Practical Applications for CAT 8

Category 8 cabling solutions have arrived with the ability to support new 25/40GBASE-T networks. It’s impressive
that the same tried-and-true twisted pair cabling and RJ-45 interface that delivered 10 megabits per second 15
years ago still play an important role in next generation networks.
But what are the practical applications for Cat 8? Where will it be deployed? First of all, these cabling systems
make sense for applications requiring speeds greater than 10 Gb/s. This goes beyond the capabilities of Cat 6A,
which has the performance specifications and flexibility to handle 10 Gb/s or slower speeds.

Also, for now, Cat 8 cabling systems will be limited to the access layer
in data center networks. Due to its distance limitations of 30 meters or
less in a two-connector channel — per IEEE, ISO, and TIA standards —
Cat 8 cabling really isn’t applicable for enterprise or premise networks.
However, for data center managers, Cat 8 offers some huge benefits.
When planning for networks greater than 10 Gb/s in the access layer,
the decision of which cable type to use largely depends on the network
topology you prefer: Top-of-Rack (ToR), End-of-Row (EoR), or Middle-of-
Row (MoR). Cat 8 will be able to support all of these topologies.

Cabling for Top-of-Rack
If you prefer a ToR topology, you now have a choice between Direct Attach Copper (DAC) or Cat 8 for copper
infrastructure. The ToR model uses a simplified cabling scheme — short intra-rack cable runs with a small number
of uplinks to the aggregate switches.
Quad small form-factor pluggable (QSFP+) DAC passive assemblies were standardized in 2010 through IEEE 802.3ba.
They are low-power solutions and have a similar form-factor to SFP+ 10 Gb/s (and future 25 Gb/s) assemblies.
However, they have a limited distance of up to seven meters. With such limited reach, they are a better fit for ToR
topologies instead of longer distances used in other topologies. QSFP+ DAC assemblies are also not backwards
compatible, and can be used for 40 Gb/s networks only.
Unlike DAC assemblies, Cat 8 cabling leverages the benefits of auto-negotiation. Auto-negotiation allows for two
Ethernet devices to connect to each other and select a common transmission speed that both devices support.
Auto-negotiation requirements are laid out in IEEE 802.3 BASE-T standards. For example, 25 Gb/s ToR switches can
communicate with 10Gb/s servers, whether over Cat 8 or Cat 6A connectivity.

This also allows for network migration to 25/40GBASE-T to be done in phases, allowing for more flexibility in terms
of timing, disruption, and cost. With staggered active gear upgrades, BASE-T solutions can allow for mixed server
speeds in each rack or cabinet supporting any combination of 1, 2.5, 5, or 10, 25, or 40 Gb/s servers, creating better
port utilization of the switches.

Cabling for End-of-Row and Middle-of-Row
EoR and MoR designs have every server cabled back to a single switch dedicated to a row of server racks.
The upside of this structured cabling approach is a simplified management environment with just one switch
to manage per row.
These topologies require longer links than those for ToR designs, and for 25 and 40 Gb/s networks in EoR
and MoR topologies, your two options are to use Cat 8 or multimode fiber. The longer cabling requirements
eliminate short-length DAC assemblies as an option.

Multimode fiber offers the benefit of working over longer distances and low power, and it can provide a
smaller cable profile. However, the high costs of fiber active equipment makes it an option that not all
end users can justify.

Category 8 can support the longer distances required in EoR and MoR designs, but it is limited to 30 meters or less. However, according to IEEE, links of 30 meters or less make
up 80 percent of data center connections in the industry.
If you require longer distances, fiber is the only option.
Cat 8 also offers the benefit of operating over low power:
it will not likely require any greater power or cooling requirements than a typical 10GBASE-T system used today.
Even if Cat 8 is not part of your immediate data center strategy, you may want to anticipate future tech refreshes in your current network infrastructure design. This means considering cable distances, connection counts, shielding,
and more. Preparing for Cat 8 now will create a simple and cost effective migration in the future.

Leviton Leads with Atlas-X1™
Altas-X1 Cat 8 connectivity uses the same form factor and termination methods as other Atlas-X1 connectors.
In fact, Atlas-X1 is the industry's first system to support shielded applications from Cat 8 to 5e
and UTP applications from Cat 6A to 5e, all from one unified connectivity platform.
This comprehensive system is made in the United States, and delivers the highest level of
verified performance across all categories to seamlessly support network
migration up to 40GBASE-T. It was the first Cat 8 system to be
independently tested and verified to meet TIA
Cat 8 channel standards.

If you have more questions about Cat 8, Leviton data center designers and engineers have extensive experience with the most popular network topologies, active equipment, and transmission methods. Many of them are active members on standards bodies that define future data center networks. You can reach them at 1-800-824-3005 or 1-425-486-2222.