Cisco Routed Optical Networking Solution Guide, Release 4.0

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How PLE works

Updated: May 5, 2026

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Overview

This section describes how EVPN-VPWS pseudowires, CEM interfaces, MPLS or segment routing transport, and supported hardware carry private-line services across packet networks.

Summary

This process ensures the transparent transmission of client Layer 1 frames over a Packet Switched Network, maintaining the integrity and format of the original traffic.

Workflow

These stages describe how the PLE works.

  1. Ethernet, OTN, Fiber Channel, SONET, or SDH PLE client traffic is carried on an EVPN-VPWS single-homed service that is created between PLE endpoints.

  2. EVPN-VPWS signalling information is carried using BGP between the PLE circuit endpoints either through direct BGP sessions or through a BGP services route-reflector.

  3. EVPN-VPWS pseudowire channel is set up between the endpoints when the CEM (Circuit Emulation) client interfaces are configured on each endpoint router and end-to-end transport connectivity using MPLS or Segment Routing transport is enabled.

  4. CEM over a packet-switched network (PSN) places the client bit streams into packet payloads with appropriate pseudowire emulation headers.

    CEM is a method through which client data can be transmitted over MPLS or Segment Routing networks in a bit-transparent manner, retaining the client Layer 1 frame between sender and receiver.

  5. The PLE initiator encapsulates the PLE client traffic and carries it using the EVPN-VPWS service, which runs on MPLS or Segment Routing transport.

  6. The PLE terminator node extracts the bit streams from the EVPN-VPWS packets and places them onto the PLE client interfaces as defined by the client attribute and CEM profile.