The source address of the first packet is set to the first address when {HEAD ~ the first packet} is related to {TAIL ~ the first service} and to the second address when the first packet is related to the second service 
is related to
The source address of the first packet is set to the first address when { HEAD ~ the first packet } is related to { TAIL ~ the first service } and to the second address when the first packet is related to the second service
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH