Description
A Virtual Local Area Network (VLAN) is a fundamental Layer 2 networking construct that creates independent logical networks within a shared physical network infrastructure. It operates by inserting a VLAN tag (defined by IEEE 802.1Q) into the Ethernet frame header. This 4-byte tag contains a 12-bit VLAN Identifier (VID), which ranges from 1 to 4094, allowing the segmentation of a single physical switch or network into thousands of distinct broadcast domains. Frames belonging to a specific VLAN are only forwarded to ports configured as members of that VLAN, effectively isolating broadcast, multicast, and unknown unicast traffic. This logical separation is enforced by network switches, which maintain forwarding tables per VLAN.
In 3GPP system architectures, VLANs play a crucial role in transport network segmentation. They are used to separate traffic from different logical entities over a common physical infrastructure. For example, in the Radio Access Network (RAN), VLANs can isolate fronthaul traffic (e.g., CPRI/eCPRI streams between a Distributed Unit (DU) and a Radio Unit (RU)) from backhaul traffic (between the DU/CU and the core network). They also separate control plane, user plane, and synchronization plane traffic, ensuring quality of service and security. Within the 5G Core network, deployed as virtualized network functions (VNFs) in data centers, VLANs are used to create isolated networks for management, northbound, southbound, and east-west traffic, aligning with cloud-native principles.
The implementation involves VLAN-aware switches and routers at network demarcation points. In a typical mobile network, a cell site router may use VLANs to separate traffic from multiple sectors or different radio access technologies before aggregating it onto a shared backhaul link. In network slicing, VLANs (often combined with other technologies like MPLS or SRv6) provide the underlying Layer 2 isolation for different network slice instances, ensuring one slice's traffic does not interfere with another's. Configuration and management of VLANs are critical for network operations, often automated through SDN (Software-Defined Networking) controllers as part of the wider transport network management defined in 3GPP specifications.
Purpose & Motivation
VLAN technology was created to address the limitations of traditional flat Layer 2 networks, which suffered from large broadcast domains, security vulnerabilities, and inflexible physical topology constraints. Before VLANs, network segmentation required separate physical switches and cabling for each department or service, leading to high costs and poor resource utilization. VLANs introduced logical segmentation, allowing a single switch to serve multiple groups as if they were on separate physical networks, thereby solving scalability and management problems in enterprise and carrier networks.
3GPP's adoption and specification of VLAN usage were driven by the evolution toward all-IP transport and cloud-native networks. As mobile networks moved from dedicated TDM/ATM links to shared Ethernet/IP transport for cost efficiency, a mechanism was needed to maintain strict traffic separation for different services (e.g., voice, data, signaling) and different tenants (e.g., mobile virtual network operators). VLANs provided a standardized, widely supported method to achieve this isolation on packet-switched networks. With the advent of 5G and network slicing, the need for strong traffic isolation became paramount. VLANs, as a proven and reliable technology, form a foundational layer for creating the isolated connectivity subnets required by end-to-end network slices, enabling the concurrent operation of diverse services with varied performance and security requirements on a common physical infrastructure.
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (54 CRs across 5 releases). Complements the general historical overview above with the evidence-based evolution of this function.
Studied in Rel-6, normative work from Rel-15.
In Release 15, the specification introduced a correction for the VLAN ID parameter to ensure its proper handling within the system. This update falls under the general scope of network management and service delivery functions. The change was part of the broader set of enhancements finalized in this release, alongside other features like IMS emergency support and URSP updates.
In Release 16, the VLAN function saw specific enhancements for 5G Virtual Networks (5G-VN), including clarified procedures for inserting and removing VLAN tags. The release introduced UPF selection based on traffic classes and VLAN, and standardized the configuration and information exchange for VLAN information. Furthermore, it provided corrections and clarifications to the technical description of VLAN tags within the system.
- Update the support of virtualized deployment with SCP distribution and the NF/NF service instance Set TS 23.501CR0926
- Transfer of N4 information for local traffic switching from SMF to I-SMF TS 23.501CR1050
- Clarification of Inserting and Removing VLAN tags for 5G-VN TS 23.501CR1083
- Extending the significance of the locality parameter TS 23.501CR1312
- Local cache information for ARP proxy TS 23.501CR1116
- Clarification of the Locality of a NF Instance TS 23.501CR1470
+ 5 more changes
In Release 17, the enhancements for the VLAN function specifically involved the support of network exposure to an Edge Application Server via a Local Network Exposure Function (Local NEF). This was facilitated by new parameters for Local NEF discovery and selection, alongside enhancements to the N4 interface for local notification procedures.
- Adding some parameters for local NEF selection TS 23.501CR2656
- Newly added parameters for Local NEF discovery TS 23.501CR2856
- N4 interface enhancement for local notification TS 23.501CR2899
- Support of Network Exposure to EAS via Local NEF. TS 29.514CR0314
- Clarification for Visited Country FQDN DNS query for SNPNs with locally assigned NIDs TS 23.501CR2963
In Release 18, the primary advancement for VLAN-like functions was the enhanced support for **Localized Services**, introducing new procedures for a UE to discover, select, access, and leave a Standalone Non-Public Network (SNPN) providing such services. This included specifications for network access control, congestion handling, and network (re-)selection specifically for accessing these localized service areas. The release also provided clarifications for enabling access and for the local switch functionality via a UPF deployed on GEO satellites.
- Support of local switch via UPF deployed on satellite for GEO backhaul case TS 23.501CR3794
- Introduction to Localized Services TS 23.501CR3842
- Enabling Access to Localized Services TS 23.501CR3992
- Support for leaving network that provides access to localized services TS 23.501CR3843
- UE discover, select and access to a Hosting network for Localized services TS 23.501CR3883
- Clarifications on Onboarding in SNPN supporting localized services TS 23.501CR3927
+ 12 more changes
In Release 19, the enhancements for the VLAN function primarily involved its integration with the new Local Offloading Management architecture. The release introduced explicit support for VLAN handling information within SM subscription data and DN-AAA server communication, and provided clarifications on VLAN handling procedures and error scenarios within the 5G System. These changes were defined alongside new procedures for I-SMF selection, insertion, and PCF awareness specifically for managing local offloading.
- Local Offloading Policy provisioning TS 23.501CR5463
- I-SMF selection/insertion based on local offloading allowed indication TS 23.501CR5604
- Local Offloading handling at I-SMF TS 23.501CR5744
- KI#1 Architecture for Local Offloading Management TS 23.501CR5752
- Local Offloading handling at I-SMF TS 23.501CR5825
- PCF's awareness of I-SMF insertion for Local Offloading Management TS 23.501CR5833
+ 10 more changes
Explore further
Broader topics and technologies where VLAN plays a role.
Defining Specifications
3GPP specifications that define or reference VLAN, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TR 21.905 vj00 | 3GPP Technical Terms and Definitions | Rel-19 |
| TR 22.804 vg30 | 5G Automation in Vertical Domains Study | Rel-16 |
| TS 22.821 vg10 | 5G LAN-type Services Requirements | Rel-16 |
| TS 23.234 vd10 | 3GPP-WLAN Interworking Index | Rel-13 |
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 23.734 vg20 | Enhancements for 5GS in Vertical Domains | Rel-16 |
| TS 28.314 vk00 | Management and Orchestration - Plug and Connect | Rel-20 |
| TR 28.833 vi01 | Technical Report on 5G LAN-type Service Management | Rel-18 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 29.890 vg00 | CT3 5G System Technical Report | Rel-16 |
| TS 32.501 vj00 | Self-Configuration of Network Elements Concepts | Rel-19 |
| TS 32.833 vb00 | Converged OSS End-to-End Management Study | Rel-11 |