May 1, 2014, Ethernet Technology Summit, Santa Clara, CA—John D'Ambrosia from Dell envisioned the paths leading to a TbE network. The efforts in defining the next-generation transport technologies is starting now.
Speed will always exist as a limiting factor in all electronics. For networks, the latest efforts are to get to 400 GbE, even though many users are still on older technologies down to 10/100 base-T. The standards groups are defining 400 GbE in the 802.3bs task force which started in March. Ratification is expected by 2017.
Until the 400 G is ready, the industry still needs the two top speeds, 40/100 GbE to address the changes in the core and server I/O data rates. Now networks need to have interoperability from 10 G to 40 G and 100 G in a single system. Systems have 10 GbE at the servers which may be feeding 1 GbE to edge devices. The 40 GbE is the datacenter backbone and the 100 GbE powers the service providers. The fact that no one really knows the final configuration for 100 G further complicates the issues, whether it should be 4 X 25 G or 10 X 10 G.
The transport and modulation technologies to choose from are QSFP (Quad Small Form-factor Pluggable) and CFPfor optical modules. A multi-lane gearbox aligns the 10/40/100 data streams which feeds the forward error correction (FEC)circuitry. These streams the go to a modulator to feed the network links.
The users will pick cables for either speed or density, 4 X 10 for 40 G or 1 x 40 G. 400 G can be 10 X 40 G or 4 X 100 G. The trend is to figure out how to build up the high end and manage the data flows. The tradeoffs between granularity and simplicity are complex. The drivers for higher bandwidth are in cloud-scale datacenters, Internet interchanges, wireless infrastructure, and video distribution. A major ecosystem issue is the need for back compatibility to the slower data rates.
For the 400 GbE families, transport is likely to be up to 500 m in parallel single-mode fibers. This solutions will depend upon the costs and the ability to develop the rest of the 400 G infrastructure. Uses will need to look at future apps and technologies to determine the best path going forward. The technologies will become more complex since latency and FEC efforts stack up.
The potential for electrical signaling with 25 G lines would be possible with a 16 X 25 G configuration, and might be upgradeable to 50 G in the future. The proliferation of lines may also invite looks at non-serial transport. For example, an optical link would have lots of choices at 100 G per wavelength. A serial protocol is not the only possibility.
In addition, 16 X 25 G may be too expensive and not dense enough to fit into a backplane or front panel. For shorter reach, there is already a specification in process for 100 Gbase-T, which would be much more space efficient. The defining parameter may be power.
The Ethernet industry is moving beyond 10 G and will soon be above 25 G. To get to 400 G and eventually to 1TbE will require getting around the pesky laws of physics. The industry needs to perform lost of R&D to enable the transition to the next speeds.