Tham khảo tài liệu 'krone - white paper - limitation of rj21 in ethernet', công nghệ thông tin, quản trị mạng phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Use of RJ-21 Connectors in 100Base-T Active Connectivity KRONE, Inc. has performed numerous site surveys of end-user networks over the past year, and it has come to our attention that many users are upgrading to new 100Base-T switches that utilize the RJ-21 connector, also commonly known as a “Telco” connector, or “Amphenol” type. It consists of a 50 pin connector that accepts 25 pairs of cable simultaneously. RJ-21 KRONE has not been recommending this type of interface to our customers due to serious technical limitations of this connector, as described in this paper. All versions of the RJ-21 that we have seen do not conform to the impedance matching requirements of KRONE’s TrueNetTM system, and consequently can seriously effect network performance. Figure 1 shows a TrueNet impedance matched channel. All components are matched for optimum performance together, and the distance plot shows a clean trace centered around a nominal 100 ohms. Impedance matching of cabling and components is critical for efficient data transmission. Research conducted by KRONE and Anixter Figure 1: A TrueNet Matched- shows that mismatched systems can be Impedance Channel standards-compliant, and still allow frame error rates approaching 25% of packets sent! (source- Anixter). Figure 2 shows the frequency trace of the channel shown in Figure 1. The impedance stays tightly controlled across the entire range of 100Base-T operation, from approximately 1 to 125 Megahertz. These charts are displayed to show a baseline for the comparisons that we will make to the RJ-21 interfaces that we have seen in the field. Figure 2: Frequency Trace of a TrueNet Channel KRONE, Inc. 6950 S. Tucson Way, Suite R Englewood, Colorado 80112 1-800-775-5766 Figure 3 shows a close-up of an RJ21 harness that was connected to a switch at an actual user site. The impedance spike here is enormous—far greater than the 100 Ohms +/- 15 called out in the standard (notice the .
