Question

I am trying to figure out how network cards work in Windows, and how the data is being relayed.

I have two hypotheses.

1.

1. Data is received by the network card.
2. The card then puts the data in an internal buffer, possibly a double buffer or a ring buffer.
3. The card accumulates data until some amount has been reached, upon which it sends an interrupt.
4. Windows copies the data from the card to the RAM and notifies appropriate handlers.

2.

1. Data is received.
2. The card puts the data in the RAM using DMA. (Does DMA guarantee that data will not be lost, or does the card still need its own buffer?)
3. The card fires an interrupt upon putting enough data in the RAM.
4. Windows receives the interrupt and copies or exposes the data to appropriate handlers.

Are either of my hypotheses correct?

Is there any message from the card or Windows if buffers are full?

In my Windows systems properties for my ethernet controller I can see properties called “Receive buffers” and “Transmit buffers”, both are set to 256.
What does this mean?

Are there any good literature on this subject? (I have Tanenbaum’s Modern Operating Systems, but it is not specifically related to Windows.)

Answer 1

Your question subsumes (at least!) three very, very broad topics:

1) how does a Layer 2 (Data Link) hardware device work?

2) How does it relate to the operating system’s network stack

… and …

3) How does it relate to the operating system’s kernel-level device driver?

The next link is actually 180 degrees opposite your original question (the API is relatively high level, your question pertains to the lowest software levels), but it wouldn’t hurt to look at the .Net API for perspective “how things work”:

• http://msdn.microsoft.com/en-us/library/4as0wz7t.aspx

‘Hope that helps … at least a little bit…

PS:

Linux is a wealth of information about implementing a network stack: all of the kernel source and all of the device drivers are completely available, and very well documented.