OSI Protocol Model
Anyone who considers protocol unimportant has never dealt with a cat. - Robert A Heinlein
Not many protocols ever mapped cleanly to the 7 layer OSI Protocol Model. But these, days, you have to know what you are looking at and some general context.
Look at this fun packet:
http://www.cloudshark.org/captures/bb145a6714b3?filter=frame.number==3
I wonder what is the record for the highest number of recognizable protocol layers in one packet?