How long can the network cable be stretched in the
2022-10-31
Theoretically, the maximum length of network cabling cannot exceed 100 meters. If the quality of the network cable is good, the tensile resistance and the performance of shielding interference are strong, the longest length can reach about 120 meters, and it is not recommended to be longer.
The reason why the network cable cannot be too long for the longest time
The only languages that the computer can recognize are 0 and 1, and the signals transmitted by the network are 0 and 1. These signals become current when they pass through the network cable, and the current intensity of the network cable is between -15V and +15V, and there is resistance when the current is transmitted through the network cable. Therefore, according to the principle of high-voltage transmission, the longer the line, the greater the voltage level must be used to transmit electricity. If the network cable is too long, but the voltage is so low, the signal will be weakened until it is lost. Therefore, the network cable should not be too long
How many meters can a network cable run?
The theoretical value of a cabling node is 100 meters. In fact, because the quality of the network cable can not be very good, the signal transmission attenuation is very large, such as the bandwidth from the route is 10 megabytes, and the bandwidth to the computer is 1M. Therefore, the length of the network cable is usually better within 50M. Of course, you shouldn't have much of a problem with 2-30M.
What is the longest length of the network cable?
The general office network cable can be connected up to about 150 meters! It is not recommended to use the network cable if it is too long; there is no restriction on using optical fiber directly!
1. The maximum distance of network cable data transmission
Friends who know more about the network know that twisted pair has an "insurmountable" "100 meters" transmission distance. Whether it is a Category 3 twisted pair with a 10M transmission rate, or a Category 5 twisted pair with a 100M transmission rate, or even a Category 6 twisted pair with a 1000M transmission rate, the maximum effective transmission distance is 100 meters.
In the integrated cabling specification, it is also clearly required that the horizontal cabling cannot exceed 90 meters, and the total length of the link cannot exceed 100 meters. That said, 100 meters is a limit for wired Ethernet, and this limit is the link length from the network card to the hub device.
2. How did the maximum distance of 100 meters come about?
What is the upper limit of the 100-meter transmission distance of the twisted pair? This requires a deep study of the deep physics of the twisted pair. The transmission of the network, in fact, is the transmission of the network signal on the twisted pair, as an electronic signal, when transmitted in the twisted pair, it must be affected by resistance and capacitance, which leads to the attenuation and distortion of the network signal. If the attenuation or distortion of the signal reaches a certain extent, it will affect the effective and stable transmission of the signal.
3. Therefore, there is a transmission distance limit for twisted pairs, so how to calculate the upper limit of 100 meters?
Category 5 UTP and Category 5 UTP are mainly for computer network services, according to the 100Base-TX regulations of Fast Ethernet, the communication rate is 100Mbps, and the time taken by 100mbps Ethernet to transmit 1 bit of data (also known as "bit time") can be calculated as follows:
1-bit time = 1/100 Mbit/s = 10 ns
Data information is transmitted through the network, and delays are generated when passing through different components, and the delay of Category 5 UTP is 5.56ns/m. When designing Ethernet, there is a trunking rule called the Golden Rule or the 5-4-3-2-1 rule, which applies not only to 10Mbps Ethernet, but also to Fast Ethernet. This rule requires that the loop collision delay should not exceed 512 bits, which is 5120ns for a 100Mbps transmission rate. In the loop, the network elements include cables, relay units, MAUs, DTEs, etc., and their delays are added up and multiplied by 2 to obtain the loop delay, and the diameter of the loop collision can also be calculated. According to this theory, the maximum distance that can be transmitted before a minimum frame is sent can be calculated. That's why the link span is limited to 100 meters.
When more than 100 meters, because the conflict cannot be detected in time, the packet that was damaged due to the conflict is transmitted and received by the receiver, and the packet is forced to be discarded because it cannot pass the verification, and the mechanism of backward and retransmission is not activated, so the packet will be lost. When the transmission rate is lower than 100 Mbps, the 100-meter length limit can be appropriately relaxed in practical applications. It must be stated that, while effective, does not meet the criteria. This must be stated during the certification test, otherwise there may be some problems, such as product warranty.
Fourth, the maximum cable distance during actual construction
As can be seen from the above, why the maximum length of the network cable should not exceed 100 meters when using PoE power supply. However, during the actual construction, in order to ensure the quality of the project, 80-90 meters are generally taken.
Please note that the transmission distance here refers to the maximum rate, such as 100M, if the rate is reduced to 10M, the transmission distance can usually be extended to 150-200m (depending on the quality of the network cable). Therefore, the transmission distance of PoE power supply is not determined by PoE technology, but by the type and quality of network cables.
Although in actual construction, a good quality network cable can break through the limit of 100 meters and the equipment can work normally, but this practice is not worth recommending. This is because potential problems do not manifest themselves immediately, but rather slowly over time, which can lead to maintenance problems down the road. In the simplest case, such as the upgrade of bandwidth, the equipment that can work normally at a distance of more than 100 meters will not work normally after the network speed is greatly improved.
The effect of cable type and quality on transmission distance
Cat 5: It is the most common standard network cable on the market, but the quality of production by different manufacturers varies greatly, especially in the domestic price-oriented environment, many manufacturers in order to reduce costs, the copper wire is replaced by copper-clad iron and copper-clad steel, resulting in a decrease in the transmission distance of the network cable, and even network instability, packet loss, etc., and equipment manufacturers often carry the black pot, which is really wrong. Therefore, if you want to make the best PoE effect, you must use a good quality network cable, and you must not affect the overall quality of the project due to small losses.
Cat 5e: Compared with Cat 5e, Cat 5e has less attenuation and crosstalk, which can provide a more solid network foundation and meet the needs of most applications (especially supporting Gigabit Ethernet 1000Base-T cabling), which brings convenience to the installation and testing of the network and becomes a better solution in current network applications. The transmission characteristics of the Category 5 cable are the same as those of the ordinary Category 5 cable, but the Category 5e cabling standard stipulates that all 4 pairs of wires of the Category 5e cable can achieve full-duplex communication.
Cat 6: The transmission frequency of this type of cable is 1MHz~250MHz, and the comprehensive attenuation crosstalk ratio (PS-ACR) of the Cat6 cabling system should have a large margin at 200MHz, which provides 2 times the bandwidth of Cat5e. The transmission performance of Category 6 cabling is much higher than that of Category 5e standards, and it is most suitable for applications with transmission rates higher than 1Gbps.
An important difference between Category 6 and Category 5e is the improved performance in terms of crosstalk and return loss, which is extremely important for the next generation of full-duplex high-speed network applications. The basic link model is eliminated in the six types of standards, and the cabling standard adopts a star-shaped topology, and the required wiring distance is: the length of the permanent link cannot exceed 90 meters, and the channel length cannot exceed 100 meters.
There is no strict difference between the Category 6 line and the Category 5 line in terms of transmission distance, that is, the maximum transmission distance of a single section is 100 meters. Of course, the transmission distance of the six types of lines can be appropriately increased, and the so-called 100 meters refers to the fact that after exceeding, it will not be able to meet the technical indicators such as 1000M bandwidth, which will bring problems such as speed reduction.
The main difference between a four-core network cable and an eight-core network cable is transmission
What is the difference in transmission distance?
The network cable is one of the mediums used as the network transmission signal, the network cable that is commonly used at present is the 8-core network cable, and some ordinary projects will use the 4-core network cable, under the 100 megabit network, the network cable relies on the internal 4 main lines to transmit the network, in a sense, the 8-core network cable and the 4-core network cable are no different in the process of transmitting the network. However, in terms of transmission effect and stability, the 4-core network cable is obviously not as good as the 8-core network cable.
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