FAQs about network cabling

1. Why cannot I use network debugging to check the cable performance?
At present, many users do not perform certification tests on the twisted pair wires installed, but conduct tests during network debugging. When the network can be connected, the installed cables are deemed to be qualified. This is not only wrong, but also very dangerous. Due to the low network traffic during network debugging, users do not feel any problems at this time. However, when the network traffic is high, it may be difficult to access the Internet. The connectivity of network debugging does not mean that the cable meets the installation standards, nor does it mean that the cable can work correctly during normal network operation. In addition, most users are currently installed with Category 5 twisted pair wires, and the network running is 10Base-T. However, 10Base-T can run either 100Base-TX or not. Therefore, it is necessary to pass the relevant certification test to verify whether the installed cable can support high-speed signals. Otherwise, a cable problem occurs only when the cable is upgraded to high-speed networks, it is no longer possible or difficult to fix.

2. What is a cable verification test and certification test?

The cable verification test is a general test of the cable's breaking, length, and whether the twisted pair connection is correct. Verify the test and do not test the electrical indicators of the cable. Certification testing is based on a certain international cable standard. It includes all the content of the verification test and the indicators of the standard test cable, such as attenuation and characteristic impedance. The verification test fails to ensure that the installed cable can pass through high-speed digital signals such as 10 m or 10 MHz. Only after passing the authentication test can the installed cable support 10 m or M signals.

3. What are the standards or specifications for cable certification testing?

At present, the international certification and testing standards for on-site installation of cables mainly include TIA 568A and ISO/IEC 11801. The former is mainly used in North America, while the latter is mainly used in Europe. In addition, some network standards have also made some provisions on cables. However, the above two types of cable standards are used for the certification test of cables installed on site. Test standards and specifications) include: cable link model, test method, required test parameter content) and test limit parameter specific values or methods) requirements for certification testing instruments.

4. What is TSB-67 standard?

Before 1995, the TIA 568A standard did not set forth the five-category twisted pair UTP5 or STP5 installed on site. More and more users are installing a large number of five-category twisted pair wires to meet the needs of high-speed networks, the user needs to perform certification tests on the installed cat5e twisted pair wires. To this end, the TIA Board published the TSB-67 standard in October 1995, which is an appendix to the TIA 568A standard, it is applicable only to the certification standard for five cat5e twisted pair wires installed on site.

5. What are the characteristics of UTP and STP cables?

At present, many users are difficult to choose between UTP5 or STP5 cable installation. Many users only know that STP cables have better anti-interference performance than UTP cables. In fact, one of the main purposes of STP cables in Europe is to prevent signals transmitted in the cables from interfering with other electrical equipment by external radiation. UTP cables are cheaper than STP cables, and are easy to install and maintain than STP cables. STP cables are more expensive than UTP, and have higher installation and construction requirements. Therefore, the construction cost is more expensive than UTP, And the maintenance cost is not as simple as UTP. STP has better anti-interference performance than UTP, but the STP shield must be connected. If a fault occurs in the shield layer, such as poor grounding or open circuit, the consequences are counterproductive. There are no standards or methods for detecting the shielding layer in the field, that is, the performance of the STP cable cannot be quantitatively described in the field.

6. What is a cable Link )?

The so-called cable link refers to the connection of a cable, including a cable, plug, socket, or jumper frame, coupler, etc. Different standards define different links, that is, testing models, such as TSB-67 specifies the Basic Link), Channel Link Channel ). It is particularly emphasized that the link is not equal to the cable, and the cable is only part of the link. If you want the installed cable system to support MHz bandwidth, it should be that the link achieves this capability, not just the cable.

7. What is cat5e twisted pair wires and their applications?

Cat5e twisted pair wires are recently released by cable manufacturers for LAN. These manufacturers claim that these cat5e lines can support signal transmission frequencies of MHz or higher. Whether these cat-5e lines can meet the frequency indicators claimed by their manufacturers, this is not the case in actual application:

First, the current maximum transmission frequency of the LAN does not exceed 100 MHz, 100Base-TX, a relatively new fast Ethernet, does not exceed MHz transmission frequency, so we haven't seen its actual application in the near future;

2. Different from links, cables can transmit at a frequency of MHz, but not equal to links. Because the link consists of cables, plugs, sockets, even coupler, and distribution frames. To obtain the cat5e link, ensure that all components in the link must meet the cat5e standard. It is meaningless only when the cable category is cat5e and the link cannot reach cat5e.

Third, there is no way to test the installation of cat5e links on site, that is, there is no standard on-site testing of the actual performance of these high-speed cables. Since there is no way to check whether the installed cable can achieve the performance of cat5e, it cannot fundamentally guarantee the actual investment.

8. What is an Impedance exception Impedance Anomaly)

The impedance is an electrical indicator of the cable and should be a constant in the cable. If the impedance along the cable is not a constant, reflection is generated when the impedance changes. Fluke's DS100 and DS2000 report impedance exceptions using the default reflection value of 15%, that is, if the reflected signal exceeds 15%, the impedance exception is reported. The characteristic impedance curve can be drawn at DSP100/2000. The ideal curve should be a straight line. If the impedance is abnormal, the peak or valley appears in the curve. The peak indicates that the impedance increases, and the Valley indicates that the impedance decreases.