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What is the maximum transmission distance of the network cable?

-Friends who know more about the network know that the twisted pair has an insurmountable transmission distance of 100 meters.

Contributed by Shanghai Jibu Automation Technology Co., Ltd. 1/9/2020 14:03:29

0 Popularity: 46

  • Keywords: network cable transmission distance
  • Abstract: Whether it is a Category 3 twisted pair with 10M transmission rate, a Category 5 twisted pair with 100M transmission rate, or even a Category 6 twisted pair with 1000M transmission rate. The longest effective transmission distance is 100 meters. In the comprehensive wiring specifications, it is also explicitly required that the horizontal wiring cannot exceed 90 meters, and the total link length cannot exceed 100 meters, which means that 100 meters is a limit for cable.

Friends who know more about the network know that the twisted pair has an insurmountable transmission distance of 100 meters. Whether it is a Category 3 twisted pair with a transmission rate of 10M, 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 longest effective transmission distance is 100 meters. In the comprehensive wiring specifications, it is also explicitly required that horizontal wiring cannot exceed 90 meters, and the total link length cannot exceed 100 meters, which means that 100 meters is a limit for cable.

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米最大距离是怎么得来的? How did you get the maximum distance of 100 meters?

What causes the 100m transmission limit of twisted pair? The transmission of the network is actually the transmission of the network signal on the twisted pair. As an electronic signal, when transmitting in the twisted pair, it must be affected by the resistance and capacitance, which leads to the attenuation and distortion of the network signal. . Signal attenuation or distortion reaches a certain level, which will affect signal transmission.

Ethernet uses CSMA / CD (Carrier Sense Multiple Access with Collision Detection), a carrier-monitoring multi-record access technology with conflict detection, to share communication channels. After the introduction of switching, this technology is still inseparable. Devices are connected to both ends of a link. These two devices may send data at the same time, causing conflicts. At this time, the collision domain is 22. The collision will lose data packets. To avoid packet loss due to collisions, Ethernet uses collision detection and backoff retransmission technologies. In order to back off and resend, you must ensure that one end can detect a collision before transmitting a data packet.

Data information is transmitted in the network, and there will be a delay when passing through different components. The delay of the five types of UTP is 5.56ns / m. When designing Ethernet, it is required to abide by a relay rule. This rule is also called the golden rule. This rule applies not only to 10 Mbps Ethernet, but also to Fast Ethernet. This rule requires that when the probation conflict delay cannot exceed 512 bits, for a transmission rate of 100mbps, it is 5120ns. In the ring, the network elements include cables , relay units, MAU, and DTE. Add their delays and multiply by 2 to get the ring delay. At the same time, the ring conflict diameter can also be calculated. According to this theory, the longest 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 damaged by the conflict is transmitted and received by the receiver. This packet is forced to be discarded because it fails the verification. Not activated, resulting in packet loss.

When the transmission rate is lower than 100mbps, in practical applications, the limit length of 100 meters can be appropriately relaxed. It must be stated that although this is actually effective, it does not meet the standard. When re-certification testing, it must be explained, otherwise some problems may occur.

实际施工时最大线缆距离 2.Maximum cable distance during actual construction

Why is the maximum length of the network cable not to exceed 100 meters when using PoE power supply? In actual construction, in order to ensure the quality of the project, generally 80-90 meters.

The transmission distance here refers to the maximum speed, such as 100m. If the speed drops to 10M, the transmission distance can usually be extended to 150-200 meters. Therefore, the transmission distance of PoE power supply is not determined by PoE technology, but the type and quality of the network cable.

Although in actual construction, a better-quality network cable can break the 100-meter limit and the equipment can work normally, but this approach is not recommended. Because some potential problems do not appear immediately, but slowly appear over time, which will cause subsequent maintenance problems. In the simplest case, for example, the upgrade of bandwidth makes the equipment that can work normally at a distance of more than 100 meters will not work normally after the network speed is greatly increased.

线缆类别和质量对传输距离的影响 3.Effect of cable type and quality on transmission distance

Category 5 cable (Cat 5) is the most common standard network cable on the market today, but the quality of production varies greatly from manufacturer to manufacturer. Especially in the domestic price-oriented environment, many manufacturers use copper wires to reduce costs. Substituting copper-clad iron and copper-clad steel has led to a decrease in the transmission distance of the network cable, and even network instability and packet loss have occurred. It is unjust for equipment manufacturers to blame. So if you want to make the best effect of PoE, you must use a good quality network cable.

Cat 5e: Compared with Cat 5e twisted pair, Cat 5e twisted pair has less attenuation and crosstalk, which can provide a more solid network foundation and meet most application requirements (especially supporting Gigabit Ethernet 1000Base-T wiring), which brings convenience to network installation and testing, and has become a better solution in current network applications. The transmission characteristics of Cat-5 cables are the same as those of Cat-5 cables, but Cat-5 cabling standards stipulate that all 4 pairs of Cat-5 cables can achieve full-duplex communication.

Category 6 (Cat 6): The transmission frequency of this type of cable is 1MHz to 250MHz. The Category 6 cabling system should have a large margin at 200MHz for the comprehensive attenuation crosstalk ratio (PS-ACR), which provides 2 times more than five Class bandwidth. The transmission performance of Category 6 cabling is much higher than the Category 5 standard, and it is most suitable for applications with transmission rates higher than 1Gbps.

An important difference between Category 6 and Category 5 is that it improves the performance in terms of crosstalk and return loss. For new generation 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 wiring standard adopts a star topology. The required wiring distance is: the length of the permanent link cannot exceed 90 meters, and the channel length cannot exceed 100 meters.

Review editor (Wang Jing)
For more information, please visit Shanghai Jibu Automation Technology Co., Ltd. ( http://c.rgwds.com/?cid=57822 )

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