Categories of twisted pair cables in computer networks. What is twisted pair

To create communication networks, computer and communications, cables made using special technology are used. Their veins are twisted together in pairs. Such products are called “twisted pair”. There are two main types of cables of this design: ftp and utp.

UTP (top) and shielded FTP (bottom)

Features of twisted pair

The main problem in protecting communication lines is their protection from interference. The signal amplitudes in the line are much smaller than those of the surrounding electrical equipment: power cable lines, electric motors, household appliances, overhead power lines. Taking into account the degree of development of electrification, it is not difficult to imagine the amount of electromagnetic interference affecting communication cables along their entire route.

In addition, the conductors inside the cable itself interact with each other, creating mutual interference. When communication lines were made using the same technology as electrical ones (in the form of overhead lines with wires on insulators), interference from neighboring conductors and high-voltage power lines was minimized by regularly changing the location of the line conductors relative to each other. This technical trick is called transposition.

Transposition using the example of a power line

The twisted pair in a modern cable is the same transposition, but made with high density. The veins are twisted together in pairs. This ensures minimal influence of individual pairs of cores on each other and increases protection from external interference.

However, the protective properties of twisted pair cables are nullified if the conditions for their installation are violated. The bending radius of such products is strictly limited and usually should not be less than eight diameters. If this is not taken into account, then geometric changes occur inside the cable, sometimes irreparable, worsening its noise immunity.

The bending radius of the twisted pair must be at least 8 cable diameters

Shielding of communication cables

However, twisting the wires does not always help to completely eliminate the influence of interference on the useful signal. In this case, the introduction of shielding shells into the design helps. Both individual pairs of cores and all cores inside the cable can be shielded. These methods are used both individually and jointly; in this case, each pair of cores is shielded and, additionally, all cores together.

However, this method of protection is effective only if the equipment housings connected by cable are grounded. Otherwise, the screen shells themselves become a source of interference, accumulating it along the entire path of the line.

Depending on the presence, absence and number of screens, a letter is added to the cable brand, meaning:

U – no screen;
S – general screen in the form of a metal braid;
F – a screen made of copper or aluminum foil or metallized tape around the cores of each pair or all of them as a whole.

The full designation of the brand consists of the above letters written through a fraction. The numerator indicates the protection of individual cores, the denominator indicates the entire cable. Next, the letters “TP” are added, meaning “twisted pair”, translated as twisted pair.

For example, the designation U/FTP indicates that the cable does not have a protective shield for individual pairs of wires, but contains a common shielding sheath. There are also combinations of their two letters, for example “SF” - metal braid and foil are used together.

It must be taken into account that when using foil for shielding, its outer surface is covered with a layer of dielectric. Therefore, when connecting the screen, you need to use only its inner surface for contact connection.

If the screen is made of foil, then a metal wire of small cross-section runs parallel to it. It is necessary for better contact when connecting to grounding devices. It also eliminates possible breaks in the foil screen that occur in places of kinks, as if bridging the places of breaks.

Which cable is better: with or without screen?

When laying communication networks, which cable is better to use, utp or ftp? It would seem that the use of shielded cables solves all problems with noise immunity, while unshielded cables cope with the problem only partially.

Not so. Let us remember the ability of the screen to accumulate noise in the absence of grounding. If the equipment to which it is connected does not have a connection to a ground loop (or its own ground loop, which is mandatory for servers), then using ftp will only make the situation worse.

In addition, FTP cables are very sensitive to low-frequency interference, the level of which in manufacturing plants is quite high due to the presence of power electrical equipment. No matter how hard you try, it is still impossible to lay communication cables at a sufficient distance from existing power lines. And cable products passing through them always radiate interference around themselves. In addition, electric motors and induction elements also emit interference. Do not forget about impulse noise that occurs during the operation of switching devices.

More utp cable, unlike ftp, has less attenuation of the useful signal. Which has a strong effect when the communication line is long.

Therefore, when deciding which cable to choose, unshielded or ftp, you need to focus on the equipment’s ability to connect the shield, the presence or absence of low-frequency interference and the total length of the communication line.

When choosing a cable, you need to pay attention to the material of its sheath. If it passes through open areas on the street, then it must be protected from exposure to sunlight. For this purpose, the outer shell is made of polyethylene, usually black. But the polyethylene sheath, which protects the cable from sunlight, temperature fluctuations and precipitation, supports combustion. Therefore, they cannot be laid openly indoors.

For use inside buildings, the shell must not support combustion and not emit halogens (fluorine, chlorine, bromine or iodine). They are not only strong oxidizing agents, but also toxic to humans. Flame-retardant sheaths are indicated by adding the letters LS (low smoke) to the cable marking for imported products or “ng” for Russian products. Non-halogen-emitting products are additionally marked HF (halogen free).

To organize most data networks, computer or telephone, cables are used. Such networks are called wired. IN last years they are most often laid using a special type of cable called “twisted pair”. The name reflects the type of arrangement of the conductors relative to each other. A twisted pair is two insulated conductors twisted together with a certain twist pitch. Typically, these two wires have another layer of insulation.

There are cables that have two, four, eight pairs of conductors under one sheath. And still, such a cable is called “twisted pair”, although there are several pairs themselves. Depending on the type of protection, there are unshielded and Shielding reduces the influence of external and internal interference, increases the reliability of the connection, and reduces the number of errors. To ensure integrity in case of excessive bends and breaks, the screen along the entire length of the cable is connected with a special non-insulated drain wire. Shielded twisted pair cable provides higher transmission speeds and partially eliminates influence and interference from other objects.

Screens can be in the form of mesh, braid, or continuous foil coating. There are cables with double protection, with foil wound over the mesh braid. According to international practice, this type The conductor has the following designation: unshielded twisted pair - UTP, shielded - STP. If the cable has a common protective screen, but individual pairs are not shielded, then such a wire is also classified as unshielded. Terminal equipment uses different types cables Which one do you need, look in the passport or description.

Depending on the structure of the conductors used, a twisted pair can be single-core or multi-core. consists of a single wire of large diameter, multi-core is a bundle of thin wires. The scope of their application is different. Single-core wires have greater rigidity, do not bend well, and can break if bent repeatedly. Their

used for laying in walls, pipes and boxes with subsequent insertion into an outlet. Multicore twisted pair has good flexibility, but does not tolerate connection to sockets. This type of cable is used to connect terminal devices to sockets.

The outer sheath of the conductors serves to protect them from moisture and mechanical damage. It has different thicknesses and is made from different materials. According to European standards, only those cables that do not emit smoke or burn are suitable for external installation.

To make work easier, different colors are used for conductors for different purposes. For example, the outer sheath color of a cable for external installation is black, orange means that the sheath material does not burn, and the color of internal conductors is usually gray. Cables consisting of twisted pairs, can have different shapes: round or flat (for laying under the floor covering).

Types of cable used in networks

Depending on the presence of protection - an electrically grounded copper braid or aluminum foil around twisted pairs, the types of this technology are determined:

unshielded twisted pair(English) UTP - Unshielded twisted pair) - without protective screen;
foil twisted pair(English) FTP - Foiled twisted pair), ) - there is one common external screen in the form of foil;
shielded twisted pair(English) STP - Shielded twisted pair) - there is protection in the form of a screen for each pair and a common external screen in the form of a mesh;
foil shielded twisted pair(English) S/FTP - Screened Foiled twisted pair ) - external screen made of copper braid and each pair in foil braid;
unprotected shielded twisted pair (SF/UTP- or from English Screened Foiled Unshielded twisted pair).The difference from other types of twisted pairs is the presence of a double external shield made of copper braiding and foil.

Shielding provides better protection from electromagnetic interference, both external and internal, etc. The screen along its entire length is connected to a non-insulated drain wire, which unites the screen in case of division into sections due to excessive bending or stretching of the cable.

Depending on the structure of the conductors, the cable is used single-core or multi-core. In the first case, each wire consists of one copper core and is called a monolith core, and in the second case, each wire consists of several and is called a bundle core.

A single-core cable does not require direct contact with connected peripherals. That is, as a rule, it is used for installation in boxes, walls, etc., followed by termination with sockets. This is due to the fact that copper strands are quite thick and with frequent bending they quickly break. However, such conductors are ideally suited for “cutting” into the connectors of socket panels.

In turn, a multi-core cable does not tolerate “cutting” into the connectors of socket panels (thin wires are cut), but behaves well when bent and twisted. In addition, stranded wire has greater signal attenuation. Therefore, multicore cable is used mainly for the manufacture of patch cords. patchcord) connecting the periphery to the sockets.

Design of twisted pair cable

A twisted pair cable consists of several twisted pairs. The conductors in pairs are made of solid copper wire with a thickness of 0.4-0.6 mm. In addition to the metric system, the American AWG system is used, in which these values are 22-26AWG. Standard 4-pair cables primarily use 0.51mm (24AWG) conductors. The thickness of the conductor insulation is about 0.2 mm, the material is usually polyvinyl chloride (English abbreviation PVC), for higher quality samples of category 5 - polypropylene (PP), polyethylene (PE). Especially high-quality cables are insulated with foamed (cellular) polyethylene, which provides low dielectric losses, or Teflon, which provides a wide operating temperature range

Also inside the cable there is a so-called “breaking thread” (usually nylon), which is used to facilitate cutting of the outer sheath - when pulled out, it makes a longitudinal cut on the sheath, which opens access to the cable core, guaranteed without damaging the insulation of the conductors. Also, the breaking thread, due to its high tensile strength, performs a protective function.

The outer sheath of 4-pair cables has a thickness of 0.5-0.9 mm depending on the cable category and is usually made of polyvinyl chloride with the addition of chalk, which increases fragility. This is necessary for precise cutting at the cut site with the cutting tool blade. In addition, for the manufacture of the sheath, polymers are used that do not support combustion and do not emit halogens when heated (such cables are marked as LSZH - Low Smoke Zero Halogen). Cables that do not support combustion and do not emit smoke are allowed to be laid and used in closed areas where air flow from the air conditioning and ventilation system can pass (so-called plenum areas).

In general, colors do not indicate special properties, but their use makes it easy to distinguish between communications with different functional purposes, both during installation and maintenance. The most common cable sheath color is grey. External cables have a black outer sheath. Orange coloring usually indicates non-flammable shell material.

Separately, it is necessary to note the markings. In addition to information about the manufacturer and type of cable, it necessarily includes meter or foot marks.

The shape of the outer sheath of a twisted pair cable can be different. The round shape is most often used. Flat cable can be used for installation under carpet.

Cables for outdoor installation must have a moisture-resistant polyethylene sheath, which is applied (as a rule) as a second layer over the usual polyvinyl chloride sheath. In addition, it is possible to fill the voids in the cable with water-repellent gel and armor it using corrugated tape or steel wire.

Cable categories

Telephone reel with cable, model 1933

There are several categories of twisted pair cable, which are numbered from CAT1 to CAT7 (correct category or category, abbreviation “CAT”, “Cat” should be written with a dot - “Cat.”, because category and cat are different things) and determine the effective transmission frequency range. A higher category cable usually contains more pairs of wires and each pair has more turns per unit length. Categories of unshielded twisted pair cable are described in the EIA/TIA 568 standard (American standard for wiring in commercial buildings) and in the international standard ISO 11801, and are also adopted by GOST R 53246-2008 and GOST R 53245-2008 (translations of one of the manufacturer's manuals).

CAT1(frequency band 0.1 MHz) - telephone cable, only one pair (in Russia they use a cable and no twists at all - “ noodles"- its characteristics are no worse, but the influence of interference is greater). In the USA it was used previously, only in a “twisted” form. Used only for voice or data transmission using a modem.

CAT2(frequency band 1 MHz) - old type of cable, 2 pairs of conductors, supported data transmission at speeds up to 4 Mbit/s, used in Token ring and Arcnet networks. Now sometimes found in telephone networks.

CAT4(frequency band 20 MHz) - the cable consists of 4 twisted pairs, was used in token ring, 10BASE-T, 100BASE-T4 networks, the data transfer rate does not exceed 16 Mbit/s over one pair, is not currently used.

CAT5(frequency band 100 MHz) - 4-pair cable, used in the construction of 100BASE-TX local networks and for laying telephone lines, supports data transfer rates of up to 100 Mbit/s when using 2 pairs.

CAT5e(frequency band 125 MHz) - 4-pair cable, advanced category 5. Data transfer rates up to 100 Mbps when using 2 pairs and up to 1000 Mbps when using 4 pairs. Category 5e cable is the most common and is used to build computer networks. Sometimes a two-pair Category 5e cable is found. The advantages of this cable are lower cost and smaller thickness.

CAT6(250 MHz frequency band) - used in Fast Ethernet and Gigabit Ethernet networks, consists of 4 pairs of conductors and is capable of transmitting data at speeds of up to 1000 Mbit/s and up to 10 gigabits over a distance of up to 50 m. Added to the standard in June 2002.

CAT6a(frequency band 500 MHz) - used in Ethernet networks, consists of 4 pairs of conductors and is capable of transmitting data at speeds up to 10 Gbps and is planned to be used for applications operating at speeds up to 40 Gbps. Added to the standard in February 2008.

CAT7(frequency band 600-700 MHz) - specification for this type cable is approved only by the international standard ISO 11801, data transfer speeds up to 10 Gbit/s. This category of cable has a common shield and shields around each pair. The seventh category, strictly speaking, is not UTP, but S/FTP (Screened Fully Shielded Twisted Pair).

CAT7a(frequency band 1200 MHz) - designed for data transmission at speeds up to 40 Gbit/s.

Each individual twisted pair that is part of a cable intended for data transmission must have a characteristic impedance of 100 ± 15 Ohms, otherwise the shape of the electrical signal will be distorted and data transmission will become impossible. The cause of problems with data transmission can be not only a low-quality cable, but also the presence of “twists” in the cable and the use of sockets of a lower category than the cable.

Crimping schemes

There are two options for crimping the connector on the cable:

to create a straight cable - to connect a network card port to a switch or hub,
to create a cross one (using crossed MDI, English. MDI-X) a cable that has an inverted connector pinout for connecting directly two network cards installed in computers, as well as for connecting some older models of hubs or switches (uplink port).

The 8P8C connector (often mistakenly called RJ45) is crimped.

Straight through cable

EIA/TIA-568A option

EIA/TIA-568B option (more commonly used)

If you need an MDI cable with external crossover, the so-called “direct” cable to connect the computer to the hub/switch, the following schemes are used:
When connecting EIA/TIA-568B, AT&T 258A 1: White-Orange 2: Orange 3: White-Green 4: Blue 5: White-Blue 6: Green 7: White-Brown 8: Brown

Old twisted pair colors: 1: blue 2: orange 3: black 4: red 5: green 6: yellow 7: brown 8: gray

When connecting EIA/TIA-568A 1: White-Green 2: Green 3: White-Orange 4: Blue 5: White-Blue 6: Orange 7: White-Brown 8: Brown

According to one of these schemes, the connectors are crimped on both sides.

- (English)

Crossover cable

Used to connect equipment of the same type (for example, computer to computer). However, some network cards are able to automatically detect the cable crimping method and adapt to it.
Option for 100 Mbps speed

If you need an MDI-X cable with internal crossover, a “crossover” cable for connection, for example, “computer-to-computer” (at speeds up to 100 Mb/s), then the EIA/TIA-568B scheme is used on one side of the cable, and EIA/TIA-568B on the other. TIA-568A

- Ethernet Cable - Color Coding Diagram (English)

Option for 1000 Mbps speed

For connections at speeds up to 1000 Mb/s, when making a “crossover” cable, one side must be crimped according to the EIA/TIA-568B standard, and the other as follows:

1: White-green 2: Green 3: White-orange 4: White-brown 5: Brown 6: Orange 7: Blue 8: White-blue

- Crossover Patchkabel Gigabit (1000 BaseT) (German)

General provisions

Twisted pair is a type of communication cable, which is presented in the form of a pair of conductors covered with insulation and twisted together with a certain pitch. Double conductors are combined into multi-pair wires, which are covered with a common protective sheath.

Depending on the pitch of twisting of pairs, the number of double cores, the material of the outer covering, the type of insulation and shielding, the area of use of the wire is determined. Such wires are part of a structured cabling system and are therefore widely used in telecommunications, video surveillance, computer networks.

To build a local home or office network, a 5e FTP cable is most often used. If you decide to create your own local computer network in your apartment or for other reasons you need a twisted pair cable, then it’s worth figuring out what type you need to purchase.

Twisted pair shielding type

Shielding is the protection of conductors (or cores) from exposure electromagnetic radiation, which may affect the transmitted data and speed.

There are several types of cable, depending on how the cores inside are shielded.

Unshielded UTP Wire

The cheapest type, limited in its use due to instability to crosstalk and EMI. Represents one or more pairs united by an outer shell.

Shielded FTP cable

It is more protected from EMR in that it has a common shield that covers all the wires with foil. It is the most popular type of cable and is used almost everywhere. It is slightly more expensive than UTP, but it ensures the integrity of the transmitted data.

Double Shielded STP Cable

This type uses double protection, that is, there is a common shield for all foil cores, plus a separate shield for each pair. One of the most reliable cables, several times more expensive than UTP and FTP, most often used in offices and production.

Many organizations use funny cable shielding markings. If you have to look for twisted pair cables via the Internet and in markets, you may encounter the following designations:

F/UTP - twisted pair with common shield;
U/UTP - completely screenless;
SF/UTP - double shield pair;
S/FTP - in it the overall screen is presented in the form of a copper braid, and the protection of each pair is made of foil.

As noted, the most common use case is an FTP cable, the price of which depends on the manufacturer, the shielding material used and the quality of the outer protective sheath.

Twisted pair by type of sheath used

Pairs of cores twisted together are connected into a single cable using an outer protective sheath. It is usually made of polyethylene or polyvinyl chloride. This polymer has excellent resistance to most solvents, alkalis and oils, does not emit toxic fumes in the air and does not deteriorate in the temperature range from -15 to +66 degrees Celsius.

In its pure form, it has excellent ductility, therefore, so that the cable can be easily bitten or torn lengthwise if necessary, chalk is added to the polyvinyl chloride. When paired, they make an excellent material for making a protective shell.

Various additives can be added to the two main components to provide the desired properties of the outer part of the FTP cable. Based on them, the division of the shell into types, which are distinguished by color, was constructed.

Low smoke non-flammable shell

Orange - made of non-flammable polymer, has the highest fire safety rating. Marked LSZH (stands for Low Smoke Zero Halogen - low smoke emission, zero halogens).

For outdoor use

Black - it contains the same polymer, but it has an additional protective layer of polyethylene, which is designed to protect the cable from external atmospheric influences; usually wires with such a sheath are used for laying on the street, in sewers or through the air.

For indoor installation

Gray is a common budget sheath, used for cables laid indoors. Quite fragile to break and break, which allows you to quickly break it in the right place.

There is always a marking on the shell indicating the type of shielding, manufacturer and category. Information is applied to the FTP cable every meter, for foreign ones it can be a foot. With its help, you can easily measure the required length or find out the length of the laid lines by simple calculation.

As a rule, cables are flat and round; round ones are used in everyday life and in offices (not counting telephone noodles, which can be found less and less often). For its installation, boxes or cable channels are provided in the baseboards, and there are also semicircular fasteners that allow you to nail the cable to the wall without damaging it.

Cable categories by number of pairs and bandwidth

As already mentioned, there can be one twisted pair or several inside the cable. Depending on their number and bandwidth, FTP cable has different categories.

Legacy twisted pair cable categories

Cat1 - operating frequency 100 kilohertz, used for voice signal transmission, popularly called “telephone noodles”.

Cat2 - the used frequency is 1 megahertz, has the ability to transmit data up to 4 Mbit/s, contains 2 pairs of conductors, is currently not used anywhere.

Cat3 - operates at a frequency of 16 megahertz, maximum speed transmission up to 10 Mbit/s, contains 4 pairs, can be used in telephone and computer networks with a length of no more than 100 m.

Cat4 - used frequency band up to 20 megahertz, transmission speed up to 16 Mbit/s, contains 4 pairs and is not used anywhere at this moment.

Widely Used Twisted Pair Categories

Cat5e is the most popular FTP cable, containing 4 pairs of conductors. Operates at a frequency of up to 125 megahertz, when using 2 pairs it provides a transfer speed of up to 100 Mbit/s, when using all pairs up to 1 Gbit/s per second.

Cat6 - operating frequency up to 250 megahertz, has 4 pairs of wires and, when all are used, provides speeds of up to 1 Gbit/s per second, at a distance of up to 50 meters it transmits up to 10 Gbit/s.

Rarely used promising categories

Cat6a - has an operating frequency of up to 500 megahertz and 4 pairs of wires, providing transmission speeds of up to 40 Gbit/s. Used to build high-speed lines.

Cat7 is a four-pair cable with an operating frequency of up to 700 megahertz and a transmission speed of up to 50 Gbit/s.

Cat7a - 4 pairs, frequency up to 1200 megahertz, can provide speeds of up to 100 Gbit/s with a length of no more than 15 meters, and up to 10 Gbit/s when using all pairs.

How to choose the right twisted pair cable for home use

The most common cable is FTP category 5e twisted pair cable. It is used to lay local networks in offices and at home, and is used to connect computers to a router or hub. And, most likely, the cable that is installed in your apartment will be of the same category.

Some providers save on twisted pair cable and pass it on to their customers budget options no shielding at all. Unshielded twisted pair can be laid inside the apartment if it is possible to lay the network away from the wiring and hide it in a cable channel.

Based on the above, we can draw a conclusion. In order to choose the right twisted pair, you need to decide on:

Required data transfer speed.

Most providers do not offer tariffs with speeds above 100 Mbit/s. However, if your equipment allows, you can build local network with speeds up to 1 Gbit/s per second.

The need for cable shielding.

When laying the wire in the baseboard, away from electrical wiring, subwoofers and other devices that emit EMR, you can use UTP to save money. It is still recommended to use an FTP cable or at least an F/UTP cable.

The installation location is where it takes place, outdoors or indoors.

If you're on the street, you'll have to buy a protected cable, which costs an order of magnitude more. For installation in an office, apartment or private house, it is enough to use a regular gray cable. Before installation in an office space, check the fire safety requirements.

Having studied what twisted pair is and what types it comes in, you can easily choose the cable that is suitable specifically for your conditions. Do not forget that right choice FTP cable is only half the battle; you also need to learn how to crimp correctly and how many cores to use.

For these purposes, you can also invite a specialist who will come with necessary equipment, will crimp the cable and configure all computers. Or you can check how the pressure test was done on the wire that the provider brought into the apartment, and do it in the same way.

24.01.2008 Carol Everett Oliver

Category 5e still accounts for the majority of horizontal cabling installations. But according to a recent study by FTM Consulting, Category 6 is increasingly being used in new projects and is expected to overtake Category 5e in the coming year. The position of the latter will be significantly weakened, and it will be used only in already operating and low-budget installations. Yet questions regarding the purpose of a Category 6 installation are asked again and again.

Modern information and voice applications, such as Gigabit Ethernet to the desktop, are designed for Category 5e. This solution has the necessary characteristics in accordance with the TIA 568-B specification. However, Category 6 provides better signal integrity over a wider bandwidth, which could be critical for a cable system to support more demanding applications in the future. Category 5e is defined in the frequency band up to 100 MHz, while Category 6 is defined in the 250 MHz band. In addition, significant improvements in the design and manufacturing process of Category 6 offer additional benefits in addition to greater bandwidth. Given the ever-increasing demand for bandwidth, which according to Moore's law doubles every year and a half, the need for speed and capacity could make the cable system obsolete if demands placed on it change.

Category 6 uses larger conductor diameters and smaller twist pitches to improve basic electrical performance such as coupling attenuation (see Figure 1). Some Category 6 cables include separators to further separate the pairs. Reduced attenuation and increased conductor size make Category 6 cable significantly more reliable in operation, which is necessary for applications requiring higher throughput, and ensures stable network operation during extreme temperature fluctuations. In addition, some Category 6 cables have exceptional balance due to their design and construction. This will make it possible to achieve immunity to noise, both internal and external to the cable.

Let's take a closer look at how physical differences affect network performance. The Nexans Data Communications Competence Center (DCCC) laboratory conducted several benchmark tests to determine signal integrity parameters for Category 5e and Category 6 cabling systems from various manufacturers. You can decide for yourself how significant this is when choosing a cable system.

REDUCING ERRORS

Category 6 was found to be less error prone than Category 5e in a previous study, and the test was conducted on multiple transceivers with different characteristics. Tests at the DCCC laboratory compared the number of errors (Cyclic Redundancy Check, CRC) for Category 5e and 6 when using a Gigabit Ethernet transceiver. Many people mistakenly believe that all transceivers are the same. However, in reality, transceivers even from the same manufacturer differ. Three devices were selected for the experiment. Gigabit Ethernet packets were transmitted over a full 100 m path with three connectors, first over Category 5e, then over Category 6.

Test results show a 13-fold reduction in CRC errors when using Category 6. Changing the cabling system to Category 6 improves the signal-to-noise ratio of the entire transport system, so transceivers can receive Ethernet packets more consistently and without errors. Thus, the better performance of Category 6 wiring results in greater network reliability. This additional headroom allows you to install network components that would otherwise result in significant downtime and additional costs.

Structured cabling systems are often installed in high-temperature areas, such as above-ceiling spaces, where there is often a temperature difference of up to 25°C during the day. These fluctuations affect the cable's performance. DCCC conducted a series of tests in which 1000BaseT signals were transmitted over 90 m over Category 5e, 6 and extended Category 6 cabling systems. At various stages of testing, the temperature was increased using an adjustable heater from 20 to 70°C in 10°C increments.

It turns out that at high temperatures, the error rate when using Category 5e wiring is significantly higher compared to Category 6 (see Figure 2). With an enhanced Category 6 cabling system, errors were even less common.

In addition to heat from external heat sources, cables are exposed to applications such as Power over Ethernet (PoE). To support power delivery over structured cabling, industry standards have defined the electrical and physical performance requirements for PoE applications. Adopted by the IEEE in 2003, the 802.3af standard defines a methodology for providing balanced power to connected end devices. Voltage power is limited physical characteristics and regulatory requirements. The 802.3af standards provide compatibility with existing equipment, so the recommendations are designed to provide Category 5e power, since most networks use 10BaseT or 100BaseTX technologies.

Applications that require power and data transmission over the same twisted pair cable, such as VoIP phones or security cameras, will eventually require more power. The IEEE 802.3 specification, known as PoE Plus, which has been in development for two years, is expected to be approved soon. As a result, the power allowed for transmission over twisted pair will increase from 13 to 60 W. As can be seen from the test results (see above), cable performance deteriorates with increasing temperature due to higher insertion loss. This may negatively impact the permissible maximum length of a fixed line or transmission path. Installing cables with best characteristics, such as Category 6, is in line with general industry trends. They use larger diameter conductors to minimize insertion loss while increasing current transfer capability.

RESISTANCE TO NOISE

Increased sensitivity to external noise becomes critical as data rates increase and higher signaling rates and complex coding are required. External sources of noise - power lines, air conditioning units, elevators, electrical equipment and interference from adjacent cables - cause voltage spikes, the so-called Electrical Fast Transient (EFT). They can radically affect the functioning of copper cables and lead to errors. There is a direct connection between balance and noise immunity. Balanced Category 6 cable is 50% more noise resistant than Category 5e.

In the DCCC tests, Category 5e, Category 6, and extended Category 6 cable were subjected to various levels of EFT while carrying Gigabit Ethernet packets. The relationship between errors and impulse noise was calculated and displayed graphically. There are significant differences in performance between balanced and unbalanced cables, as well as between Category 5e and Category 6 (see Figure 3).

INVESTMENT JUSTIFICATION

One of the main reasons for choosing Category 5e is the cost savings. Larger conductor diameters, smaller twist pitches and complex manufacturing processes make Category 6 cables more expensive. But everything is relative.

Yes, in terms of materials, Category 6 is 30-50% more expensive. But in reality, if you take into account the total cost information system, this discrepancy turns out to be negligible. In construction projects computing system All costs are usually divided into the following four categories:

Software (51%);

Equipment (22%);

Network infrastructure (20%);

Training and documentation (7%).

It should be taken into account that 20% of the investment in network infrastructure is distributed between passive and active components, as well as the costs of design and project management. Of this amount, wiring accounts for less than half, and cables account for only 35% of the remainder. Therefore, cabling for local systems represents less than 3% of the total project budget. The cost of switching from Category 6 to Category 5e turns out to be less than 1% of total costs.

Research shows that within life cycle telecommunications wiring has gone through at least two generations network equipment. The conclusion is obvious: designers and installers of cabling systems should opt for more advanced wiring. If you want your cabling system to support current and future applications, given the benefits of Category 6, investing in it is the minimum required. If noise, temperature fluctuations, and increasing speeds do not matter to you, then Category 5e is quite sufficient. The choice is yours.

Carol Everett Oliver is manager of BerkTek, the US division of Nexans, RCDD.