Using the Two-Way Active Measurement Protocol (TWAMP)
- 25 Jan 2024
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Using the Two-Way Active Measurement Protocol (TWAMP)
- Updated on 25 Jan 2024
- 13 Minutes to read
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Two-Way Active Measurement Protocol (TWAMP) is a protocol used to measure round-trip IP performance between any two TWAMP-enabled units deployed in a network. With TWAMP, you can reliably perform in band, round-trip performance measurements and identify performance issues by sending test packets to a unit that reflects them back.
TWAMP packet generation provides the ability to perform one- and two-way delay and delay variation in a Layer-3 network, as well as packet loss measurements.
TWAMP defines two protocols:
- TWAMP control protocol (not supported by Accedian)
- TWAMP test protocol (supported by Accedian)
Only TWAMP reflection is currently supported on the FSX Performance Element. You can create a maximum of 100 active TWAMP sessions that reflect up to 1000 packets per second (PPS).
Note: This function is only to be used with TWAMP when connecting to Layer-3 TWAMP session sender devices.
Setting Up TWAMP Generator Measurements
TWAMP generator instances are used to calculate delay measurements between two end points. Measurements and calculations are performed at the generating end only.
Note: You must enable TWAMP reflection at the end point.
To set up or modify a TWAMP generator instance
Access the page SOAM ▶TWAMP ▶Generator ▶Configuration.
A listing of all existing TWAMP generator instances is displayed.Click Add to create a TWAMP generator session or click the TWAMP session index to edit an existing TWAMP generator session.
Note: If you plan to use one-way delay measurements, you must enable time synchronization on the units at each end of the probe.
- Complete the required fields, then click Apply.
For more information on specific parameters, refer to the following tables.
TWAMP Generator (SOAM ▶TWAMP ▶Generator ▶Configuration)
| Parameter | Description |
|---|---|
| Index | The index assigned to the TWAMP instance. |
| Session Name | The name assigned to the TWAMP instance. Maximum length: 31 characters. |
| Enable | The state of the TWAMP instance. When enabled, TWAMP packets are sent at the specified interval. Note: This parameter is disabled by default. Click to enable. |
| Interval (ms) | The time at which this TWAMP instance transmits packets expressed in milliseconds. |
| Reference Period (min) | The reference period for the TWAMP instance, expressed in minutes. Range: 1–1440 minutes Default: 15 minutes Note: This value must be at least 10 times the value of the Interval parameter. |
| Packet Size | The size of TWAMP samples, expressed in bytes. Note: The size value indicated here does not include protocol headers (VLAN tags, UDP, IP, Ethernet) or the four FCS bytes. Minimum value: 14 bytes Maximum value: 1472 bytes (IPv4) and 1452 bytes (IPv6) Default value: 41 bytes Note: If you choose to use a packet size smaller than 41 bytes, you must ensure that the reflector being used supports frame padding, as defined by RFC-5357. Similarly, if you observe that packets are not being reflected, try increasing the packet size to at least 41 bytes. |
UDP Parameters
| Parameter | Description |
|---|---|
| Destination IP Address | The remote peer IP address. |
| Source UDP Port | The UDP source port. The default value is 10000. Other acceptable values are in the range of 1024–65535. |
| Destination UDP Port | The UDP destination port. The default value is 862. Other acceptable values are in the range of 1024–65535. |
| Diff-Serv CodePoint (DSCP) | The DSCP class selector setting for the transmitted packets. Expected length: 6 bits |
| Explicit Congestion Notification (ECN) | The ECN value. This value can be used to associate an ECN value with the TWAMP packets, thereby simulating ECN in the customer network. Note: The ECN bits are the last two bits of the IP ToS field. Range: 0–3 |
| VLAN 1 Priority | The priority bits of the first VLAN. This value can be used to associate a priority value with the first VLAN. Range: 0–7 |
Packet Loss
| Parameter | Description |
|---|---|
| Continuity Check Threshold (sample) | The number of consecutive sampling periods that can be lost before triggering the Continuity Loss alarm. The alarm status is rounded up to the next full second. Range: 2–200 Default value: 10 |
| Packet Loss Rate (%) | The threshold, expressed as a percentage, at which an Excessive Packet Loss (EPL) alarm is triggered. Range: 0–100 % |
Two-Way Measurements
| Parameter | Description |
|---|---|
| Maximum Delay (msec) | The two-way delay allowed for each sample in the Reference Period. This value is used in conjunction with the Delay Threshold to trigger the alarm TWAMP_TW_MAX_DELAY_ALERT. |
| Delay Threshold (sample) | The number of consecutive samples exceeding the Maximum Delay that are allowed before triggering the two-way delay alarm for this Reference Period. |
| Average Delay Threshold (msec) | The average two-way delay is calculated from samples taken during the reference period. Exceeding this threshold triggers the alarm TWAMP_AVG_ DELAY_ALERT. |
| Maximum Delay Variation (msec) | The maximum two-way delay variation threshold to monitor during a test period. This value is used in conjunction with the Delay Variation Threshold to trigger the alarm TWAMP_MAX_DV_ALERT. |
| Delay Variation Threshold (sample) | The number of consecutive samples exceeding the Maximum Delay Variation that are allowed before declaring the two-way delay variation alarm for this Reference Period. |
| Average Delay | The average two-way delay variation is calculated from samples taken during the reference period. Exceeding this threshold triggers the alarm TWAMP_AVG_DV_ALERT. |
One-Way Near End Measurements
| Parameter | Description |
|---|---|
| Maximum Delay (msec) | The one-way near-end delay allowed for each sample in the Reference Period. This value is used in conjunction with the Delay Threshold to trigger the alarm TWAMP_NE_OW_MAX_DELAY_ALERT. |
| Delay Threshold (sample) | The number of consecutive samples exceeding the Maximum Delay that are allowed before declaring the one-way near-end delay alarm for this Reference Period. |
| Average Delay Threshold (msec) | The average one-way near-end delay is calculated using the samples taken during the reference period. Exceeding this threshold triggers the alarm TWAMP_NE_OW_AVG_DELAY_ALERT. |
| Maximum Delay Variation (msec) | The maximum one-way near-end delay variation threshold to monitor during a test period. This value is used in conjunction with the Delay Variation Threshold to trigger the alarm TWAMP_NE_OW_MAX_DV_ALERT. |
| Delay Variation Threshold (sample) | The number of consecutive samples exceeding the Maximum Delay Variation that are allowed before declaring the one-way near-end delay variation alarm for this Reference Period. |
| Average Delay Variation Threshold (msec) | The average one-way near-end delay variation is calculated using the samples taken during the reference period. Exceeding this threshold triggers the alarm TWAMP_NE_OW_AVG_DV_ALERT. |
One-Way Far-End Measurements
| Parameter | Description |
|---|---|
| Maximum Delay (msec) | The one-way far-end delay allowed for each sample in the Reference Period. This value is used in conjunction with the Delay Threshold to trigger the alarm TWAMP_FE_OW_MAX_DELAY_ALERT. |
| Delay Threshold (sample) | The number of consecutive samples exceeding the Maximum Delay that are allowed before triggering the one-way far-end delay alarm for this Reference Period. |
| Average Delay Threshold (msec) | The average one-way far-end delay is calculated using samples taken during the reference period. Exceeding this threshold triggers the alarm TWAMP_FE_OW_AVG_DELAY_ALERT. |
| Maximum Delay Variation (msec) | The maximum one-way far-end delay variation threshold to monitor during a test period This value is used in conjunction with the Delay Variation Threshold to trigger the alarm TWAMP_FE_OW_MAX_DV_ALERT. |
| Delay Variation Threshold (sample) | The number of consecutive samples exceeding the Maximum Delay Variation that are allowed before triggering the one-way far-end delay variation alarm for this Reference Period. |
| Average Delay Variation Threshold (msec) | The average one-way far-end delay variation is calculated using samples taken during the reference period. Exceeding the threshold triggers the alarm TWAMP_FE_OW_AVG_DV_ALERT. |
Deleting a TWAMP Generator Instance
To delete a TWAMP generator instance
Access the page SOAM ▶TWAMP ▶Generator ▶Configuration.
Select the TWAMP instance index you wish to delete by clicking it.
Click Delete.
Viewing TWAMP Generator Session Results
To view a summary of all TWAMP generator session results
Access the page SOAM ▶TWAMP ▶Generator ▶Results.
Click a session index to view its detailed results.
Tip: Select the Poll Every n Seconds box, then enter a number representing the frequency with which the TWAMP generator results will be refreshed.
For more information on specific parameters, refer to the following table.
TWAMP Generator Session Results (SOAM ▶TWAMP ▶Generator ▶Results)
TWAMP Generator Results
| Parameter | Description |
|---|---|
| Index | The unique identifier assigned to the probe. |
| Session Name | The name of the probe. |
| Status Codes | The current state (active or inactive) for all TWAMP alarms for the following status codes:
|
| Local Sync | Indicates whether or not the local clock is in sync with its configured reference clock (PTP, NTP or GPS). |
| Remote Sync | Indicates whether or not the remote clock is in sync with its configured reference clock (PTP, NTP or GPS). |
| Protocol | The protocol used by this session's protocol is UDP. |
| Period | The number of periods that have elapsed since the session was first enabled. |
| Period Time | The start time of the current period. |
Packet Statistics
| Parameter | Description |
|---|---|
| Tx Count | The number of TWAMP packets that have been sent over the previous and current period. |
| Rx Count | The number of TWAMP packets that have been received over the previous and current period. |
Packet Loss
| Parameter | Description |
|---|---|
| Nbr Samples | The total number of samples included in the period. |
| Nbr Lost Packets | The total number of packets during the period that were not received by the other end. |
| Loss Ratio | The ratio between the number of packets that were lost during the period and the total number of packets that were sent, expressed as a percentage. |
| Nbr Out of Order | The total number of packets during the period that were received in a different order than what they were sent in. |
| Nbr Duplicate | The total number of packets during the period that were received more than once. |
| Nbr Gaps | The total number of gaps that have been detected from the sequence of packets that were received during the period. This value is calculated based on the Sequence Number field of the TWAMP packet header of the received packets. |
| Largest Gap | The longest uninterrupted sequence of missing packets that was detected from the sequence of packets that were received during the period. This value is calculated based on the Sequence Number field of the TWAMP packet header of the received packets. |
| Two-Way Delay | |
| Parameter | Description |
| --- | --- |
| Instantaneous Delay | The two-way instantaneous delay value, expressed in microseconds. This is the latest two-way delay value measured when the window was last refreshed. |
| Nbr Samples | The total number of samples included in the period. |
| Minimum Delay | The two-way delay of the fastest sample collected over the period, expressed in microseconds. |
| Maximum Delay | The two-way delay of the slowest sample collected over the period, expressed in microseconds. |
| Average Delay | The average delay of the samples during the reference period, expressed in microseconds. |
| Nbr Threshold Exceeded | The number of times the two-way delay has exceeded the value of the Maximum Delay parameter |
Two-Way Delay Variation
| Parameter | Description |
|---|---|
| Instantaneous DV | The two-way instantaneous delay variation value, expressed in microseconds. This is the latest two-way delay variation measured when the window was last refreshed. |
| Nbr Samples | The total number of samples included in the period. |
| Minimum DV | The two-way delay variation, expressed in microseconds, of the samples with the smallest delay skew over the period. |
| Maximum DV | The two-way delay of the samples with the highest delay skew over the period, expressed in microseconds. |
| Average DV | The average two-way delay variation of the samples during the reference period, expressed in microseconds. |
| Nbr Threshold Exceeded | The number of times the two-way delay variation exceeded the value of the parameter Maximum DV. |
One-Way Near-End Delay
| Parameter | Description |
|---|---|
| Instantaneous Delay | The one-way instantaneous delay value, expressed in microseconds. This is the latest one-way delay value measured when the window was last refreshed. |
| Nbr Samples | The total number of one-way near-end samples included in the period. |
| Minimum Delay | The one-way delay of the fastest sample collected over the period, expressed in microseconds. |
| Maximum Delay | The one-way delay of the slowest sample collected over the period, expressed in microseconds |
| Average Delay | The average one-way near-end delay of the samples during the reference period, expressed in microseconds. |
| Nbr Threshold Exceeded | The number of times the one-way near-end delay has exceeded the value of the Maximum Delay parameter. |
One-Way Near-End Delay Variation
| Parameter | Description |
|---|---|
| Instantaneous DV | The one-way instantaneous delay variation value, expressed in microseconds. This is the latest one-way delay variation measured when the window was last refreshed. |
| Nbr Samples | The total number of one-way near-end delay variation samples included in the period. |
| Minimum DV | The one-way near-end delay variation, expressed in microseconds, of the samples with the smallest delay skew over the period. |
| Maximum DV | The one-way near-end delay of the samples with the highest delay skew over the period, expressed in microseconds. |
| Average DV | The average one-way near-end delay variation of the samples during the reference period, expressed in microseconds. |
| Nbr Threshold Exceeded | The number of times the one-way near-end delay variation exceeded the value of the parameter Maximum DV. |
One-Way Far-End Delay
| Parameter | Description |
|---|---|
| Instantaneous Delay | The one-way instantaneous delay value, expressed in microseconds. This is the latest one-way delay value measured when the window was last refreshed. |
| Nbr Samples | The total number of one-way far-end samples included in the period. |
| Minimum Delay | The one-way far-end delay of the fastest sample collected over the period, expressed in microseconds. |
| Maximum Delay | The one-way far-end delay of the slowest sample collected over the period, expressed in microseconds. |
| Average Delay | The average one-way far-end delay of the samples during the reference period, expressed in microseconds. |
| Nbr Threshold Exceeded | The number of times the one-way far-end delay has exceeded the value of the Maximum Delay parameter. |
One-Way Far-End Delay Variation
| Parameter | Description |
|---|---|
| Instantaneous DV | The one-way instantaneous delay variation value, expressed in microseconds. This is the latest one-way delay variation measured when the window was last refreshed. |
| Nbr Samples | The total number of one-way far-end delay variation samples included in the period. |
| Minimum DV | The one-way far-end delay variation, expressed in microseconds, of the samples with the smallest delay skew over the period. |
| Maximum DV | The one-way far-end delay of the samples with the highest delay skew over the period, expressed in microseconds. |
| Average DV | The average one-way far-end delay variation of the samples during the reference period, expressed in microseconds. |
| Nbr Threshold Exceeded | The number of times the one-way far-end delay variation exceeded the value of the parameter Maximum DV. |
Viewing the TWAMP Generator Session Status
To view the TWAMP generator session status
Access the page SOAM ▶TWAMP ▶Generator ▶Status.
Click a session index to view its detailed results.
Tip: Select the Poll Every n Seconds box and enter a number representing the frequency with which the TWAMP generator status data will be refreshed.
For more information on specific parameters, refer to the following table.
TWAMP Generator Session Status (SOAM ▶TWAMP ▶Generator ▶Status)
| Parameter | Description |
|---|---|
| Index | The unique identifier assigned to the probe. |
| Session Name | The name of the probe. |
| Local Sync | Indicates whether or not the local clock is in sync with its configured reference clock (PTP, NTP or GPS). |
| Remote Sync | Indicates whether or not the remote clock is in sync with its configured reference clock (PTP, NTP or GPS). |
| Status Codes | The current state (active or inactive) for all TWAMP alarms for the following status codes:
|
Setting Up a TWAMP Reflector
To set up a TWAMP reflector
Access the page SOAM ▶TWAMP ▶Configuration.
Enter values in the required fields, then click Apply.
For more information on specific parameters, refer to the following table.
TWAMP Configuration (SOAM ▶TWAMP ▶Configuration)
| Parameter | Description |
|---|---|
| Enable | Check box to view the state of the instance. Default value: Disabled . |
| UDP Port | A port cannot be defined as the UDP port here if it is already in use for any of the following features:
|
Viewing TWAMP Statistics
To view TWAMP statistics
- Access the page SOAM ▶TWAMP ▶Statistics.
For more information on specific parameters, refer to the following table.
TWAMP Reflector Statistics (SOAM ▶TWAMP ▶Statistics)
| Parameter | Description |
|---|---|
| Index | Index assigned to the TWAMP instance. |
| Protocol | The protocol used by the test session. |
| Dst Port | Destination UDP port used by session-reflector. |
| IP Src | IP address of session-sender. |
| Src Port | Source UDP port used by session-sender. |
| Rx Packets | Number of TWAMP packets received from the session-sender. |
| Tx Packets | Number of TWAMP packets transmitted back to the session-sender. |
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