There are many Ethernet cables that can be bought. Often these cables are supplied free with equipment that uses Ethernet connectivity in some way or another.
There are several different varieties of Ethernet cable that can be obtained: speed variations, crossover cables, Cat 5, Cat 5e, Cat6, Cat 6a, Cat 7etc..
Normally Ethernet cables will be bought and there is no major need to understand what is inside or on the connectors, although it can be both interesting and helpful on some occasions. Even so, an understanding of the different types of Ethernet cable and the maximum lengths that should be used is helpful.
The commonly used network cables: Cat 5, Cat 5e, Cat 6, Cat 6a, Cat7 all have different levels of performance, and therefore to is necessary to buy or select the right cable for the right application.
These network cables are used for connecting a variety of network elements from Ethernet switches and Ethernet routers to computers, servers and other network items - if there is an Ethernet interface, they can be connected using Ethernet cables.
Ethernet cable basics
The Ethernet cables for connectivity in most office and home environments rely on twisted wire pairs within an overall cable - Cat 5, Cat 6 and Cat 7 all used this format. Twisting the wires together enables the currents to balance, i.e in one wire the current is moving in one direction, and int he other wire of the pair the current is going in the other, enabling the overall fields around the twisted pair to cancel.
In this way, data can be transmitted over considerable lengths without the need for undue precautions.
As several twisted pairs are contained within a particular network cable, the number of twisted per unit length is arranged to be different for each pair - the rate being based on prime numbers so that no two twists ever align. This reduces crosstalk within the cable.
The Ethernet cables are available in a variety of lengths as patch cables, or the cable itself is available for incorporating into systems, buildings, etc. The terminations can then be made to the required connector using a crimp tool. These network cables are available in a variety of lengths - long Ethernet cables are available, some of the longest being up to 75 metres.
Earlier network cables were unshielded, but later ones were shielded to improve the performance. For example an unshielded twisted pair (UTP) cable may be satisfactory for a short run between a computer and router, but a foil shielded cable, FTP, is best longer runs or where the cable passes through areas of high electrical noise.
There are different methods that can be used for shielding Ethernet cables. The most common is to place a shield around each twisted pair. This not only provides shielding for the cable externally, but also reduces crosstalk between the internal twisted pairs as well. Manufacturers can further enhance the performance by placing shielding around all the wires in the cable just under the cable sheath. There are different codes used to indicate the differs types of shielding:
- U/UTP - Unshielded cable, unshielded twisted pairs
- F/UTP - Foil shielded cable, unshielded twisted pairs
- U/FTP - Unshielded cable, foil shielded twisted pairs
- S/FTP - braided shielded cable, foil shielded twisted pairs
Where: TP = twisted pair, U = unshielded, F = foil shielded, S = braided shielding.
A further difference within the Ethernet cables whether Cat 5, Cat 5e, Cat 6, Cat 6e, or Cat 7 can be whether solid or stranded wires are used within the cable. As the description implies, a solid cable uses a single piece of copper for the electrical conductor within each wire of the cable whilst stranded wire uses a series of copper strands twisted together. Although when buying a patch cable, it may not be necessary to know this, when installing a long cable run it may be important as each type is slightly more suitable for different applications.
- Stranded cable: This type of wire is more flexible and it is more applicable for Ethernet cables where the cable may be moved - often it is idea for patch leads at desks or general connections to PCs, etc where some movement may be needed and expected.
Solid cable: Solid cable is not as flexible as the stranded type, but it is also more durable. This makes it best for use in permanent installations like cable installations under floors, embedded in walls and the like.
Categories for Ethernet cables
A variety of different cables are available for Ethernet and other telecommunications and networking applications. These network cables that are described by their different categories, e.g. Cat 5 cables, Cat-6 cables, etc, which are often recognised by the TIA (telecommunications Industries Association) and they are summarised below:
- Cat-1: This is not recognised by the TIA/EIA. It is the form of wiring that is used for standard telephone (POTS) wiring, or for ISDN.
- Cat-2: This is not recognised by theTIA/EIA. It was the form of wiring that was used for 4Mbit/s token ring networks.
- Cat-3: This cable is defined in TIA/EIA-568-B. It is used for data networks employing frequencies up to 16 MHz. It was popular for use with 10 Mbps Ethernet networks (100Base-T), but has now been superseded by Cat-5 cable.
- Cat-4: This cable is not recognised by the TIA/EIA. However it can be used for networks carrying frequencies up to 20 MHz. It was often used on 16Mbps token ring networks.
- Cat-5: This is not recognised by the TIA/EIA. This is the network cable that is widely used for 100Base-T and 1000Base-T networks as it provides performance to allow data at 100 Mbps and slightly more (125 MHz for 1000Base-T) Ethernet. The Cat 5 cable superseded the Cat 3 version and for a number of years it became the standard for Ethernet cabling. Cat 5 cable is now obsolete and therefore it is not recommended for new installations.
Cat 5 cable uses twisted pairs to prevent internal crosstalk, XT and also crosstalk to external wires, AXT.
Although not standardised, the Cat 5 cable normally uses 1.5 - 2 twists per centimetre.
Cat-5e: This form of cable is recognised by the TIA/EIA and is defined in TIA/EIA-568, being last revised in 2001. It has a slightly higher frequency specification that Cat-5 cable as the performance extends up to 125 Mbps.
Cat-5e can be used for 100Base-T and 1000Base-t (Gigabit Ethernet). Cat 5e standard for Cat 5 enhanced and it is a form of Cat 5 cable manufactured to higher specifications although physically the same as Cat 5. It is tested to a higher specification to ensure it can perform at the higher data speeds. The twisted pairs within the network cables tend to have the same level of twisting as the Cat 5 cables.
- Cat-6: This cable is defined in TIA/EIA-568-B provides a significant improvement in performance over Cat5 and Cat 5e. During manufacture Cat 6 cables are more tightly wound than either Cat 5 or Cat 5e and they often have an outer foil or braided shielding. The shielding protects the twisted pairs of wires inside the Ethernet cable, helping to prevent crosstalk and noise interference. Cat-6 cables can technically support speeds up to 10 Gbps, but can only do so for up to 55 metres - even so this makes them relatively long Ethernet cables.
The Cat 6 Ethernet cables generally have 2+ twists per cm and some may include a nylon spline to reduce crosstalk, although this is not actually required by the standard.
Cat-6a: The “a” in Cat 6a stands for “Augmented” and the standard was revised in 2008. The Cat 6a cables are able to support twice the maximum bandwidth, and are capable of maintaining higher transmission speeds over longer network cable lengths. Cat 6a cables utilise shielded which is sufficient to all but eliminate crosstalk. However this makes them less flexible than Cat 6 cable.
Cat-7: This is an informal number for ISO/IEC 11801 Class F cabling. It comprises four individually shielded pairs inside an overall shield. It is aimed at applications where transmission of frequencies up to 600 Mbps is required.
Further descriptions of Cat-5 and Cat-5e cables are given below as these are widely used for Ethernet networking applications today.
|ETHERNET CABLE PERFORMANCE SUMMARY|
|CATEGORY||SHIELDING||MAX TRANSMISSION SPEED (AT 100 METERS)||MAX BANDWIDTH|
|Cat 3||Unshielded||10 Mbps||16 MHz|
|Cat 5||Unshielded||10/100 Mbps||100 MHz|
|Cat 5e||Unshielded||1000 Mbps / 1 Gbps||100 MHz|
|Cat 6||Shielded or Unshielded||1000 Mbps / 1 Gbps||>250 MHz|
|Cat 6a||Shielded||10000 Mbps / 10 Gbps||500 MHz|
|Cat 7||Shielded||10000 Mbps / 10 Gbps||600 MHz|