Release Notes for Ultra Cloud Core: Session Management Function, Release 2025.03.0

First Customer Ship (FCS)

14-Aug-2025

End of Life (EoL)

14-Aug-2025

End of Software Maintenance (EoSM)

12-Feb-2027

End of Vulnerability and Security Support (EoVSS)

12-Feb-2027

Last Date of Support (LDoS)

29-Feb-2028

Product impact

Feature

Description

Upgrade

Reduced Capability support on SMF

This feature allows the SMF to support High Latency Communication sessions for Reduced Capabilities UEs.
SMF supports the connectivity of Reduced Capability UEs with the network by defining a new RAT type as RedCap.

Commands introduced:

·         user-plane-buffering-mgmt true: This CLI is configured under DNN profile to enable buffering at UPF.

·         hlcom true: This CLI is configured under DNN profile to enable HLCOM sessions for entire DNN.

·         policy extended-buffering extbuff { sbpc sbpc_count ddnd ddnd_count | dbpc dbpc_count dbd dbd_duration } : This CLI is configured under the Policy Extended buffering to define the SBPC, DDND, DPDC and DBD parameters.

·         priority priority_val ruledef ruledef_name actiondef actdef_name event im-entry/paging_failure: This CLI is configured under Policy Event Management to define to define the event policy.

·         ruledef ruledef_name condition { rat matches redcap | hlcom is true }: This CLI is configured under Policy Rule Management to define the rule.

Default Setting: Disabled–Configuration Required

Software Reliability

Event failure logs for N2HO procedure

With this feature, the consistent event failure logs are enhanced to support the N2HO procedure for the SMF and vSMF interfaces.

Software Reliability

Failure handling for IPAM chunk operations

IPAM failure handling prevents IP mismatch between SMF and UPF, which reduces call failures and improves operational efficiency. This feature enables IPAM to trigger failure handling when SMF fails to notify or apply chunk operations on UPF.

Commands introduced:
failure-handling route-updates deactivate and no failure-handling route-updates deactivate in the ipam configuration.

Commands enhanced:

·         N4AssociationUpdateReq message type in profile failure-handling interface pfcp message type configuration.

·         assoc-setup and route-update conditions and retry-ignore and retry-continue actions for N4AssociationUpdateReq message type.

Upgrade

S4-SGSN session handover and mobility management for 2G and 3G networks

This feature details the handling of Modify Bearer Requests (MBR) and handover scenarios within the context of 2G and 3G support for S4SGSN in SMF. It outlines the procedures for user location changes, inter-RAT handovers (4G to 3G/2G and 3G/2G to 4G ), intra-RAT handovers (3G SGW handovers), and handovers involving dedicated bearers.

This ensures that the sessions are maintained during handovers, minimizing disruption to user applications.

Ease of Use

NF-Set based Subscription towards NRF

SMF supports enhanced subscription criteria, enabling improved handling of NRF notifications for NF Set-based changes. Previously, SMF supported only {{nfInstanceId}}-based subscriptions. The enhanced subscription criteria improve SMF's ability to accurately track and respond to dynamic changes in NF Sets, such as peer additions or removals.

Command introduced:

nf-subscription-params nfSetCond—Used to configure NF Set-based subscription criteria.

Default Setting: Disabled–Configuration Required

Upgrade

Support to save PGW CDR records on local storage

This feature enables SMF to save PGW CDR records on local storage. CDR support is supported with Legacy Interfaces (Gx / Gy).

Upgrade

Scaling Converged Core Cluster with Node Labeling and Required Affinity

This feature enables the dynamic addition of servers to a running cluster without disrupting existing deployments. It allows seamless scalability to meet growing demands and minimizes downtime, enhancing operational continuity.

Upgrade

QoS negotiation for 2G and 3G sessions

This feature introduces Quality of Service (QoS) negotiation capabilities for 2G and 3G subscribers utilizing the S4-SGSN in SMF. It enables dynamic and automated adjustments to the QoS parameters of the default bearer based on triggers originating from the Home Location Register (HLR) or PCF.

This allows the network to adapt to changing conditions and subscriber needs, optimizing resource utilization and enhancing the user experience.

Ease of Use

NF Discovery based on Preferred Locality

SMF includes the 3gpp-Sbi-Discovery preferred-locality HTTP header when communicating with the SCP. By populating this header, SMF enables more efficient NF selection based on locality during peer NF discovery, resulting in optimized network function interactions and improved service delivery.

Ease of Use

Enhanced QoS Flow-Based Charging Support for 4G Roaming

This feature extends QoS Flow-Based Charging (QBC) to 4G roaming, enabling precise per-QoS flow charging for outbound roamers, improving billing accuracy, and ensuring compliance with roaming agreements.

The solution collects charging data at H-PLMN, generates QBC usage reports, and exchanges charging parameters during session establishment. It dynamically negotiates QBC capabilities with the Charging Function (CHF) and updates rules based on CHF responses. CLI commands allow customization of QBC profiles and triggers, while backward compatibility ensures existing homer behavior remains unaffected. The feature supports 4G homer-4G roamer, 4G homer-5G roamer, and 5G homer-4G roamer scenarios for seamless interoperability.

Software Reliability

SMF Failure Handling of HTTP Status Code 429

This feature enables SMF to specifically handle the 429 error code, rather than treating it as a generic failure and using the standard failure handling template.
When the SMF receives a 429 response, it can be configured to blocklist the congested peer NF for a specific duration. This prevents the SMF from sending additional requests to the overloaded peer, allowing the peer to recover, and mitigating the impact of congestion on the SMF's operations. The duration for blocklisting can be determined by the retry-after value received in the 429 response or by a locally configured value.

Upgrade

2G and 3G session attach and detach procedures over GTPv1

This feature includes details on 2G and 3G session attach and detach support on SMF for v1SGSN. It captures the GTPv1 messages/procedure and information elements that are translated to GTPv2 equivalents.

Software Reliability

IPv6 transport on N4 interface

SMF now supports IPv6 addresses for both N4 and Sx interfaces.

Default timer value for IDFT tunnel removal during N2/N26 handover

Previous Behavior: During the N2 or N26 (4G to 5G) handover, when the IDFT is enabled but the timeout value is not configured, the IDFT tunnel gets deleted during the last N4 leg of handover (execution phase).

New Behavior: When the IDFT is enabled during the N2 or N26 (4G to 5G) handover but the timeout is not configured, SMF considers 15 seconds as the default timeout value for N2/N26 handover IDFT timer. When the timer expires, SMF proceeds to delete the IDFT tunnel at UPF post the handover.

HSS-initiated QoS modification handling for 4G sessions

Previous Behavior:

1.     During HSS-initiated QoS modification for 4G sessions, the procedure metrics are pegged as “Success” for some failure scenarios.

2.     In case the procedure is aborted due to another higher priority procedure like Handover, policy decision received in PCF update response is not processed once the other procedure (Handover) is completed.

3.     For HSS-initiated QoS modification triggered by the modify bearer command, PCF sends an empty SmPolicyDecision in  the 200 OK SM policy update response when the PCF decides not to update the policies. SMF does not send any modify bearer failure indication to SGW in this scenario.

4.     In HSS-initiated QoS modification triggered by Modify Bearer command, when the SMPolicyUpdateResponse message from PCF is received without any change in policy, SMF triggers UBR and N4 modification message even though there is no change in QoS parameters.

New Behavior:

1.     For HSS-initiated QoS modification, the procedure metrics are pegged properly for failure scenarios.

2.     In case the procedure is aborted due to another higher priority procedure like handover, policy decision received in PCF update response is processed once the other procedure (Handover) is complete.

3.     For HSS-initiated QoS modification triggered by modify bearer command, PCF sends an empty SmPolicyDecision in the 200 OK SM policy update response when the PCF decides not to update the policies. SMF sends the modify bearer failure indication to SGW and the corresponding procedure is marked as failure.

4.     In HSS-initiated QoS modification triggered by modify bearer command, when SMPolicyUpdateResponse from PCF is received without any change in policy, modify bearer failure indication is sent to SGW and the corresponding procedure is marked as failure.

Inter-PLMN SGW handover between homer and roamer for 4g-Only UE

Previous Behavior:

1.     When the ModifyBearerRequest received for SGW change homer to roamer handover to SMF, the SMF sends ModifyBearerResponse with the interplmn_ho_not_configured cause value.

2.     When the ModifyBearerRequest received for SGW change roamer to homer handover to SMF, the SMF sends N4ModificationRequest to UPF with these values:

·         N3 PDR is created

·         S5 UL PDR is deleted and recreated

·         Update FAR

New Behavior:

1.     When the ModifyBearerRequest received for SGW change homer to roamer handover to SMF, the SMF sends N4ModificationRequest to UPF with these values:

·         S5 UL PDR is deleted and recreated

·         Update FAR

2.     When the ModifyBearerRequest received for SGW change roamer to homer handover to SMF, the SMF sends N4ModificationRequest to UPF with these values:

·         S5 UL PDR is deleted and recreated

·         Update FAR

New causes to support DHCP lease expiry

Previous Behavior: Upon session release triggered due to DHCP lease expiry, SMF was sending GTP cause "Reactivation Requested" in case of 4G and N1 SM Cause "missing or unknown DNN" in case of 5G sessions.

New Behavior: Upon session release due to DHCP lease expiry, SMF sends EGTP Cause 73:"No resources available" in case of 4G and N1 SM Cause 26:"Insufficient Resources" in case of 5G sessions.

PLMN-Change charging trigger for 4G sessions

Previous Behavior: The SMF could not detect Public Land Mobile Network (PLMN) changes, that is when a subscriber is moving from a roaming 4G network to the home 4G network.

New Behavior: With the introduction of the Roaming Quota-Based Charging (QBC) feature, the SMF now supports PLMN change detection and PLMN-Change charging trigger, ensuring accurate billing during roaming scenarios.

SMF Response Update for Cancelled 4G to 5G Handover

Previous Behavior: During the handover of a User Equipment (UE) from 4G to 5G, if the handover was cancelled and the AMF handover cancel request collides with the AMF release request at the SMF, the SMF sent a "400 Bad Request" message to the AMF.

New Behavior: During the handover of a UE from 4G to 5G, if the handover was cancelled and the AMF handover cancel request collides with the AMF release request at the SMF, the SMF now sends a "200 OK" message to the AMF.

Transport source validation for PFCP messages

Previous Behavior: The SMF accepted and processed PFCP messages from any transport, even if the message came from a different source than the one originally associated with the UPF. This could allow untrusted sources to send messages to the SMF.

New Behavior: The SMF now checks that all inbound PFCP messages (except association setup and heartbeat) come from the expected UPF transport. If a message comes from an unrecognized source, it is rejected.

Customer Impact: This update improves security by ensuring only messages from trusted UPFs are accepted.

Update to file-write CLI Command Behavior

Previous Behavior: The file-write option could not be executed without specifying a bulk filter.

New Behavior: The file-write CLI command can now be executed without a bulk filter. However, when executed without a bulk filter, it will return an error response.

User location handling in charging updates

Previous Behavior: If the user location information was missing in the PDU Session Modification message, the SMF used to clear the previously stored user location information. Consequently, any subsequent CHFUpdate messages sent by the SMF used to have an empty value for User Location Information IE in the QFI Container Information attribute.

New Behavior: If the PDU Session Modification message does not include user location information, the SMF now retains the previously stored user location. This ensures that the CHFUpdate message continues to include the correct user location information from the SMF context.

Customer Impact: This change prevents the loss of user location data in charging updates, ensuring consistency and accuracy in location-based charging and reporting. Customers benefit from improved reliability and compliance in charging records, particularly for regulatory or billing purposes.

Session-AMBR and vSMF prioritization updates

Previous Behavior:

1. If the qos-profile is either not configured or does not specify a sess-ambr (Session-AMBR) value, the vSMF does not include sess-ambr in the Create-QER in N4EstdReq during an IBR call. There is no default value for sess-ambr.

2. QFI from hSMF is not updated in the vSMF session and CDL.

New Behavior:

1. A new default value of 1GBps is added for session-ambr. This is applicable only if session-ambr is not configured.

2. The vSMF now correctly prioritizes QFI, 5QI, and ARP values received from the hSMF.

Customer Impact: The sess-ambr now has a default value and vSMF prioritizes QFI values received from hSMF.

CSCwo47678

WIFI-LTE HO - N7 res sent with diff chgID for same RG-SID, N4 metering method sent wrongly

CSCwo85533

400 for SM Context Update with HO cancel

CSCwp05175

Mismatch session type/RAT at SMF & UPF during 4G to 5G N26 HO failure during prep stage

CSCwp05307

N26 Handover issues in 4G to 5G Handover

CSCwp08247

SMF does not select PCF based on GEO locality when the preferred locality is exhausted

CSCwp08393

SMF - MBFI missing - request sent for SE_AMBR_CH, Policy update res with only revatimer,

CSCwp11802

Observing cli is broken in the current release of SMF for IPV6 prefix delegation feature

CSCwp12479

Follow-Up on CSCwo90545: Inconsistent SMF Processing of HO Cancel and AmfInitRelease during collision

CSCwp19986

N26 Handover IDFT default timeout in 4G to 5G Handover

CSCwp30140

wifi->lte: Removal of dnn profile inbetween, service pod restart seen

CSCwp35358

Quota Exhaust Retry Reason Logged Incorrectly in PDU Release Procedure

CSCwp63545

Remove EdrTransactionIdKys field from app-infra, and rename the csv filename with node name prepended to it.

CSCwp65691

show subscriber failopen is not giving the option to list N40OFF and N40DD together

CSCwp85819

One way audio on OBR 5G testing with roaming operator

CSCwq10045

Home SMF is not sending the N7 rule-inactive message to the PCF when the V-SMF rejects the NW_RES_MOD_REQ

CSCwq10394

QFI changes during IBR attach on n16 by H-SMF, any sx-rep-req is rejected by V-SMF post attach

CSCwq56686

PCSCF restoration in between Idle exit not handled

CSCwq46345

Rolling upgrade from JUL main to main branch getting failed with CEPS and session loss.

CSCwq61695

For half attach scenarios for 2g/3g over 5g, SmContextCreateReq is treated as HO request

Ultra Cloud Core SMI

2025.03.1.10

Ultra Cloud CDL

1.12.2

Ultra Cloud Core UPF

2025.03.0

Ultra Cloud cnSGWc

2025.03.0

ccg-2025.03.0.SPA.tgz

The SMF offline release signature package. This package contains the SMF deployment software, NED package, as well as the release signature, certificate, and verification information.

2025.03.0

ncs-6.4.5-ccg-nc-2025.03.0.tar.gz

The NETCONF NED package. This package includes all the yang files that are used for NF configuration.

Note that NSO is used for the NED file creation.

6.4.5

ncs-6.1.14-ccg-nc-2025.03.0.tar.gz

6.1.14

Microsoft Windows

Open a command line window and type the following command:

> certutil.exe -hashfile <filename.extension> SHA512

Apple MAC

Open a terminal window and type the following command:

$ shasum -a 512 <filename.extension>

Linux

Open a terminal window and type the following command:

$ sha512sum <filename.extension>

OR

$ shasum -a 512 <filename.extension>

Note:       <filename> is the name of the file. <extension> is the file type extension (for example, .zip or .tgz).

SMF documentation

Session Management Function

cnSGWc documentation

Serving Gateway Function

SMI documentation

Subscriber Microservices Infrastructure

UPF documentation

User Plane Function

Service request and additional information

Cisco Support