hi kiran, > not exactly, skb->head onwards has all the layer >headers. Depending on where in the stack the skbuff >is, skb->data may be pointing to the next protocol >header. i undetstood it that eg. from tcp to ip layer at ip later skb->data contains tcp header and application data. Thanks for your help. one last thing i want to know that is kernel allocates total size of all tcp/ip layer headers + data at start of building packet headers? If yes where can i find that line in kernel source? regards, parag.