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.