| 摘要 |
Empty GRE packets are used to ensure in-order delivery of data packets for a session to a UE during intra-EUTRAN handover involving SGW relocation. In particular, a PGW sends an empty GRE packet per PDN session of the UE to a source SGW upon handover execution to indicate the end of pre-handover data packets delivered to the source SGW. Upon receipt of the empty GRE packet, the source SGW generates an end marker packet, and sends it to the source eNodeB. The source eNodeB forwards buffered, pre-handover data packets not delivered to the UE, followed by the end marker packet, to the target eNodeB, either directly (X2 interface) or indirectly (GTP-U tunnel between source and target SGWs). The target eNodeB then sends the pre-handover data packets, and post-handover data packets delivered to it by the PGW, to the UE in order, in reliance on the end marker packet.
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