Description
The Local PDN Gateway (L-GW) is a core network user plane function that acts as the gateway between the User Equipment (UE) and a local data network or the internet, but is deployed in a decentralized manner, often at the network edge near the radio base station (e.g., eNodeB in LTE, gNB in 5G). Architecturally, it incorporates the functions of a traditional PDN Gateway (PGW), such as IP address allocation, packet filtering, policy enforcement, and charging, but within a localized scope. In LTE, it is a logical component that can be collocated with the HeNB (Home eNodeB) in a residential or enterprise setting for LIPA, or deployed at a network aggregation point for SIPTO. In 5G, its functions are subsumed by the User Plane Function (UPF) when deployed at the edge, with the Local UPF being the equivalent entity.
How it works depends on the deployment scenario. For Local IP Access (LIPA), the L-GW is integrated with the HeNB Gateway or the HeNB itself. When a UE attaches and requests a LIPA connection, the Mobility Management Entity (MME) selects the collocated L-GW, and user plane traffic is routed directly from the HeNB to the L-GW and then to the local network (e.g., a home or enterprise LAN), without traversing the operator's core network. This provides low latency and offloads local traffic. For Selected IP Traffic Offload (SIPTO), the L-GW is deployed at a network aggregation point (like a regional data center). The MME or SGSN selects this L-GW based on traffic routing policies, allowing specific IP traffic (e.g., internet traffic) to exit to the internet locally, reducing load on the central PGW and core network transport.
Key components and interfaces include the S5/S8 interface (GTP-based) for communication with the Serving Gateway (SGW) in 3GPP architectures, though in localized deployments like LIPA, this path may be internal. It also implements the Gi interface toward the external PDN (Packet Data Network). The L-GW performs per-bearer packet processing, applying Quality of Service (QoS) policies, and interacts with the Policy and Charging Rules Function (PCRF) for dynamic policy control. Its role is critical for enabling edge computing, low-latency applications (like industrial IoT, AR/VR), and efficient traffic management by bringing gateway functions closer to the user.
Purpose & Motivation
The L-GW was created to solve the problems of network congestion, latency, and inefficient routing for local traffic. In traditional mobile architectures, all user plane traffic, even traffic destined for a local network in the same building as the base station, was routed through a centralized PGW deep in the core network. This 'tromboning' effect introduced unnecessary latency, consumed backhaul and core network resources, and was inefficient for bandwidth-intensive or delay-sensitive applications.
The initial motivation in Release 10 was to support residential and enterprise femtocell (HeNB) deployments with Local IP Access (LIPA), allowing UEs to access local resources (e.g., printers, media servers) directly without impacting the macro network. This addressed the limitation of previous femtocell architectures that still backhauled all traffic to the core. Subsequently, the concept was extended to Selected IP Traffic Offload (SIPTO) at the network edge to offload internet-bound traffic, reducing load on central gateways and improving user experience for services like video streaming.
Historically, L-GW paved the way for network edge intelligence and traffic localization. It addressed the growing demand for mobile data and the need for more efficient network architectures. The limitations of a purely centralized gateway model became apparent with the rise of IoT and real-time applications. L-GW, and its evolution into the Local UPF in 5G, directly motivated the shift toward distributed user planes and edge computing, which are foundational to 5G's low-latency and high-efficiency promises.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (25 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-10, normative work from Rel-15.
In Release 15, the primary new introduction for the L-GW function was the **Extended Local Emergency Number List**. This list was specifically defined to not apply to the CS domain, and procedures were added for its storage and for correctly deleting the list upon a PLMN change.
- Clarify that the newly introduced Extended Local Emergency Number List does not apply to the CS domain TS 24.008CR3128
- Extended and local emergency numbers and applicable domain for call initiation TS 24.301CR3012
- Storage of extended local emergency numbers TS 24.301CR3013
- Running 36.300 CR to introduce assistance information for local cache TS 36.300CR1076
- Correct Extended Local Emergency Numbers List deletion upon PLMN change TS 24.301CR3097
- Identify the Local Emergency Number List TS 24.008CR3122
In Release 16, the L-GW function was enhanced to support **Restricted Local Operator Services (RLOS)**, including specific authentication, security handling, and a request indication for these services. The release also introduced procedures for the local release of dedicated EPS bearers following inter-RAT mobility to NB-IoT. Furthermore, it specified the sending of the EPS bearer context status information element during a Tracking Area Update procedure after mobility from N1 mode when a local bearer had been deactivated.
- Support for Restricted Local Operator Services in EPC TS 23.401CR3491
- Dedicated Bearers for Ethernet in EPC - IOPS / LIPA / SIPTO@LN aspects TS 23.401CR3508
- Support of restricted local operator services TS 24.301CR3160
- Restricted local operator services request indication TS 24.301CR3161
- Authentication and security handling for restricted local operator services TS 24.301CR3162
- Local release of dedicated EPS bearers after inter-RAT mobility to NB-IoT TS 24.301CR3234
+ 1 more changes
In Release 17, enhancements for the L-GW function included the local deactivation of User Plane resources for a specific MA PDU session type and introduced a correction for restricted local operator services. The release also defined the application of ARP priority levels by the MME based on local configuration and added a missing local detach procedure prior to transitioning to the EMM-DEREGISTERED state. Furthermore, it addressed the handling of the local IP address during TFT negotiation for 5G-4G interworking scenarios.
- Local deactivation of UP resource for an MA PDU session with PDN leg - 24301 Part TS 24.301CR3657
- ARP PL applied by MME per local configruation TS 23.401CR3648
- Correction in the restricted local operator services TS 24.301CR3456
- Miss local detach procedure before entering EMM-DEREGISTERED state TS 24.301CR3480
- Local IP address in TFT negotiation in 5GS for 5G-4G interworking TS 24.008CR3263
In Release 18, enhancements to the L-GW function included the introduction of IPv4 and IPv6 local address types. The release also provided a correction to the condition for triggering a Tracking Area Update procedure for the local release of a PDN connection. Furthermore, it defined PDN Gateway selection procedures for IMS emergency calls in scenarios involving Gateway Core Network sharing.
In Release 19, enhancements to the L-GW function focused on improving local management and resilience. The updates introduced procedures for a local detach during periods of unavailability in 4G and for the local release of the signalling connection based on upper layer requests. Furthermore, specifications were refined to update NR Femto Gateway functionality and to align local UPF aspects with SA2 agreements.
Explore further
Broader topics and technologies where L-GW plays a role.
Defining Specifications
3GPP specifications that define or reference L-GW, 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 23.401 vj50 | Evolved Packet System (EPS) Stage 2 Description | Rel-19 |
| TS 24.008 vj50 | 3GPP TS 24008: Core Network Protocols | Rel-19 |
| TS 24.301 vj60 | NAS protocol for Evolved Packet System | Rel-19 |
| TS 25.401 vj00 | UTRAN Overall Architecture | Rel-19 |
| TS 25.410 vj00 | Iu Interface Introduction for UTRAN | Rel-19 |
| TS 25.413 vj00 | Radio Access Network Application Part (RANAP) | Rel-19 |
| TS 25.467 vj00 | UTRAN Architecture for 3G Home Node B | Rel-19 |
| TS 33.320 vj00 | H(e)NB Subsystem Security Architecture | Rel-19 |
| TS 33.545 vj20 | Security for NR Femto Subsystem | Rel-19 |
| TS 36.300 vj00 | E-UTRAN Radio Interface Protocol Architecture Overview | Rel-19 |
| TS 36.413 vj10 | S1 Application Protocol (S1AP) | Rel-19 |
| TS 36.423 vj10 | X2 Application Protocol (X2AP) Specification | Rel-19 |
| TS 36.875 vd10 | Dual Connectivity Extension Requirements | Rel-13 |