The MIB Module for managing the General Packet Radio 
Service(GPRS) iSGSN protocol on Servicing GPRS Support
Node (SGSN). 
In the Alcatel/Cisco SGSN architecture, a Telecom part 
(T-unit) and Datacom part (D-unit) have been defined.  
The Datacom part is in charge of managing the Gn interface 
with the GPRS backbone. The Telecom part is in charge of 
managing the Gb interface with the BSS. 
The iSGSN protocol is the high layer protocol of the 
interface between the Datacom part and Telecom part. 
It supports the relay function between the Gb and Gn 
protocol stacks, and intra SGSN nodes management.