25 Gigabit Ethernet Is Arriving to Make a Difference

Date Announced: 06 Oct 2016

25 Gigabit Ethernet (25GbE) is a proposed standard for Ethernet connectivity in a data center environment, developed by IEEE 802.3 task force P802.3by. It was formed in July 2014 to support the specification of single-lane 25Gb Ethernet and dual-lane 50Gb Ethernet technology. Companies like Google, Microsoft, Arista and Mellanox formed the 25 Gigabit Ethernet consortium in 2014. Some may question the need for this technology, but they will soon see thebenefits. 25 Gigabit Ethernet is arriving to make a difference.

Single-lane design makes 25 Gigabit Ethernet shine. It means the electrical signaling on the chip that would power an Ethernet port. Because the design of 40 GbE was based on 10 GbE, a 40 Gigabit chip is manufactured with four pins, which create four channels, also known as lanes, of 10 Gbps signaling. Originally, 100 GbE had a similar heritage, with its initial design in 2010 using ten lanes of 10 Gbps. As standards bodies sought to improve the efficiency of 100 GbE in the coming years, its second generation was built on a totally new signaling scheme: four individual lanes of 25 Gbps. Reducing the number of pins on the chip makes it less expensive to produce and less power-hungry.

The single-lane design will give 25 GbE a lower cost per bit than 10 GbE, enabling cloud providers and large-scale data center operators to deploy fewer switches while still scaling their network infrastructure to meet demand. When compared to 40 GbE, the 25 GbE specification is also expected to lower power and cooling costs significantly in two ways: having only one pin on the chip draws less power, as does having to deploy fewer switches.

Cloud computing is another factor that drives 25 GbE. Not only are cloud providers looking to decrease cost and improve density, but improvements in server speeds has rendered to 10 GbE, which is too slow. Many of these environments have standardized on a top of rack (ToR) technology, and keeping up with these connections at 10 GbE requires more switches in the rack and therefore higher cost. Accordingly, the earliest deployments of 25 GbE will take place in cloud and hyper scale data centers, followed later by enterprise data centers. 25 GbE also works from a scalability standpoint. With up-links migrating to 100 GbE using the same type of technology, it makes sense to increase the switch-server speed at the edge to 25 GbE.

The 100G standards such as 100GBASE-LR4 and 100GBASE-ER4 are comprised of four lanes of 25 GbE over single-mode fiber using course wavelength division multiplexing (CWDM) technology. The 100GBASE-SR4 standard is with 4x25G per lane over multimode fiber. 100GBASE-SR4 QSFP28 fiber optic transceivers are available for this application and have been successfully deployed in operational networks. With the same footprint as the 40G QSFP+ for four 10G lanes, the QSFP28 essentially offers 250 percent more density. It also supports direct attach copper cable assemblies, and active optical cable assemblies. SFP28 optical transceiver modules for one lane of 25G are also available and most often seen where one QSFP28 cable breaks out to four SFP28 cables. With 4x25G per lane component technology already available, the process to go to a single 25G lane is a simple one that requires very minor changes and significantly reduces cost compared to 40 GbE using four 10G lanes.

As a professional manufacturer in optical communication industry, Fiberstore provides a complete range of fiber optic products to meet the market demands. And recently 25G SFP28 to SFP28 DAC and 100G QSFP28 to 4 SFP28 DAC are launched. 

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