While not officially considered “over the hill,” Ethernet recently celebrated its big “4-0.” Since its birth in 1973 and the publication of the 10BASE-T Ethernet standard in 1990, a lot has changed. Every five to seven years, Ethernet has grown up by a factor of 10—in speed that is.

Just take a look at twisted-pair cabling alone. We went from 10BASE-T with a data rate of 10 Mb/s over category 3 cabling in 1990, to 100BASE-TX at 100 Mb/s over category 5 in 1995, to 1000BASE-T at 1 Gb/s over category 5e or higher in 1999, to 10GBASE-T at 10 Gb/s over category 6A in 2006. And now we’re less than two years away from 40GBASE-T at 40 Gb/s over future category 8 cabling. Fiber is another story—moving from 1 Gb/s over multimode and singlemode fiber in 1998 to 10 Gb/s in 2003 to 100 Gb/s in 2010. That’s speed increased by a factor of 100 in just 12 years!

I am honored to have taken part in the development of higher performing cabling to support the different generations of Ethernet standards with some vital principles staying the same.


What Has Stayed the Same

I became involved in cabling standards development in 1989 when the TIA-568 standard was being developed, around the same time that the IEEE 10BASE-T standard was published. TIA-568 established the framework for structured cabling that still exists today, including the hierarchical star topology for horizontal and backbone cabling, the standardization of 100 Ohm balanced twisted-pair cabling in the horizontal with a maximum channel distance of 100 meters, and the standardization of the venerable 8-position modular (RJ45) connector termination in the work area.

Although a lot has changed since then, there are certain principles that remain the same. One such principle is the principle of “backwards compatibility” with previous generations of cabling. For example, category 6A cabling, which is designed to support 10GBASE-T (10 Gigabit) applications up to 100 meters is also fully backwards compatible with all lower categories of cabling and will support 1000BASE-T, 100BASE-TX and 10BASE-T applications. Higher category components (cables, cords and connectors) can be substituted for lower category components in a channel and provide full functionality with equal to or better performance.

In planning a new data center, it is therefore sensible to install a cabling system that can support at least two generations of Ethernet over a 10 year lifespan. For copper switch-to-server connections that means category 6A (for now) and for fiber backbone switch-to-switch connections that means either 0M4 laser-optimized multimode or single mode optical fiber. But watch out—category 8 is just around the corner for copper.

What Lies Ahead

Driven by the need for higher speed switch-to-server connections in today’s virtualized data centers, the IEEE 802.3bq 40GBASE-T task force is well on their way to defining the topology, reach objectives, cabling requirements and the power consumption of the next generation physical layer interface (PHY) to transmit at speeds of 40 Gb/s. At the same time, the TIA 42.7 subcommittee is developing the category 8 cabling standards to support the future 40GBASE-T standard.

While 40GBASE-T is intended to be used for switch-to-server connections in the data center, the ability to interoperate with legacy slower-speed Ethernet technologies through autonegotiation is a goal that is here to stay. This is facilitated by the use of the 8-pin modular (RJ-45) connector, and TIA is therefore developing the category 8 cabling standard to include this recognized de facto interface. Category 8 cabling is specified to 2 GHz, or four times the bandwidth specified for Category 6A cabling and twice the bandwidth specified for Category 7A cabling.

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Some Key Considerations

Category 8 on the horizon might be a reason for data center managers to hold off on a cabling upgrade to a lesser performing category 7 or 7A shielded cabling. One drawback of Category 7 and 7A is that it uses a different IEC connector design that is not backwards compatible with the 8-pin modular (RJ-45) connector, and therefore would require an adapter patch cord to interface with legacy equipment. And just to make it more interesting, there is a version of Category 8 cabling called Class II that is based on improved Category 7A components.

40 years is a significant milestone for Ethernet. IEEE 802 celebrated the event on November 11 at the Hyatt Regency Reunion in Dallas, TX. While a lot has changed and Ethernet has come a long way, the trend of doubling networking speeds every two years is obviously continuing and that means some key considerations for those planning to build or upgrade a data center in next five years.