Default Bearer & Always-on IP in 5G

Hi all. In LTE, there are default bearer & always-on ip. But 5G, do not have, right?

For 5G in case of NSA it’s same all bearer established at 4G side which get modify after SCG addition.

For SA case we have concept of PDU session establishment where concept of Gtp-u session there.

In NSA, signaling is via 4G. I want to compare with SA.
But SA, PDU session establishment is triggered when UE wants to connect to external PDN network for traffic.
Do you hear default bearer & always-on IP at 5G SA?

Always on IP connectivity is not mandatory in SA. During LTE days, most requirements are targeted towards the data hungry mobile devices. So, having always on connectivity makes sense there. But SA needs to accomodate both those data hungry devices and also the low throughout, battery efficient devices like IoT devices. I think this is why MM and SM procedures are seperated in SA. Due to this, when a default QoS rule(mind you, we deal with QoS rules and flows in SA due to the new SDAP layer. There might be a mapping between these QoS rules/flows and LTE default bearer to support IRAT use cases) is deleted for an active PDN, UE will disconnect that PDN but still retains MM context.

I think so.
In LTE, PDW is responsible for allocating UE with an IP address, and PGW play the roles in both CP and UP, each time UE is connected to LTE network, PDN will assign an IP address for UE.
But NR, serving UPF is not responsible for IP address allocation, it should be done by UPF terminating PDU session for UE. So 5G NR, when UE has PDU session establishment success, it will have an IP address.

Session Management function (SMF) is responsible for UE IP address allocation & managment