[ns] "class_ " of agent.h

[Manimaran Selvaraj <ms8@ece.msstate.edu>]

Hi all,
This one is a very basic question.
Could some one tell me the actual use of the variable "int class_" of
agent.h? The comment says /* class to place in packet header */
What does class actually refer to? I checked the packet header chapter
#12 as well as agents chapter #10,  but couldnt get the info.

Thanks.

-mani