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MX Series Router As Junos Multi-Access User Plane

Overview

Junos Multi-Access User Plane on a single MX Series router can function in four modes:

  • As a combined SGW user plane (SGW-U) and PGW user plane (PGW-U) in a single MX series router. The combined SGW-U/PGW-U is referred to as a SAEGW-U (System Architecture Evolution Gateway-User Plane). The SAEGW-U interoperates with a third-party SAEGW-C through a combined Sxab interface.
  • As a standalone SGW user plane (SGW-U). The SGW-U interoperates with a third-party SGW-C through a the Sxa interface and one or more Juniper or third-party PGW-Us over one or more S5/8-U interfaces.
  • As a standalone PGW user plane (PGW-U) in a single MX router. The PGW-U interoperates with a third-party PGW-C through a the Sxb interface and one or more Juniper or third-party SGW-Us over one or more S5/8-U interfaces.
  • As a standalone user plane function (UPF) for carrying 5G traffic. The UPF interoperates with a third-party session management function (SMF).

Configuring Junos Multi-Access User Plane on an MX Series router is essentially the same for each of these functions. This topic describes this configuration process.

As Figure 1 shows, Juniper’s MX SAEGW-U interoperates with a third-party SAEGW-C through a combined Sxab interface.

Figure 1: MX Series SAEGW-U in the CUPS Wireless Network Architecture MX Series SAEGW-U in the CUPS Wireless Network Architecture

As Figure 2 shows, the SGW-U interoperates with a third-party SGW-C through a the Sxa interface and one or more Juniper or third-party PGW-Us over one or more S5/8-U interfaces. The PGW-U interoperates with a third-party PGW-C through a the Sxb interface and one or more Juniper or third-party SGW-Us over one or more S5/8-U interfaces.

Figure 2: MX Series SGW-U and PGW-U in the CUPS Wireless Network Architecture MX Series SGW-U and PGW-U in the CUPS Wireless Network Architecture

As Figure 3 shows, Juniper’s MX UPF interoperates with a third-party SMF through the N4 interface.

Figure 3: MX Series UPF in the 5G CUPS Wireless Network Architecture MX Series UPF in the 5G CUPS Wireless Network Architecture

The MX as SAEGW-U, SGW-U, PGW-U or UPF supports the following CUPS interfaces:

  • Sxab/Sxa/Sxb/N4—Packet Forwarding Control Protocol (PFCP) enables communication between the Junos Multi-Access User Plane and the control plane. PFCP encodes TLV messages for transport over UDP/IP. This interface can also transport user data packets (GTP-U based) between the user plane and control plane. Junos Multi-Access User Plane runs PFCP as the control protocol with the third-party control plane to set up data paths for wireless subscribers.

  • S1-U/N3—This interface is the data path between an eNodeB and the Junos Multi-Access User Plane. Application data packets from end-user equipment are encapsulated over GTP. For upstream packets, Junos Multi-Access User Plane is responsible for GTP tunnel termination and forwarding the user packets to the core. For downstream packets from core, Junos Multi-Access User Plane adds the GTP header and forwards to eNodeB(s). The data plane handles IP packets encapsulated in GTP-U from/to eNodeBs that arrive for the mobile subscribers and performs routing to/from the external Internet.

  • S5/8-U—The S5/8-U interface is the data path between an SGW-U and a PGW-U.

  • N9—Interface between two UPFs.

  • SGi/N6—Interface to the core Internet, supporting IPv4.

Junos Multi-Access User Plane provides purely the user plane function in the form of an MX router that interacts with a third-party control plane function. The MX router receives instructions from the control plane through the Sxab/Sxa/Sxb/N4 interface using PFCP. Based on those instructions, the MX routing engine manages user plane sessions and programs data paths in the anchor PFEs. For the MX router to provide the user plane functionality, it must contain the following minimum elements:

  • At least one anchor PFE interface–An anchor PFE interface is a line card interface that has no physical interface connection, but rather provides the core processing of data traffic by doing the following:

    • Encoding/decoding of GTP-U packets. The anchor PFE interface decodes GTP-U packets from eNodeBs and forwards them to the core network and encodes IPv4 packets from the core network and forwards them to eNodeBs.

    • Enforces class of service and firewall filter rules on subscriber sessions

    • Collects statistics on data usage for charging/accounting purpose

  • At least one signalling/control interface-This is the Sxab/Sxa/Sxb/N4 interface in the CUPS architecture. The signalling/control interface is a physical interface that does the following:

    • Sends/receives PFCP packets to/from the control plane

  • At least one ingress interface-This is the S1-U or N3 or the S5/8-U or N9 interface in the CUPS architecture, depending on where the device is in the data stream. The ingress interface is a physical interface that does the following:

    • As the S1-U or N3 interface, forwards GTP-U packets between eNodeBs and the anchor PFE.

    • As the S5/8-U or N9 interface, receives GTP-U packets from the downstream UPF.

  • At least one egress interface-This is the SGi or N6 or the S5/8-U or N9 interface in the CUPS architecture, depending on where the device is in the data stream. The egress interface is a physical interface that does the following:

    • As the SGi or N6 interface, forwards IPv4 packets between the anchor PFE and the core network.

    • As the S5/8-U or N9 interface, sends GTP-U packets to the upstream UPF.

Note:

You can configure all interface types on the same line card, as long as that line card supports all of the interface types. See Table 1 for a list of line card support by interface type.

Configuring Junos Multi-Access User Plane on an MX Router

As Figure 4 shows, a standard setup of an MX router as either an SAEGW-U, an SGW-U, a PGW-U, or a UPF includes an ingress line card, and egress line card, and a recommended two anchor PFE line cards operating redundantly.

Figure 4: Standard setup for MX router as Junos Multi-Access User Plane Standard setup for MX router as Junos Multi-Access User Plane
  • The ingress line card provides the S1-U interface (SAEGW-U, SGW-U), the S5/8-U interface (PGW-U), or the N3 interface (UPF). , The ingress line card also provides the Sxab interface (SAEGW-U), the Sxa interface (SGW-U), the Sxb interface (PGW-U), or the N4 interface (UPF).

  • The anchor PFE line cards provide the core processing of data traffic through internal pfe- interfaces. At least one anchor PFE card is required, but two are recommended to provide redundancy.

  • The egress line card provides the SGi interface (SAEGW-U, PGW-U), the S5/8-U interface (SGW-U), or the N6 interface (UPF).

  • You can configure all of this functionality on a single line card as long as that line card supports all of the Junos Multi-Access User Plane functionality. We show separate line cards here for simplicity and recommended setup.

To configure Junos Multi-Access User Plane on an MX router, perform the following configuration procedures in the listed order:

DDoS Attack Protection Configuration

Define DDoS attack protection for PFCP protocol traffic.

  1. Configure protection for the PFCP protocol.
  2. Configure GTP path management protection.

GRES Configuration

The graceful Routing Engine switchover (GRES) feature in Junos OS enables a router with redundant Routing Engines to continue forwarding packets, even if one Routing Engine fails. GRES preserves interface and kernel information. Traffic is not interrupted.

Configure Graceful Restart (GRES).

Chassis Configuration for the Anchor PFE Line Cards

Define each Packet Forwarding Engine (PFE) on each anchor PFE line card as an anchor interface.

  1. Enable enhanced IP network services.
  2. Configure slots for anchor PFE processing.

Interface Configuration

Configure the interfaces needed.

  1. Define the egress interface (SGi, S5/8-U, or N6). This interface is on the egress line card.
  2. Define the interface that connects to the control plane function (Sxab, Sxa, Sxb, or N4). This interface is on the ingress line card.
  3. Define the ingress interface (S1-U, S5/8-U, N3). This interface is on the ingress line card.
  4. Define the UPF local address and Mobile Edge interface.
    Note:

    If you are connecting to multiple control planes, define the local address under the control-plane-peers stanza for each control plane function (CPF) rather than define a single loopback address.

    Note:

    mif.0 is used in the default inet.0 routing instance. Junos OS creates a default APN with inet.0 as the routing instance. If you want to configure other routing instances, you must create mif interfaces with unit numbers other than 0.

  5. Assuming two anchor PFE linecards, each with two PFEs, define the anchor PFE interfaces.
    Note:

    You cannot mix primary and secondary anchor PFEs on the same MPC. An MPC can have only either primary anchor PFEs or secondary anchor PFEs.

    CAUTION:

    Changing the anchor PFE redundancy configuration once sessions are active kills all active sessions.

Mobile Edge Configuration

Once you’ve configured all of the necessary interfaces, you can configure the MX router to be a UPF.

  1. Configure the connection to the control plane.
    Note:

    If you are connecting to multiple control planes, define the local address under the control-plane-peers stanza for each CPF. The loopback address, however, is still required for Lawful Intercept to function.

  2. Configure the connection to the access network through the S1-U or N3 interface. if applicable.
  3. Configure the connection to the core network peers through the S5/8-U or N9 interface, if applicable.
  4. Define the interfaces that will provide the anchor PFE functionality.
Release History Table
Release
Description
21.3R1
Starting in Junos OS Release 21.3R1, Junos Multi-Access User Plane provides a long-route implementation as a replacement for a filter-based implementation to steer traffic to the anchor Packet Forwarding Engine removing the need for a firewall filter to route GTP packets.