Gigabit Ethernet and cat6 cabling

In September 1997, the ISO/IEC JTC1 SC25 WG3 Standards Committee decided to develop two new types of cables for the next version of ISO 11801, the two new types of cables are divided into six categories/Class E and seven categories/Class F according to their performance. The decision aroused great interest in the cabling industry and some standards committees (especially the American organization TIA/EIA and the European CENELEC.
In addition to the work carried out by the Cabling Standards Board, the LAN Standards Board is also developing technology to implement Gigabit transmission on Existing structured cable systems. As a special LAN technology, the Gigabit Ethernet network, which was studied in, has aroused widespread attention in the network industry. The most challenging task facing the IEEE 802.3 committee is to develop a reliable and robust Gigabit Ethernet technology that can run on existing five/D-level systems.
As we all know, Ethernet technology is closely related to Cabling Technology. How can we develop the Gigabit Ethernet technology to support the next generation of cables, especially the recommended cat6/Category E cables?
IEEE 802.3 Gigabit Ethernet
The Gigabit Ethernet project started in 1996 and has completed a lot of work. The main purpose of the Gigabit Ethernet project is to provide 1 Gbps bandwidth for backbone networks and provide a natural Upgrade Method for existing Fast Ethernet networks, at the same time, make full use of existing network management tools and corresponding training.
In order to maintain the maximum collision area with a diameter of 200, the minimum CSMA/CD carrier time has been extended from the current 512 bits to 512 bits (4096 bits ), the minimum information package size is still 64 bytes. The carrier expansion feature solves the inherent timing problem of CSMA/CD without modifying the minimum package size. Although these changes may affect the performance of small information packets, these changes have been offset by the sudden transfer of information packets in the CSM/CD algorithm.
To reduce the time for Gigabit Ethernet products to enter the market, both 1000BASE-SX,-LX, and-CX can adapt to the time-tested Fiber Channel technology. 8 B10 NRZ (not normalized) encoding method is used to provide a valid baud rate of 1.25Gbaud. Therefore, it can provide a data rate of 1 Gbps at full speed.
The 1000BASE-SX series uses low-cost short-wave CDcompact disc, optical disc lasers) or VCSEL (Vertical Cavity Surface Emitting Laser) transmitters, while the 1000BASE-LX series uses relatively expensive long-wave lasers. The 1000BASE-CX series intends to connect high-performance servers to high-speed peripheral devices using short jumper cables in the wiring room.
The 1000BASE-T series is a new design that supports a large number of installed five-category cabling systems. The complex digital signal processing (DSP) technology is used to overcome the defects of Category 5 lines. 1000BASE-T uses all 4 pairs of twisted pair wires during transmission and works in full duplex mode. This design uses PAM-5 (5 Level Pulse Amplification Modulation) encoding to transmit 250 Mbps on each line. Bidirectional transmission requires that all four lines must use a hybrid magnetic field line to the transceiver port, because the perfect hybrid magnetic field line cannot be provided, so the transmission and receiving circuits cannot be completely isolated. Any sending and receiving lines will return to the device. Therefore, to reach the 10-10 error rate BER), the echo must be offset. 1000BASE-T cannot filter the frequencies concentrated on MHz. However, it can filter the frequencies after 80 MHz using the Scrambling Technology and grid encoding. An appropriate scheme should be used to offset crosstalk in order to address the limitations imposed by the five-category cable on the near-end crosstalk (in the case of PSNEXT) in such a high frequency range. Grid encoding can enhance the anti-interference capability. This conclusion applies to all situations above.
End users may be confused about the cables used to support 1000BASE-T. Although Category 5 cabling systems have been installed with such technical support, it is important to note that the new cabling transmission parameters must also be satisfactory. These parameters include ripple loss, level remote crosstalk ELFEXT), propagation delay and delay distortion. Therefore, if the cable meets the requirements of Category 5 cables (1998) or Category 5 cables, it will support BASE-T. If the installed cables only meet the Category 5 cabling standard (1995), the cabling system should be measured and certified according to the new cabling parameters before connecting to the 1000BASE-T device.
Do I need 6 types of cabling?
At present, there is a lot of debate in the cabling industry regarding whether cat6 cabling is required (even in the current draft phase). In order to make a correct analysis, let's look back at the situation where category 3 cabling became popular in 1992 and Category 5 cabling was just proposed. Cheap 10 Mbps is developed based on three types of cabling for Ethernet (10 BASE-T) and 25 Mbps atm lan. 100BASE-T2 and 155.5 Mbps CAP64 atm lan require the use of complex DSP technology to overcome the limitations of three types of wiring. As category-5 cabling is adopted by many end users, the cheap 100 Mbps (100BASE-TX) Ethernet and 155.5 Mbps nrz atm lan have also been developed and improved on the basis of category-5 cabling.
The actual situation shows that the total cost for each user to connect to 100BASE-T4 using three types of cabling, for example, from the router to the NIC, including the cable, is 164, on the basis of the five-category cabling, 132 BASE-TX only costs 24%. In contrast, the average connection cost per user is reduced.
There is no doubt that the same development will happen again in the 1000BASE-T LAN technology. Because 1000BASE-TX is designed to work in two-to-one transmission and two-to-receive modes, therefore, Echo Cancellation in full duplex mode is not required. To reduce the time to enter the market, the mlt-3 encoding method used by 100BASE-TX will be selected, the bandwidth efficiency of the MLT-3 is 4 bits per Hz, so the bandwidth is 125 MHz. This is well limited to the NEXT and PSNEXT ranges of cat6 cabling, so crosstalk offset is unnecessary. From the perspective of current semiconductor technology, the absence of ECHO and Crosstalk cancellation devices will reduce at least 50% of the overall complexity of the 1000BASE-TX design (compared with the current 1000BASE-T design ). Grid encoding technology may need to be improved to ensure compliance with EMC requirements.
By extension, if the data rate increases from 500 Mbps to 600 Mbps per pair, this design can be used in 1.2 Gbps systems. Therefore, cat6 cabling not only reduces the cost of electronic devices supporting Gigabit Ethernet, but also provides basic facilities for LAN technologies that may exceed 1 Gbps in the future.
The investment in cabling infrastructure will be considered a long-term investment, and cabling facilities should also be considered as an asset. According to the International cabling standard ISO 11801, the expected life of a cabling system is at least 10 years. During this period, PC technology will be greatly improved. For the moment, although the desktop system does not need to use 1 Gbps, it is mainly caused by the limitation of the current PC internal bus structure, because the bus determines the data exchange rate between the processor, memory, and other peripheral devices such as NICs. The famous Moore's law predicts that the number of transistors on a chip doubles every 18 months. This is often used to describe the growth rate of PC Processor performance. That is to say, the performance of PCs is doubled every 18 months. Based on these facts, the PCI 2 bus may appear in the middle PC within three years. Similarly, in the lifecycle of the cabling system, it is very likely that 1000BASE-TX technology will be applied to the desktop system.
Possible applications
Let's think about the huge throughput that those applications will need. Multimedia Applications are becoming the basic requirements of the customized PC. Intel has introduced the MMX (MultiMedia Exchange, MultiMedia Exchange) technology, which will greatly promote MultiMedia application. The emergence of multimedia business and multimedia information transmission dramatically affects the LAN design. In the future, multimedia business applications will inevitably require higher bandwidth and lower response time to achieve satisfactory performance. According to Intel, in the future, computer commerce will be the communication between screens, and commerce will be established between Visual connection PCs Visual Connected pcs and vcpcs using Intel structures. The AGP (accelerated graphics interface) interface launched in 1997 supports MMX technology for low-cost, high-performance 3D graphics applications. With the emergence of low-cost DVDDigital Versatile Disk, Digital general-purpose Disk), scanners and digital cameras will bring users a new interactive, intuitive and life-Oriented Computer experience, users can input their own unique visual data into the software. The file size will increase dramatically, and a large number of bitmap images and images will be used to guide the operation, making the files and documents more interesting and more friendly. Visual Computing will require higher bandwidth than the current LAN.
Conclusion
Over the past five years, the IT (information technology) industry has made great progress in network technology. More and more end users enter the network, which promotes the development of complex and transaction-based application software. The enhancement of PC performance and the doubling of digital signal processing capabilities, as well as the increasing storage capacity of silicon wafers, have created new business opportunities for software developers to develop applications requiring a large amount of bandwidth. As a result, the file size increases rapidly. All these trends have higher requirements on the network. Cabling infrastructure is its central nervous system. It must ensure its efficient operation and avoid network paralysis. In this way, the end user should select at least five lines to ensure the normal operation of the network. 6 lines are recommended for newly installed systems, this will ensure that the Gigabit Ethernet technology can economically meet current and future needs.