RJ45 cable and lan connectors

RJ45 connector use and origin

The RJ45 connector or port is a connection interface used mainly to interconnect data exchange networks between computers and other devices. The RJ45 rosette is rectangular and with a tab-shaped element that acts as a safeguard so that the cable does not come out of its interface.

It has a total of 8 pins, although not all are always used, since it will depend on the use of the cable and the speed of the network. The twisted pair cable known as UTP will be connected to this port. It was first used in 1991, and was designed by the EIA (Electronic Industries Alliance), from which the TIA / EIA-568-B, 568-A and 568-B1 standard was born, which basically defines the order of connectors and colors on the connector.

The most common use of this cable is networks under the Ethernet standard, being a serial-type interface that is capable of operating up to 10 Gbps currently, although there are implementations of 40 Gbps. Surely it sounds like the 802.3 standard, which is worked on in the first layer of the OSI model: 10BASE-T (connection to 10 Mbps), 100BASE-TX and 100BASE-T (connection to 100 Mbps), 1000BASE-T (connection to 1 Gbps) and 10GBASE-T (10 Gbps connection). There are other standards or variants for coaxial cables, for fiber optic cables and other types, but we will only focus on the RJ45 today.

The male connector measures approximately 2 cm long and is almost always made of transparent plastic to visualize the connection mode of your cables, in direct or cross mode. At its end it has metal connectors that have previously passed through each connector to make contact with its copper core. Higher category cables have these metal encapsulated connectors.

RJ45 rosette or thief

If in the previous case we have the Rj45 male connector, the rosette will be the female one, a hole with identical stockings as in the previous case and which will always have 8 connection wires for the 8 cables.

We are talking about a rosette or hub when instead of a connector we have several of them with the aim of multiplying the connection, although in that case it is only to power some device.

RJ45 color code

Before looking at the types of RJ45 cable we have, we consider it very important to know the order of the RJ45 conductors and to identify the colors of these conductors to know what they carry.

In this section we must distinguish two types of connection called crossover cable and direct cable whose functions are different, as well as the distribution of cables in the connector.

Direct cable

The direct cable is used to connect for two devices that are not the same, for example, our computer with a router, switch or hub. There are two ways to distribute the cables in the connector, according to the T568A standard and according to the T568B. in case changes it will work identically, and most importantly, both ends of the cable will be exactly the same.

A direct cable, in addition to providing network connection, is also used for telephone connection, sometimes in JR45 or more commonly in RJ11, and for network and power supply (PoE or Power over Ethernet).

Let's see in the following table the distribution according to T568A:

In the T568B standard, the reordering of cables would be as follows:

Both one end and the other must be exactly the same, and the distribution of functions will remain as shown in the table according to usage. TX stands for Transceive data (channel for transmitting data) and RX Receive data (channel for reviving data).

Crossed wire

If what we want is to interconnect two equal equipment, for example, post PC, we will need a crossover cable. Only this can give us a full-duplex connection and the possibility of sending and receiving simultaneously on two network interfaces that a priori send output signals.

In this case what we will have to do is use the T568A standard on one end of the cable and the T568B on the other end such that:

Basically the two pairs corresponding to orange and green are crossing, in this way we can obtain speeds of the 10 / 100BASE-T standard.

But there is still another way of connection so that in this case it conforms to the 1000BASE-T standard:

So we are crossing absolutely everything with the aim that the TX and RX signals become bidirectional and can send at the same time as listening.

Is all this necessary? Automatic crossover cable

Well, the truth is that currently it is not strictly necessary, since the 1000BASE-T or Gigabit Ethernet network interfaces add an automatic configuration function MDI / MDI-X that selects the mode in which the device is working to make it compatible. with any type of cable.

What is an RJ45 crimper

We will all have noticed that mounting one of these cables by hand is not easy at all due to having to place 8 cables fully aligned in parallel and with exactly the same length.

For this there is the crimping or crimping machine, a kind of pliers that has pliers to compress the male connector and thus get the end contacts to cross the conductors to make them functional. In turn, it compresses the two parts of the connector, leaving the cables sealed and fixed inside so that they do not leak. Once an RJ45 is crimped the connector can never be reused again.

The current crimpers also offer compatibility with other types of network connectors such as RJ11 for telephone use, and even purely electrical or coaxial connectors such as the metric or faston type.

RJ45 cable types

We already know how an RJ45 connector is, two different connection modes it has, although currently it almost does not matter, and even how to do them manually at home. So now it is time to know the different types of cables that we will find in the market.

Here we will basically find two types of specifications or cable families, the first in a distribution by categories and the second for its construction and type of shielding and shielding. They really both go hand in hand so even seeing them separately we are going to see their relationships.

RJ45 cable categories

The cables are divided into categories according to their construction, among which we find 7 different ones. Each of them is oriented to be used in one standard or several, providing better or worse performance and consequently more or less data transmission capacity.

Although it is true that not having a cable of a lower category than the supposedly necessary will not perform worse, the certifications will indicate that the cable that we buy will ensure that performance that we request. It is similar to degrees of IP protection, the more the better, but there are cases in which a waterproof mobile phone has ended up in the trash, the same could happen here.

Let's see then what are these categories:

Cat 5 Cat 5e Cat 6 Cat 6e Cat 7 Cat 7a Cat 8

It no longer belongs to the TIA / EIA standard because it is considered a low-performance cable. It is an unshielded twisted pair cable, used in Fast Ethernet (100 Mbps) networks that will support transmissions of up to 100 MHz with little noise.

If we buy a cheap cable and the typical Chinese that is under your house, it is possibly 5e. They may or may not have shielding and are capable of working on Gigabit ethernet networks at 1000 Mbps and transmitting at frequencies of up to 100 MHz defined in TIAEIA-568-B.

Another one of very common use and that is sometimes included in routers, switches and other network equipment is that of Cat 6. Also defined in the previous standard, it is used for GbE networks although it supports frequencies of 250 MHz, as it has shielding and greater resistance to external noise.

These are already less frequencies, although in 10G routers one is almost always included. This cable falls within the high range and is capable of transporting up to 10 Gigabits per second at frequencies up to 500 MHz.

Cat 7 is not very common yet, with cables almost always used for data centers and 10GbE networks with low loss rates. It supports frequencies of 600 MHz and is defined in the ISO-11801 standard, having a joint and individual shield for each twisted pair.

Above the previous one we have a category with cables that are capable of transmitting at a frequency of 1000 MHz and speeds of up to 10 or 40 Gbps if they are of good quality.

And if we want the best available on the market, we have to go to the last certified category, 8. Maximum internal and external protection, and even the connector of these cables provide us with Ethernet speeds of 40 Gbps and frequencies of 2000 MHz.

All these cables are supposed to ensure these features up to 100 meters away. Even so, for long distances fiber optic is always recommended, as they are invulnerable to electromagnetic noise from the outside.

Types of RJ45 cables by their construction

These cables in turn will be classified in one of the above categories, but their abbreviations basically depend on the type of insulation that they have in their twisted pairs and the outer covering. The more insulation, the stronger they will be against electromagnetic interference from the outside and therefore the greater the frequency they can transport.

It seems obvious by now, but twisted pair cables get their name for having 4 pairs of twisted cables in groups of two to reduce the effects of outside electromagnetic frequencies.

UTP FTP STP SFTP SSTP

Unshielded Twisted Pair

It will be an unshielded braided cable, so all the stranded pairs coexist in the same plastic covering without any element to isolate them. These cables belong to categories 5 and 5e normally.

Foiled Twisted Pair

For the construction of this cable, an external shield has been used that surrounds all the cable pairs at the same time, which will normally be made of aluminum and plastic. In turn, each twisted pair will or will not be separated from the others with a plastic cover in addition to the conductor itself. These cables belong to categories 5e and 6.

Shielded Twisted Pair

We now have cables that belong to categories 6 or 6e. In this case we have an individual shield in each twisted pair to isolate them from their peers, giving us an impedance of about 150 Ω

Screened Foiled Twisted Pair

Or single shielded laminated cable, based on FTP cable, but with LSZH metal mesh which in turn covers the overall shield. This sheet performs the same function as that of a coaxial cable, connecting to ground to discharge electromagnetic interference from outside and from the pairs themselves. These cables belong to category 6 or higher.

Screened Shielded Twisted Pair

We keep adding words to the cable and with it protection. In this case we are talking about very high quality cables and belonging to categories higher than 6 in all cases. These are individually shielded in aluminum in each twisted pair, and also externally shielded in aluminum, even with LSZH metallic braiding to provide it with greater rigidity and grounding.

Conclusions on RJ45 cables

UTP cable is one of the most widely used cables in today's networks, eventually replaced by fiber optic cables for trunks, with the aim of interconnecting several large local area networks or even metropolitan area WAN networks.

Only data centers implement fiber in their internal networks, since RJ45 cables increasingly offer greater benefits at a very similar price as we can see if we go to Amazon for example and look for Cat 5 or Cat 8 cables. We leave you now with a few interesting networking tutorials:

What type of cables do you use in your network? Have you ever looked at cable distribution and construction?