CenturyLink uses industry-standard testing to help ensure that your ethernet-enabled services perform correctly at turn-up and continue to meet your business needs. Below, is a detailed explanation of our testing methodology. If you have any questions, please contact your provisioning team representative or your network operations center (NOC) technician.
CenturyLink uses two types of EtherSAM tests:
In the telecom industry, this testing is also known as ITU-T Y.1564 and replaces the RFC2544 testing—which is now outdated. View the full test methodology.
Service configuration testing tests each stream individually to verify that the stream configuration in the network is correct.
The default configuration for this test is that each phase CIR/EIR/"traffic ramp police rate” will run for 5 seconds each for each stream. Given this, stream 1 should take approximately 15 seconds to complete before it moves on to stream 2; stream 2 should take 15 seconds to complete before moving on to stream 3, etc.
Note: The configuration test is the only test where the EIR and “overshoot” are used. Additionally, the EtherSAM service configuration is highly customizable to fit the service attributes of an ethernet service, whether it is a simple E-Line point-to-point or an IPVPN that uses ethernet as an access method.
Service performance tests test all enabled streams—at the same time—to verify that the network can handle all your purchased streams at the same time and at the purchased rate.
Note: The service performance test only uses the CIR value defined in the stream. All enabled streams are running at the same time (in parallel). Each stream receives a pass/fail verdict.
Note: The EtherSAM test results (available upon request) provide information for a “birth certificate” which might be delivered to you upon the completion of the service order.
Occasionally, the new service may require additional testing. The EtherSAM (ITU-T Y.1564) as defined in the default or customized frameworks may not provide the information required to understand why a service does not work as expected at the layer 4 of the OSI model, this is especially true for TCP.
To address such shortage, the IETF and multiple vendors and service providers worked on a standardized framework for TCP throughput testing, such testing methodology is called RFC 6349, it is defined in https://tools.ietf.org/html/rfc6349.
CenturyLink has chosen EXFO as their vendor for test instruments and service assurance equipment in its central offices, in addition to the RFC6349 test suite, EXFO has also provided their own contribution to TCP testing, they call this test methodology application ExacTCP, it is based in 6349 and other RFCs that provide further standardization, TCP window control, capability of running a single TCP stream on the pipe and reduction of the number of variables at play compared to other testing methodologies. Both RFC6349 and ExacTCP methodologies implemented by EXFO are FPGA hardware based and dedicated just for the test.
CenturyLink understands that, in some instances, if none of the three described standardized methodologies are able to provide satisfactory results or are unable to help to resolve a circuit throughput issue observed at the upper layers of the OSI model, the CenturyLink technician might fall back to test with iPerf, but note that because of the lack of standardization, iPerf has been proven to be more time consuming and in average requiring more truck rolls than the standardized methodologies in most cases.
| Layer 4
|ITU-T Y.1564sam UDP||UDP flow capable, EMIX packets that emulate real world traffic, QoS markings validation using differentiated services||Yes|
|ExacTCP||Customizable to 1 TCP flow connection, TCP RWIN scaling as per RFC1323||Yes|
|RFC6349||Multiple TCP flows, Path MTU Discovery. Calculates BDP for multiple TCP windows||Yes|
|iPerfv2||Open Source, available for multiple platforms, UDP & TCP, incompatible with iPerfv3||No|
|iPerfv3||Open Source, available for multiple platforms, UDP & TCP, incompatible with iPerfv2||No|