Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

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Interfaces and Hardware Component Configuration Guide for Cisco 8000 Series Routers, Cisco IOS XR Releases

Ethernet frame delay measurement for L2VPN services

Updated: September 8, 2026

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This topic describes how Ethernet frame delay measurement complies with the ITU-T Y.1731 standard, using Delay Measurement Message (DMM) and Delay Measurement Reply (DMR) to periodically measure one-way or two-way frame delay.

The Ethernet frame delay measurement is a performance monitoring process that

  • complies with the ITU-T Y.1731 standard, which provides comprehensive fault management and performance monitoring recommendations

  • utilizes DMM and DMR protocol data units, and

  • measures frame delay and delay variation between point-to-point Maintenance End Points (MEPs).

Table 1. Feature History Table

Feature Name

Release Information

Feature Description

Ethernet frame delay measurement for L2VPN services

 Release 26.3.1

Introduced in this release on: Centralized Systems (8400 [ASIC:K100]) )(select variants only*)

*This feature is now supported on Cisco 8404-SYS-D routers.

Ethernet frame delay measurement for L2VPN services

 Release 25.4.1

Introduced in this release on: Fixed Systems (8010 [ASIC: A100], 8700 [ASIC: K100])(select variants only*)

*This feature is now supported on:

  • 8011-32Y8L2H2FH

  • 8011-12G12X4Y-A/D

  • 8711-48Z-M

Ethernet frame delay measurement for L2VPN services

 Release 24.4.1

Introduced in this release on: Fixed Systems (8200 [ASIC: P100], 8700 [ASIC: P100, K100])(select variants only*); Modular Systems (8800 [LC ASIC: P100])(select variants only*)

*This feature is now supported on:

  • 8212-48FH-M

  • 8711-32FH-M

  • 8712-MOD-M

  • 88-LC1-12TH24FH-E

  • 88-LC1-36EH+A8:B12

  • 88-LC1-52Y8H-EM

Ethernet frame delay measurement for L2VPN services

Release 7.5.3

You can now monitor L2VPN networks and avoid impact to your customers' operations by accurately measuring frame round-trip delays and jitters between two maintenance endpoints (MEPs).

This feature lets you detect end-to-end connectivity, loopback, and link trace on MEPs. It reports service performance to your end customers, helping improve technical and operational tasks such as troubleshooting and billing.

This feature introduces the cfm-delay-measurement probe command.

You can measure frame delay in the Layer 2 networks to detect end-to-end connectivity, loopback, and link trace on Maintenance End Points (MEPs) and also report service performance that helps to improve technical and operational tasks such as troubleshooting, billing, and so on. Frame delay is the duration between the time the source node transmits the first bit of a frame and the time the same source node receives the last bit of the frame.

The frame delay measurement uses these protocol data units (PDUs):

  • Delay Measurement Message (DMM)—DMM is used to measure frame delay and frame delay variation between a pair of point-to-point Maintenance End Points (MEPs).

  • Delay Measurement Response (DMR)—DMR is the delay measurement response sent by the destination MEP. When an MEP receives a DMM frame, the responder MEP responds with a DMR frame. The DMR frame carries a reply information and a copy of the timestamp contained in the DMM frame.

Note

DMM sessions (using CFM) are not supported with MACsec enabled on the core interface, as this requires pre-encryption timestamping in the interface group.

We support one-way and two-way frame delay measurement.

Frame Delay Measurement

Description

One-way frame delay measurement (1DM)

  • Measures the frame delay on a unidirectional link between the MEPs.

  • 1DM requires that clocks at both the transmitting MEP and the receiving MEPs are synchronized.

  • Measuring frame-delay variation does not require clock synchronization and the variation can be measured using 1DM and DMR frame combination.

Two-way frame delay measurement

  • Measures the frame delay on a bidirectional link between the MEPs.

  • Two-way delay measurement does not require the clocks at both the transmitting MEP and the receiving MEPs to be synchronized.

  • The two-way frame delay is measured using only DMM and DMR frames.

Topology

Let's see how a round-trip frame delay is measured with this sample topology.

  • The sender MEP (Router-1) transmits a frame containing delay measurement request information and the timestamp at the which router sends the DMM.

  • When packets pass through each interface, timestamps are written into DMMs and DMRs at both local and peer MEPs.

  • When the DMM leaves the local interface, the TX timestamp is added to the packet.

  • When the receiver MEP (Router-2) receives the frame, records the timestamp at which the receiver MEP receives the frame with the delay measurement request information and the remote MEP (Router-2) responds with an DMR adding the remote TX timestamp to the packet as it leaves the remote interface.

To measure a round-trip delay for a traffic exchange between Router-1 and Router-2, four timestamps get populated as the packet moves through the network.

  • Router-1 adds the TxTimestampF when DMM packet is transmitted.

  • Router-2 adds RxTimestampF when DMM packet is received by it.

  • Router-2 adds TxTimestampB when DMR packet it transmitted.

  • Router-1 adds RxTimestampB when DMR is received by it

The round-trip delay is calculated using the following formula:

Delay = (RxTimestampB – TxTimestampF) - (TxTimestampB – RxTimestampF)
	   = RxTimestampB – TxTimestampF - TxTimestampB + RxTimestampF
	   = (RxTimestampF – TxTimestampF) - (TxTimestampB – RxTimestampB)

Configure Ethernet frame delay measurement for L2VPN services

Use this procedure to configure Ethernet Frame Delay Measurement for L2VPN Services:

Procedure

  1. Configure L2VPN service.

    Example:

    
Router# configure
Router(config)# l2vpn
Router(config-l2vpn)# xconnect group evpn_vpws_203
Router(config-l2vpn-xc)# p2p evpn_vpws_phy-100
Router(config-l2vpn-xc-p2p)# interface GigabitEthernet0/0/0/2.100
Router(config-l2vpn-xc-p2p)# neighbor evpn evi 30001 target 30001 source 50001
Router(config-l2vpn-xc-p2p)# commit

  2. Enable CFM service continuity check.

    Example:

    Router# configure
Router(config)# l2vpn
Router(config-l2vpn)# xconnect group evpn_vpws_203
Router(config-l2vpn-xc)# p2p evpn_vpws_phy-100
Router(config-l2vpn-xc-p2p)# interface GigabitEthernet0/0/0/2.100
Router(config-l2vpn-xc-p2p)# neighbor evpn evi 30001 target 30001 source 50001
Router(config-l2vpn-xc-p2p)# commit

  3. Enable CFM on the interface.

    Example:

    
Router(config)# interface GigabitEthernet0/0/0/2.100 l2transport
Router(config-subif)# encapsulation dot1q 100
Router(config-subif)# rewrite ingress tag pop 1 symmetric
Router(config-subif)# mtu 9100
Router(config-subif)# ethernet cfm
Router(config-if-cfm)# mep domain bd-domain service bd-service mep-id 4001
Router(config-if-cfm-mep)# sla operation profile test-profile1 target mep-id 1112
Router(config-if-cfm-mep)# commit

  4. Configure Ethernet frame delay measurement.

    Example:

    Router(config)# ethernet sla
Router(config-sla)# profile EVC-1 type cfm-delay-measurement
Router(config-sla-prof)# probe
Router(config-sla-prof-pb)# send packet every 1 seconds
Router(config-sla-prof-pb)# schedule
Router(config-sla-prof-schedule)# every 3 minutes for 120 seconds
Router(config-sla-prof-schedule)# statistics
Router(config-sla-prof-stat)# measure round-trip-delay
Router(config-sla-prof-stat-cfg)# buckets size 1 probes
Router(config-sla-prof-stat-cfg)# buckets archive 5
Router(config-sla-prof-stat-cfg)# commit

  5. Verify the configuration.

    Example:

    Router# show ethernet cfm local meps interface GigabitEthernet0/0/0/2.100 verbose
Up MEP on GigabitEthernet0/0/0/2.100 MEP-ID 4001
================================================================================
Interface state: Up MAC address: 0c11.6752.3af8
Peer MEPs: 1 up, 0 with errors, 0 timed out (archived)
CCM generation enabled: Yes, 10s (Remote Defect detected: No)
AIS generation enabled: No
Sending AIS: No
Receiving AIS: No
Sending CSF: No
Receiving CSF: No
Packet Sent Received
------ ---------- ---------------------------------------------------------
CCM 19 9 (out of seq: 0)
DMM 473 0
DMR 0 473

    In this example, observe that the sent and received DMM and DMR packets are same. So there is no delay in frame transimission.