estimating one or more network conditions of a network using {HEAD ~ a comparison} between the certain time and {TAIL ~ the acquired timestamp} 
estimating one or more network conditions of a network using { HEAD ~ a comparison } between the certain time and { TAIL ~ the acquired timestamp }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL