Feature Description

The User Plane function (UPF) requires the Bearer level information (BLI) for each QoS flow like QFI for 5G and Bearer Id for 4G, 5G QoS Identifier (5QI) allocation and retention priority (ARP), and Charging ID, to support inline services. The Bearer QCI Support feature facilitates this requirement with the SMF.

Note
The Bearer QCI Support feature also includes support for Bli_ID and QFI values in the “Create PDR” message.

The SMF sends the Bearer QoS Class Identifier (QCI) Information Element (IE), which is cisco proprietary IE, in the PFCP session establishment request and PFCP session modification request. The UPF implicitly derives the deletion indication. If a BLI ID is no longer associated with any PDR, the UPF removes it from the PFCP session context. The UPF adds the 5QI or QCI value in the EDR. Currently, the Bearer QCI field is used for 5G to add the 5QI.

The BLI is reported to the UPF as shown in the following table. The formats and encoding and decoding of these IEs are the same as other 3GPP IEs as described in TS 29.244.

Information

Elements

Mandatory

/Optional

Data TypeDescription

valid

guint8

Validity of the Bearer level information IE

bli_id

Mandatory

PfcpBliId

QoS flow identifier (QFI) of 5G or Bearer ID (4G)

qci

Optional

PfcpQci

Used by PGW-C, not relevant for SMF

_5qi

Optional

Pfcp5qi

5QI associated with the QoS flow

arp

Mandatory

PfcpArp

ARP comprises of pre-emption capability, Pre-emption vulnerability, and priority level.

charging_id

Optional

PfcpChargingId

Charging ID associated with the QoS flow or Bearer (or both).

Bearer Level Information ID

The unique ID for each Bearer level information sent from SMF. The recommended value of this IE is QFI (in 5G) or Bearer-id (in 4G). The format of IE is as below:

Bits

Octets

8

7

6

5

4

3

2

1

1 to 2

Type = 232 (decimal)

3 to 4

Length = 1

5

BLI_ID value

6 to n+4

These octets are present only if explicitly specified

QCI : This is not applicable for 5G. It is used in CUPS, if required.

Bits

Octets

8

7

6

5

4

3

2

1

1 to 2

Type = 233 (decimal)

3 to 4

Length = 1

5

QCI value

6 to n+4

These octets are present only if explicitly specified

5QI: The SMF uses this this IE to send the 5QI value.

Bits

Octets

8

7

6

5

4

3

2

1

1 to 2

Type = 234 (decimal)

3 to 4

Length = 1

5

5QI value

6 to n+4

These octets are present only if explicitly specified

ARP: The ARP value is sent with this IE.

Note
From SMF, the ARP value is encoded as arp->pci)<<4) | arp->pl)<<2)| arp->pvi)

Bits

Octets

8

7

6

5

4

3

2

1

1 to 2

Type = 235 (decimal)

3 to 4

Length = 1

5

ARP value

6 to n+4

These octets are present only if explicitly specified

Charging ID: The Charging IE is sent with this IE.

Bits

Octets

8

7

6

5

4

3

2

1

1 to 2

Type = 236 (decimal)

3 to 4

Length = 1

5

Charging Id value

6 to n+4

These octets are present only if explicitly specified

Triggers for Bearer Level Information IE

The following are the triggers for sending the BLI IE in PFCP messages:

PFCP Session Establishment Message

The Bearer level information IE is sent for each new QoS flow with the unique QFI ID. This IE is added in the policy decision in the N7 Policy Control Create Response message from the PCF. Therefore, SMF sends multiple instances of this IE, in a single PFCP message.

PFCP Session Modification Message:

Any new QoS flow addition or new PCC rule referring to an existing QoS flow that results in a new QER or PDR IE that has a new Bearer level information IE for each unique QFI ID.

The BLI IE is not included in the PFCP Session Modification Message if the modification is for IDFT tunnels.