Difference between Ethernet cables ?

Difference between Ethernet cables?

Not all Ethernet cables are the same, so what is the difference, and how do you know which you should use? In this short guide we take a look at the technical and physical differences between the Ethernet cables available on broadband buyer.

Ethernet cables are grouped into sequentially numbered categories (e.g CAT5) based on different specifications; sometimes the category is updated with further clarification or testing standards (e.g. CAT5e, CAT6a). These categories are how we can easily know what type of cable we need for a specific application. For our IP Surveillance ( IP Camera, Access Control, BAS, Intrusion ... etc) CAT6 is recommended to install, including PoE based design. 

Manufacturers are required to adhere to the standards which makes our lives easier.

CAT Technical differences

The difference in Ethernet cable specification is not as easy to see as physical changes; so let’s look at what each category does and does not support. Below is a chart for reference when picking cable for your application based on the standards for that category.

Difference between Ethernet cables
	Length	10Mb/s	100Mb/s	1GbE	10GbE	PoE	Mhz
CAT5	100	Y	Y			Y	100
CAT5e	100	Y	Y	Y		Y	100
CAT6	100 (55 for 10GbE)	Y	Y	Y	Y	Y	250
CAT6a	100	Y	Y	Y	Y	Y	500

You may notice that as the category number gets higher, so does the speed and Mhz of the wire. This is not a coincidence, because each category brings more stringent testing for eliminating crosstalk (XT) and adding isolation between the wires.

Category 5 cable was revised in 2001, and mostly replaced with Category 5 Enhanced (CAT5e) cable which did not change anything physically in the cable, but instead applied more stringent testing standards for crosstalk. Category 6 was revised between 2002 with Category 6 Augmented (CAT6a) in 2008 that provided testing for 500 Mhz communication (compared to CAT6 - 250 Mhz). The higher communication frequency eliminated alien crosstalk (AXT) which allows for longer range at 10 GB/s.

Physical Differences

So how does a physical cable eliminate interference and allow for faster speeds? It does it through wire twisting and isolation. Cable twisting was invented by Alexander Graham Bell in 1881 for use on telephone wires that were run along side power lines. He discovered that by twisting the cable every 3-4 utility poles, it reduced the interference and increased the range. Twisted pair became the basis for all Ethernet cables to eliminate interference between internal wires (XT), and external wires (AXT).

There are two main physical differences between CAT5 and CAT6 cables, the number of twists per cm in the wire, and sheath thickness.

Cable twisting length is not standardised but typically there are 1.5-2 twists per cm in CAT5(e) and 2+ twists per cm in CAT6. Within a single cable, each colored pair will also have different twist lengths based on prime numbers so that no two twists ever align. The amount of twists per pair is usually unique for each cable manufacturer.

Many CAT6 cables also include a nylon spline which helps eliminate crosstalk. Although the spline is not required in CAT5 cable, some manufacturers include it anyway. In CAT6 cable, the spline is not required either as long as the cable tests according to the standard.

The nylon spline helps reduce crosstalk in the wire, with the thicker sheath protecting against Near End Crosstalk (NEXT) and Alien Crosstalk (AXT), which both occur more often as the frequency (Mhz) increases. In this picture below, the CAT5e sheath has the thinnest sheath versus CAT6 but it also was the only one with the nylon spline.

Shielded (FTP) vs. Unshielded (UTP)

Because all Ethernet cables are twisted, manufacturers use shielding to further protect the cable from interference. For example, Unshielded Twisted Pair (UTP) can easily be used for cables between your computer and the wall but you will want to use Foil Shielded Cable (FTP) for areas with high interference and running cables outdoors or inside walls.

There are different ways to shield an Ethernet cable, but typically it involves putting a shield around each pair of wire in the cable. This protects the pairs from crosstalk internally. Manufacturers can further protect cables from alien crosstalk with additional cable shielding beneath the sheath. The diagram below shows the different types of Ethernet shielding and the codes used to differentiate them.