| Description | When the GSN behaves as SGSN, the T3-TUNNEL timer is used
for mobility management. When a roaming MS moves from one
SGSN(Old SGSN) to a another SGSN(New SGSN), this timer is
started by the 'Old SGSN'. While the timer is running, the
T-PDUs received by the 'Old SGSN' (from the GGSN), and any
buffered T-PDUs are forwarded to the 'New SGSN'.
When the GSN behaves as GGSN, the GGSN starts this timer
after receiving a Update PDP Context request message from
'New SGSN'. An Update PDP context request shall be sent by
SGSN as part of mobility management intimating that MS has
moved to this SGSN. While the timer is running, the GGSN will
not be forwarding any PDUs to the requesting 'New SGSN'. |