I studied through my network interface driver and gained sufficient understanding of the network stack. I have a network stack for my ARM device and now in stage of interfacing this stack to my network driver in the ARMDevice . I know now that I have to just replace for(q = p; q != NULL; q = q->next) { /* Send the data from the pbuf to the interface, one pbuf at a time. The size of the data in each pbuf is kept in the ->len variable. */ send data from(q->payload, q->len); } send data from(q->payload, q->len); with my driver specific code to send the packet . Very nice ! But when I compile this code , its going to ask where this driver specific senddata is defined , the header file or library . How do I resolve this part of the riddle . Its a little newbie kind of question . But I have tried , I give up now. Plz help. Regards Sraddha