At OFC 2024 we were privately showing what we believe is the first 1.6T network Ethernet traffic generator. Actually, Keysight showed two of them to prove this was not just a unicorn box. It was amazing to see hundreds of trillions of packets flow over the days of the show with no errors and short forward error correction (FEC) tails. At one point I had to jog my memory as to what is larger than a trillion.
At the show, we had a customer ask why they needed to test their transceivers/receivers (optics) with an Ethernet protocol tester (layer 2/3) if they were fully testing at layer 1 with bit error ratio testers (BERTs) and getting the required results. So here is a very short technical answer that deserves its own white paper. The reality is with the introduction of FEC, testing with BERTs is not enough because it is possible to have acceptable BERT test results but have less than ideal FEC results. Without getting into too many details, an Ethernet traffic generator can look at FEC results across all lanes of traffic, which is effectively a system level test.
The importance of testing:
Let’s make this a little more real. Years ago, while working at a service provider Metro Ethernet company, my team had to qualify a router for a standard set of optics. I knew the optics worked. I had “tested” the router myself by plugging in the optics in and seeing if it could pass traffic. Was I ever wrong. Once we connected the box to a traffic generator and passed line rate traffic at high/low temperatures and high/low voltages with small packets, we saw problems with some of the optics in that box. We needed hardware fixes and I learned my lesson – proper testing is critical to success.
Fig 1: Ethernet speeds from the 2024 Ethernet Roadmap from the Ethernet Alliance
This diagram from the Ethernet Alliance shows the introduction of new Ethernet speeds over the years. The big takeaway for me from this graph is the shorter time periods for new standards to go to market. The time from a standard being available to a product coming to market is also decreasing, while the complexity to support the ever-faster Ethernet speeds also increases. With the addition of PAM4 signaling for 400GE and higher speeds, the level of difficulty in testing has increased as the final end-users’ requirements for higher reliability and in-network performance are well beyond those set in the industry standards.
Then there is the nature of the data itself. We have very demanding protocols like MACSec that require on the fly encryption of data at line rate plus the ability to change encryption keys on the fly without dropping packets. These scenarios are not easy to create manually and require tools like Ethernet traffic generators.
Power and cooling:
Along with ensuring that data flows well, there is the additional challenge of power and cooling. The new 400ZR/ZR+ and the latest 800ZR Coherent optics, shown at OFC 2024, when run at line rate use close to 30 watts of power. In other words, this is two to three times the power consumption and heat generation of previous generations of LAN optics. In recent multi-vendor interoperability plug-fests, we noticed that when these new coherent optics were run at line-rate, they would overheat as a result of the network equipment not being able to cool them. Some solutions may not even support full chassis implementations of optics due to the increased cooling requirements. Optics manufacturers need to test their optics to not only ensure that the bits are being received but that the clock data recovery, state mechanisms and protocols are all working as designed – at line rate and in production-like environmental conditions.
Conclusion:
So in real world deployments, while doing baseline layer 1 testing is critically important, testing with layer 2/3 protocols under different environmental and stressed conditions with Ethernet traffic generators will often uncover issues that affect device performance in deployments.
As we push the envelope with higher Ethernet speeds and longer optical reach distances, Ethernet traffic generators play a critical role to ensure reliable and deliverable solutions. This applies to optics manufacturers, network equipment manufacturers, enterprise/service providers and hyperscalers. For more on this topic, check out our Ethernet traffic generators and protocol load test products.