Physical Layer Testing

Test. Improve. Repeat.

Physical Layer testing is more important than ever

Testing Ethernet using 56/112 Gbps SerDes and advanced modulation formats like PAM-4 require extra focus on the Physical Layer (Layer 1). At these high speeds, signal integrity degrades quickly after transmission over few meters due to things like frequency dependent loss, inter-symbol interference and cross talk.

Standards and technology evolve rapidly, and developers of semiconductors and network equipment need to verify the performance of their products before they reach the market. Therefore, Ethernet test equipment must include tools for testing at Layer 1 as well as L2 & L3 traffic generation and analysis. Furthermore, test equipment must be future proof with the flexibility to add new test and management features as standards and new use cases evolve.

The Physical Layer functions are handled in the PHY and include the PCS, FEC, PMA, PMD and AN sub-layers.

PCS lane level testing

The PCS sublayer of the PHY operates on a number of parallel PCS lanes. After transmission these lanes needs to be identified and aligned relative to each other. A typical test case therefore involves to insert user-defined skew per Tx PCS lane to test that the DUT’s receiver is able to handle skew variations appropriately within the limits defined by the standard.

Forward Error Correction testing

The Forward Error Correction (FEC)  is an important part of the PCS sublayer that needs to be tested as well. There are several different types of FEC-schemes dependent on the specific Ethernet speed. PRBS generators and error inserting from the Ethernet test equipment can be used to verify the BER performance both pre- and post-FEC.

Equalization

The FEC can only work if the amount of pre-FEC bit errors is not too high. For transmission of high-speed Ethernet over electrical cables equalizers are needed at both the transmitter and the receiver to improve the signal integrity. The equalizers must be tuned to optimize the signal quality for each lane and the specific transmission medium used.

Auto-Negotiation and Link Training

Auto Negotiation (AN) and Link Training (LT) are key elements of Ethernet transmission over electrical connections and can reduce overall installation time, minimize the risk of configuration mistakes and optimize performance. During the AN process, two connected devices exchange information about their transmission speeds and FEC abilities and agree on a common set of transmission parameters. LT is then used to automatically tune the transmit equalizer settings at each device for minimum BER at the selected transmission speed.

Although the AN and LT protocols are standardized by IEEE802.3 it has proven challenging for developers of semiconductors and network equipment to verify performance of their products. Slight differences in implementations may cause products to fail in interoperability tests against third parties. And often vendors have a hard time troubleshooting what the root cause of the malfunctioning.

Xenas’ Z800 Freya ANLT Test Appliance is designed for performance verification and troubleshooting of the AN/LT protocols.

Z800 Freya Test Modules

For advanced Layer 1 testing Xena, offers the Xena Z800 Freya test modules supporting up to 800Gbps over 112G SerDes and PAM-4 and a range of advanced Layer 1 test features. Z800 Freya can be installed in either the robust scalable 4U XenaBay with space for up to 12 test modules, or the small, easy-to-transport 1U XenaCompact with just one test module.

Z800 FreyaCompact ANLT Test Appliance

Xena’s award-winning Z800 FreyaCompact ANLT Test Appliance makes it quick and easy to test AN/LT protocol implementations on 112G SerDes-enabled devices.

The user-friendly software lets developers step through the protocols one message at a time to identify possible errors or timing issues in the implementation.

The Z800 FreyaCompact ANLT Test Appliance can also test the true equalizer performance of a remote unit by disabling automatic equalizer adaptations in the tester unit.

Xena’s test solutions for Physical Layer

Broad range of test modules

Xena offers a selection of test modules for testing all Ethernet speeds from 10Mbps to 800Gbps.

Our range includes the latest Ethernet technology with 112G-based SerDes and PAM-4 in our Z800 Freya product line. For testing and debugging AN/LT protocols we offer our dedicated Z800 Freya Compact ANLT Test Appliance.

Easy-to-use software

Xena’s test solutions include feature-rich software for generating Ethernet traffic and analyzing the result. The primary tool is XenaManager.

There are also test suites for running standard tests such as RFC2544, RFC2889, RFC3918 and Y.1564, and specialized AN/LT tests along with a comprehensive range of powerful scripting and test automation options such as Xena OpenAutomation (XOA), an open-source test automation framework featuring a Python API that runs on any OS.

Robust chassis choices

Choose between the robust scalable 4U XenaBay with space for up to 12 test modules, or the small, easy-to-transport 1U XenaCompact with just one test module.

Exceptional value

All our solutions include the Xena Value Pack which consists of 3 years’ SW updates, 3 years’ HW warranty, free online/email support for the lifetime of the product and free product training.

Together with our low port-pricing, this represents significant savings on the TCO of your Ethernet traffic generation and analysis solutions.

Xena solutions

… for testing Physical Layer 1

White Papers

… for Physical Layer 1