{HEAD ~ The ALR} cross references this URN to find {TAIL ~ a URL} for the target, such as the URL for the VLR 105 and contacts the VLR to start a session with the target device 
{ HEAD ~ The ALR } cross references this URN to find { TAIL ~ a URL } for the target , such as the URL for the VLR 105 and contacts the VLR to start a session with the target device
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH