M fast Ethernet

Source: Internet
Author: User

Fast Ethernet is a new type of LAN. Its name is "Fast", which means that the exponential data rate can reach 100 Mbps, 10 times the data rate of standard Ethernet. It includes two technologies: 100BASE-T and 100VG-AnyLAN. 100BASE-T 100BASE-T is proposed by the high-speed Ethernet alliance composed of companies such as DEC, Sun, Intel, 3Com, and SMC. The goal is to speed up the speed of 100BASE-T. Many vendors launched products related to 100BASE-T by the end of 1994. The high-speed Ethernet Alliance also established industrial standard testing procedures to ensure the interoperability of 100BASE-T products produced by various manufacturers. One of the notable features of www.2cto.com 100BASE-T is that it tries its best to adopt the mature technology of IEEE 802.3 Ethernet. Therefore, it can be easily transplanted to the traditional standard Ethernet environment. 100BASE-T is different from traditional Ethernet in physical layer. The affiliated unit interface of the original 10 Mbps Ethernet is replaced by the new media-independent interface, and the physical media used in the interface also changes accordingly. To transmit data streams over Mbps on five unshielded twisted pair wires, 100BASE-T adopts multi-level MLT-3 and channel coding adopts 4B/5B encoding. In addition, to facilitate the upgrade of the user's network from 10 Mbps to 100 Mbps, The 100BASE-T standard also provides the automatic speed listening function. This function allows an adapter or switch to send at 10 Mbps and Mbps, and work at the fastest speed that the device on the other end can achieve. 100VG-AnyLAN 100VG-AnyLAN is based on 100BASE-VG technology, where VG stands for Voice Grade and uses unshielded twisted pair wires as physical media. The Federal Communications Commission specifies that the signal frequency on unshielded twisted pair wires must be lower than 30 MHz. To transmit Mbps data streams using the existing unshielded twisted pair wires, 100VG-AnyLAN uses the four-digit signal technology. This technology connects each node and hub with four pairs of unshielded twisted pair wires. Information is transmitted simultaneously on four pairs of twisted pair wires for half-duplex communication. Because there are many 4 pairs of unshielded twisted pair wires, 100VG-AnyLAN is also called 4-UTP 100VG-AnyLAN. The network topology of www.2cto.com 100VG-AnyLAN is the same as that of 100BASE-T. 100VG-AnyLAN adopts 5B/6B, non-zero conversion, and Scrambling Technology on the channel. This technology not only improves coding efficiency, but also enhances data anti-noise and anti-error code capabilities, the implementation of the timed Recovery Circuit is simplified. The MAC layer of 100VG-AnyLAN is completely different from that of CSMA/CD on Ethernet. It requires priority access. This method is essentially a sequential access method. It avoids conflicts and ensures the maximum waiting time of users not to exceed the sum of the time required for sending one frame of information by other users, ensuring the network latency performance during heavy load. In addition, 100VG-AnyLAN uses a priority mechanism to meet different service requirements of different businesses. Therefore, it is suitable for real-time service transmission and multimedia information transmission. The disadvantage of 100VG-AnyLAN is that its MAC layer is incompatible with Ethernet, so it is difficult for a large number of 10 Mbps Ethernet users to transition to 100VG-AnyLAN. In addition, although the technology was initially promoted and supported by companies such as IBM, AT&T, and HP, only a few companies such as HP currently provide related products.

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