packet header length

[Yan Yu <yanyu@catarina.usc.edu>]

Hello, all,
   I have a Q about the header length. 
For example for a cbr traffic packet, the data length is 512 bytes. but 
at each layer, it will add a header for that layer. so from the trace 
file, the packet length for cbr packet at MAC layer is 544, or 594. so I 
guess the  extra bytes ( more than 512 ) is packet header, or piggybacked 
something (I did DSR simulation).
So I am wondering what is the packet header length of each layer? for 
eample, the header lengths for network routing layer, MAC layer,  and 
physical layer? I guess they are protocl specific? btw, from the source 
files, e.g. mac-802_11.h, there are so many structures definition there, 
I got confused, and did not know which one is the right header definition?? 

so I am wondering where I can find those information? Is there a function 
that I get this info from C++ or tcl?

Thanks in advance!
yan