Optimizing Switch to Server Connectivity via High-Speed Breakouts

This article was created and contributed by Panduit.

Some of the most important goals of any data center are to optimize power consumption and floor space while also having a fiber optic infrastructure that is future-proofed.  With good planning and use of breakout cabling these goals can be more easily attained.

Cisco Network switches are now available with ports up to 800G while Server NICs are only available in 25G, 50G or 100G with 200G on the horizon.  To optimize port utilization, the switches and optics are designed to be able to operate as multiple lower speed interfaces to handle 4x or 8x NICs per switch port.  By using higher speed optical modules in switch ports, users can reduce the number of switches and optical modules by 75% while maintaining the same amount of servers. This improves rack density and, at greater than 10W per optical modules, it substantially reduces the power which in turn reduces the power needed to cool each rack. To achieve this fiber breakout cabling is needed.

Breakout cabling can be achieved in two ways: 

1. MPO to multiple duplex LC fiber harnesses (figure 1)
2. MPO to breakout cassette to multiple LC Fiber patch cords (figure 2)

The advantage of using a single breakout harness is that it will have the lowest Insertion Loss as only two connectors are in each channel.  However, these harnesses are often needed to be customized for each port and can be harder to route in high density areas.  In contrast,  the addition of a cassette offers the flexibility of using standard MPO to MPO and duplex LC to duplex LC fiber assemblies which can easily be changed for exact length for each run.  Having separate fiber assemblies is also an advantage in case of damage.  If a harness is damaged the entire assembly must be replaced bringing down 4 Servers.

Breakout options by data rate:

Future proofing – avoiding rip and replace

If planned correctly, using pluggable optics and breakout cabling provides a simple migration path for next generation optics.  Re-using existing fiber enables huge cost and deployment time savings.  If you get your fiber infrastructure right today, you can avoid ripping and replacing your cable plant for multiple migration upgrades.  OM4 can handle reaches of 100m up to 800G for all but BiDi optical modules, but putting in higher grade multimode cabling such as OM5 or Panduit's SignatureCore OM4+ will extend that into 1.6Tb and possibly more.

Overview

Widening the radix of switch using pluggable optics and using breakout cables offers very important advantages:

• Flattens the network architectures
  • Using 4x100G optical modules in a single port eliminates layers in your fabric which reduces latency and number of switches required.
• Higher density in switch front panel
• Greater power efficiency (Gb/W)
• Reduces changes of rip and replacing cabling

Recommendations

Choose partners who are experts and have complementary capabilities to help you optimize your design and future proof your data centers.  Together WWT, Cisco, and Panduit offer the technology, quality, and reliability to assist you in all design aspects.  Learn more about WWT and Panduit capabilities.