UPF Path Management and Restoration

Feature Summary and Revision History

Summary Data

Table 1. Summary Data

Applicable Product(s) or Functional Area

SMF

Applicable Platform(s)

SMI

Feature Default Setting

Disabled – Configuration Required

Related Changes in this Release

Not Applicable

Related Documentation

Not Applicable

Revision History

Table 2. Revision History
Revision Details Release

Heartbeat on Sx

2023.01.0

First introduced.

2020.02.0

Feature Description

The heartbeat monitors the status of a UPF node in terms of its responsiveness. It initiates a bilateral flow of request and response between the SMF and the UPF. It has the following actions:

  • The SMF periodically sends a signal in the form of a heartbeat request to the registered UPF node. This action helps in determining if the SMF is in active or not.

  • If the SMF doesn’t receive a response from the UPF after the exhausted retransmission attempts, then the SMF recognizes a failure instance. It purges the UPF node-mapped subscribers.

You can control the following:

  • The number of heartbeat requests that SMF sends to UPF.

  • The interval between consecutive requests.

  • The duration until which the SMF waits for a response.

Standards Compliance

The heartbeat transmission between SMF and UPF complies with the following standards:

  • 3GPP TS 23.527

  • 3GPP TS 23.007, version 15.4.0

How it Works

You can configure the Heartbeat capability at the interface-level, UPF profile group-level, or both. The interface-level configuration is mandatory. If the interface-level configuration is unavailable, then the Heartbeat parameters get configured with the default values. The profile-level configuration overrides the interface-level configuration.

The Heartbeat feature also extends to achieve high-availability for the Node Manager.

Interface and profile-level Heartbeat

The SMF-UPF interaction to detect the UPF path failure using the Heartbeat messages involves the following steps:

  1. The SMF sends a Heartbeat request message to the discovered UPF instances or profile groups based on the configured schedule.

  2. If the UPF instance or profile is alive, it sends a Heartbeat response to the SMF indicating that it’s operational. In case the UPF doesn’t send a Heartbeat response, then the SMF retransmits the Heartbeat request. It's based on the configured interval and the number of permitted attempts.

  3. After the configured count of Heartbeat message reattempts gets exhausted and the SMF doesn’t receive a response from UPF, then the SMF starts the Session release procedure for the subscribers that are associated with that UPF.

Heartbeat and High-availability in Node Manager

Each UPF instance is associated with a primary and secondary Node Manager. The secondary Node Manager acts as a standby system on which the primary manager fails over. The primary Node Manager is responsible for the IP allocation and managing the association-specific messages such as association create, update, or delete request.

Configuration Support for the UPF Path Management and Restoration

This section describes how to configure the support for monitoring the UPF status.

Configuring the support for detecting the UPF status using the Heartbeat feature involves the following steps:

Configuring the Heartbeat at the Interface Level

To configure the Heartbeat at the interface-level, use the following sample configuration: 

config 
    instance instance-id gr_instance_id 
        endpoint pfcp 
            interface { n4 | sxa } 
                heartbeat 
                    interval interval 
                        max-retransmissions max_retry_count 
                        retransmission-timeout retry_interval_count 
                        end

NOTES:

  • instance instance-id gr_instance_id —Specify the GR instance ID.

  • endpoint pfcp —Specifies the endpoint configuration mode.

  • interface { n4 | sxa } —Configures the N4 or Sxa interface over which the Heartbeat messages get exchanged between the SMF and the UPF.

  • Heartbeat —Specifies the Heartbeat configuration.

  • interval interval —Specify the Heartbeat interval in seconds. The accepted range is 60–360. The default value is 60 seconds.


    Note

    Setting the interval to 0, disables the Heartbeat feature.

  • max-retransmissions max_retry_count —Specify the maximum retries for the Packet Forwarding Control Protocol (PFCP) Heartbeat request. Must be in the range of 0–10. The default value is 3.

  • retransmission-timeout retry_interval_count —Specify the Heartbeat retransmission timeout in seconds. Must be in the range of 1–20. The default value is 5.

Verifying the Heartbeat Configuration for the SMF

This section describes how to verify the heartbeat configuration for the SMF.

Use the show running-config instance instance-id gr_instance_id endpoint pfcp command to view and verify the feature configuration.

The following is a sample output of the show command.

show running-config instance instance-id 1   endpoint pfcp
 instance instance-id 1 
  endpoint pfcp
   interface n4
    heartbeat
     interval               61
     retransmission-timeout 3
     max-retransmissions    5
     exit
    exit
   exit
 exit
exit 
 interface sxa
  heartbeat
   interval               300
   retransmission-timeout 15
   max-retransmissions    0
   exit
  exit
exit

Configuring the Heartbeat at the UPF Group Level

To configure the Heartbeat at the UPF group level, use the following sample configuration:
config 
    profile upf-group group_name 
        heartbeat 
            interval interval 
            retransmission-timeout max_retry  
            max-retransmissions retry_count  
            end

NOTES:

  • profile upf-group group_name —Specify the UPF group for which the Heartbeat feature must be enabled.

  • interface —Configures the N4 interface over which the Heartbeat messages get exchanged between the SMF and the UPF.

  • heartbeat —Specifies the Heartbeat configuration.

  • interval interval —Specify the Heartbeat interval in seconds. Must be in the range of 60–360. The default value is 60 seconds.

    Setting the interval to 0, disables the Heartbeat feature.

  • max-retransmissions max_retry —Specify the maximum retries for the Packet Forwarding Control Protocol (PFCP) Heartbeat request. Must be in the range of 0–10. The default value is 3.

  • retransmission-timeout retry_count —Specify the Heartbeat retransmission timeout in seconds. Must be in the range of 1–20. The default value is 5.

Verifying the Heartbeat Configuration for the UPF Group Level

This section describes how to verify the heartbeat configuration for the UPF group level.

Use the show running-config profile upf-group command to view and verify the feature configuration.

The following is a sample output of the show command.

show running-config profile upf-group
 profile upf-group upfGroup1
  heartbeat
   interval               62
   retransmission-timeout 3
   max-retransmissions    2
   exit
  exit
 exit

Associating UPF Group to Individual UPF Network Configuration

This section describes how to associate a UPF group with a UPF configuration.

In this scenario, each UPF network configuration includes the UPF profile that associates every UPF instance with a UPF profile.

To associate an UPF group profile with a network configuration, use the following sample configuration:

config 
    profile network-element upf upf_profile_name 
        upf-group-profile upf_group_name 
        end

NOTES:

  • profile network-element upf upf_profile_name —Configure the UPF network configuration.

  • upf-group-profile upf_group_name —Specify the UPF group name that must be associated to the specified UPF network configuration.

Verifying the Association of the UPF Group with the Individual UPF

This section describes how to verify the association of the UPF group with the individual UPF.

Use the show running-config profile network-element upf command to view and verify the feature configuration.

The following is a sample output of the show command.

profile network-element upf upf1
 n4-peer-address ipv4 209.165.200.238
 n4-peer-port      8805
 upf-group-profile upfGroup1
 dnn-list          [ intershat intershat1 intershat2 ]
 capacity          65535
 priority          65535

OAM Support

This section describes the operations, administration, and maintenance information for this feature.

Bulk Statistics

The following statistics are supported for the heartbeat-related UPF path management feature.

  • nodemgr_upf_heartbeat_fail_stats

  • nodemgr_upf_hb_msg_stats

The SMF maintains these bulk statistics triggered during the heartbeat request and response procedure.

nodemgr_upf_heartbeat_fail_stats

  • Description:

    The counter that gets updated per UPF when it fails to respond to a heartbeat request.

  • The nodemgr_upf_heartbeat_fail_stats counter supports the following labels:

    Labels:

    • Label: upf_heartbeat_req_tx

      Label Description: Label for the heartbeat request that the SMF sends.

    • Label: upf_heartbeat_req_retx

      Label Description: Label for the retransmitted heartbeat request

    • Label: upf_heartbeat_rsp_rx

      Label Description: Label for the heartbeat response that the SMF receives.

nodemgr_upf_hb_msg_stats

  • Description:

    The counter for all heartbeat messages for the specified UPF

For more information on bulk statistics support for SMF, see the UCC 5G SMF Metrics Reference document.