Updated: Mar. 5^th, 2020

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The network interface card is a passive component and run by CPU. The I/O is all run by CPU, if the CPU could support more function, the network interface card could support more functions.If the efficiency of CPU is not enough, the network interface card would packet loss or 802.3x Flow Control Pause Packet because of full load.

The half-duplex function allows only an equipment to transmit the information at the same time. There will be collisions if the two equipments transmit to each one at the same time. The full-duplex function could support two-way transmission between two equipments.

There will be collision if users receive carrier wave from others before send the information 64 byte. At the same time MAC will automatically overtime to 21, 21 ~ 22, 21 ~ 23, 21 ~ 216 bit time for at least 16 times tests and then it will abandon the convection of packet, besides sending the signal to upper layer.There will be a collision late Collision if users receive carrier wave from others after send the information 64 byte. The reason is that the length of meshes is over the standard or the equipment is not “Half-duplex” from the other.

Under the Half-duplex situation, it only supports the “Back Pressure”. As the chip receives not enough storage it would take a collision to delay the work time and make the other to into a delay time so that it can avoid packet loss.Under the Full-duplex situation it only supports the802.3x Flow Control. As the chip could send the 802.3x Flow Control Pause Packet that the temporary storage time >0 and make sure the other won’t send the package in certain time to avoid storage to run out. The time of flow control is around 0x0001 ~ 0xffff. But there will be a Packet loss if the other equipment did not support 802.3x flow control.Any equipment could support “Back Pressure”, but certain equipment should be opened so as to support 802.3x.

The storage of HUB chip is quire low ,the package information is transmitted by certain method—one gate input and n gates output, that is bisynchronous output.If it is necessary to debug the users have to apply this function.The storage of switch chip is quite stabile; the package information would be stored and then transmitted by the Mac address DA/SA which is provide by Switch engine —one gate input and the original one gate output. By using this method the users could make the most usage of the transmission and avoid losing package through transmitting.