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Making Progress Toward 400 Gigabit Ethernet

by Greg.Hankins on ‎11-27-2012 09:21 AM (1,174 Views)

I want to give you a quick overview and update on the industry’s progress toward 400 GbE as the next Ethernet speed.  Though 100 GbE is only two years old, it’s important that we start working on the next speed now, so that we have the technology shipping when there is demand from network operators to deploy higher speed Ethernet.  The Call for Interest (CFI) to start the 400 GbE Study Group that will work on defining a new Ethernet standard was just announced yesterday, and is scheduled to be held on March 18, 2013 at the next IEEE Plenary meeting.

Here’s a little history on how we chose 400 GbE as the next Ethernet speed.  First, the IEEE 802.3 Ethernet Bandwidth Assessment (BWA) Ad Hoc was formed in 2011 to evaluate future Ethernet wireline bandwidth needs.  The BWA gathered input from the industry so that we would have accurate bandwidth growth data and requirements for the next Ethernet speed.  The full report was released in July, and found continuing growth of bandwidth demands in core and transport layers beyond 100 GbE.  If you are just interested in a summary and overview of the findings, then have a look at Scott Kipp’s NANOG56 presentation from last month.  Next, the IEEE 802.3 Higher Speed Ethernet Consensus (HSE) Ad Hoc first met in July to develop consensus on the next speed of Ethernet based on the BWA data.  The November IEEE Plenary meeting was just held a couple of weeks ago, where the HSE Ad Hoc made progress on the draft 400 GbE CFI presentation.

Why Not TbE?

I’d really love for us to build TbE!  But, in order to make TbE economically feasible the cost per bit needs to be at or below the cost of 100 GbE.  This means it would make sense for us to reuse current 100 Gbs technology, which implies a TbE architecture using 40 x 25 Gbps signaling lanes.  Unfortunately, reusing 25 Gbps signaling means the resulting size of the pluggable media module, and the large amount of interface signals would simply be impractical to develop.  Several good presentations were given at the IEEE HSE Consensus Ad Hoc meeting in September about why we should work on 400 GbE now and defer TbE for a few years.  There are a couple of alternatives to 25 Gbps signaling, such as using advanced multilevel or phase modulation signaling, but these are still immature technologies that need more development before we can get the performance and low-cost manufacturing needed for volume production.  Higher signaling rates will make TbE more feasible, but this technology isn’t expected to be available for the next several years.

What’s Next?

As the 400 GbE CFI is now scheduled for March 2013, it means we will have the 400 GbE standard in mid-2015 at the earliest.  It’s likely that the first generation of 400 GbE will use 16 x 25 Gbps signaling and that the first interfaces will be available in the 2016 timeframe.  The questions that still need to be answered are the physical layer specifications for reaches and media, and this is what the Study Group will start working to define first.  As we had for 100 GbE, the interfaces for 400 GbE will use a pluggable media module which gives network operators the most flexibility and choice. It’s likely that the 400 GbE media module will be called CDFP, which is short for “CD (400) Form-factor Pluggable”.  As 400 GbE evolves with faster signaling technology, the second generation is expected to use 8 x 50 Gbps signaling which the Optical Internetworking Forum is already beginning to define.  The third generation of 400 GbE is expected to use 4 x 100 Gbps signaling which has more advanced electrical and optical signaling technology that is being worked on in labs today.  These key 100 Gbps signaling technologies will also be the building blocks for TbE and aren’t expected until after 2020.  Stay tuned for more updates as we follow the road to 400 GbE!