When to use Cat 6a

I’ve been seeing Category 6a cable if a few datacenters recently and thought it might be a good idea to review when and why we would use this type of cabling.

Wiring

The Category 6a cabling is wired the same as Category 5e at 1000BaseTX speeds.  Note: that you can get away with splitting two sets of pairs off of Cat5e, but this only allows 100BaseT Ethernet.

Pinouts come in either T568A or T568B.  B seems to be more widely used.

Borrowed directly from Wikipedia. 🙂

How Does Cat6a Provide 10GBaseT?

You might be wondering, “How can Cat6a provide higher bandwidth than Cat5e if the pinouts and twisted pairs are the same?”

The answer is found in how the cable is prepared.  Category 6a wire uses 22AWG wire size as opposed to the Cat5e size of 24AWG.  The additional size allows for less of a loss of signal and in Ethernet terms, this means an increase in speed.  Category 5e reaches transmitions of 100MHz where Category 6a can reach 500 MHz.  (Cat6 reaches the 250 MHz which limits the distance it can run to less than the 100 Meters that we’ve become accustomed to)

The second property that makes Cat6a different is the amount of insulation around each wire.  Cat6a wires have a longitudinal separator.  This separator insulates each of the four wire pairs from crosstalk with the other twisted pairs.  By eliminating the noise from other twisted pairs, a much cleaner electrical signal can reach it’s destination.

When should I use Cat6a?

Being an engineer that’s excited about newer technologies, I would always want to work with the latest standards so I can get the largest benefit.  But when it comes to Category 6a cabling, this isn’t really a good practice.  There are several factors that might make you consider using the older Cat5e cabling.

Price-  Category 6a cabling is much more expensive than category 5e.  Especially if you don’t see your network growing to 10Gb speeds any time in the near future, stick with old reliable.

Distance would calculate into this equation as well.  Longer runs means more materials, so perhaps your long runs should be Cat5e and short runs like server to switch or switch to switch could be Cat6a.

Corners-  Cat6a has more insulation which makes the cables thicker.  This makes the cables more rigid and more difficult to bend.  The additional bending difference may mean you should stick with Cat5e.

Tie Downs-  Be careful if you’ve got minimal space to hold your cables such as a small area of a server rack.  Many datacenter engineers like to use tie downs to secure cables to the sides of the server rack which makes them look nice, but part of why Cat6a provides higher speeds is because of the extra insulation.  Crimping these cables down with a tie down can negate some of that insulation making it less effective.

Current Network equipment-  Obviously if your switches are only cabable of 1000BaseT then Cat6a cables may be a waste of money.