squid flow digram

[srnoam]

Hello all,
I have been searching for squid flow chart/diagram for a while now, I have
decided to try & do it my self.
I can follow an object through most of the functions but after I get a MISS on
an object I can't understand  which function "decide" to forward it to origin
server, so the question is : How the where the forwarding to oriin server is
done? 
O fcourse I have the same problem after mapping with ICP requests & ICP_MISS
reply, I guess I am missing something.
Thanks,
Noam