Setting Up Delay Measurements

15 Apr 2022
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Setting Up Delay Measurements

Updated on 15 Apr 2022
8 Minutes to read
Contributors

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DMM measurements (delay and delay variation) work as follows.

A DMM frame is sent from the originating unit to the remote unit. When the DMM frame is received by the remote unit, it sends a DMR to the originating unit. The reception of the DMM frame by the remote unit and the transmission of the DMR also involve some processing time that may or may not be accounted for. DMM measurements are measurements of network delay and network delay variation. The unit needs to eliminate the processing time in order to get a true measurement of the network delay and delay variation. This is accomplished by the use of four timestamps:

a = Time that the DMM frame is transmitted by the originating unit
b = Time that the DMM frame is received by the remote unit
c = Time that the DMR frame (DMM response) is transmitted by the remote unit
d = Time that the DMR frame is received by the originating unit

Using these timestamps, the originating unit calculates one-way and two-way delay as follows:

One-Way Network Delay = d – c
Two-Way Network Delay = d – a – (c – b)

This is the two-way delay (including remote processing time) minus the remote processing time.

To configure DMM instances

Access the page SOAM ▶CFM ▶DMM ▶Configuration.
All existing Delay Measurement Instances are displayed.
Click Add to create a DMM instance or click the DMM instance index to edit an existing DMM instance.

Note: One-way delay measurements require time synchronization, via NTP, on units at each probe end.

Complete the required fields, then click Apply.

For more information on specific parameters, refer to the following table.

DMM Configuration (SOAM ▶CFM ▶DMM ▶Configuration)

Parameter	Description
Index	The index of the delay measurement instance.
DMM Name Name	The name of the delay measurement instance.
MEP Index MEP idx	The index assigned to the Maintenance association End Point.
MEPID	The local Maintenance association End Point Identifier.
Remote MEPID R-MEPID	The remote Maintenance association End Point Identifier.
Priority	Priority value used in VLAN tags, if present, in the transmitted frame.
Enable	Check box to enable sending DMM frames at the specified interval.
Sampling Interval (msec) Interval	The time at which this delay measurement instance issues DMM frames. Expressed in milliseconds.
Reference Period (min)	Reference period in seconds for the delay measurements.

One-Way Delay

Parameter	Description
Enable	Check box to enable one-way delay measurement for this DMM instance.
Maximum Allowed Value (msec)	Maximum one-way delay in the Reference Period. Expressed in milliseconds. If a certain number (set by next field value) of consecutive measurements exceeds this value, an alarm is triggered.
Instantaneous Threshold (sample)	The number of consecutive measurements exceeding the Maximum Allowed value that triggers a one-way delay alarm for this Reference Period.
Average Threshold (msec)	One-way average delay threshold, expressed in milliseconds, that triggers the average one-way delay alarm for this Reference Period. Note: The threshold is expressed in milliseconds but with microsecond granularity. Consequently, values such as 1.001 milliseconds are acceptable.

One-Way Delay Variation

Parameter	Description
Enable	Select to enable One-way delay variation measurements for this DMM instance.
Maximum Allowed Value (msec)	Maximum one-way delay variation, expressed in milliseconds, to monitor in the Reference Period. If a certain number (set by next field value) of consecutive measurements exceeds this value, an alarm is triggered.
Instantaneous Threshold (sample)	Number of consecutive measurements exceeding the Maximum Allowed Value that triggers a one-way delay variation alarm for this Reference Period.
Average Threshold (msec)	One-way average delay variation threshold, expressed in milliseconds, that triggers the average one-way delay variation alarm for this Reference Period. Note: The threshold is expressed in milliseconds, but with microsecond granularity. Consequently, values such as 1.001 ms are acceptable.

Two-Way Delay

Parameter	Description
Enable	Check box to enable Two-way delay measurement for this DMM instance.
Maximum Allowed Value (msec)	Maximum two-way delay, expressed in milliseconds, to monitor in the Reference Period. If a certain number (set by next field value) of consecutive measurements exceeds this value, an alarm is triggered.
Instantaneous Threshold (sample)	Number of consecutive measurements exceeding the Maximum Allowed Value that triggers a two-way delay alarm for this Reference Period.
Average Threshold (msec)	Two-way average delay threshold, expressed in milliseconds, that triggers the average two-way delay alarm for this Reference Period. Note: The threshold is expressed in milliseconds, but with microsecond granularity. Consequently, values such as 1.001 ms are acceptable.

Two-Way Delay Variation

Parameter	Description
Enable	Indicates whether the Two-way delay variation is computed by this DMM instance.
Maximum Allowed Value (msec)	Maximum two-way delay variation, expressed in milliseconds, to monitor in the Reference Period. If a certain number (set by next field value) of consecutive measurements exceeds this value, an alarm is triggered.
Instantaneous Threshold (sample)	Specify the number of consecutive measurements exceeding the Maximum Allowed Value that triggers a two-way delay variation alarm for this Reference Period.
Average Threshold (msec)	Specify the two-way average delay variation threshold, expressed in milliseconds, that triggers the average two-way delay variation alarm for this Reference Period. Note: The threshold is expressed in milliseconds but with microsecond granularity. Consequently, values such as 1.001 ms are acceptable.

CAUTION: Deleting a DMM instance will also delete all SA metrics that use this DMM instance as the metric source.

To delete a delay measurement instance

Access the page SOAM ▶CFM ▶DMM ▶Configuration.
Click the index of the DMM instance to delete.
Click Delete.

Viewing Delay Measurement Results

To view delay measurement results details

Note: For more information on how delay measurements results are calculated, "Setting Up Delay Measurements".

Access the page SOAM ▶CFM ▶DMM ▶Results.
The results for all Delay Measurement Instances are displayed.
Click the Index of the DMM instance you want to view the DMM results.

For more information on specific parameters, refer to the following table.

DMM Results (SOAM ▶CFM ▶DMM ▶Results)

Parameter	Description
Index	The index of the delay measurement instance.
Name	The name of the delay measurement instance.
MEP Index MEP idx	The index assigned to the Maintenance association End Point.
MEPID	The local MEP's Maintenance association End Point Identifier.
Remote MEPID R-MEPID	The remote MEP's Maintenance association End Point Identifier.
Priority	The priority value used in VLAN tags, if present, in the transmitted frame.
Period	The number of periods that elapsed since measurement started.
Period Time	The time when the previous period was completed.
Result Codes	The current value, expressed in microseconds, for DMM results: OAD: One-Way Average Delay OADV: One-Way Average Delay Variation TAD: Two-Way Average Delay TADV: Two-Way Average Delay Variation

One-Way Delay

Parameter	Description
Average Alarm	Indicates whether an alarm is raised (Active) because the current average one-way delay is greater than or equal to the average threshold.
Instantaneous Alarm	Indicates if an alarm has been raised (Active) because the instantaneous threshold has been reached. This threshold is the consecutive number of times the one-way delay was greater than or equal to the maximum value.
Instantaneous Delay	The one-way instantaneous delay, expressed in microseconds.
Period	Gives the results for the previous and current periods. The previous period is indicated in Period Time.
Nbr Samples	Total number of samples in the period.
Minimum Delay	The minimum delay, expressed in microseconds, over one period.
Maximum Delay	The maximum delay, expressed in microseconds, over one period.
Average Delay	The average delay, expressed in microseconds, over one period.
Nbr Threshold Exceeded	Number of times the one-way delay exceeded the value of the Maximum Delay parameter.

One-Way Delay Variation

Parameter	Description
Average Alarm	Indicates if an alarm has been raised (Active) because the current average one-way delay variation is greater than or equal to the average threshold.
Instantaneous Alarm	Indicates if an alarm has been raised (Active) because the instantaneous threshold has been reached. This threshold is the consecutive number of times the one-way delay variation was greater than or equal to the maximum value.
Instantaneous DV	The one-way instantaneous delay variation, expressed in microseconds.
Period	Gives the results for the previous and current periods. The previous period is indicated in Period Time.
Nbr Samples	Total number of samples in the period.
Minimum DV	The minimum delay variation over one period, expressed in microseconds.
Maximum DV	The maximum delay variation over one period, expressed in microseconds.
Average DV	The average delay variation over one period, expressed in microseconds.
Nbr Threshold Exceeded	Number of times the one-way delay variation exceeded the value of the Maximum DV parameter.

Two-Way Delay

Parameter	Description
Average Alarm	Indicates if an alarm is raised (Active) because the current average two-way delay is greater than or equal to the average threshold.
Instantaneous Alarm	Indicates if an alarm has been raised (Active) because the instantaneous threshold has been reached. This threshold is the consecutive number of times the two-way delay was greater than or equal to the maximum value.
Instantaneous Delay	The two-way instantaneous delay, expressed in microseconds.
Period	Gives the results for the previous and current periods. The previous period is indicated in Period Time.
Nbr Samples	Total number of samples in the period.
Minimum Delay	The minimum delay, expressed in microseconds, over one period.
Maximum Delay	The maximum delay, expressed in microseconds, over one period.
Average Delay	The average delay over one period, expressed in microseconds.
Nbr Threshold Exceeded	Number of times the two-way delay exceeded the value of the Maximum Delay parameter.

Two-Way Delay Variation

Parameter	Description
Average Alarm	Indicates if an alarm is raised (Active) because the current average two-way delay variation is greater than or equal to the average threshold.
Instantaneous Alarm	Indicates if an alarm has been raised (Active) because the instantaneous threshold has been reached. This threshold is the consecutive number of times the two-way delay variation was greater than or equal to the maximum value.
Instantaneous DV	The two-way instantaneous delay variation, expressed in microseconds.
Period	Gives the results for the previous and current periods The previous period is indicated in Period Time.
Nbr Samples	Total number of samples in the period.
Minimum DV	The minimum delay variation over one period, expressed in microseconds.
Maximum DV	The maximum delay variation over one period, expressed in microseconds.
Average DV	The average delay variation over one period, expressed in microseconds.
Nbr Threshold Exceeded	Number of times the two-way delay variation exceeded the value of the Maximum DV parameter.

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