[FIX Protocol] CompIDs in the Message

Assumption (A=sellside, B=buyside, X=third party):

			SenderCompID (49)	OnBehalfOfCompID (115)	TargetCompID (56)	DeliverToCompID (128)
Send from A to B via X
1)		A sends to X	A		X	B
2)		X sends to B	X	A	B
B responds to A via X
1)	B sends to X		B		X	A
2)	X sends to A		X	B	A