Micro and Macro Mobility Management

At a micro level, the SGSN tracks the current routing area or cell in which the handset
is operating. At a macro level, the network needs to keep track of the current SGSN.
This information is stored in the HLR, VLR, and Gateway GPRS Service Node (GGSN).
The more radical proposals of IP everywhere argue that the HLR, VLR, and GGSN
could be replaced with DHCP servers, which could handle dynamic IP4 address allocation,
subscriber profiles, and access policies using standard Microsoft Active Directory
software. However, the HLR and VLR capability is very well proven within hundreds
of GSM networks, so it is unlikely that this change will happen quickly if at all. 294