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Junos Multi-Access User Plane


With Junos OS Release 19.4R1, we introduce Junos Multi-Access User Plane, a software solution that turns your MX router into a high-capacity user plane function called a System Architecture Evolution Gateway-User Plane (SAEGW-U). This MX SAEGW-U interoperates with a third-party SAEGW-C (control plane function), per 3GPP Release 14 Control User Plane Separation (CUPS) architecture, to provide high-throughput 4G and 5G fixed-wireless access service with support for 5G non-stand-alone (NSA) mode.

Junos Multi-Access User Plane Overview

The 3GPP Release 8 introduced the Evolved Packet Core (EPC) for core network architecture. As Figure 1 shows, the four main EPC network elements are:

  • Serving Gateway

  • Packet Data Network (PDN) Gateway

  • Mobility Management Entity

  • Home Subscriber Server

Figure 1: 3GPP Release 8 Evolved Packet Core Architecture
Release 8 Evolved Packet Core Architecture

User Equipment (UE) has control and data path connectivity to the EPC network elements over eNodeB base stations. The EPC provides data connectivity to external networks such as the Internet.

3GPP Release 14 introduced CUPS. CUPS stands for Control and User Plane Separation, providing the architecture enhancements for the separation of functionality in the EPC’s serving gateway (SGW) and PDN gateway (PGW). As Figure 2 shows, both the serving gateway and the PDN gateway of the EPC can be separated into their control plane and user plane functions. CUPS introduces new interfaces, Sxa and Sxb, between the control plane and user plane functions of the SGW and PGW, respectively. CUPS enables control plane and user plane functions to be deployed, scaled and operated separately while integrated over a standard reference interface.

Figure 2: 3GPP Release 14 CUPS Architecture
3GPP Release
14 CUPS Architecture

The control plane provides the following functionality:

  • Receives traffic rules and actions

  • Triggers accounting (volume and time of traffic)

  • Makes session level announcements

  • Receives usage information

  • Receives user plane status information

  • Northbound integration with the signaling plane

The user plane provides the following functionality:

  • Subscriber tunnel encapsulations (GTP-U)

  • Packet routing and forwarding

  • QoS and buffering

  • Policy enforcement

  • Statistics gathering and reporting

  • Optional advanced services

The Junos Multi-Access User Plane solution is to provide a combined SGW user plane (SGW-U) and PGW user plane (PGW-U) in a single MX series router (see Figure 3). The combined SGW-U/PGW-U is referred to as a SAEGW-U (System Architecture Evolution Gateway-User Plane). Juniper’s MX SAEGW-U can interoperate with a third-party combined SGW-C/PGW-C, hereafter referred to as SAEGW-C, through a combined Sxa/Sxb interface.


Juniper’s MX SAEGW-U communicates with the third-party SAEGW-C over the Sxa/Sxb interface through Packet Forwarding Control Protocol (PFCP) as specified in 3GPP TS 29.244.

Figure 3: Junos Multi Access User Plane SAEGW-U
Junos Multi
Access User Plane SAEGW-U

Benefits of Junos Multi-Access User Plane

With this functional separation, the control plane and user plane have very distinct deployment requirements and can be in different physical locations. While the control plane function is very complex, the user plane function simply requires high packet processing capability and rich policy enforcement. The user plane can be more distributed than the control plane and located closer to end-user access points, such as a radio access network (RAN), enabling higher bandwidth per user while delivering lower latency. Control plane and user plane separation provides the following benefits:

  • Independent scaling of the user and control planes.

  • Network architecture flexibility including:

    • Ability to deploy from the edge to the core.

    • Ability to segregate different traffic types and services across different user planes while maintaining a common or single control plane.

  • Operational flexibility

  • Easier migration path from 4G to 5G services. CUPS is optional for 4G, but is an integral part of the 5G network architecture.


For more information and full instructions on how to configure Junos Multi-Access User Plane, see Junos Multi-Access User Plane User Guide.