Hi All, can someone please explain me, how the kernel handles different transfer rates of different net_devices? Or in other words: How does the systemcall send() know, when to block? An example: cat /dev/zero | pv | nc -u <someip> will show different throughput speeds depending on the network device, the packets are sent over (wlan0 will be slower than eth0). - Can someone point out the location in the linux kernel source, where this is handled? - If I register a net_device. How do I signal to the upper network layers that my driver can only accept packets at a certain rate? I tried stopping the egress queue by calling netif_stop_queue(), but this only has the effect that the queue overruns. I have the feeling that I'm missing out a very vital point on how the kernel's networking subsystem works. Unfortunately, Understanding Linux Network Internals couldn't help me out here. Thanks, Christian