hi, yes i got it but still i am not getting correct value of MAX_TCP_HEADER. what i got in tcp.h is #define MAX_TCP_HEADER (128 + MAX_HEADER) then the question is MAX__HEADER value? i also got it in include/linux/netdevice.h that #define MAX_HEADER (LL_MAX_HEADER + 48) i am using i386 platform. using ETHERNET protocol and ipv4 packet format. can you please tell me what is then value of final MAX_HEADER. i think it should be 32 as i am not using any AX25. regrads, parag.