What are Y.1564 and EtherSAM really about?

The names of ITU-T Y.1564 and EtherSAM are used many times interchangeably, but in reality, there are some important differences between them.

Y.1564

Rectified Y.1564 is a Quality of Service (QoS) and network performance ITU-T Ethernet-based service test methodology. This out-of-service testing procedures tests service turn-up, installation and troubleshooting of Ethernet-based services with the goal of assuring and verifying committed service level agreement (SLA) performances.

What makes the Y.1564 standard unique is that it enables complete validation of Ethernet SLA in one test.

Single-provider-view-of-Ethernet-service-areas

The focus of ITU-T Y.1564 is:

  • Validation tool – The methodology serves as a validation tool, ensuring that the network complies with the SLA by ensuring that a service meets its key performance indicators (KPI) at different rates, within the committed range.
  • Meeting KPI objectives – It ensures that all services carried by the network meet their KPI objectives at their maximum committed rate, validating that under maximum load the network devices and paths can service all the traffic as designed.
  • Soaking test – Service testing can be performed for a medium to long test period, confirming that network elements can properly carry all services while under a significant load extended over a significant period of time (sometime referred to as a soaking test).


Background

Prior to Y.1564, the most widely used testing tool to assess the performance of Ethernet-based services, was IETF RFC 2544, which was created to evaluate the performance characteristics of network devices in a lab. Since it includes throughput, burstability, frame loss and latency, with the lack of other standards, it became commonly used in real networks and is being used in Ethernet-networks globally. However, it does not include all required measurements such as packet jitter, QoS measurement and multiple concurrent service levels.

Unique offerings

Contrary to other methodologies, Y.1564 supports current service providers’ offerings, which typically consist of multi-services. It allows them to simultaneously test all services and measure if they qualify to the committed SLA attributes.

On top of that it also validate the different QoS mechanisms provisioned in the network to prioritize the different service types – allowing service providers faster deployment (as the need for repeated tests is eliminated) and easier service and network troubleshooting.

Bandwidth-profile

High flexibility

Y.1564 enables very high flexibility in simulating testing scenarios that are very close to the real active network traffic. It defines test streams (or “flows”) with service attributes aligned the Metro Ethernet Forum (MEF) 10.2 definitions. These Test Flows can be classified using various mechanisms, such as 802.1q VLAN, 802.1ad, DSCP and class of service (CoS) profiles.

These services are defined at the UNI level with different frame and bandwidth profile such as the service’s maximum transmission unit (MTU) or frame size, committed information rate (CIR), and excess information rate (EIR).With up 5 different frame sizes in single test.

RFC2544 vs. Y.1564:

While existing methodologies, such as RFC 2544, work in the link level – measuring its maximum performance, Y.1564 uses a different method. By deploying Y. 1564, KPIs (such are Bandwidth CIR/EIR/DISCARDED traffic, Frame Loss, Frame Delay and Frame Delay Variation) are measured and compared to expected values for each service. This ensures that it is within its committed range, or the threshold defined for guaranteed traffic, such as CIR (committed information Rate).

Y.1564 (EtherSAM) RFC 2544
Throughput Tests performance at the CIR and ensures that the KPI are met constantly during the test. Excess and discard are not ignored and measured as well, ensuring policing and shaping mechanisms were properly configured in the network. RFC 2544 only focuses on the maximum capabilities of a link with no separation of the committed and excess traffic, thus testing at the EIR level which is not guaranteed by the committed SLA (or more accurately the CIR).
Frame Delay Provides the peak latency and average latency measures during the test on all generated frames. Thus assuring that deviation out of the committed range or defined are identified, resulting in the actual latency of the service. RFC2544 tests one frame  in every test time, which doesn’t take into consideration any variation or peak that can occur over a longer test period.
Frame Loss Frame loss is measure is done during throughput test allowing for fast identification for any frame lost and reducing the service test time. Frame loss is measured during rate distribution throughput test, in which frames are generated at specific intervals of transmission rates. However frame loss distribution doesn’t align with committed and excess rate profiles leaving important KPI out.
Frame Delay Variation Frame delay variation is tested during testing with traffic generated up to the CIR ,ensuring proper traffic prioritization and forwarding. Not being tested by RFC2544. Requires additional test.


Additional resources:

To learn more about Telco Systems’ T-Metro 8001, which offers advanced OAM supporting hundreds of services with ITU-T Y.1731 SLM, RFC 2544 and Y.1564 measuring the network performance, click here

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