| CPC H04W 40/22 (2013.01) [H04L 45/74 (2013.01); H04L 69/22 (2013.01)] | 15 Claims |

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1. A downlink data transmission method, comprising:
obtaining, by a first node, a mapping relationship between an Internet Protocol (IP) address of a destination node configured by a donor centralized unit (donor CU) and a Backhaul Adaptation Protocol (BAP) address of the destination node, wherein the first node is a donor distributed unit (donor DU);
determining, by the first node, the BAP address of the destination node based on the mapping relationship and the IP address of the destination node that is carried in a downlink data packet, wherein a BAP header of the downlink data packet includes first information indicating that the BAP header does not include a routing path identifier of the downlink data packet, and wherein the BAP header of the downlink data packet includes a BAP address of a source node of the downlink data packet;
determining, by the first node, a first path between the first node and the destination node based on a differentiated services code point (DSCP) or a flow label carried in the downlink data packet; and
sending, by the first node, the downlink data packet to the destination node on the first path based on the BAP address of the destination node.
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