The service mapping module stores {HEAD ~ a table} that maps {TAIL ~ services} to access point names 
maps
The service mapping module stores { HEAD ~ a table } that maps { TAIL ~ services } to access point names
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH