Receiving Packets

Packets arrive at the kernel at unpredictable times. All modern device drivers use interrupts (discussed in Chapter 14) to inform the kernel (or the system) of the arrival of a packet. The network driver installs a handler routine for the device-specific interrupt so that each time an interrupt is raised — whenever a packet arrives — the kernel invokes the handler function to transfer the data from the network card into RAM, or to notify the kernel to do this some time later.

Nearly all cards support DMA mode and are able to transfer data to RAM autonomously. However, these data still needs to be interpreted and processed, and this is only performed later.

Continue reading here: Traditional Method

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