In one embodiment, each global interface includes {TAIL ~ a request agent} , a directory agent and {HEAD ~ a slave agent}  
In one embodiment , each global interface includes { TAIL ~ a request agent } , a directory agent and { HEAD ~ a slave agent }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH