I have a quad port network card and I am trying to send one packet with size of 121 byes to each network interface every
 250 us.

I am using pcap.h for this purpose. Currently I am using a time to create 250usec and I send four packets to four 
network interfaces consecutively. I have one more similar network card installed in another PC running winxp. These two 
network cards are connected together through four cross wires. I am using the second PC for monitoring.

As I am running four pcap_sendpacket() functions consecutively, there would be about 20us delay between the first and 
second interface packets and the same for second and third and so on.

Is there any way to send packets simultaneously or at least reduce the delay to few us.

Do you think if I use for timers and calibrate them I can do the job or not?

Regards,
Mohammad