Are You Ready For 400G Ethernet?

The rapid development in telecom industry is driving massive demand for higher bandwidth and faster data rate, from 10G to 40G and 100G, will this keep going on? The answer is definitely “Yes”. Some time ago, migration from 10G to 40G or 25G to 100G has been a hot spot among data center managers. While recently, 400G solutions and 400G components are coming. Are you ready for 400G? This article will share some information about 400G Ethernet.

Overview of 400G

In the past couple of years, modules with four 25/28G lanes or wavelengths are the solutions for 100G Ethernet. However, they were expensive at the beginning. Until 2016, the optical components industry has responded to the demands with 100G solutions that already cost less per gigabit than equivalent 10G and 40G solutions, and new developments to further drive down cost and increase bandwidths. The next generation is 400G Ethernet. The IEEE has agreed on PSM4 with four parallel fibers for the 500 meters 400GBASE-DR4 specification that is part of the IEEE802.3bs standard being developed for approval by the end of 2017. The industry is already developing optical components for 400G Ethernet solutions. The following figure shows telecom and datacom adoption timelines.

Telecom and datacom adoption timelines

We can visually see that telecom/enterprise applications first adopted 100G technology in the form of CFP modules. Data centers generally did not adopt 100G interfaces until the technology matured and evolved towards denser, lower power interfaces, particularly in the form of QSFP28 modules. However, as the hyperscale data center market scales to keep pace with machine-to-machine communications needs, data center operators have become the first to demand transmission modules for data rates of 400G and beyond. Therefore, the 400G era is now upon us.

Modules for 400G

We know that the QSFP28 modules for 100G Ethernet and SFP28 modules for 25G Ethernet are now the dominant form factors. Though CFP, CFP2 and CFP4 modules remain important for some applications, they have been eclipsed by QSFP28 modules. To support higher bandwidth, what is the right module for 400G? The first CFP8 modules are already available. QSFP-DD is backward compatible with QSFP, and OSFP may deliver better performance, especially as networks move to 800G interfaces.

CFP8 module: CFP8 module is the newest form factor under development by members of the CFP multisource agreement (MSA). It is approximately the size of CFP2 module. As for bandwidth density, it respectively supports eight times and four times the bandwidth density of CFP and CFP2 module. The interface of CFP8 module has been generally specified to allow for 16 x 25 Gb/s and 8 x 50 Gb/s mode.

100G CFP to 400G CFP8

QSFP-DD module: QSFP-DD refers to Quad Small Form Factor Pluggable Double Density. It uses eight 25G lanes via NRZ modulation or eight 50G lanes via PAM4 modulation, which can support optical link of 200 Gbps or 400 Gbps aggregate. In addition, QSFP-DD module can enable up to 14.4 Tbps aggregate bandwidth in a single switch slot. As it is backwards compatible with QSFP modules, QSFP-DD provides flexibility for end users and system designers.

QSFP-DD vs QSFP

OSFP module: OSFP (Octal Small Form Factor Pluggable) with eight high speed electrical lanes is able to support 400G (8x50G). It is slightly wider and deeper than the QSFP but it still supports 36 OSFP ports per 1U front panel, enabling 14.4 Tbps per 1U. The OSFP is able to meet the projected thermal requirements for 800 Gbps optics when those systems and optics become available in the future.

OSFP module

Conclusion

Judging from the current trends, 400G will become the mainstream in the near future. But there are still some challenges for it to overcome, such as high capacity density, low power consumption, ever lower cost per bit, and reliable large-scale manufacturing capabilities. You never know what surprise the network will bring to you, let’s wait and see the 400G’s time.

400G CDFP Vs. CFP8 Module

400 Gigabit Ethernet was planned to be released in December this year. It is designed to meet IEEE P802.3bs Task Force standard and to apply to both metro and long-haul networks. The 400GbE operates over 100 m of multimode fiber, 500 m of singlemode fiber, 2 km of SMF, and 10 km of SMF. 400G CDFP and CFP8 are two form factors of 400G Ethernet technology. This article would give a introduction to 400G CDFP and CFP8 modules and make a comparison between them.

400G Ethernet

Introduction to 400G CDFP Module

The CDFP is short for 400 (CD in Roman numerals) Form factor Pluggable, which is designed to provide a low cost, high density 400 Gigabit Ethernet solution. It features as front panel, hot-pluggable, 16 channel and 400 Gbps module. CDFP will be a short reach module, which enables 4 Terabit line cards. From the perspective of interface, it is very similar to the QSFP and CXP modules. CDFP developers have targeted using the developing IEEE802.3bs specification for Ethernet 400GBaseSR, 400GBaseLR.

  • 5 meter direct attach cables
  • 100 meter multimode fiber
  • 500 meter parallel singlemode fiber
  • 2 kilometers of duplex singlemode fiber

400G CDFP Module

Figure2: 400G CDFP Module

Information About 400G CFP8 Module

Following CFP2 and CFP4 naming, CFP8 module was proposed in the year 2015. CFP8 is a new form factor which is still under development by members of the CFP multisource agreement (MSA). The form factor of CFP8 is amounting to CFP2, but it supports 4 × 100G and 400G, for example, 4×CFP2’s 1×100G. The CFP8 uses a new 16 × 25G electrical I/O connector. The CFP8’s interface has been generally specified to allow for 16 × 25 Gb/s and 8 × 50 Gb/s mode. From the point of bandwidth density, the CFP8 module is eight times larger than the CFP module and four times larger than the CFP2 module.

400G CFP8 module operation

Figure3: 400G CFP8 module operation

Example IEEE specifications supported by CFP8:

  • 400GBASE-SR16 parallel MMF (16x25G NRZ)
  • 400GBASE-FR8/LR8 duplex SMF (8x50G PAM4 WDM)
  • 400GBASE-DR4 parallel SMF (4x100G PAM4)
  • CDAUI-16, CDAUI-8

Form factors of CFP modules

Figure4: Form factors of CFP modules

Among all the specifications on the above, 400GBaseDR4 is the most revolutionary one. 400GBaseDR4 uses 4x100G parallel SMF PAM4 signaling technology. This technology is also aimed at fitting in the CFP4 21.5-mm width module size, while using 12 (SMF) fibers within a 1×12 MPO optical connector and the host board electrical 56-pin edge connector.

Low power consumption is also a distinctive feature of CFP8. Active optical modules have been widely deployed in the process of data transmission, but some of them or some copper applications really cost a lot and consumes much power. CFP8 module uses internal mid-board optical or electrical interconnect flyovers and bulkhead MPO or MXC connectors to connect the switch. This reduces power consumption to a great extent.

400G CFDP Vs. CFP8
—Form factor

CDFP was proposed earlier than CFP8, it has larger form factor than CFP8.

—Supported fiber type

CDFP supports passive and active copper cable, active optical cable and multimode fiber while CFP8 supports singlemode and multimode fiber.

—Transmission distance

CFP8 modules support longer data link distance compared with CDFP modules.

—Applications

The CDFP modules provide a very versatile solution for data center interconnects. CFP8 would be used in high-density 4x100GbE fan-out applications, such as datacom applications or in ITU-T for telecom applications.

Conclusion

This article mainly discussed about CDFP, CFP8 and their differences in form factor, supported fiber type, transmission distance and applications. There is no doubt that 400G Gigabit Ethernet is an irresistible trend for future Ethernet development.