Thanks for replying. I also read up the gsm 9.02 spec and figured out that MAP UL message that goes from VLR (of visited n/w) is the message that I am intersted in. What I couldnt figure out was that how is this message routed to home HLR, say for example, visited country is Singapore & home country is Malaysia. So how does the VLR in Sinapore figure out the HLR of home service provider in Malaysia?
Is it based on IMSI? if so how does the routing happen? Based on GTT?