There are various category of cable.
In general the higher the category the more twist
and the less susceptible the cable is to electromagnetic interference.
The higher the category the more stringent the specification are
for crosstalk and system noise.
Higher cable categories typically support higher frequencies and higher speeds
I wouldn’t try to remember all the categories of cable if I were you.
Just see this as an explanation of the various categories
you may encounter in networks or in documentation.
Category 1 was previously used for telephones and modems.
So category 1 is a grade of unshielded twisted cabling
designed for telephone communications and was it one time the most common on
premise wiring, this is not suitable for data transmission.
Category 2 was previously used for telephones and data networks up to 4 Mbps.
Category 3 was used previously for data networks up to 10 Mbps.
It's now generally used for telephones.
category 4 defined up to 20 MHz with speeds up to 16 Mbps.
category 5 is defined up to 100 MHz speeds of 10 or 100 Mbps when using 2 pairs
and 1 Gbps when using 4 pairs
Category 1, 2 and 4 are no longer used.
Category 3 is no longer used in data networks.
And generally category 5 is no longer used, but there’s a lot of installations
that have category 5, so you may still come across it.
Cat5e was an improvement on Cat5, it supports frequencies up to 100 MHz
and supports speed up to 1 Gbps.
It has a maximum distance of a 100 meters
and is similar to Cat5 but improve the Cat5 specification
by reducing noise and signal interference
so some crosstalk was improved with the new specification.
The category 5 specification improves upon the category 5 specification
by tightening some crosstalk specifications and introducing new crosstalk
specifications that will not present in the original category 5 specification.
The bandwidth of Cat5 and Cat5e is the same.
In other words 100 MHz and the physical cable construction is the same
and in reality is that most Cat5 cables meet Cat5e specification.
Though it may not be tested or certified as such.
Category 6 defines frequencies up to 250 MHz and increases
the number of pair twist per inch to reduce signal noise and interference.
It supports 10 Gbps but only up to 55 meters.
The type of specifications in Cat6 guarantee 100 meters runs at 1 Gbps
so category 6 cable commonly referred to us Cat6
is the standardize cable for the gigabit Ethernet
and is backward compatible with Cat5 or Cat5e
and Cat3 cable standards compared to Cat5 or Cat5e
Cat6 f1atures more stringent specifications for crosstalk and system noise.
The cable standards provide performance up to 250 MHz
and is suitable for 10Base-T, 100Base-TX or Fast Ethernet
and 1000BaseT or gigabit Ethernet as well as 10 gigabit Ethernet.
Cat6a or augmented Cat6 defined frequencies up to 500 MHz
which is twice that of Cat6.
It also includes improvements with regards to crosstalk
and support speeds up to 10 Gbps
but in this case with the extended cable length of a 100 meters.
Cat6 maximum cable length was 55 meters
in a favorable environment but only 37 meters in an environment
where a lot of crosstalk to place such as when cables are bundled together.
So cat6a or Cat6a improved the specification allowing for 10 Gbps up to 100 meters.
Category 7 or Cat 7 defined frequencies up to 600 MHz
and supports speeds of up to 10 Gbps up to 100 meters.
The connectors in Cat7 can be terror connectors rather than 8P, 8C or 8 physician
8 contact which we commonly refer to as Rj-45 connector.
So here’s an example of a terror connector and Cat7
notice the pairs of cable in Cat7 are protected by a foil shield
the twisting of pairs and the number of turns per inch, is also increased
to protect from crosstalk and in addition has a 10 copper Twinax
category7 is also known as class F and also has a classFa
which defined frequencies up to 100 MHz per second
and which in theory supports speeds up to 40 Gbps and 100 Gbps at 50 meters.
This is currently an ISO or ISO's standard
but is not recognized by the TIA/EIA.
For brand new installations, it’s generally recommended that Cat6a or Cat7 be use.
If reusing existing Cat6 cabling, cable segments must be tested up to 350 MHz
and limited by TIA/EIA recommendations.
Now Category8 is the next generation twisted pair cabling specification
and is being develop to support 40 Gbps
in other words 4 times the speed of 10 Gigabit Ethernet.
The technical recommendation for Category8 was released in March 2013
and has both class 1 and class 2
in other words category8.1 cable and category8.2 cables.
Category8.1 is fully backward compatible and interoperable with category6a
using Rj-45 connectors.
Category8.2 is interoperable with category7 cabling
using either Rj-45 or terror connectors.