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10G-25G-100G Network Upgrade: An Inevitable Roadmap for Future Data Centers

February 12, 2019

10G - 25G - 100G Network Upgrade: An Inevitable Roadmap for Future Data Centers

Driven by the bandwidth requirements of private and public cloud data centers and communication service providers, 100G experienced significant uptake, making network upgrade a necessary and inevitable trend. Until now, the majority of server vendors have already offered 25 Gigabit Ethernet NICs as the standard I/O option in their servers, driving the latest Ethernet speed transitions from 10G to 25G, 100G and beyond. Although 1G, 10G and 40G still represent a significant share of the enterprise market’s Ethernet ports, a transition to 25G and 100G has already happened more quickly than ever before. This post will highlight the evolutionary path of 25G, then give a comparison of 10G-40G-100G and 10G-25G-100G migration paths to help users make better choices for network upgrade.

10G-40G-100G Upgrade Path

While 100G and beyond is the next major milestone in hyperscale data center speeds, 40G may yet still have longevity in the industry. Traditional enterprises with tier 2 and tier 3 data centers that have lower density requirements and smaller budgets can reliably leverage the 40G architecture with 10G service speeds as the current building block.

40G Network Overview

Official development of 40G Gigabit Ethernet began in 2008, and is approved in 2010. It enables the transfer of Ethernet frames at 40 Gigabit per second. 40GbE runs on Quad Small Form Factor Pluggable (QSFP+) cabling, which can support high-bandwidth applications like video on demand and high-performance computing. The 40G network uses four transmission channels, each with a data rate of 10Gbps, making it higher efficiency and lower management cost. In data centers, 40G switches are used as the aggregation/leaf switches, while they can act as core/spine switches for small and medium enterprises.

As for now, 40G is developing rapidly and has gradually become a suitable solution for many small and medium-sized enterprises, but its development faces difficulties. Due to insufficient business and high product price for a long time, operators are still hesitating about whether to adopt 40G system. They may choose to skip 40G and directly deploy 100G systems. As for now, 100G technology is developing rapidly. Different from 40G, 100G has done a better job in standard follow-up, technical solution unification and industrial chain development. Therefore, the price of 100G products is expected to be reduced to the same level as 40G soon. At present, 100G has occupied the majority of the high-speed network market share and significantly curb the growth of the 40G market.

10G-40G-100G Migration Path

In this path, 10G equipment and cabling systems invested in the past will be utilized. 40G QSFP+ module is composed of 4 parallel 10G channels and 100G QSFP+ modules support a parallel channel rate of 10×10G. Therefore, in this type of 100G migration, the single-channel rate is based on 10G, while the migration path from 10G to 40G to 100G requires more fibers, resulting in more complicated cabling and higher cost. On the other hand, when QSFP modules are used in longer distance, such as QSFP+ LR4 optical module, they integrates 4 channels of 10G into one optical fiber link through wavelength division multiplexing (WDM). And this is part of the reason why the cost of QSFP optical modules remains high, especially for 40G modules with a longer transmission distance, such as QSFP+ ER4, which also increases cost for 100G network upgrade. Due to these two reasons, the 40G-100G migration path can cost much more.

10G-25G-100G Upgrade Path

Data centers are expanding at an unprecedented pace, driving the need for higher bandwidth between the server and switches. To cater to this trend, networking and the Ethernet industry are moving from 10G to 25G which offers significant density, cost and power benefits for server to top-of-rack connections.

Evolutionary Path of 25G

Ever since the 25GbE was initially proposed in 2014, companies like Google, Microsoft, Arista, and Mellanox, etc. have been pushing the development of the 25GbE standard for top-of-rack server networking. Up to till now, 25G products like 25G switch or SFP28, 25G DAC and AOC cables have received more and more recognition, and 25G servers are also becoming widespread, making preparations for 100G upgrade. These 25G network switches are often used as the ToR or leaf switches to connect the servers and terminal equipment. 25G Ethernet is an incremental update from 10G Ethernet. So for 25G and 10G Ethernet switches with the same port density, 25G switches and optics provide 2.5 times more performance and bandwidth than 10G Ethernet solution. And the high performance 25G SFP28 uses single-lane 25G SerDes technology similar in operation to 10G SFP+. These benefits allow existing 25G switch architectures to support link speeds faster than 10G with no increase in cable/trace interconnect, while keeping pace with the faster and richer growth trajectory of networking bandwidth, which helps reduce the power consumption and cost. Since the business needs to upgrade constantly, 25G network will be more popular in the future. Figure 1 highlights some of the key milestones of the 25G network from the year of 2014 to 2018.

EvolutionaryFigure 1: Evolutionary Path of 25G Ethernet

10G-25G-100G Migration Path

The single-channel 25G speed is 2.5 times the transmission efficiency of 10G, while in a 100G network, only 4 channels 25G modules are needed to achieve the 4×25Gb/s mode. This will greatly save fiber links, but this migration path will eliminate the original 10G equipment in the system. Even so, 25G servers and 100G switches have become ubiquitous in hyperscale data centers, gradually replacing previous 10G servers and 40G switches. This speed migration has boosted overall system throughput by 2.5x with small incremental costs. As the Ethernet industry continues to innovate and lay a path to higher networking speeds like 200G and 400G, the 25G-100G upgrade has been developed as an inevitable roadmap for future data centers. In general, this migration path is more economical. Its advantages are as follows:

1. Single-channel 4x25G modules will be cheaper than 10x10G modules. With the popularity of 25G technology, the price of QSFP28 modules continues to decrease.

2. The power consumption of 4x25G SFP28 is much lower than that of typical 10x10G SFP+, which also gives 25G an advantage in operating costs.

3. For optical fiber links, migrating from 10G to 100G requires using 10x10G channels, but only 4 channels are needed for 25G to 100G connections, which can greatly save link resources.

Migration Paths Comparison: 10G-40G-100G vs 10G-25G-100G

Before the 25GbE specification was released, the 10G-40G upgrade path is predominantly adopted as an option for enterprises, service providers and data centers to scale beyond 10GbE. However, with the emergence of 25GbE, 25G-100G upgrade path has gained more momentum by offering the cost per bit, power consumption and server rack density advantages which are the necessary enablers for widespread speed transition.

10GFigure 2: 10G - 40G vs 25G - 100G Upgrade Path Comparison

It can be easily found that there are some obvious advantages in the process of 10G-25G-100G migration compared to 10G-40G-100G path:

1. 25G-100G migration path can offer both CapEx (capital expenditures) and OpEx (operational expenditures) savings through backward compatibility, for investment protection and seamless migrations with consistent rack-design and reuse of the existing cabling infrastructure, avoiding costly and complex changes.

2. Single-lane 25G SerDes technology utilized in 100G to 25G connectivity is similar to that in 40G to 10G connectivity, but the performance is increased by 2.5 times, thus reducing the power and cost per gigabit significantly. This power savings will in turn result in lower cooling requirements and operational expenditure for data center operators. By reusing the existing cabling infrastructure, the 25G Ethernet enables seamless network migration to avoid costly and complex changes.

3. 25G Ethernet provides higher port and system density than a comparable 40G solution. The 25G-100G (4x25G lanes) networking migration path provides a lower cost per unit of bandwidth by fully utilizing switch port capabilities when compared to 40G-100G upgrade path.Therefore, upgrading directly from 40G to the faster 100G is cost prohibitive compared to the 25G Ethernet connectivity.

CurrentFigure 3: Current vs Future High Speed Ethernet Upgrade Mode

Suggestions for Choosing 100G Network Upgrade Path

The most important condition when planning to upgrade your network is to consider your business scale and future expansion. For some leading and giant companies, upgrading from 25G to 100G is the optimal way, as 25G has its obvious advantages which can satisfy the growing needs of the network. For a long term development, these big enterprises and data centers are willing to pay much higher fees to ensure the performances. While, for some small and medium enterprises, it is not necessary to give up your original 40G network and eagerly pursue 10G-25G-100G migration path. Because you should make sure your network adapters support 25G network. This one may seem obvious, as not all servers are shipping with 25G network adapters. In this case, it means you need to run additional connections by buying more switches and cabling, which can be a big cost. In a word, choose 10G-25G-100G migration path may imply additional fees. If the current network can fit your needs enough, you can stay in 40G, and upgrade to 100G on this base. But if you are planning a new network, you may have more choices. You don’t have to think about wasting your previous investment, and the only thing you need to consider is your business development and how much you are willing to cost for future network migration.


The demand for higher Ethernet speed and performance never stops for future data centers. By offering more bandwidth and higher port density with reduced power consumption and cost, the 10G-25G-100G upgrade path overturns the traditional 10G-40G-100G connectivity to improve data center efficiency, thus laying the foundation for further upgrade to 200G and 400G. But choosing which migration path mainly depends on specific demands and conditions, so it is better for network managers to look for some professional suggestions before making the decision. FS supplies various optical products and solutions to meet diverse applications in data centers and enterprise networks. If you want to know more details about 100G networks, please visit FS.COM.


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