Description
Bearer Control Mode (BCM) is a fundamental concept within the 3GPP packet core architecture, specifically defined in the context of the GPRS Tunnelling Protocol (GTP) for the S5/S8 and S4/S11 interfaces, and within the Evolved Packet Core (EPC) for the S5/S8 interfaces using GTPv2. It is a parameter negotiated during the establishment of a Packet Data Protocol (PDP) context in 2G/3G GPRS or a PDN connection in 4G EPS and 5G systems. The BCM value dictates which entity—the User Equipment (UE) or the network (specifically the Packet Data Network Gateway, PGW, in EPS, or the Gateway GPRS Support Node, GGSN, in GPRS)—is authorized to initiate procedures for modifying the characteristics of a bearer, such as its Quality of Service (QoS) parameters. This negotiation occurs in the Create Session Request/Response or Activate PDP Context Request/Response messages.
Architecturally, BCM is a control-plane attribute managed by the core network's policy and charging control (PCC) framework. The PGW/GGSN, acting as the Policy and Charging Enforcement Function (PCEF), receives the authorized QoS from the Policy and Charging Rules Function (PCRF). The BCM setting determines how these authorized QoS changes are enacted towards the UE and the radio access network. When the network is in control (a specific BCM value), the PGW/GGSN can proactively initiate a Bearer Resource Modification procedure to upgrade or downgrade a bearer's QoS based on PCRF decisions, application demands, or network conditions. This is signaled to the UE via the Mobility Management Entity (MME) or Serving GPRS Support Node (SGSN).
In operation, if BCM is set to 'UE-only' mode, the UE must request any QoS changes via a Bearer Resource Modification Request. The network then evaluates this request against its policies. In network-controlled modes, the PGW/GGSN can trigger modifications independently. This centralizes critical QoS and policy decisions within the network operator's domain, ensuring consistent application of business rules, traffic steering policies, and charging rules. It prevents the UE from arbitrarily requesting high-QoS resources, which is crucial for preventing fraud, managing congestion, and ensuring fair resource utilization among all subscribers.
The role of BCM is integral to dynamic policy enforcement and session management. It works in concert with the QoS Class Identifier (QCI), Allocation and Retention Priority (ARP), and other bearer-level parameters. By controlling the initiation point for bearer modification, BCM enables sophisticated network-driven services like sponsored data, on-demand QoS boosting for video streaming, and seamless QoS adaptation during handovers. It is a key enabler for the network's ability to provide differentiated services and implement advanced PCC scenarios defined in 3GPP specifications.
Purpose & Motivation
Bearer Control Mode was created to address the need for network operators to maintain authoritative control over the allocation and modification of bearer resources, which are directly tied to Quality of Service, network capacity, and revenue. In early mobile data systems, allowing the UE uncontrolled ability to request high-QoS bearers posed significant risks, including potential network resource exhaustion, QoS fraud (where a UE illegitimately requests premium QoS), and challenges in applying consistent policy and charging rules. BCM provides a standardized mechanism to dictate where the control point resides, solving these operational and business problems.
Historically, as services evolved from simple best-effort internet access to rich multimedia and latency-sensitive applications, the requirement for dynamic, session-aware QoS management became critical. The introduction of the PCC architecture in 3GPP Release 7 formalized the separation of policy control from bearer management. BCM is a logical component of this architecture, ensuring that the entity enforcing policy (the PCEF in the PGW/GGSN) also has the procedural authority to modify bearers to align with those policies. This was a significant advancement over static, pre-configured bearer QoS.
The creation of BCM was motivated by the limitation of earlier, more static bearer management approaches. It enables the network to be proactive and intelligent. For example, an IMS voice call requires a dedicated bearer with a guaranteed bit rate. With network-controlled BCM, the PCRF can instruct the PCEF to establish this bearer automatically when the call is set up, without relying on a UE request, ensuring faster and more reliable service establishment. It also allows the network to downgrade QoS during congestion based on subscriber tier or service type, optimizing the experience for all users.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (96 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-7, normative work from Rel-15.
In Release 15, the BCM function was enhanced with the introduction of **Service Gap Control**, including its basic procedures, feature negotiation, and specific UE behaviors when the service gap timer is running. It also introduced the capability to support **15 EPS Bearer IDs in NAS**, requiring new UE and network NAS capabilities, and enabled attach procedures without a PDN connection for supporting UEs. Furthermore, the release included clarifications and corrections for Service Gap Control, such as allowing mobile-originating signaling and data while the timer is running in connected mode.
- Introduction of Service Gap Control; basics and feature negotiation TS 24.301CR2982
- Service Gap Control feature; non supporting UEs TS 24.301CR2983
- Service Gap Control; UE behaviour service gap timer is running TS 24.301CR2984
- Support of 15 EPS Bearer IDs in NAS TS 24.301CR3009
- Service Gap Control feature cleanup and corrections TS 24.301CR3010
- Addition of UE and network NAS capabilities for support of 15 EPS bearers TS 24.301CR3015
+ 12 more changes
In Release 16, the BCM function was enhanced with new procedures for EPS bearer management during inter-system mobility and congestion control. Key additions included the local release of dedicated EPS bearers after inter-RAT mobility to NB-IoT and corrections for APN-based and NAS-level mobility management congestion control. The release also introduced the association of NSSAI with the default EPS bearer context and refined behaviors for service gap control and EPS bearer context status reporting after mobility from 5GS.
- Default EPS bearer context activation for accessing RLOS TS 24.301CR3194
- NAS security mode control handling in case of RLOS access TS 24.301CR3218
- Small data rate control parameters received in EPS TS 24.301CR3245
- Update timer T3448 for CP congestion control in 5GS TS 24.301CR3215
- Local release of dedicated EPS bearers after inter-RAT mobility to NB-IoT TS 24.301CR3234
- Applying APN rate control at inter-system change TS 24.301CR3287
+ 8 more changes
In Release 17, the BCM function was enhanced with an addition to the UE requested bearer resource modification procedure and introduced a specific authorization check for C2 pairing during bearer resource modification. It also included clarifications and corrections regarding EPS bearer handling, such as for GBR EPS bearers and deactivation scenarios related to UUAA failure or revocation. Furthermore, the release defined the specific EPS bearer identity to be used for the 3GPP PS data off functionality.
- C2 pairing authorization at bearer resource modification TS 24.301CR3532
- Resolving the Editor's note related to supporting paging timing collision control as a capability for MUSIM in EPS TS 24.301CR3568
- Using Service Request procedure for removing paging restrictions in EPS for MUSIM UE that uses the control plane CIoT EPS optimization TS 24.301CR3564
- PDN connections associated with the EPS bearer identities for which paging is restricted TS 24.301CR3548
- UUAA completion after default EPS bearer context activation TS 24.301CR3593
- Uplink control during EPS UUAA-SM TS 24.301CR3615
+ 9 more changes
In Release 18, the BCM (Bearer Control Mode) function was enhanced with specific corrections and clarifications to EPS bearer handling procedures. These included fixes for the UE requested bearer resource modification procedure for URSP provisioning, collision handling for bearer release modification, and the handling of DEACTIVATE EPS BEARER commands with PTI mismatches. Furthermore, the release introduced a new QCI 10 for QoS control specifically for satellite access and provided clarifications for operations involving bearers without a TFT.
- UE unavailability period reporting for enhanced discontinuous coverage overrides mobility management congestion control - EPS TS 24.301CR3939
- Abnormal case of invalid EPS bearer ID in Remote UE Report message TS 24.301CR3868
- Collision handling for the modification procedure to release the bearer TS 24.301CR3845
- EPS bearer handling after CPSR with active flag not having bearer resource (24.301) TS 24.301CR3941
- Corrections to the UE requested bearer resource modification procedure for URSP provisioning in EPS TS 24.301CR4005
- Correction to EPS bearer ID handling.by adding missing bullet TS 24.301CR4064
+ 5 more changes
In Release 19, the enhancements for Bearer Control Mode primarily focused on expanding and refining RAT utilization control for EPS. Key new capabilities included extending this control to satellite E-UTRAN and NG-RAN, storing the control information in non-volatile memory, and applying it during procedures like periodic tracking area updating and GUTI reallocation. The release also introduced corrections and clarifications for the associated information elements and their handling in various NAS messages and network-initiated procedures.
- Control of UE RAT utilization by EPS TS 24.301CR4077
- Addition of satellite E-UTRAN and satellite NG-RAN in RAT utilization control TS 24.301CR4107
- Storing RAT utilization control information in non-volatile-memory TS 24.301CR4119
- RAT utilization control information for equivalent PLMNs TS 24.301CR4111
- Control of UE RAT utilization in EPS TS 24.301CR4138
- Invalid EPS bearer identity in the Data container IE in the EMM TRANSPORT message TS 24.301CR4494
+ 32 more changes
Explore further
Broader topics and technologies where BCM plays a role.
Defining Specifications
3GPP specifications that define or reference BCM, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.060 vj00 | GPRS Service Description Stage 2 | Rel-19 |
| TS 24.301 vj60 | NAS protocol for Evolved Packet System | Rel-19 |