Full speed ahead with 400G Ethernet!

We’re making greater use of data networks than ever. Think about it: how many of these network-dependent technologies do you see being used every day?

• Internet of Things (IoT)
• cloud-based computing
• EDGE computing
• virtual reality
• ultra-high-definition (4K and 8K) video streaming
• artificial intelligence

The answer: probably more than you think.

And these are just today’s technologies. Who knows what future innovations will drive network traffic up even higher? Plus, the 5G era is just getting started, so expect this network usage trend to snowball.

That’s why network and data center operators continue to work with equipment manufacturers to validate 400G Ethernet-capable network elements in their labs. The success of this lab work has helped operators meet service level agreements (SLAs) with their customers who expect faster, larger-capacity data flows while also lowering cost and power consumption per bit (and increasing their own profitability). 

All of this means it’s full speed ahead with 400G!

How fast are 400G links? A quick technical deep dive

The quick answer: the actual line rate of a 400G Ethernet link is 425 Gbit/s. Yes, you read that right.

The IEEE P802.3bs standard defines the technical specifications of the 400G Ethernet data rate. The standard also establishes a mandatory forward error correction (FEC) mechanism to not only detect errors in the transmission but also correct them. The additional bits required for the FEC mechanism are included in the 425Gbit/s line rate.

What even makes 400Gbit/s transmission possible? It’s the adoption of 4-level pulse amplitude modulation (PAM4). Using PAM4, operators implement 8 lanes of 50G or 4 lanes of 100G for different form factors (i.e., OSFP and QSFP-DD). This optical transceiver architecture supports transmission of up to 400 Gbit/s Ethernet data over either multiwavelength or parallel fibers.

However, multilevel modulation creates higher analysis complexity, so we need advanced tools such as PAM4 eye diagram histograms and pre-emphasis and equalization capabilities to manage this complexity.

400G network deployments: where are we now?

Network operators are currently testing new network devices such as switches and routers that can support 400G client interfaces as well as other 400G transport equipment. They are also upgrading their infrastructure to support the surge in bandwidth requirements.

400G network deployments: what are the challenges?

In a word: several.

Optical transceivers are the most critical element of this rollout. Their development maturity, availability, cost, and reliability directly shape network deployments, affecting scalability, performance, and the ability to meet growing data demands.

Furthermore, many different types of transceivers are typically used in different environments over varying distances. QSFP56-DD and OSFP transceivers are being used in 400G networks in carrier labs and data centers while coherent optics are being deployed in data center interconnect, metro applications and submarine networks.

Meanwhile, in large data centers, port densification continues. Operations teams are increasing the capacity of aggregation links by upgrading them from 50GE to 100GE, and 100GE to 400GE links.

Network testing and monitoring have also become more important than ever. After all, the performance of 400G links is vital for the success of new 5G-enabled services. Latency measurements remain a key industry benchmark as operators assess the quality of experience offered by service providers. Optimal quality of experience also depends on data throughput, frame loss, latency variation (jitter) and other parameters.

With all the challenges inherent to 400G links, plug-and-play network deployment is just not realistic. Network operators will need to invest to make sure their networks efficiently support all services promised by new and emerging technologies. Investments must cover the physical (layer 1: fibers, connectors, connections, etc.) and higher level [layer 2 (Data Link-Ethernet) and layer 3 (Network – IP)] components.

400G network testing requirements: what are they?

Requirements differ based on context. Let’s talk about testing in the field, in carrier labs, and about testing services delivered.

400G testing in the field

Field technicians and engineers must upgrade their testing procedures to include elements required for 400G transmission. On the physical testing side, technicians must be able to assess connectors, interfaces and fibers for the higher performance standards required at 400G.

400G transceivers must be validated using criteria like:

• Bit error rate assessment
• Excessive skew
• Power consumption
• Temperature monitoring
• Physical evaluation of the signal using a pre-emphasis

400G Ethernet testing in carrier labs

Carriers are receiving new components from network equipment manufacturers, but they must thoroughly evaluate and stress these components in their own labs before using them in a 400G network. So carriers test and benchmark using standardized test procedures based on, for instance, RFC 2544 or bit error rate measurement.

Service delivery

The end customer is concerned about the performance of the service they receive. The quality of that service is determined by factors such as throughput, latency, jitter and frame loss. Service-level agreements (SLAs) define these parameters based on recognized, standardized procedures such as ITU-T Y.1564.

In order to meet SLA objectives, operators must validate not only layer 2 Ethernet frame performance, but also layer 3 IPv4 and IPv6 packet efficiency.

Is your transport network ready for 400G technology?

We are in the midst of a digital transformation in high-speed transport networks and the deployment of 400G technology is one of its most important enablers.

That’s why massive investment in solutions for 400G (and beyond) continue. A solid, reliable network infrastructure based on 400G links is being deployed, enabling a virtually limitless number of network connections.

Get the right testing, monitoring and analysis tools

EXFO’s FTBx-88480 Series offers all the test applications and advanced tools required to validate 400G networks. This solution is future-proof in that it not only supports current optical interfaces, but it's designed to handle new optical technologies as they become available—and built to go to 800G with a simple software upgrade.

EXFO’s FTBx-88480 solution includes the unique Open Transceiver System (OTS) that supports QSFP28, QSFP+, SFP28, SFP+ and SFP interfaces. It also supports coherent transceivers, including 100ZR, 400ZR and OpenZR+.

Upgrading network infrastructure is a constant challenge. EXFO’s solutions empower operators to tackle it successfully—now and in the future.