Configure Performance Measurement

Network performance metrics is a critical measure for traffic engineering (TE) in service provider networks. Network performance metrics include the following:

  • Packet loss

  • Delay

  • Delay variation

  • Bandwidth utilization

These network performance metrics provide network operators information about the performance characteristics of their networks for performance evaluation and help to ensure compliance with service level agreements. The service-level agreements (SLAs) of service providers depend on the ability to measure and monitor these network performance metrics. Network operators can use Segment Routing Performance Measurement (SR-PM) feature to monitor the network metrics for links and end-to-end TE label switched paths (LSPs).

The following table explains the functionalities supported by performance measurement feature for measuring delay for links or SR policies.

Table 1. Performance Measurement Functionalities

Functionality

Details

Profiles

You can configure different default profiles for different types of delay measurements. Use the "interfaces" delay profile type for link-delay measurement. The "sr-policy" delay profile type is used for SR policy delay measurements. Delay profile allows you to schedule probe and configure metric advertisement parameters for delay measurement.

Protocols

Two-Way Active Measurement Protocol (TWAMP) Light (using RFC 5357 with IP/UDP encap).

Probe and burst scheduling

Schedule probes and configure metric advertisement parameters for delay measurement.

Metric advertisements

 Advertise measured metrics periodically using configured thresholds. Also supports accelerated advertisements using configured thresholds.

Measurement history and counters

Maintain packet delay and loss measurement history, session counters, and packet advertisement counters.

Measurement Modes

The following table compares the different hardware and timing requirements for the measurement modes supported in SR PM.

Table 2. Measurement Mode Requirements

Measurement Mode

Sender:

PTP-Capable HW and HW Timestamping

Reflector:

PTP-Capable HW and HW Timestamping

PTP Clock Synchronization between Sender and Reflector

One-way

Required

Required

Required

Two-way

Required

Required

Not Required

One-Way Measurement Mode

One-way measurement mode provides the most precise form of one-way delay measurement. PTP-capable hardware and hardware timestamping are required on both Sender and Reflector, with PTP Clock Synchronization between Sender and Reflector.

Delay measurement in one-way mode is calculated as (T2 – T1).

Figure 1. One-Way

The PM query and response for one-way delay measurement can be described in the following steps:

  1. The local-end router sends PM query packets periodically to the remote side once the egress line card on the router applies timestamps on packets.

  2. The ingress line card on the remote-end router applies time-stamps on packets as soon as they are received.

  3. The remote-end router sends the PM packets containing time-stamps back to the local-end router.

  4. One-way delay is measured using the time-stamp values in the PM packet.

Two-Way Measurement Mode

Two-way meaurement mode provides two-way measurements. PTP-capable hardware and hardware timestamping are required on both Sender and Reflector, but PTP clock synchronization between Sender and Reflector is not required.

Delay measurement in two-way mode is calculated as ((T4 – T1) – (T3 – T2))/2

Figure 2. Two-Way

The PM query and response for two-way delay measurement can be described in the following steps:

  1. The local-end router sends PM query packets periodically to the remote side once the egress line card on the router applies timestamps on packets.

  2. Ingress line card on the remote-end router applies time-stamps on packets as soon as they are received.

  3. The remote-end router sends the PM packets containing time-stamps back to the local-end router. The remote-end router time-stamps the packet just before sending it for two-way measurement.

  4. The local-end router time-stamps the packet as soon as the packet is received for two-way measurement.

  5. Delay is measured using the time-stamp values in the PM packet.

Usage Guidelines and Limitations

The following usage guidelines and limitations apply:

  • SR PM is supported on hardware that supports Precision Time Protocol (PTP). This requirement applies to both one-way and two-way delay measurement.

    See the Configuring Precision Time Protocol chapter in the System Management Configuration Guide for Cisco NCS 5500 Series Routers for Restrictions for PTP and the Timing Hardware Support Matrix.

Link Delay Measurement

The PM for link delay uses the IP/UDP packet format defined in RFC 5357 (TWAMP-Light) for probes. Two-Way Active Measurement Protocol (TWAMP) adds two-way or round-trip measurement capabilities. TWAMP employs time stamps applied at the echo destination (reflector) to enable greater accuracy. In the case of TWAMP Light, the Session-Reflector doesn’t necessarily know about the session state. The Session-Reflector simply copies the Sequence Number of the received packet to the Sequence Number field of the reflected packet. The controller receives the reflected test packets and collects two-way metrics. This architecture allows for collection of two-way metrics.

Usage Guidelines and Restrictions for PM for Link Delay

The following restrictions and guidelines apply for the PM for link delay feature for different links.

  • For broadcast links, only point-to-point (P2P) links are supported. P2P configuration on IGP is required for flooding the value.

  • For link bundles, the hashing function may select a member link for forwarding but the reply may come from the remote line card on a different member link of the bundle.

  • For one-way delay measurement, clocks should be synchronized on two end-point nodes of the link using PTP.

Configuration Example: PM for Link Delay

This example shows how to configure performance-measurement functionalities for link delay as a global default profile. The default values for the different parameters in the PM for link delay is given as follows:

  • probe measurement mode: The default measurement mode for probe is two-way delay measurement. If you are configuring one-way delay measurement, hardware clocks must be synchronized between the local-end and remote-end routers using precision time protocol (PTP). See Measurement Modes for more information.

  • protocol: Interface delay measurement using RFC 5357 with IP/UDP encap (TWAMP-Light).

  • burst interval: Interval for sending probe packet. The default value is 3000 milliseconds and the range is from 30 to 15000 milliseconds.

  • computation interval: Interval for metric computation. Default is 30 seconds; range is 1 to 3600 seconds.

  • periodic advertisement: Periodic advertisement is enabled by default.

  • periodic-advertisement interval: The default value is 120 seconds and the interval range is from 30 to 3600 seconds.

  • periodic-advertisement threshold: Checks the minimum-delay metric change for threshold crossing for periodic advertisement. The default value is 10 percent and the range is from 0 to 100 percent.

  • periodic-advertisement minimum change: The default value is 1000 microseconds (usec) and the range is from 0 to 100000 microseconds.

  • accelerated advertisement: Accelerated advertisement is disabled by default.

  • accelerated-advertisement threshold: Checks the minimum-delay metric change for threshold crossing for accelerated advertisement. The default value is 20 percent and the range is from 0 to 100 percent.

  • accelerated-advertisement minimum change: The default value is 500 microseconds and the range is from 0 to 100000 microseconds. 

RP/0/0/CPU0:router(config)# performance-measurement delay-profile interfaces 
RP/0/0/CPU0:router(config-pm-dm-intf)# probe
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# measurement-mode one-way
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# burst-interval 60
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# computation-interval 60
RP/0/0/CPU0:router(config-pm-dm-intf-probe)# exit

RP/0/0/CPU0:router(config-pm-dm-intf)# advertisement periodic
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# interval 120
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# threshold 20
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# minimum-change 1000
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# exit

RP/0/0/CPU0:router(config-pm-dm-intf)# advertisement accelerated
RP/0/0/CPU0:router(config-pm-dm-intf-adv-acc)# threshold 30
RP/0/0/CPU0:router(config-pm-dm-intf-adv-acc)# minimum-change 1000
RP/0/0/CPU0:router(config-pm-dm-intf-adv-per)# exit

Configure the UDP Destination Port

Configuring the UDP port for TWAMP-Light protocol is optional. By default, PM uses port 862 as the TWAMP-reserved UDP destination port for delay.

The UDP port is configured for each PM measurement probe type (delay, loss, protocol, authentication mode, etc.) on querier and responder nodes. If you configure a different UDP port, the UDP port for each PM measurement probe type must match on the querier and the responder nodes.


Note
The same UDP destination port is used for delay measurement for links and SR Policy.

This example shows how to configure the UDP destination port for delay.

Router(config)# performance-measurement 
Router(config-perf-meas)# protocol twamp-light
Router(config-pm-protocol)# measurement delay unauthenticated 
Router(config-pm-proto-mode)# querier-dst-port 12000

Enable PM for Link Delay Over an Interface

This example shows how to enable PM for link delay over an interface.

RP/0/0/CPU0:router(config)# performance-measurement 
RP/0/0/CPU0:router(config-perf-meas)# interface TenGigE0/0/0/0
RP/0/0/CPU0:router(config-pm-intf)# next-hop ipv4 10.10.10.2 // Optional IPv4 or IPv6 next-hop address
RP/0/0/CPU0:router(config-pm-intf)# delay-measurement 
RP/0/0/CPU0:router(config-pm-intf-dm)# exit

The source and destination IP addresses used in the OAM packet are determined by the IP address present on the interface where the delay-measurement operation is enabled and the setting of the optional next-hop address.

When the next-hop address is not specified, the following rules apply to determine the source and destination IP addresses used in the OAM packet:

  • If an IPv4 address is configured under the interface, then:

    • OAM packet source IP address = Interface's IPv4 address

    • OAM packet destination IP address = 127.0.0.0

  • Else, if an IPv6 global address is configured under the interface, then:

    • OAM packet source IP address = Interface's IPv6 global address

    • OAM packet destination IP address = 0::ff:127.0.0.0

When the next-hop {ipv4 | ipv6} address is configured, the following rules apply to determine the source and destination IP addresses used in the OAM packet:

  • If a next-hop IPv4 address is configured, then:

    • OAM packet source IP address = Interface's IPv4 address

    • OAM packet destination IP address = Configured next-hop IPv4 address


    Note
    If there is no IPv4 address configured under the interface, then the delay-measurement probe does not send OAM packets.

  • If a next-hop IPv6 address is configured, then:

    • OAM packet source IP address = Interface's IPv6 global address

    • OAM packet destination IP address = Configured next-hop IPv6 address


    Note
    If there is no IPv6 global address configured under the interface, then the delay-measurement probe does not send OAM packets.

This example shows how to enable PM for link delay over an interface with IPv4 address configured:


interface TenGigE0/0/0/0
 ipv4 address 10.10.10.1 255.255.255.0

performance-measurement
 interface TenGigE0/0/0/0
  delay-measurement

This example shows how to enable PM for link delay over an interface IPv6 address configured:


interface TenGigE0/0/0/0
 ipv6 address 10:10:10::1/64

performance-measurement
 interface TenGigE0/0/0/0
  delay-measurement

This example shows how to enable PM for link delay over an interface with a specified next-hop IPv4 address: 


interface TenGigE0/0/0/0
 ipv4 address 10.10.10.1 255.255.255.0

performance-measurement
 interface TenGigE0/0/0/0
  next-hop ipv4 10.10.10.2
  delay-measurement

This example shows how to enable PM for link delay over an interface with a specified next-hop IPv6 address:


interface TenGigE0/0/0/0
 ipv6 address 10:10:10::1/64

performance-measurement
 interface TenGigE0/0/0/0
  next-hop ipv6 10:10:10::2
  delay-measurement

Verification

RP/0/0/CPU0:router# show performance-measurement profile interface
Thu Dec 12 14:13:16.029 PST

-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
Interface Delay-Measurement:
  Profile configuration:
    Measurement Type                            : Two-Way
    Probe computation interval                  : 30 (effective: 30) seconds
    Type of services                            : Traffic Class: 6, DSCP: 48
    Burst interval                              : 3000 (effective: 3000) mSec
    Burst count                                 : 10 packets
    Encap mode                                  : UDP
    Payload Type                                : TWAMP-light
    Destination sweeping mode                   : Disabled
    Periodic advertisement                      : Enabled
      Interval                                  : 120 (effective: 120) sec
      Threshold                                 : 10%
      Minimum-Change                            : 500 uSec
    Advertisement accelerated                   : Disabled
    Threshold crossing check                    : Minimum-delay


RP/0/0/CPU0:router# show performance-measurement summary detail location 0/2/CPU0

Thu Dec 12 14:09:59.162 PST

-------------------------------------------------------------------------------
0/2/CPU0
-------------------------------------------------------------------------------
Total interfaces                                : 1
Total SR Policies                               : 0
Total RSVP-TE tunnels                           : 0
Total Maximum PPS                               : 2000 pkts/sec
Total Interfaces PPS                            : 0 pkts/sec
Maximum Allowed Multi-hop PPS                   : 2000 pkts/sec
Multi Hop Requested PPS                         : 0 pkts/sec (0% of max allowed)
Dampened Multi Hop Requested PPS                : 0% of max allowed
Inuse Burst Interval Adjustment Factor          : 100% of configuration


Interface Delay-Measurement:
  Total active sessions                         : 1
  Counters:
    Packets:
      Total sent                                : 26
      Total received                            : 26
    Errors:
        TX:
          Reason interface down                 : 0
          Reason no MPLS caps                   : 0
          Reason no IP address                  : 0
          Reason other                          : 0
        RX:
          Reason negative delay                 : 0
          Reason delay threshold exceeded       : 0
          Reason missing TX timestamp           : 0
          Reason missing RX timestamp           : 0
          Reason probe full                     : 0
          Reason probe not started              : 0
          Reason control code error             : 0
          Reason control code notif             : 0
    Probes:
      Total started                             : 3
      Total completed                           : 2
      Total incomplete                          : 0
      Total advertisements                      : 0

SR Policy Delay-Measurement:
  Total active sessions                         : 0
  Counters:
    Packets:
      Total sent                                : 0
      Total received                            : 0
    Errors:
        TX:
          Reason interface down                 : 0
          Reason no MPLS caps                   : 0
          Reason no IP address                  : 0
          Reason other                          : 0
        RX:
          Reason negative delay                 : 0
          Reason delay threshold exceeded       : 0
          Reason missing TX timestamp           : 0
          Reason missing RX timestamp           : 0
          Reason probe full                     : 0
          Reason probe not started              : 0
          Reason control code error             : 0
          Reason control code notif             : 0
    Probes:
      Total started                             : 0
      Total completed                           : 0
      Total incomplete                          : 0
      Total advertisements                      : 0

RSVP-TE Delay-Measurement:
  Total active sessions                         : 0
  Counters:
    Packets:
      Total sent                                : 0
      Total received                            : 0
    Errors:
        TX:
          Reason interface down                 : 0
          Reason no MPLS caps                   : 0
          Reason no IP address                  : 0
          Reason other                          : 0
        RX:
          Reason negative delay                 : 0
          Reason delay threshold exceeded       : 0
          Reason missing TX timestamp           : 0
          Reason missing RX timestamp           : 0
          Reason probe full                     : 0
          Reason probe not started              : 0
          Reason control code error             : 0
          Reason control code notif             : 0
    Probes:
      Total started                             : 0
      Total completed                           : 0
      Total incomplete                          : 0
      Total advertisements                      : 0

Global Delay Counters:
  Total packets sent                            : 26
  Total query packets received                  : 26
  Total invalid session id                      : 0
  Total missing session                         : 0

RP/0/0/CPU0:router# show performance-measurement interfaces detail
Thu Dec 12 14:16:09.692 PST

-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------

-------------------------------------------------------------------------------
0/2/CPU0
-------------------------------------------------------------------------------

Interface Name: GigabitEthernet0/2/0/0 (ifh: 0x1004060)
  Delay-Measurement                 : Enabled
  Loss-Measurement                  : Disabled
  Configured IPv4 Address           : 10.10.10.2
  Configured IPv6 Address           : 10:10:10::2
  Link Local IPv6 Address           : fe80::3a:6fff:fec9:cd6b
  Configured Next-hop Address       : Unknown
  Local MAC Address                 : 023a.6fc9.cd6b
  Next-hop MAC Address              : 0291.e460.6707
  Primary VLAN Tag                  : None
  Secondary VLAN Tag                : None
  State                             : Up

  Delay Measurement session:
    Session ID          : 1

    Last advertisement:
      Advertised at: Dec 12 2019 14:10:43.138 (326.782 seconds ago)
      Advertised reason: First advertisement
      Advertised delays (uSec): avg: 839, min: 587, max: 8209, variance: 297

    Next advertisement:
      Threshold check scheduled in 1 more probe (roughly every 120 seconds)
      Aggregated delays (uSec): avg: 751, min: 589, max: 905, variance: 112
      Rolling average (uSec): 756

    Current Probe:
      Started at Dec 12 2019 14:15:43.154 (26.766 seconds ago)
      Packets Sent: 9, received: 9
      Measured delays (uSec): avg: 795, min: 631, max: 1199, variance: 164
      Next probe scheduled at Dec 12 2019 14:16:13.132 (in 3.212 seconds)
      Next burst packet will be sent in 0.212 seconds
      Burst packet sent every 3.0 seconds 
      Probe samples:
        Packet Rx Timestamp       Measured Delay (nsec)
        Dec 12 2019 14:15:43.156          689223
        Dec 12 2019 14:15:46.156          876561
        Dec 12 2019 14:15:49.156          913548
        Dec 12 2019 14:15:52.157         1199620
        Dec 12 2019 14:15:55.156          794008
        Dec 12 2019 14:15:58.156          631437
        Dec 12 2019 14:16:01.157          656440
        Dec 12 2019 14:16:04.157          658267
        Dec 12 2019 14:16:07.157          736880

You can also use the following commands for verifying the PM for link delay on the local-end router.

Command

Description

show performance-measurement history probe interfaces [interface]

Displays the PM link-delay probe history for interfaces.

show performance-measurement history aggregated interfaces [interface]

Displays the PM link-delay aggregated history for interfaces.

show performance-measurement history advertisement interfaces [interface]

Displays the PM link-delay advertisement history for interfaces.

show performance-measurement counters [interface interface] [location location-name]

Displays the PM link-delay session counters.

You can also use the following commands for verifying the PM for link-delay configuration on the remote-end router.

Command

Description

show performance-measurement responder summary [location location-name]

Displays the PM for link-delay summary on the remote-end router (responder).

show performance-measurement responder interfaces [interface]

Displays PM for link-delay for interfaces on the remote-end router.

show performance-measurement responder counters [interface interface] [location location-name]

Displays the PM link-delay session counters on the remote-end router.

Configure a Static Delay Value on an Interface

You can configure an interface to advertise a static delay value, instead of the measured delay value. When you configure a static delay value, the advertisement is triggered immediately. The average, minimum, and maximum advertised values will use the static delay value, with a variance of 0.

Scheduled probes will continue, and measured delay metrics will be aggregated and stored in history buffer. However, advertisement threshold checks are suppressed so that there are no advertisements of the actual measured delay values. If the configured static delay value is removed, the next scheduled advertisement threshold check will update the advertised measured delay values.

The static delay value can be configured from 1 to 16777215 microseconds (16.7 seconds).

This example shows how to configure a static delay of 1000 microseconds: 

RP/0/0/CPU0:router(config)# performance-measurement 
RP/0/0/CPU0:router(config-perf-meas)# interface TenGigE0/0/0/0
RP/0/0/CPU0:router(config-pm-intf)# delay-measurement 
RP/0/0/CPU0:router(config-pm-intf-dm)# advertise-delay 1000

Running Configuration


performance-measurement
 interface GigabitEthernet0/0/0/0
  delay-measurement
   advertise-delay 1000
  !
 !
!

Verification

RP/0/RSP0/CPU0:ios# show performance-measurement interfaces detail

--------------------------------------------------------------------------------
0/0/CPU0
--------------------------------------------------------------------------------

Interface Name: GigabitEthernet0/0/0/0 (ifh: 0x0)
  Delay-Measurement                 : Enabled

. . .

    Last advertisement:
      Advertised at: Nov 29 2021 21:53:00.656 (7.940 seconds ago)
      Advertised reason: Advertise delay config
      Advertised delays (uSec): avg: 1000, min: 1000, max: 1000, variance: 0

. . .

SR Performance Measurement Named Profiles

You can create a named performance measurement profile for delay or liveness.

Delay Profile

This example shows how to create a named SR performance measurement delay profile. 

Router(config)# performance-measurement delay-profile sr-policy profile2
Router(config-pm-dm-srpolicy)# probe
Router(config-pm-dm-srpolicy-probe)# burst-interval 60
Router(config-pm-dm-srpolicy-probe)# computation-interval 60
Router(config-pm-dm-srpolicy-probe)# protocol twamp-light
Router(config-pm-dm-srpolicy-probe)# tos dscp 63

Router(config-pm-dm-srpolicy)# advertisement
Router(config-pm-dm-srpolicy-adv)# periodic
Router(config-pm-dm-srpolicy-adv-per)# interval 60
Router(config-pm-dm-srpolicy-adv-per)# minimum-change 1000
Router(config-pm-dm-srpolicy-adv-per)# threshold 20
Router(config-pm-dm-srpolicy-adv-per)# commit

Apply the delay profile for an SR Policy. 

Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy TEST
Router(config-sr-te-policy)# color 4 end-point ipv4 10.10.10.10
Router(config-sr-te-policy)# performance-measurement
Router(config-sr-te-policy-perf-meas)# delay-measurement delay-profile name profile2

Router(config-sr-te-policy)# candidate-paths 
Router(config-sr-te-policy-path)# preference 100
Router(config-sr-te-policy-path-pref)# explicit segment-list LIST1
Router(config-sr-te-pp-info)# weight 2

Router(config-sr-te-policy-path-pref)# explicit segment-list LIST2
Router(config-sr-te-pp-info)# weight 3

Running Configuration

Router# show run segment-routing traffic-eng policy TEST

segment-routing
 traffic-eng
  policy TEST
   color 4 end-point ipv4 10.10.10.10
   candidate-paths
    preference 100
     explicit segment-list LIST1
      weight 2
     !
     explicit segment-list LIST2
      weight 3
     !
    !
   !
   performance-measurement
    delay-measurement
     delay-profile name profile2

Verification 

Router# show performance-measurement profile named-profile delay sr-policy name profile2

----------------------------
0/RSP0/CPU0
----------------------------
SR Policy Delay Measurement Profile Name: profile2
  Profile configuration:
    Measurement mode                            : One-way
    Protocol type                               : TWAMP-light
    Encap mode                                  : UDP
    Type of service:
      PM-MPLS traffic class                     : 6
      TWAMP-light DSCP                          : 63
    Probe computation interval                  : 60 (effective: 60) seconds
    Burst interval                              : 60 (effective: 60) mSec
    Packets per computation interval            : 1000
    Periodic advertisement                      : Enabled
      Interval                                  : 60 (effective: 60) sec
      Threshold                                 : 20%
      Minimum-change                            : 1000 uSec
    Advertisement accelerated                   : Disabled
    Advertisement logging:
      Delay exceeded                            : Disabled (default)
    Threshold crossing check                    : Maximum-delay
    Router alert                                : Disabled (default)
    Destination sweeping mode                   : Disabled
    Liveness detection parameters:
      Multiplier                                : 3
      Logging state change                      : Disabled
On-Demand SR Policy 
Router(config-sr-te)# on-demand color 20
Router(config-sr-te-color)# performance-measurement delay-measurement
Router(config-sr-te-color-delay-meas)# delay-profile name profile2 
Router(config-sr-te-color-delay-meas)# commit

Running Configuration

Router# show run segment-routing traffic-eng on-demand color 20

segment-routing
 traffic-eng
  on-demand color 20
   performance-measurement
    delay-measurement
     delay-profile name profile2

Liveness Profile

This example shows how to create a named SR performance measurement liveness profile. 

Router(config)# performance-measurement liveness-profile sr-policy name profile3 
Router(config-pm-ld-srpolicy)# probe 
Router(config-pm-ld-srpolicy-probe)# burst-interval 60
Router(config-pm-ld-srpolicy-probe)# measurement-mode loopback
Router(config-pm-ld-srpolicy-probe)# tos dscp 10
Router(config-pm-ld-srpolicy-probe)# liveness-detection
Router(config-pm-ld-srpolicy-probe)# multiplier 5
Router(config-pm-ld-srpolicy-probe)# commit

Apply the Liveness Profile for the SR Policy

This example shows how to enable PM for SR policy liveness for a specific policy.

For the same policy, you cannot enable delay-measurement (delay-profile) and liveness-detection (liveness-profile) at the same time. For example, if delay measurement is enabled, use the no delay-measurement command to disable it, and then enable the following command for enabling liveness detection. 

Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy TRST2
Router(config-sr-te-policy)# color 40 end-point ipv4 20.20.20.20
Router(config-sr-te-policy)# candidate-paths 
Router(config-sr-te-policy-path)# preference 50
Router(config-sr-te-policy-path-pref)# explicit segment-list LIST3
Router(config-sr-te-pp-info)# weight 2

Router(config-sr-te-policy-path-pref)# explicit segment-list LIST4
Router(config-sr-te-pp-info)# weight 3

Router(config-sr-te-policy)# performance-measurement
Router(config-sr-te-policy-perf-meas)# liveness-detection liveness-profile name profile3

Running Configuration

Router# show run segment-routing traffic-eng policy TRST2

segment-routing
 traffic-eng
  policy TRST2
   color 40 end-point ipv4 20.20.20.20
   candidate-paths
    preference 50
     explicit segment-list LIST3
      weight 2
     !
     explicit segment-list LIST4
      weight 3
     !
    !
   !
   performance-measurement
    liveness-detection
     liveness-profile name profile3
    !

Verification 

Router# show performance-measurement profile named-profile delay

-----------
0/RSP0/CPU0
-----------

SR Policy Liveness Detection Profile Name: profile1
  Profile configuration:
    Measurement mode                            : Loopback
    Protocol type                               : TWAMP-light
    Type of service:
      TWAMP-light DSCP                          : 10
    Burst interval                              : 60 (effective: 60) mSec
    Destination sweeping mode                   : Disabled
    Liveness detection parameters:
      Multiplier                                : 3
      Logging state change                      : Disabled

SR Policy Liveness Detection Profile Name: profile3
  Profile configuration:
    Measurement mode                            : Loopback
    Protocol type                               : TWAMP-light
    Type of service:
      TWAMP-light DSCP                          : 10
    Burst interval                              : 60 (effective: 60) mSec
    Destination sweeping mode                   : Disabled
    Liveness detection parameters:
      Multiplier                                : 3
      Logging state change                      : Disabled

On-Demand SR Policy

For the same policy, you cannot enable delay-measurement (delay-profile) and liveness-detection (liveness-profile) at the same time. For example, to disable delay measurement, use the no delay-measurement command, and then enable the following command for enabling liveness detection. 

Router(config-sr-te)# on-demand color 30
Router(config-sr-te-color)# performance-measurement 
Router(config-sr-te-color-pm)# liveness-detection liveness-profile name profile1
Router(config-sr-te-color-delay-meas)# commit

Running Configuration

Router# show run segment-routing traffic-eng on-demand color 30

segment-routing
 traffic-eng
  on-demand color 30
   performance-measurement
    liveness-detection
     liveness-profile name profile1
    !

Verification

Router# show performance-measurement profile named-profile liveness sr-policy name profile1

--------------------
0/RSP0/CPU0
--------------------
SR Policy Liveness Detection Profile Name: profile1
  Profile configuration:
    Measurement mode                            : Loopback
    Protocol type                               : TWAMP-light
    Type of service:
      TWAMP-light DSCP                          : 10
    Burst interval                              : 60 (effective: 60) mSec
    Destination sweeping mode                   : Disabled
    Liveness detection parameters:
      Multiplier                                : 3
      Logging state change                      : Disabled

Delay Normalization

Performance measurement (PM) measures various link characteristics like packet loss and delay. Such characteristics can be used by IS-IS as a metric for Flexible Algorithm computation. Low latency routing using dynamic delay measurement is one of the primary use cases for Flexible Algorithm technology.

Delay is measured in microseconds. If delay values are taken as measured and used as link metrics during the IS-IS topology computation, some valid ECMP paths might be unused because of the negligible difference in the link delay.

The Delay Normalization feature computes a normalized delay value and uses the normalized value instead. This value is advertised and used as a metric during the Flexible Algorithm computation.

The normalization is performed when the delay is received from the delay measurement component. When the next value is received, it is normalized and compared to the previous saved normalized value. If the values are different, then the LSP generation is triggered.

The following formula is used to calculate the normalized value:

  • Dm – measured Delay

  • Int – configured normalized Interval

  • Off – configured normalized Offset (must be less than the normalized interval Int)

  • Dn – normalized Delay

  • a = Dm / Int (rounded down)

  • b = a * Int + Off

If the measured delay (Dm) is less than or equal to b, then the normalized delay (Dn) is equal to b. Otherwise, Dn is b + Int.

Example

The following example shows a low-latency service. The intent is to avoid high-latency links (1-6, 5-2). Links 1-2 and 5-6 are both low-latency links. The measured latency is not equal, but the difference is insignificant.

We can normalize the measured latency before it is advertised and used by IS-IS. Consider a scenario with the following:

  • Interval = 10

  • Offset = 3

The measured delays will be normalized as follows:

  • Dm = 29

    a = 29 / 10 = 2 (2.9, rounded down to 2)

    b = 2 * 10 + 3 = 23

    In this case, Dm (29) is greater than b (23); so Dn is equal to b+I (23 + 10) = 33

  • Dm = 31

    a = 31 / 10 = 3 (3.1, rounded down to 3)

    b = 3 * 10 + 3 = 33

    In this case, Dm (31) is less than b (33); so Dn is b = 33

The link delay between 1-2 and 5-6 is normalized to 33.

Configuration

Delay normalization is disabled by default. To enable and configure delay normalization, use the delay normalize interval interval [offset offset] command.

  • interval – The value of the normalize interval in microseconds.

  • offset – The value of the normalized offset in microseconds. This value must be smaller than the value of normalized interval.

IS-IS Configuration


router isis 1
 interface GigEth 0/0/0/0
  delay normalize interval 10 offset 3
  address-family ipv4 unicast
   metric 77

SR Policy End-to-End Delay Measurement

The PM for SR Policy uses the IP/UDP packet format defined in RFC 5357 (TWAMP-Light) for probes. Two-Way Active Measurement Protocol (TWAMP) adds two-way or round-trip measurement capabilities. TWAMP employs time stamps applied at the echo destination (reflector) to enable greater accuracy. In the case of TWAMP Light, the Session-Reflector doesn’t necessarily know about the session state. The Session-Reflector simply copies the Sequence Number of the received packet to the Sequence Number field of the reflected packet. The controller receives the reflected test packets and collects two-way metrics. This architecture allows for collection of two-way metrics.

The extended TE link delay metric (minimum-delay value) can be used to compute paths for SR policies as an optimization metric or as an accumulated delay bound.

There is a need to monitor the end-to-end delay experienced by the traffic sent over an SR policy to ensure that the delay does not exceed the requested “upper-bound” and violate SLAs. You can verify the end-to-end delay values before activating the candidate-path or the segment lists of the SR policy in forwarding table, or to deactivate the active candidate-path or the segment lists of the SR policy in forwarding table.


Note
The end-to-end delay value of an SR policy will be different than the path computation result (for example, the sum of TE link delay metrics) due to several factors, such as queuing delay within the routers.

Restrictions and Usage Guidelines for PM for SR Policy Delay

Hardware clocks must be synchronized between the querier and the responder nodes of the link using PTP for one-way delay measurement.

Configuring Performance Measurement Parameters

This example shows how to configure performance-measurement parameters for SR policy delay as a global default profile. The default values for the different parameters in the PM for SR policy delay is given as follows:

  • probe: The default mode for probe is one-way delay measurement. See Measurement Modes for more information.

  • burst interval: Interval for sending probe packet. The default value is 3000 milliseconds and the range is from 30 to 15000 milliseconds.

  • computation interval: Interval for metric computation. Default is 30 seconds; range is 1 to 3600 seconds.

  • protocol:

    • twamp-light: SR Policy delay measurement using RFC 5357 with IP/UDP encap. This is the default protocol.

  • tos: Type of Service

    • dscp value: The default value is 48 and the range is from 0 to 63.

    • traffic-class value: The default value is 6 and the range is from 0 to 7.

  • advertisement threshold-check: minimum-delay/maximum-delay - The default value of periodic advertisement threshold-check is maximum-delay.

  • periodic advertisement: Periodic advertisement is enabled by default.

  • periodic-advertisement interval: The default value is 120 seconds and the interval range is from 30 to 3600 seconds.

  • periodic-advertisement threshold: Checks the minimum-delay metric change for threshold crossing for periodic advertisement. The default value is 10 percent and the range is from 0 to 100 percent.

  • periodic-advertisement minimum-change: The default value is 500 microseconds (usec) and the range is from 0 to 100000 microseconds.

  • accelerated advertisement: Accelerated advertisement is disabled by default.

  • accelerated-advertisement threshold: Checks the minimum-delay metric change for threshold crossing for accelerated advertisement. The default value is 20 percent and the range is from 0 to 100 percent.

  • accelerated-advertisement minimum: The default value is 500 microseconds and the range is from 1 to 100000 microseconds. 

Router(config)# performance-measurement delay-profile sr-policy
Router(config-pm-dm-srpolicy)# probe
Router(config-pm-dm-srpolicy-probe)# burst-interval 60
Router(config-pm-dm-srpolicy-probe)# computation-interval 60
Router(config-pm-dm-srpolicy-probe)# protocol twamp-light
Router(config-pm-dm-srpolicy-probe)# tos dscp 63
Router(config-pm-dm-srpolicy-probe)# exit
Router(config-pm-dm-srpolicy)# advertisement
Router(config-pm-dm-srpolicy-adv)# periodic
Router(config-pm-dm-srpolicy-adv-per)# interval 60
Router(config-pm-dm-srpolicy-adv-per)# minimum-change 1000
Router(config-pm-dm-srpolicy-adv-per)# threshold 20
Router(config-pm-dm-srpolicy-adv-per)# exit

Router(config-pm-dm-srpolicy-adv)# accelerated
Router(config-pm-dm-srpolicy-adv-acc)# minimum-change 1000
Router(config-pm-dm-srpolicy-adv-acc)# threshold 10
Router(config-pm-dm-srpolicy-adv-acc)# exit

Router(config-pm-dm-srpolicy-adv)# threshold-check minimum-delay
Router(config-pm-dm-srpolicy-adv)# exit
Router(config-pm-dm-srpolicy)#

Configure the UDP Destination Port

Configuring the UDP port for TWAMP-Light protocol is optional. By default, PM uses port 862 as the TWAMP-reserved UDP destination port for delay.

The UDP port is configured for each PM measurement probe type (delay, loss, protocol, authentication mode, etc.) on querier and responder nodes. If you configure a different UDP port, the UDP port for each PM measurement probe type must match on the querier and the responder nodes.


Note
The same UDP destination port is used for delay measurement for links and SR Policy.

This example shows how to configure the UDP destination port for delay.

Router(config)# performance-measurement 
Router(config-perf-meas)# protocol twamp-light
Router(config-pm-protocol)# measurement delay unauthenticated 
Router(config-pm-proto-mode)# querier-dst-port 12000

Enable Performance Measurement for SR Policy

This example shows how to enable PM for SR policy delay for a specific policy.

Router(config)# segment-routing traffic-eng
Router(config-sr-te)# policy foo
Router(config-sr-te-policy)# performance-measurement
Router(config-sr-te-policy-perf-meas)# delay-measurement

SR Policy Probe IP/UDP ECMP Hashing Configuration

This example shows how to configure SR Policy ECMP IP-hashing mode.

  • The destination IPv4 address 127.x.x.x – 127.y.y.y is used in the Probe messages to take advantages of 3-tuple IP hashing (source-address, destination-address, and local router ID) for ECMP paths of SR-MPLS Policy.


    Note
    The destination IPv4 address must be 127/8 range (loopback), otherwise it will be rejected.

  • One PM session is always created for the actual endpoint address of the SR Policy.

  • You can specify the number of IP addresses to sweep. The range is from 0 (default, no sweeping) to 128.

  • Platforms may have a limitation for large label stack size to not check IP address for hashing.

Router(config)# performance-measurement delay-profile sr-policy 
Router(config-pm-dm-srpolicy)# probe 
Router(config-pm-dm-srpolicy-probe)# sweep 
Router(config-pm-dm-srpolicy-probe-sweep)# destination ipv4 127.0.0.1 range 28

Verification

Router# show performance-measurement sr-policy 
Mon Jan 20 18:48:41.002 PST

-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------

Policy Name                LSP ID Tx/Rx         Avg/Min/Max/Variance            
 -----------------------------------------------------------------------------
srte_c_10_ep_192.168.0.4   2      6/6           27012/26906/27203/106       


Router# show performance-measurement sr-policy name srte_c_10_ep_192.168.0.4 detail verbose
Mon Jan 20 18:44:22.400 PST

-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
SR Policy name: srte_c_10_ep_192.168.0.4
  Color                       : 10
  Endpoint                    : 192.168.0.4
  Number of candidate-paths   : 1

  Candidate-Path:
    Instance                  : 2
    Preference                : 100
    Protocol-origin           : Configured
    Discriminator             : 100
    Source address            : 192.168.0.2
    Reverse path label        : Not configured
    Number of segment-lists   : 1
    Last advertisement:
      No advertisements have occured
    Next advertisement:
      Check scheduled at the end of the current probe (roughly every 30 seconds)
      Aggregated delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
      Rolling average (uSec): 45218
    Last probe:
      Packets Sent: 9, received: 9
      Measured delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
    Current Probe:
      Started at Jan 20 2020 18:44:19.170 (3.453 seconds ago)
      Packets Sent: 3, received: 3
      Measured delays (uSec): avg: 26588, min: 26558, max: 26630, variance: 30
    Next probe scheduled at Jan 20 2020 18:44:34.166 (in 11.543 seconds)
    Next burst packet will be sent in 1.543 seconds
    Burst packet sent every 5.0 seconds 
    Liveness Detection: Disabled

    Segment-List              : R4
        16004
      Number of atomic paths  : 3
      Last advertisement:
        No advertisements have occured
      Next advertisement:
        Aggregated delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
        Rolling average (uSec): 45218
      Last probe:
        Packets Sent: 9, received: 9
        Measured delays (uSec): avg: 45218, min: 26512, max: 82600, variance: 18706
      Current probe:
        Packets Sent: 3, received: 3
        Measured delays (uSec): avg: 26588, min: 26558, max: 26630, variance: 30
      Liveness Detection: Disabled

      Atomic path:
        Hops                  : 127.0.0.0
        Session ID            : 33554434
        Last advertisement:
          No advertisements have occured
        Next advertisement:
          Aggregated delays (uSec): avg: 45407, min: 26629, max: 82600, variance: 18778
          Rolling average (uSec): 45407
        Last Probe:
          Packets Sent: 3, received: 3
          Measured delays (uSec): avg: 45407, min: 26629, max: 82600, variance: 18778
        Current Probe:
          Packets Sent: 1, received: 1
          Measured delays (uSec): avg: 26630, min: 26630, max: 26630, variance: 0
        Probe samples:
          Packet Rx Timestamp       Measured Delay (nsec)
          Jan 20 2020 18:44:19.198        26630730
        Liveness Detection: Disabled

      Atomic path:
        Hops                  : 127.0.0.1
        Session ID            : 33554435
        Last advertisement:
          No advertisements have occured
        Next advertisement:
          Aggregated delays (uSec): avg: 45128, min: 26521, max: 81961, variance: 18607
          Rolling average (uSec): 45128
        Last Probe:
          Packets Sent: 3, received: 3
          Measured delays (uSec): avg: 45128, min: 26521, max: 81961, variance: 18607
        Current Probe:
          Packets Sent: 1, received: 1
          Measured delays (uSec): avg: 26576, min: 26576, max: 26576, variance: 0
        Probe samples:
          Packet Rx Timestamp       Measured Delay (nsec)
          Jan 20 2020 18:44:19.198        26576938
        Liveness Detection: Disabled

      Atomic path:
        Hops                  : 192.168.0.4
        Session ID            : 33554433
        Last advertisement:
          No advertisements have occured
        Next advertisement:
          Aggregated delays (uSec): avg: 45119, min: 26512, max: 81956, variance: 18607
          Rolling average (uSec): 45119
        Last Probe:
          Packets Sent: 3, received: 3
          Measured delays (uSec): avg: 45119, min: 26512, max: 81956, variance: 18607
        Current Probe:
          Packets Sent: 1, received: 1
          Measured delays (uSec): avg: 26558, min: 26558, max: 26558, variance: 0
        Probe samples:
          Packet Rx Timestamp       Measured Delay (nsec)
          Jan 20 2020 18:44:19.198        26558375
        Liveness Detection: Disabled


Router# show performance-measurement history probe sr-policy 
Mon Jan 20 18:46:55.445 PST

-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------

SR Policy name: srte_c_10_ep_192.168.0.4
  Color                       : 10
  Endpoint                    : 192.168.0.4

  Candidate-Path:
    Preference                : 100
    Protocol-origin           : Configured
    Discriminator             : 100
    Delay-Measurement history (uSec):
      Probe Start Timestamp     Pkt(TX/RX)   Average       Min       Max
      Jan 20 2020 18:46:34.174         9/9     26880     26684     27070
      Jan 20 2020 18:46:19.174         9/9     26899     26822     27004
      Jan 20 2020 18:46:04.173         9/9     26813     26571     27164
      Jan 20 2020 18:45:49.172         9/9     26985     26713     27293
      Jan 20 2020 18:45:34.172         9/9     26744     26557     27005
      Jan 20 2020 18:45:19.171         9/9     26740     26435     27093
     Jan 20 2020 18:45:04.171         9/9     27115     26938     27591
      Jan 20 2020 18:44:49.171         9/9     26878     26539     27143
      Jan 20 2020 18:44:34.171         9/9     26824     26562     27265
      Jan 20 2020 18:44:19.170         9/9     26944     26558     27422
      Jan 20 2020 18:44:06.543         9/9     45218     26512     82600

    Segment-List              : R4
      16004
      Delay-Measurement history (uSec):
        Probe Start Timestamp     Pkt(TX/RX)   Average       Min       Max
        Jan 20 2020 18:46:34.174         9/9     26880     26684     27070
        Jan 20 2020 18:46:19.174         9/9     26899     26822     27004
        Jan 20 2020 18:46:04.173         9/9     26813     26571     27164
        Jan 20 2020 18:45:49.172         9/9     26985     26713     27293
        Jan 20 2020 18:45:34.172         9/9     26744     26557     27005
        Jan 20 2020 18:45:19.171         9/9     26740     26435     27093
        Jan 20 2020 18:45:04.171         9/9     27115     26938     27591
        Jan 20 2020 18:44:49.171         9/9     26878     26539     27143
        Jan 20 2020 18:44:34.171         9/9     26824     26562     27265
        Jan 20 2020 18:44:19.170         9/9     26944     26558     27422
        Jan 20 2020 18:44:06.543         9/9     45218     26512     82600

      Atomic path:
        Hops                  : 127.0.0.0
        Delay-Measurement history (uSec):
          Probe Start Timestamp     Pkt(TX/RX)   Average       Min       Max
          Jan 20 2020 18:46:34.174         3/3     26927     26747     27070
          Jan 20 2020 18:46:19.174         3/3     26982     26970     27004
          Jan 20 2020 18:46:04.173         3/3     26895     26647     27164
          Jan 20 2020 18:45:49.172         3/3     27054     26764     27293
          Jan 20 2020 18:45:34.172         3/3     26801     26694     27005
          Jan 20 2020 18:45:19.171         3/3     26807     26524     27093
          Jan 20 2020 18:45:04.171         3/3     27226     26938     27591
          Jan 20 2020 18:44:49.171         3/3     26976     26644     27143
          Jan 20 2020 18:44:34.171         3/3     26880     26679     27265
          Jan 20 2020 18:44:19.170         3/3     26994     26630     27422
          Jan 20 2020 18:44:06.543         3/3     45407     26629     82600

      Atomic path:
        Hops                  : 127.0.0.1
        Delay-Measurement history (uSec):
          Probe Start Timestamp     Pkt(TX/RX)   Average       Min       Max
          Jan 20 2020 18:46:34.174         3/3     26865     26705     26988
          Jan 20 2020 18:46:19.174         3/3     26846     26822     26881
          Jan 20 2020 18:46:04.173         3/3     26787     26581     26939
          Jan 20 2020 18:45:49.172         3/3     26954     26728     27180
          Jan 20 2020 18:45:34.172         3/3     26724     26577     26957
          Jan 20 2020 18:45:19.171         3/3     26705     26452     27032
          Jan 20 2020 18:45:04.171         3/3     27043     26972     27124
          Jan 20 2020 18:44:49.171         3/3     26848     26550     27062
          Jan 20 2020 18:44:34.171         3/3     26800     26562     27204
          Jan 20 2020 18:44:19.170         3/3     26927     26576     27327
          Jan 20 2020 18:44:06.543         3/3     45128     26521     81961

      Atomic path:
        Hops                  : 192.168.0.4
        Delay-Measurement history (uSec):
          Probe Start Timestamp     Pkt(TX/RX)   Average       Min       Max
          Jan 20 2020 18:46:34.174         3/3     26848     26684     26967
          Jan 20 2020 18:46:19.174         3/3     26871     26833     26913
          Jan 20 2020 18:46:04.173         3/3     26759     26571     26876
          Jan 20 2020 18:45:49.172         3/3     26947     26713     27163
          Jan 20 2020 18:45:34.172         3/3     26708     26557     26939
          Jan 20 2020 18:45:19.171         3/3     26708     26435     27075
          Jan 20 2020 18:45:04.171         3/3     27078     27016     27138
          Jan 20 2020 18:44:49.171         3/3     26812     26539     27043
          Jan 20 2020 18:44:34.171         3/3     26793     26582     27181
          Jan 20 2020 18:44:19.170         3/3     26911     26558     27308
          Jan 20 2020 18:44:06.543         3/3     45119     26512     81956


Router# show performance-measurement counters sr-policy name srte_c_10_ep_192.168.0.4 
Mon Jan 20 18:47:55.499 PST

-------------------------------------------------------------------------------
0/0/CPU0
-------------------------------------------------------------------------------
SR Policy name: srte_c_10_ep_192.168.0.4
  Candidate-Path:
    Instance                  : 2
    Preference                : 100
    Protocol-origin           : Configured
    Discriminator             : 100
    Packets:
      Total sent                                : 141
      Total received                            : 141
    Errors:
      Total sent errors                         : 0
      Total received errors                     : 0
    Probes:
      Total started                             : 16
      Total completed                           : 15
      Total incomplete                          : 0
      Total advertisements                      : 2
    Segment-List              : R4
      16004
      Packets:
        Total sent                              : 141
        Total received                          : 141
      Errors:
        Total sent errors                       : 0
        Total received errors                   : 0
      Probes:
        Total started                           : 16
        Total completed                         : 15
        Total incomplete                        : 0
        Total advertisements                    : 2