FS 25G Portfolio for Data Center 25G/100G Leaf-Spine Network

Updated on Jan 8, 2021 by

Note: FS has discontinued Cumulus Linux system for N-series switches. As per our policy, customers will continue to get support from FS technical assistance team, and the valid warranty provided is maintained on the product. For customers who are interested in FS N-series switches, you can choose either bare metal ones or those loaded with FSOS.


25G Ethernet is a standard for Ethernet connectivity, which is developed by IEEE 802.3 Task Force P802.3by. Looking back at the evolution of Ethernet standard, 40G and 100G standards have long been active in the market since 2010, while 25G standard was not introduced until 2016. It seems that 25G standard is a step backward, as 40G and 100G already exist. But in fact, the emergence of 25G standard indicates that the market needs a cost-optimized solution for server-to-switch connectivity.


What Is 25G/100G Leaf-Spine Network and Why Use It?

25G/100G Leaf-Spine network architecture contains two layers — the spine layer and the leaf layer. The spine layer is the backbone of the network, where every leaf switch is interconnected with every spine switch. The leaf layer consists of 25G access switches that connect to devices such as 25G servers, firewalls, and edge routers.

In general, 25G can provide 2.5 times the performance of 10G as well as offer higher bandwidth at the same power consumption. When data center operators apply 25G based server, 25G offers the benefit of reusing the same server rack designs and works with the same cabling infrastructure. In addition, most switch silicons that support 25G and 100G are backward compatible with 10G and 40G speeds, providing great flexibility to mix and match port speeds with a gradual migration to higher speed servers.


How to Design a 25G/100G Leaf-Spine Network?

In cloud and hyper-scale data centers, the Leaf-Spine network can create a fast, predictable, scalable, and efficient communication architecture for data center switches. When designing a Leaf-Spine architecture, there is one important factor to consider—oversubscription ratio. It is the ratio between downlink ports (to servers/storage) and uplink ports (to spine switches). Generally speaking, a 3:1 oversubscription rate between leaf and spine layer is deemed acceptable. The following figure shows a typical 25G/100G Leaf-Spine network architecture.how-to-design-25g100g-leaf-spine-network.jpg

Figure 1: 25G/100G Leaf-Spine Network Design


FS Provides A Full 25G Portfolio for 25G/100G Leaf-Spine Network Deployment

Since the introduction of 25G Ethernet, its low-cost and high-efficiency advantages have been favored by many cloud computing providers. Therefore, many suppliers provide a variety of 25G products. FS can offer a complete range of 25G products. The 25G products are available in switches, modules, cables, etc. Now we will introduce a series of FS 25G products to guide your purchase.25g100g-leaf-spine-network-deployment.jpg

Figure 2: FS 25G/100G Leaf-Spine Network Solutions

N8520-48B6C 25G Leaf Switch

N8520-48B6C 25G switch is a ToR or Leaf switch that combines with Cumulus Linux network operating system, which can be deployed in a wide range of opening networks, including large scale layer 2 and layer 3 cloud designs, overlay networks, virtualized or traditional enterprise data center networks. Additionally, the N8500-48B6C switch is equipped with abundant advanced Layer 2 and Layer 3 features, such as VXLAN, MLAG, IPv4/IPv6, and so on, which make it ideal for traditional or fully virtualized data centers.25g-switch.png

Figure 3: FS N8500-48B6C 25GbE ToR/Leaf Switch

25G Server Adapter

25G server adapter (PCI Express x8 Dual Port SFP28) based on Intel XXV710® chipset, is compatible with PCIe x16 slot. It delivers excellent performance for 25GbE connectivity that is backward compatible with 1/10GbE, making the migration to a higher speed easier.25g-nic.jpg

Figure 4: FS 25G Server Adapter

25G Fiber Transceivers

For connections between leaf switches and servers, FS offers 25G SFP28 (including 25GBASE-SR, 25GBASE-LR, and 25GBASE-ER) and 25G WDM SFP28 transceivers. For all those transceivers, we provide a lifetime warranty to ensure product quality and the transceivers are all compatible with famous brands such as Cisco, Arista, Brocade, Mellanox, etc.to satisfy varied needs on the market.25g-transceiver.jpg

Figure 5: FS 25G SFP28 Fiber Transceivers

25G DAC/AOC Cables

For short-distance cabling solutions within a rack or between adjacent racks, FS provides 25G SFP28 DAC cables for transmission distance less than 5m, 25G SFP28 AOC cables for up to 30m. In addition, FS supplies 100G QSFP28 to 4x25G SFP28 DAC/AOC cables to achieve direct connections between spine switches and servers. They are the ideal cables for the interconnection of switches, routers, storage devices, and servers.dac-aoc.jpg

Figure 6: FS 25G SFP28 DAC/AOC Cables


FAQs on FS 25G Products for 25G/100G Leaf-Spine Network

FS provides a wide variety of 25G portfolio for 25G/100G Leaf-Spine network deployment. Here are some frequently mentioned questions for your reference when purchasing them.

Q: Why would I trust FS compatible direct attach cables?

A: Besides the price advantage compared to branded cables, FS DACs also maintain the same performance and reliability. To satisfy customers' needs of high performance, all of our DACs are tested multiple times in mainstream original brand switches in the test center before shipped out. What's more, using compatible optics in brand devices will not negatively affect manufacturers' warranty if that's your concern.

Q: Can I connect switch-to-server using copper cables for under 5 meters?

A: Yes. FS provides SFP28 DAC copper cables for server-to-switch connectivity under 5 meters.

Q: What kind of cables should I use for the distance longer than 5 meters?

A: FS offers SFP28 AOC cables or SFP28 modules with LC cables for distance longer than 5 meters.

Q: Can I have different compatibilities for each end of my direct attach cables?

A: Yes. FS supplies customized dual compatibility solutions for direct attach cables so that you can choose compatibilities for each end individually. All you need to do is to select "Dual Compatibility Solutions" option in Compatible Brands drop-down box and note down your devices' model on the custom page.

Q: Does FS provide customized Arista Networks 25G DAC cables?

A: Yes. FS provides cost-effective customized 25G DAC cables compatible with major brands like Cisco, Arista, Juniper, Mellanox, Generic, etc.

Q: What lengths do FS offer for 100G QSFP28 to 4x25G SFP28 passive direct attach copper breakout cables?

A: FS offers 100G QSFP28 to 4x25G SFP28 passive direct attach copper breakout cables in 1m, 2m, 3m, 5m and inquiries for customized length are also welcomed.

Q: Can the SFP28 be used in SFP+ slot, and what speed will I get?

A: Yes. SFP28 is backward compatible with SFP+ ports and will work sufficiently. But SFP+ is designed to operate at 10Gb/s instead of SFP28 at 25Gb/s. Therefore, you will get 10G.

Q: Does FS offer 25G CWDM 80km modules?

A: No. FS currently provides 25G CWDM modules with the wavelength from 1270nm to 1330nm of 10km.

Q: What is the maximum power consumption of FS QSFP28-LR4-100G transceivers?

A: The maximum power consumption of FS QSFP28-LR4-100G transceivers is 3.5W. If it draws greater than 3.5W, FS can not guarantee the performance since there are other dependencies like airflow direction, ambient temperature, elevation and etc.

Q: Which single-mode 100G QSFP28 module that compatible with Arista can be used to break out 100G in 4x25G lanes?

A: Among the 100G QSFP28 modules, FS recommends QSFP-100G-PSM4 to meet your needs.

Q: Can FS 100G QSFP28 to 25G SFP28 module support Juniper devices?

A: Yes. FS 100G QSFP28 to 25G SFP28 modules not only support Juniper devices but also support other major brands like Cisco, Arista, Dell, Mellanox, Generic, Extreme, etc.

Q: Does FS provide 25G modules that support both Arista and Mellanox switches?

A: Yes. FS provides 25G modules that can support both switches, for example, SFP-25G-SR.

Q: Does FS offer 25G BiDi modules?

A: Yes. FS offers both 25G BiDi and industrial 25G BiDi SFP28 modules with a transmission distance of 10km.

Q: Can the N8520-48B6C 25G switch operate at 10/25G for the SFP ports and 40/100G for the QSFP ports?

A: Yes. This switch supports up to 48 x 10/25 GbE and 6 x 40/100 GbE connections.

Q: Can N8520-48B6C 25G switch support otu4 channelization on the 100G interfaces?

A: Yes. This N8500-48B6C can support otu4 channelization on the 100G interfaces for sure.

Q: Do FS 25G/100G switches support VXLAN with the MP-BGP EVPN control plane?

A: Yes. FS N-Series bare-metal switches such as N8520-48B6C and N8520-32C can support EVPN. And the switches that come pre-loaded with the Cumulus system can also support EVPN.

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