gNB-2 authenticates the request and returns the full UE context in the Retrieve UE Context Response. It echoes the new node's UE XnAP ID (1) and allocates its own Old NG-RAN node UE XnAP ID = 2, so the two ends are now cross-referenced.

The security context is the load-bearing payload here (carried in the message but not on the arrow): NCC = 2 plus the 32-byte K_NG-RAN* next-hop key. With these the target derives fresh AS keys (K_gNB*) for the resumed connection — vertical key derivation, giving forward security so the new cell cannot read prior traffic.

Also handed over: UE-AMBR 256 Mbps (DL and UL) and one PDU-session resource to set up:

PDU Session	Type	Slice	QoS flow	5QI
5	IPv4	SST 10 / SD 0x203040	QFI 1	9

5QI 9 is a standardized non-GBR flow (default best-effort bearer, e.g. TCP-based or buffered-video traffic).

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