UPF Control plane
5.8.2.11 Parameters for N4 session management
These parameters are used by SMF to control the functionality of the UPF as well as to inform SMF about events occurring at the UPF.
The N4 Session Establishment procedure as well as the N4 Session Modification procedure provide the control parameters to the UPF, the N4 Session Release procedure removes all control parameters related to an N4 session, and the N4 Session Level Reporting procedure informs the SMF about events related to the PDU Session that are detected by the UPF.
The parameters over N4 reference point provided from SMF to UPF comprises an N4 Session ID and may also contain:
- Packet Detection Rules (PDR) that contain information to classify traffic (PDU(s)) arriving at the UPF;
- Forwarding Action Rules (FAR) that contain information on whether forwarding, dropping or buffering is to be applied to a traffic identified by PDR(s);
- Multi-Access Rules (MAR) that contain information on how to handle traffic steering, switching and splitting for a MA PDU Session;
- Usage Reporting Rules (URR) contains information that defines how traffic identified by PDR(s) shall be accounted as well as how a certain measurement shall be reported;
- QoS Enforcement Rules (QER), that contain information related to QoS enforcement of traffic identified by PDR(s);
- Session Reporting Rules (SRR) that contain information to request the UP function to detect and report events for a PDU session that are not related to specific PDRs of the PDU session or that are not related to traffic usage measurement.
- Trace Requirements;
- Port Management Information Container in 5GS;
5.8.2.11.3 Packet Detection Rule
The following table describes the Packet Detection Rule (PDR) containing information required to classify a packet arriving at the UPF. Every PDR is used to detect packets in a certain transmission direction, e.g. UL direction or DL direction.
Table 5.8.2.11.3-1: Attributes within Packet Detection Rule
Attribute | Description | Comment | |
N4 Session ID | Identifies the N4 session associated to this PDR. NOTE 5. |
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Rule ID | Unique identifier to identify this rule. |
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Precedence | Determines the order, in which the detection information of all rules is applied. |
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Packet | Source interface | Contains the values "access side", "core side", "SMF", "N6-LAN", "5G VN internal". | Combination of UE IP address (together with Network instance, if necessary), CN tunnel info, |
Detection | UE IP address | One IPv4 address and/or one IPv6 prefix with prefix length (NOTE 3). | packet filter set, application ID, Ethernet PDU Session |
Information. NOTE 4. | Network instance (NOTE 1) | Identifies the Network instance associated with the incoming packet. | Information and QFI are used for traffic detection. Source interface identifies the |
| CN tunnel info | CN tunnel info on N3, N9 interfaces, i.e. F-TEID. | interface for incoming packets |
| Packet Filter Set | Details see clause 5.7.6. | where the PDR applies, e.g. from access side (i.e. up-link), |
| Application ID |
| from core side (i.e. down-link), |
| QoS Flow ID | Contains the value of 5QI or non-standardized QFI. | from SMF, from N6-LAN (i.e. the |
| Ethernet PDU Session Information | Refers to all the (DL) Ethernet packets matching an Ethernet PDU session, as further described in clause 5.6.10.2 and in TS 29.244 [65]. | DN or the local DN), or from "5G VN internal" (i.e. local switch). |
| Framed Route Information | Refers to Framed Routes defined in clause 5.6.14. | Details like all the combination possibilities on N3, N9 interfaces are left for stage 3 decision. |
Packet replication and detection carry on information | Packet replication skip information NOTE 7 | Contains UE address indication or N19/N6 indication. If the packet matches the packet replication skip information, i.e., source address of the packet is the UE address or the packet has been received on the interface in the packet replication skip information, the UP function neither creates a copy of the packet nor applies the corresponding processing (i.e., FAR, QER, URR). Otherwise the UPF performs a copy and applies the corresponding processing (i.e., FAR, QER, URR). |
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NOTE 6 | Carry on indication | Instructs the UP function to continue the packet detection process, i.e., lookup of the other PDRs without higher precedence. |
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Outer header removal | Instructs the UP function to remove one or more outer header(s) (e.g. IP+UDP+GTP, IP + possibly UDP, VLAN tag), from the incoming packet. | Any extension header shall be stored for this packet. | |
Forwarding Action Rule ID (NOTE 2) | The Forwarding Action Rule ID identifies a forwarding action that has to be applied. |
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Multi-Access Rule ID (NOTE 2) | The Multi-Access Rule ID identifies an action to be applied for handling forwarding for a MA PDU Session. |
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List of Usage Reporting Rule ID(s) | Every Usage Reporting Rule ID identifies a measurement action that has to be applied. |
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List of QoS Enforcement Rule ID(s) | Every QoS Enforcement Rule ID identifies a QoS enforcement action that has to be applied. |
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NOTE 1: Needed e.g. if: - UPF supports multiple DNN with overlapping IP addresses; - UPF is connected to other UPF or AN node in different IP domains. - UPF "local switch", N6-based forwarding and N19 forwarding is used for different 5G LAN groups. NOTE 2: Either a FAR ID or a MAR ID is included, not both. NOTE 3: The SMF may provide an indication asking the UPF to allocate one IPv4 address and/or IPv6 prefix. When asking to provide an IPv6 Prefix the SMF provides also an IPv6 prefix length. NOTE 4: When in the architecture defined in clause 5.34, a PDR is sent over N16a from SMF to I-SMF, the Packet Detection Information may indicate that CN tunnel info is to be locally determined. This is further defined in clause 5.34.6. NOTE 5: In the architecture defined in clause 5.34, the rules exchanged between I-SMF and SMF are not associated with a N4 Session ID but are associated with a N16a association. NOTE 6: Needed in the case of support for broadcast/multicast traffic forwarding using packet replication with SMF-provided PDRs and FARs as described in clause 5.8.2.13.3.2. NOTE 7: Needed in the case of packet replication with SMF-provided PDRs and FARs as described in clause 5.8.2.13.3.2, to prevent UPF from sending the broadcast/multicast packets back to the source UE or source N19/N6. | |||
5.8.2.11.4 QoS Enforcement Rule
The following table describes the QoS Enforcement Rule (QER) that defines how a packet shall be treated in terms of bit rate limitation and packet marking for QoS purposes. All Packet Detection Rules that refer to the same QER share the same QoS resources, e.g. MFBR.
Table 5.8.2.11.4-1: Attributes within QoS Enforcement Rule
Attribute | Description | Comment |
N4 Session ID | Identifies the N4 session associated to this QER |
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Rule ID | Unique identifier to identify this information. |
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QoS Enforcement Rule correlation ID (NOTE 1) | An identity allowing the UP function to correlate multiple Sessions for the same UE and APN. | Is used to correlate QoS Enforcement Rules for APN-AMBR enforcement. |
Gate status UL/DL | Instructs the UP function to let the flow pass or to block the flow. | Values are: open, close, close after measurement report (for termination action "discard"). |
Maximum bitrate | The uplink/downlink maximum bitrate to be enforced for the packets. | This field may e.g. contain any one of: - APN-AMBR (for a QER that is referenced by all relevant Packet Detection Rules of all PDN Connections to an APN) (NOTE 1). - Session-AMBR (for a QER that is referenced by all relevant Packet Detection Rules of the PDU Session) - QoS Flow MBR (for a QER that is referenced by all Packet Detection Rules of a QoS Flow) - SDF MBR (for a QER that is referenced by the uplink/downlink Packet Detection Rule of a SDF) - Bearer MBR (for a QER that is referenced by all relevant Packet Detection Rules of a bearer) (NOTE 1). |
Guaranteed bitrate | The uplink/downlink guaranteed bitrate authorized for the packets. | This field contains: - QoS Flow GBR (for a QER that is referenced by all Packet Detection Rules of a QoS Flow) - Bearer GBR (for a QER that is referenced by all relevant Packet Detection Rules of a bearer) (NOTE 1). |
Averaging window | The time duration over which the Maximum and Guaranteed bitrate shall be calculated. | This is for counting the packets received during the time duration. |
Down-link flow level marking | Flow level packet marking in the downlink. | For UPF, this is for controlling the setting of the RQI in the encapsulation header as described in clause 5.7.5.3. |
QoS Flow ID | QoS Flow ID to be inserted by the UPF. | The UPF inserts the QFI value in the tunnel header of outgoing packets. |
Paging Policy Indicator | Indicates the PPI value the UPF is required to insert in outgoing packets (see clause 5.4.3.2). | PPI applies only for DL traffic. The UPF inserts the PPI in the outer header of outgoing PDU. |
Packet rate (NOTE 1) | Number of packets per time interval to be enforced. | This field contains any one of: - downlink packet rate for Serving PLMN Rate Control (the QER is referenced by all PDRs of the UE belonging to PDN connections using CIoT EPS Optimisations as described in TS 23.401 [26]). - uplink/downlink packet rate for APN Rate Control (the QER is referenced by all PDRs of the UE belonging to PDN connections to the same APN using CIoT EPS Optimisations as described in TS 23.401 [26]). |
NOTE 1: This parameter is only used for interworking with EPC. | ||
5.8.2.11.6 Forwarding Action Rule
The following table describes the Forwarding Action Rule (FAR) that defines how a packet shall be buffered, dropped or forwarded, including packet encapsulation/decapsulation and forwarding destination.
Table 5.8.2.11.6-1: Attributes within Forwarding Action Rule
Attribute | Description | Comment |
N4 Session ID | Identifies the N4 session associated to this FAR. | NOTE 9. |
Rule ID | Unique identifier to identify this information. |
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Action | Identifies the action to apply to the packet | Indicates whether the packet is to be forwarded, duplicated, dropped or buffered. When action indicates forwarding or duplicating, a number of additional attributes are included in the FAR. For buffering action, a Buffer Action Rule is also included and the action can also indicate that a notification of the first buffered and/or a notification of first discarded packet is requested (see clause 5.8.3.2). |
Network instance (NOTE 2) | Identifies the Network instance associated with the outgoing packet (NOTE 1). | NOTE 8. |
Destination interface (NOTE 3) (NOTE 7) | Contains the values "access side", "core side", "SMF", "N6-LAN", "5G VN internal" or "5G VN N19". | Identifies the interface for outgoing packets towards the access side (i.e. down-link), the core side (i.e. up-link), the SMF, the N6-LAN (i.e. the DN or the local DN), to 5G VN internal (i.e. local switch), or to 5G VN N19 (i.e. N19 interface). |
Outer header creation (NOTE 3) | Instructs the UP function to add an outer header (e.g. IP+UDP+GTP, VLAN tag), IP + possibly UDP to the outgoing packet. | Contains the CN tunnel info, N6 tunnel info or AN tunnel info of peer entity (e.g. NG-RAN, another UPF, SMF, local access to a DN represented by a DNAI) (NOTE 8). Any extension header stored for this packet shall be added. The time stamps should be added in the GTP-U header if QoS Monitoring is enabled for the traffic corresponding to the PDR(s). |
Send end marker packet(s) (NOTE 2) | Instructs the UPF to construct end marker packet(s) and send them out as described in clause 5.8.1. | This parameter should be sent together with the "outer header creation" parameter of the new CN tunnel info. |
Transport level marking (NOTE 3) | Transport level packet marking in the uplink and downlink, e.g. setting the DiffServ Code Point. | NOTE 8. |
Forwarding policy (NOTE 3) | Reference to a preconfigured traffic steering policy or http redirection (NOTE 4). | Contains one of the following policies identified by a TSP ID: - an N6-LAN steering policy to steer the subscriber's traffic to the appropriate N6 service functions deployed by the operator, or - a local N6 steering policy to enable traffic steering in the local access to the DN according to the routing information provided by an AF as described in clause 5.6.7. or a Redirect Destination and values for the forwarding behaviour (always, after measurement report (for termination action "redirect")). |
Request for Proxying in UPF | Indicates that the UPF shall perform ARP proxying and / or IPv6 Neighbour Solicitation Proxying as specified in clause 5.6.10.2. | Applies to the Ethernet PDU Session type. |
Container for header enrichment (NOTE 2) | Contains information to be used by the UPF for header enrichment. | Only relevant for the uplink direction. |
Buffering Action Rule (NOTE 5) | Reference to a Buffering Action Rule ID defining the buffering instructions to be applied by the UPF (NOTE 6) |
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NOTE 1: Needed e.g. if: - UPF supports multiple DNN with overlapping IP addresses; - UPF is connected to other UPF or NG-RAN node in different IP domains; - UPF "local switch" and N19 forwarding is used for different 5G LAN groups. NOTE 2: These attributes are required for FAR action set to forwarding. NOTE 3: These attributes are required for FAR action set to forwarding or duplicating. NOTE 4: The TSP ID is preconfigured in the SMF, and included in the FAR according to the description in clauses 5.6.7 and 6.1.3.14 of 23.503 [45] for local N6 steering and 6.1.3.14 of 23.503 [45] for N6-LAN steering. The TSP ID action is enforced before the Outer header creation actions. NOTE 5: This attribute is present for FAR action set to buffering. NOTE 6: The buffering action rule is created by the SMF and associated with the FAR in order to apply a specific buffering behaviour for DL packets requested to be buffered, as described in clause 5.8.3 and clause 5.2.4 in TS 29.244 [65]. NOTE 7: The use of "5G VN internal" instructs the UPF to send the packet back for another round of ingress processing using the active PDRs pertaining to another N4 session of the same 5G VN group. NOTE 8: When in architectures defined in clause 5.34, a FAR is sent over N16a from SMF to I-SMF, the FAR sent by the SMF may indicate that the I-SMF is to locally determine the value of this attribute in order to build the N4 FAR rule sent to the actual UPF controlled by the I-SMF. This is further defined in clause 5.34.6. NOTE 9: In the architecture defined in clause 5.34, the rules exchanged between I-SMF and SMF are not associated with a N4 Session ID but are associated with a N16a association. | ||
5.8.2.11.5 Usage Reporting Rule
The following table describes the Usage Reporting Rule (URR) that defines how a packet shall be accounted as well as when and how to report the measurements.
Table 5.8.2.11.5-1: Attributes within Usage Reporting Rule
Attribute | Description | Comment |
N4 Session ID | Identifies the N4 session associated to this URR |
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Rule ID | Unique identifier to identify this information. | Used by UPF when reporting usage. |
Reporting triggers | One or multiple of the events can be activated for the generation and reporting of the usage report. | Applicable events include: - Start/stop of traffic detection with/without application instance identifier and deduced SDF filter reporting; Deletion of last PDR for a URR; Periodic measurement threshold reached; Volume/Time/Event measurement threshold reached; Immediate report requested; Measurement of incoming UL traffic; Measurement of discarded DL traffic; MAC address reporting in the UL traffic; unknown destination MAC/IP address; end marker packet has been received. |
Periodic measurement threshold | Defines the point in time for sending a periodic report for this URR (e.g. timeofday). | This allows generation of periodic usage report for e.g. offline charging. It can also be used for realizing the Monitoring time of the usage monitoring feature. It can also be used for realizing the Quota-Idle-Timeout, i.e. to enable the CP function to check whether any traffic has passed during this time. |
Volume measurement threshold | Value in terms of uplink and/or downlink and/or total byte-count when the measurement report is to be generated. |
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Time measurement threshold | Value in terms of the time duration (e.g. in seconds) when the measurement report is to be generated. |
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Event measurement threshold | Number of events (identified according to a locally configured policy) after which the measurement report is to be generated. |
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Inactivity detection time
| Defines the period of time after which the time measurement shall stop, if no packets are received. | Timer corresponding to this duration is restarted at the end of each transmitted packet. |
Event based reporting | Points to a locally configured policy which is identifies event(s) trigger for generating usage report. |
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Linked URR ID(s) | Points to one or more other URR ID. | This enables the generation of a combined Usage Report for this and other URRs by triggering their reporting. See clause 5.2.2.4, TS 29.244 [65]. |
Measurement Method | Indicates the method for measuring the network resources usage, i.e. the data volume, duration, combined volume/duration, or event. |
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Measurement information | Indicates specific conditions to be applied for measurements | It is used to request: - measurement before QoS enforcement, and/or - to pause or set to active a measurement as for the Pause of charging described in clause 4.4.4 and clause 4.23.14 of TS 23.502 [3], and/or - to request reduced reporting for application start/stop events. |
