Performance Measurement with TWAMP

by Maksym Dmitriiev  

Two-Way Active Measurement Protocol (TWAMP) is a standard protocol, defined in RFC 5357, that is used to measure network performance. It is used for network SLA compliance checks between Versa VOS and a 3rd party appliance which supports TWAMP protocol. Administrators can use TWAMP Control along with TWAMP Light for periodic network monitoring and on-demand network quality checks. TWAMP cannot be used for automatic traffic steering decisions or data path change, however you can consider measurement results for network optimization tasks. Versa VOS also supports TWAMP Light only for the use case where TWAMP Control is not required or not supported by 3rd party appliance.

1. TWAMP protocol overview

Versa Operating System (VOS) provides flexible support of TWAMP protocol, enabling operators to accurately measure end-to-end network performance and assure service quality. VOS supports two modes of TWAMP:

• Full TWAMP implementation includes a Control channel along with test sessions (child sessions) for datapath performance measurement. This is a standard operational mode that provides comprehensive, standards-compliant visibility and is ideal for multi-vendor environments where interoperability is critical.
• TWAMP Light implementation is a lightweight mode that eliminates the need for a Control channel while still delivering accurate datapath performance measurements (e.g., latency, jitter, packet loss).

The Control channel in Full TWAMP mode uses a control client which communicates with a control server to negotiate test parameters such as measurement interval, dynamic child session setup and coordinate multiple TWAMP child sessions. These sessions are carried out between a session sender, which generates probe packets, and a session reflector, which returns them. With this approach, it is easier to automate large-scale network performance testing. TWAMP Light focuses only on the datapath test traffic, where a sender transmits probe packets and a reflector echoes them back.SLA statistics measured by TWAMP protocol are injected into Versa Analytics platform which allows operators to gain real-time visibility into network performance, proactively detect degradation, and correlate datapath quality with application experience. It is recommended to have clock synchronized using NTP protocol between Sender and Receiver to have more accurate one-way latency measurements. Versa acts as TWAMP sender and another 3rd party device acts as TWAMP receiver. The sender initiates the session and sends TWAMP test packets to the peer test-session receiver (also called as twamp-reflector), to measure datapath quality. The receiver receives the test packets, timestamps the arrival time and immediately reflects the packet back to the sender. In this scenario example of a Full TWAMP is implemented. The benefit in having Full TWAMP is due to a simplified configuration, as child sessions parameters are set by TWAMP Sender and negotiated dynamically with TWAMP receivers. Full TWAMP ensures the two can negotiate a test session without requiring manual alignment of parameters in multi-vendor environment. In case of TWAMP Light all datapath measurement sessions must be pre-build manually.

2. TWAMP configuration example on VOS

Configuring Full TWAMP mode includes two steps. The first step is TWAMP Control connection configuration and the second step is child sessions configuration. To configure the TWAMP Control connection open the Device Template (or service template) then navigate to Networking -> TWAMP -> Control and click on +Add to create a new TWAMP Control session. Below is recommended configuration for TWAMP Control channel

• Enable Connection
• Auto Start should be enabled
• Select Routing Instance from where to initiate the connection
• Server IP is a remote peer IP or receiver IP
• Client IP is a Sender IP from where the session will be initiated
• Set Server TCP port
• Enable Max Reconnect

For the child session which will actually measure path characteristics use the following configuration under Device Template (or service template) -> Networking -> TWAMP -> Light. * When first configuring it, you should click “Create Child Session” from Control session menu as per below screenshot. Child session configuration should be the following:

• Enable True
• Profile default True

 

• Select Routing Instance
• Control Connection that is used for control of a child session
• Reflector IP is a Sender IP from where the session will be initiated
• Reflector UDP port is 862 as per standard
• Sender IP is a remote peer IP or receiver IP
• Sender UDP port 49152 is a recommendation to have single source port in order to simply identify the related child session in Analytics
• Peer Vendor is Non-Versa
• Reflector mode set to stateless (as child sessions will start, measure, stop lifecycle and not a permanent)
• Enable Test Session
• Enable LEF for logging to Analytics
• Number of packets forever
• Repeat forever
• Repeat interval set to 60
• Session timeout 65
• Measurement interval 60

As a result of this configuration, a child session will be automatically created every minute to collect and push aggregated data into Analytics

3. Cisco configuration example

In this scenario Cisco router acts as TWAMP Responder with Control Server. The below configuration enables TWAMP to accept Control Channel session on UDP port 862. Once Control Channel is UP, Cisco router will act as a session reflector, which will dynamically respond to test sessions initiated by VOS.

ip sla responder twaamp
ip sla responder twamp-control 862

4. Versa Analytics data for TWAMP

Open Analytics menu. Navigate to Dashboard -> System -> Measurements Select your appliance and click on magnifying glass icon to see details of the datapath measurement. Data such as Two way delay, Forward & Reverse Delay, jitter or delay variation, TX & RX packets and errors for selected time interval will appear. Additionally on the bottom of Analytics section you can find similar aggregated statistics in a table view.

5. Summary

This article provides recommendations and guidance of how to configure TWAMP with a Control channel on Versa VOS and Cisco devices. It covers step-by-step setup procedures, highlighting key configuration parameters and best practices. Additionally, it covers analysis of TWAMP measurement data using Versa Analytics, offering insights into network performance, latency, and jitter for effective network troubleshooting and optimization.