{hscale=2}
ms = MS,BSS
msc = MSC
hlr = HLR proxy
home = Home HLR

ms -> msc	Location Updating Request (IMSI Attach)
msc -> hlr	Send Auth Info Request
hlr <> hlr	No proxy cache data available for this subscriber
hlr () home	mslookup finds the home HLR
hlr -> home	Send Auth Info Request
hlr <- home	Send Auth Info Result
		with 5 auth tuples
hlr () .	(1) Keep a copy of the auth tuples
msc <- hlr	Send Auth Info Result
msc () .	MSC stores 5 auth tuples,
		uses the first one now,
		and keeps the rest for later requests
ms () msc	Authentication
msc -> hlr	Update Location Request
hlr -> home	Update Location Request
hlr <- home	Insert Subscriber Data Request
		(with subscriber's MSISDN)
hlr () .	proxy HLR caches the MSISDN
msc <- hlr	Insert Subscriber Data Request
msc -> hlr	Insert Subscriber Data Result
hlr -> home	Insert Subscriber Data Result
hlr <- home	Update Location Result
msc <- hlr	Update Location Result
ms <- msc	Location Updating Accept
hlr <> .	After successful Update Location, check the cache
hlr () .	(2) Ask for more auth tuples to cache
		(amount of tuples configurable)
hlr -> home	Send Auth Info Request
hlr <- home	Send Auth Info Result
hlr () .	store 5 more tuples
hlr -> home	Send Auth Info Request
hlr <- home	Send Auth Info Result
hlr () .	store yet 5 more tuples