Deletion of an IPoE or PPPoE session also triggers deletion of any corresponding GTP sessions. This deletion is subject to a configurable hold time. When the subscriber returns with the same GGSN/P-GW parameters within the hold time, the GTP connection is not re-signaled. This avoids releasing resources (such as IP addresses) too quickly on the GGSN/P-GW. This is useful in the following cases:
non-seamless control plane mobility with WLAN-GW
Because of SHCV usage, the UE is completely removed, but should reconnect quickly, preferably with the same IP address. Having a short hold time avoids the P-GW releasing the IP address.
IP handover from Wi-Fi-GW to RAN
In some cases, Wi-Fi connectivity is lost before wireless data connectivity is established. By holding the GTP session active on the WLAN-GW, the IP address is also held on the GGSN/P-GW until the RAN connection is complete.
While a GTP session is in hold, all downstream traffic is dropped, but no error indication messages are sent.