What is the duplex mismatch?

Have you ever had a problem with a network server to 100Mb / s connected, but do not have the ability to perform file transfers for about 1-2 Mb /s ? It is an interesting and surprisingly often, the problem could be in exactly this way.

The first step to determine if they belong to this problem is to try to perform multiple file transfers simultaneously. If you are, say, 5 file transfers, you will see 1-2 Mb / s for each transfer individual thing 5 10MB / s data transfer rate overall aggregate? If you do, then you probably have a duplex mismatch problem in the network.

Duplex mismatch is where the end of the connection you are trying to run in full-duplex mode, while the other ends trying to run in half-duplex mode. The end full-duplex is transmitted when sending traffic on the link, while the end of half-duplex sends only if the connection is idle. The result is that the end full duplex is often clobbering packets transmitted from the end of the half-duplex ‘. Since the end of full duplex has no concept of collisions clobbered packets of the TCP layer of the compound in which the “1-2 Mbit / s ” come a limit for each connection is bad.

With a managed switch to see late collisions and multiple collisions on the end of the half-duplex connection and usually transmit and receive errors on full-duplex connection. These errors are rapidly increasing counter and is easy to recognize a problem if you know what you are looking for. There is also an equally simple solution-just manually set both ends of the connection will operate in full-duplex mode. Once you have this simple change is return to normal speed file transfer should find the server in question.

Once you have the unique behavior of duplex mismatch problem is easy to see. Remember, as a potential problem, if you think about duplex mismatch speed very low transfer rates of Ethernet connections, which must operate at much higher speeds. It ‘also interesting to note that this problem only applies really for Ethernet connections 10 and 100 Mb / s for gigabit connections do not have a half-duplex mode.

Duplex mismatch is a problem that makes lifting his head from time to time. It is a rapid control that can be done to make sure that it is not the cause of a problem, or may not be a problem in the future!