name: PDG
full_form: Packet Data Gateway
context: An example of this case is mobility between two I-WLAN 3GPP IP access systems. The problem to be solved is to retain the IPsec tunnel even when the IP address of the UE changes due to mobility. There are two cases here: the PDG remains the same or the PDG changes. If PDG remains the same, the existing IPsec tunnel could be maintained. In order to achieve this, a mechanism proposed in TR 23.882, Annex E, is MOBIKE. For MOBIKE to work, it is required that the PDG remains the same while the UE moves. If the PDG changes, then it is not a matter of maintaining the IPSec tunnel, but creating a new one with the target PDG. In such case, the focus becomes the mechanisms on the S2 interface, not what happens between the new PDG and the UE. Another possible solution to retain the IPsec tunnel when the PDG remains fixed would be the use of an IP mobility mechanism (e.g. Mobile IP). The Mobile IP Home Agent would have to be e.g. located between the PDG and the UE, but close to the PDG, ensuring
description: The Packet Data Gateway (PDG) is a network function that provides access to packet data services for user equipment (UE). It acts as an entry point for UEs to access the network and manages IPsec tunnels for secure communication.
explanation: The context describes PDG's role in managing UE access, maintaining IPsec tunnels during mobility, and its interaction with other network components. This justifies classifying PDG as a Network Function, which is responsible for controlling and managing network resources.
section_title: 6.1	The source access system has a UE-PDG tunnel
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