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DMM measurements (delay and delay variation) work as follows. A DMM frame is sent from an originating unit to one of the remote devices linked to the Cisco Provider Connectivity Assurance Sensor Control. When the DMM frame is received by the remote device, it sends a DMR to the originating unit.
DMM measurements are measurements of network delay and network delay variation. The remote device needs to eliminate processing time in order to obtain 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)
▶ To configure a delay measurement reflection end point
Access the page SOAM ▶ CFM ▶ DMM ▶ Configuration.
A listing of all existing Delay Measurement instances (reflectors) is displayed.(Optional) To limit the view to only certain reflection end points, enter a value on which to filter, then click Search. You can filter by index value, DMM name, MEP idx, MEPID, RMEPID, Priority, Interval, or whether or not the end point has been enabled.
Note: Enter an asterisk ( * ) as a wildcard to replace one or several characters.In the Index column of the table, click the value associated with the end point for which you want to view detailed information.
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 |
Name DMM Name | The name of the delay measurement instance. |
Enable | Select this box to enable reflecting DMM frames on the remote device specified above |
▶ 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.
Complete the required fields, then click Apply.
For more information on specific parameters, refer to the following tables.
DMM Configuration (SOAM ▶ CFM ▶ DMM ▶ Configuration)
Parameter | Description |
---|---|
Index | The index of the delay measurement instance |
DMM 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 | Enables sending DMM frames at the specified interval. |
Sampling Interval Interval | The time at which this delay measurement instance issues DMM frames. Expressed in milliseconds. |
Reference Period | Reference period in minutes for the delay measurements. |
One-Way Delay
Parameter | Description |
---|---|
Enable | Enables one-way delay measurement for this DMM instance. |
Maximum Allowed Value | 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 | The number of consecutive measurements exceeding the Maximum Allowed value that triggers a one-way delay alarm for this Reference Period. |
Average Threshold | 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 | 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 | Number of consecutive measurements exceeding the Maximum Allowed Value that triggers a one-way delay variation alarm for this Reference Period. |
Average Threshold | 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 | Enables two-way delay measurement for this DMM instance. |
Maximum Allowed Value | Maximum two-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 | The number of consecutive measurements exceeding the Maximum Allowed value that triggers a two-way delay alarm for this Reference Period. |
Average Threshold | 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 milliseconds are acceptable. |
Two-Way Delay Variation
Parameter | Description |
---|---|
Enable | Select to enable Two-way delay variation measurements for this DMM instance. |
Maximum Allowed Value | 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 | 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 | 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. |
▶ To delete a delay measurement instance
Access the page SOAM ▶ CFM ▶ DMM ▶ Configuration.
Click the index of the DMM instance to delete.
Click Delete.
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