Cabling Solution for Data Center Top-of-Rack Deployment
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Cabling Solution for Data Center Top-of-Rack Deployment

Posted on by FS.COM

Data centers are constantly seeking the well-designed cabling models and architectures to meet the demands for cost-effective and smooth data center transition. Top-of-Rack (ToR) is a popular data center architecture which can help users to eliminate cabling nightmares, bottlenecks and rigidity while building a network foundation for modern data center applications, as well as providing a clear path for future growth. Today, an extensive range of fiber and direct cabling connectivity products which help data center operators deploy a ToR architecture in a cost-effective way will be presented here.

Introduction to ToR

Top-of-Rack (ToR) is one of the data center cabling architecture models which contributes to an agile infrastructure because the ToR switch supports multiple I/O interfaces, including GbE (Gigabit Ethernet), 10 GbE and 40 GbE. In a ToR configuration, small access switches placed in the top of each cabinet connect directly to the equipment in the cabinet via P2P (point to point) cabling. In fact, the actual physical location of the switches is not necessary needed to locate at the top of the rack. With a flatter switch architecture, ToR can help reduce the latency in data center and support an agile and predictable way of growing server and storage capacity. ToR can also simplify and shorten cable runs and facilitate the replication of rack configurations. Thus, it is ideal for data centers that require a cabinet-at-a-time deployment and cabinet-level management. The picture below shows us a typical architecture of ToR.


Physical Layer Options for ToR

At the physical layer, ToR has been designed to promote the modular data center expansion and leaner interconnect solution because this architecture supports modular deployment of data center racks as each rack can come in-built with all the necessary cabling / switches and can be deployed quickly on-site. Additionally, in ToR architecture, fibers are used as the primary media to support all transmission protocols over a unified fabric. This is because fiber cabling is more flexible than copper. It can support the transition from GbE to 10 GbE now, and enabling the transition to 40/100 GbE in the future.

    In rack:

  • Cabling within the rack depends on connectivity requirements, which can be optimized for interface speed, latency, and cost of optics and transceiver
  • Copper options: SFP+ DAC (10GSFP+ Cu)
  • Fiber options: 10GBASE-SR SFP+ for short reach over MMF
    Outside rack (uplink to aggregation layer):

  • Fiber (OM3 and OM4) if available; MMF recommended for lower cost on the fiber and the optics required for termination
  • Fiber from rack (EDA) terminates at the aggregation layer (HDA) (EDA: Equipment Distribution Area; HDA: Horizontal Distribution Area)

The following is one of the connectivity samples with fiber and direct attach technology.

Sample: ToR-physical-options

FS.COM Product Solution for ToR

FS.COM offers a comprehensive solution for data center ToR deployment including cables, transceiver optics and direct attach cabling products to satisfy various demands on data rate. Depending on different layers, we offer the different solutions:

Between Rack Servers and ToR Switch Within Rack

For interconnection between rack servers and ToR switch within rack, the Category 6a (Cat 6a) Ethernet patch cables or SFP+ direct attach cables can be used. The cable length depends on the distance from the rack server to the ToR switch that is limited to the vertical height of the cabinet.

Data Rate Distance Cable & Optics Direct Attach
Up to 10 Gbps Limited to the vertical height of the cabinet Cat6a Ethernet patch cables SFP+ DACs


ToR Switch to Network Switch

When connecting the ToR switch to network switch, it requires increased transmission speeds and distances. For distances below 15 m, the SFP+ direct attach cable is still an ideal option. But if the distances are more than 15 m, we recommend you to use the multimode fiber with the corresponding optics. In addition, for distances less than 100 m, the SFP+ AOC (active optical cable) is a viable option.

Data Rate Distance Cable & Optics Direct Attach
Up to 10 Gbps Less than 15 m OM1/OM2 LC patch cables & 10GBASE-SR SFP+ optics SFP+ DACs/AOCs
15 metres to 30 metres SFP+ AOCs
30 metres to 100 metres OM3/OM4 LC patch cables & 10GBASE-SR SFP+ optics
More than 100 meters /


Network to Core Switch

At the core of data center, direct attach cables designed with QSFP+ connectors can be used for short distance transmission of up to 15 m to support up to 40Gbps. To support distances above 15 m, the OM3 or OM4 fiber is recommended to use with the QSFP+ optics. In addition, for distances less than 100 m, the QSFP+ AOC is a viable option.

Data Rate Distance Cable & Optics Direct Attach
Up to 10 Gbps Less than 15 m OM1/OM2 LC patch cables & 10GBASE-SR SFP+ optics SFP+ DACs/AOCs
15 metres to 30 metres SFP+ AOCs
30 metres to 100 metres OM3/OM4 LC patch cables & 10GBASE-SR SFP+ optics
More than 100 meters /
Up to 40 Gbps Less than 15 m OM3/OM4 MTP patch cables & 40GBASE-SR4 QSFP+ optics QSFP+ DACs/AOCs
15 metres to 30 metres QSFP+ AOCs
30 metres to 100 metres
More than 100 meters OM3/OM4 MTP patch cables & 40GBASE-CSR4 QSFP+ optics /
Up to 100 Gbps Less than 15 m OM3/OM4 MTP patch cables & 100GBASE-SR4 QSFP28 optics /
15 metres to 30 metres /
30 metres to 100 metres /

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