The friend who knows the maximum distance of the network data transmission to the network knows that the twisted pair has an "insurmountable" "100 meter" transmission distance. Whether it is a three-type twisted pair with a transmission rate of 10M, or a Category 5 twisted pair with a transmission rate of 100M, or even a Category 6 twisted pair with a transmission rate of 1000M, the farthest effective transmission distance is 100 meters. In the integrated wiring specification, it is also explicitly required that the horizontal wiring cannot exceed 90 meters, and the total length of the link cannot exceed 100 meters. That is to say, 100 meters is a limit for wired Ethernet, which is the link length from the network card to the hub device.
The transmission of the network is actually the transmission of the network signal on the twisted pair. As an electronic signal, when transmitted in the twisted pair, it is inevitably affected by the resistance and capacitance, which leads to the attenuation and distortion of the network signal. Attenuation or distortion of the signal to a certain extent will affect the effective and stable transmission of the signal. Therefore, the twisted pair has a transmission distance limit, so how do you calculate the upper limit of 100 meters? Category 5 UTP and Super Category 5 UTP are mainly for computer network services. According to Fast Ethernet's 100Base-TX specification, the communication rate is 100mbps, and the time taken by 100mbps Ethernet to transmit 1 bit of data (aka "bit time" Can be calculated as follows: 1-bit time = 1/100mbps = 10ns Ethernet is CSMA/CD (Carrier Sense Multiple Access with Collision Detection), carrier sense multiple access technology with collision detection (carrier sense multi-point access / collision Detecting) Sharing communication channels, when introduced into the exchange, is still inseparable from this technology. A device is connected to both ends of a link. The two devices may send data at the same time, causing a collision. The collision domain is 2. The conflict will lose the packet. To avoid packet loss due to collisions, Ethernet uses collision detection and back-retransmission techniques. In order to do back-off and re-send, you must ensure that one end can detect the conflict before transmitting a packet. The smallest frame length of Ethernet is 64 bytes, which is 512 bits. Calculated at a rate of 100 mbps, transmitting 512 bits takes 512 bits * 10 ns = 5120 ns. Data information is transmitted over the network and is delayed when passing through different components. The delay for Category 5 UTP is 5.56 ns/m. When designing Ethernet, it is required to follow a relay rule, also known as the Golden Rule or the 5-4-3-2-1 rule. This rule 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 5120 ns for a transmission rate of 100 mbps. In the loop, the network components have cables, relay units, MAUs, and DTEs. Adding their delays and multiplying by 2, the loop delay is obtained, and the loop collision diameter can also be calculated. According to this theory, the farthest distance that a signal can transmit before a minimum frame is transmitted can be calculated. This is why the link span is limited to 100 meters. When it exceeds 100 meters, because the conflict cannot be detected in time, the packet destroyed by the conflict is transmitted and received by the receiver. The packet is forced to be discarded because it cannot pass the verification. At this time, the mechanism for resending the retransmission is not It is activated, which will result in the loss of the package. When the transmission rate is lower than 100 mbps, the limit length of 100 meters can be appropriately relaxed in practical applications. It must be stated that this is actually effective, but it does not meet the standards. In the certification test, it must be explained, otherwise there will be some problems, such as product warranty. The maximum cable distance during actual construction can be seen from the above. When using PoE power supply, why should the maximum length of the network cable not exceed 100 meters? However, in actual construction, in order to ensure the quality of the project, it is generally 80-90 meters. 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 150-200 meters (depending on the quality of the network cable). Therefore, the PoE power transmission distance is not determined by PoE technology, but by the cable type and quality. Although the actual quality of the network cable can break through the limit of 100 meters in the actual construction, the equipment can work normally, but this is not recommended. Because some potential problems are not immediately presented, but appear slowly over time, which can cause subsequent maintenance problems. The simplest case, such as the upgrade of the bandwidth, makes the equipment that can work normally at a distance of more than 100 meters will not work properly after the network speed is greatly improved. The influence of cable category and quality on transmission distance Category 5 (Cat 5) is the most common standard network cable on the market today, but the quality produced by different manufacturers varies greatly, especially in the domestic price-oriented environment. In order to reduce the cost, many manufacturers replaced the copper wire with copper-clad iron and copper-clad steel, which led to a decline in the transmission distance of the network cable, and even the phenomenon of network instability and packet loss, and the equipment manufacturers often turned black pots, which is really embarrassing. Therefore, if you want to make PoE the best effect, you must use a good quality network cable, not because of small loss, affecting the overall quality of the project.
Super Category 5 (Cat 5e): Compared to Category 5 twisted pair, Super Category 5 twisted pair has less attenuation and crosstalk, providing a more solid network foundation for most applications (especially supporting Gigabit) Ethernet 1000Base-T cabling) brings convenience to network installation and testing, and has become a better solution for current network applications. The transmission characteristics of the Super Category 5 line are the same as those of the ordinary Category 5 line, but the Category 5 cabling standard stipulates that all four pairs of lines of the Category 5 cable can achieve full duplex communication.
Category 6 (Cat 6): This type of cable has a transmission frequency of 1MHz to 250MHz. The Category 6 cabling system should have a large margin at 200MHz. The integrated attenuation crosstalk ratio (PS-ACR) should have a large margin, which provides twice the super five. The bandwidth of the class. The transmission performance of Category 6 cabling is much higher than the Category 5 standard and is best suited for applications with transmission rates above 1Gbps. An important difference between Category 6 and Category 5 is that it improves performance in terms of crosstalk and return loss. For a new generation of full-duplex high-speed network applications, excellent return loss performance is extremely important. The basic link model is eliminated in the six categories of standards. The cabling standard uses a star topology. The required cabling 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 in the transmission distance between the Category 6 and Super Category 5 lines, that is, the maximum transmission distance of a single segment is 100 meters. Of course, the six types of lines can be appropriately increased in the transmission distance. The so-called 100 meters refers to the technical indicators such as 1000M bandwidth that cannot be met, which brings about problems such as speed drop.
The transmission of the network is actually the transmission of the network signal on the twisted pair. As an electronic signal, when transmitted in the twisted pair, it is inevitably affected by the resistance and capacitance, which leads to the attenuation and distortion of the network signal. Attenuation or distortion of the signal to a certain extent will affect the effective and stable transmission of the signal. Therefore, the twisted pair has a transmission distance limit, so how do you calculate the upper limit of 100 meters? Category 5 UTP and Super Category 5 UTP are mainly for computer network services. According to Fast Ethernet's 100Base-TX specification, the communication rate is 100mbps, and the time taken by 100mbps Ethernet to transmit 1 bit of data (aka "bit time" Can be calculated as follows: 1-bit time = 1/100mbps = 10ns Ethernet is CSMA/CD (Carrier Sense Multiple Access with Collision Detection), carrier sense multiple access technology with collision detection (carrier sense multi-point access / collision Detecting) Sharing communication channels, when introduced into the exchange, is still inseparable from this technology. A device is connected to both ends of a link. The two devices may send data at the same time, causing a collision. The collision domain is 2. The conflict will lose the packet. To avoid packet loss due to collisions, Ethernet uses collision detection and back-retransmission techniques. In order to do back-off and re-send, you must ensure that one end can detect the conflict before transmitting a packet. The smallest frame length of Ethernet is 64 bytes, which is 512 bits. Calculated at a rate of 100 mbps, transmitting 512 bits takes 512 bits * 10 ns = 5120 ns. Data information is transmitted over the network and is delayed when passing through different components. The delay for Category 5 UTP is 5.56 ns/m. When designing Ethernet, it is required to follow a relay rule, also known as the Golden Rule or the 5-4-3-2-1 rule. This rule 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 5120 ns for a transmission rate of 100 mbps. In the loop, the network components have cables, relay units, MAUs, and DTEs. Adding their delays and multiplying by 2, the loop delay is obtained, and the loop collision diameter can also be calculated. According to this theory, the farthest distance that a signal can transmit before a minimum frame is transmitted can be calculated. This is why the link span is limited to 100 meters. When it exceeds 100 meters, because the conflict cannot be detected in time, the packet destroyed by the conflict is transmitted and received by the receiver. The packet is forced to be discarded because it cannot pass the verification. At this time, the mechanism for resending the retransmission is not It is activated, which will result in the loss of the package. When the transmission rate is lower than 100 mbps, the limit length of 100 meters can be appropriately relaxed in practical applications. It must be stated that this is actually effective, but it does not meet the standards. In the certification test, it must be explained, otherwise there will be some problems, such as product warranty. The maximum cable distance during actual construction can be seen from the above. When using PoE power supply, why should the maximum length of the network cable not exceed 100 meters? However, in actual construction, in order to ensure the quality of the project, it is generally 80-90 meters. 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 150-200 meters (depending on the quality of the network cable). Therefore, the PoE power transmission distance is not determined by PoE technology, but by the cable type and quality. Although the actual quality of the network cable can break through the limit of 100 meters in the actual construction, the equipment can work normally, but this is not recommended. Because some potential problems are not immediately presented, but appear slowly over time, which can cause subsequent maintenance problems. The simplest case, such as the upgrade of the bandwidth, makes the equipment that can work normally at a distance of more than 100 meters will not work properly after the network speed is greatly improved. The influence of cable category and quality on transmission distance Category 5 (Cat 5) is the most common standard network cable on the market today, but the quality produced by different manufacturers varies greatly, especially in the domestic price-oriented environment. In order to reduce the cost, many manufacturers replaced the copper wire with copper-clad iron and copper-clad steel, which led to a decline in the transmission distance of the network cable, and even the phenomenon of network instability and packet loss, and the equipment manufacturers often turned black pots, which is really embarrassing. Therefore, if you want to make PoE the best effect, you must use a good quality network cable, not because of small loss, affecting the overall quality of the project.
Super Category 5 (Cat 5e): Compared to Category 5 twisted pair, Super Category 5 twisted pair has less attenuation and crosstalk, providing a more solid network foundation for most applications (especially supporting Gigabit) Ethernet 1000Base-T cabling) brings convenience to network installation and testing, and has become a better solution for current network applications. The transmission characteristics of the Super Category 5 line are the same as those of the ordinary Category 5 line, but the Category 5 cabling standard stipulates that all four pairs of lines of the Category 5 cable can achieve full duplex communication.
Category 6 (Cat 6): This type of cable has a transmission frequency of 1MHz to 250MHz. The Category 6 cabling system should have a large margin at 200MHz. The integrated attenuation crosstalk ratio (PS-ACR) should have a large margin, which provides twice the super five. The bandwidth of the class. The transmission performance of Category 6 cabling is much higher than the Category 5 standard and is best suited for applications with transmission rates above 1Gbps. An important difference between Category 6 and Category 5 is that it improves performance in terms of crosstalk and return loss. For a new generation of full-duplex high-speed network applications, excellent return loss performance is extremely important. The basic link model is eliminated in the six categories of standards. The cabling standard uses a star topology. The required cabling 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 in the transmission distance between the Category 6 and Super Category 5 lines, that is, the maximum transmission distance of a single segment is 100 meters. Of course, the six types of lines can be appropriately increased in the transmission distance. The so-called 100 meters refers to the technical indicators such as 1000M bandwidth that cannot be met, which brings about problems such as speed drop.
The advantage of USB Cable Type C is that it supports higher current, that is that more current can be passed by Type-C in the same time. In this way, the charging speed of the device can be accelerated. At present, the charging current of most Type-C data lines is generally 2A. If the charging rate of 3A is to be reached, a high-current wall charging matching it is required. That is to say, if the wall charge only supports 1A, whether it is charged with 2A or 3A data line, there is no difference fundamentally. If the current supported by the wall charging is 2A, and the type-C data cable of 2A/3A is matched, the effect can be significantly changed.
In addition, the device equipped with the Type-C interface can be charged by connecting the mobile power supply through the Type-C cable or Usb C Cable. Users do not need to carry the charging cable, but can have the wall charging and Type-C cable. In addition, when selecting a Type-C charging cable, We should pay attention to the current limit. The charging data cable 1A does not have fast charging performance, 2A is the most commonly used Type-C charging data line, and 3A is the best data line at present. If you want to have fast charging effect, you must choose the Type-C charging data line with 3A current.
The highlights of Type-C interface are thinner design, faster transmission speed (USB3.1 up to 10Gbps) and stronger power transmission (up to 100W).The biggest feature of Type-C double-sided plugable interface is that it supports double-sided insertion of USBinterface. Officially solved the USB never insert the worldwide problem, the front and the back of the random plug.The USB Cable used with it must also be thinner and lighter.
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