Thanks for the replies.
So just to confirm are you guys suggesting that an MO call (i need to confirm this) will be handeled first by the serving MSC which would pass it to a GMSC or does the serving MSC usually act as the GMSC itself ???? I am asking as I need to know the usual way most networks are setup.
Also, do GSM networks usually implement optimal routing where an MSC in A parties GSM network is able to interrogate B parties HLR and route directly to B parties VMSC ??