csma cd与交换机（与交换机CSMA CD）.docVIP

csma cd与交换机（与交换机CSMA CD） CSMA/CD this thing, with the network switch, not much. Turn, rarely write this, talk about when to use CSMA/CD conflict detection mechanism in Ethernet About when to use Ethernet CSMA/CD detection mechanism, this problem just two days ago and friends were discussed. Search on the Internet and for a long time, there are also some colleagues do not understand, especially some beginner CCNA, no work experience with colleagues. Here, I put my views on the blog and the basis for discussion. In the end when the Ethernet using CSMA/CD detection mechanism to avoid conflict lies in the network in what kind of work mode (full duplex or half duplex) work, the card will automatically and network access devices (e.g. switch or hub) to negotiate to determine when CSMA/CD is used to avoid the conflict detection mechanism. I think about what is CSMA/CD you network or network engineers should know, here is not to do too much to explain. As we all know, Ethernet mode has two kinds, one is in full duplex mode, a half duplex mode. We analyze the two modes in the end is not using the CSMA/CD conflict detection mechanism. 1. In full duplex mode Ethernet using CSMA/CD detection mechanism to avoid conflict? In this mode the Ethernet is not required to use the CSMA/CD conflict detection mechanism. We know that the full duplex mode can send and receive data simultaneously. We think, the card may at the same time to send two packets? Its impossible。 Absolutely not may appear at the same time the card receives two or more than two at the same time to send data requests, even CPU could not do it at the same time at the same time with two or more than two instructions. This time, if we assume that the network card enabled CSMA/CD mechanism to detect conflicts, ask him what a conflict detection channel? We can know that card in the received data packet to be sent, like a line like a send out, how could the conflict? This time someone may ask, that received? It may receive