in place where nothing in addition needs to be done?

Yes, RAN needs the QoS profile to map the QoS flow to the DRB.

UPF and UE perform Session-AMBR enforcement and the UPF performs counting of packets for charging.

Now the UPF and the UE is in duty? How could an UE be trusted to enforce it?

According to TS 23.501 - 5.7.2.6 Aggregate Bit Rates, it seems that the AMBR is limited layer by layer (i.e. UE - RAN - UPF).
In my personal opinion, it didn’t have a big impact even if UE has some problems.

For 5QI I cannot find where it should be enforced.

You may refer to the SMF and PCF to find relevant codes and the QFI and 5QI are controlled by the SMF.

Also in the GTP message protocol ETSI TS 129 281 I find not reference of QER, where is the inclusion of it defined by the specifications? Is this a custom approach of free5gc?

While the GTP message is delivered through the N3 (or N9) interface, UPF will use its destination IP address to retrieve the PDR to perform the correct handling procedure.
In addition, the QER is included in the PDR, therefore, the GTP message won’t have such fields directly associated with QER.

#3

Thanks a lot for the detailed reply. This is very helpful.

#4