This application discloses a data transmission method, a related apparatus, and a network. The method may include: determining, by a first controller in available transit switches in a data center network, available transit switches respectively transiting m groups of data, where one available transit switch is configured to transit at least one group of the data, and a difference between quantities of groups of the data transited by any two available transit switches does not exceed a second threshold; and instructing, by the first controller, the destination network node to send routing information to the source network node, where the routing information includes an identifier of an available transit switch configured to transit a data group transmitted by the source network node to the destination network node. The foregoing solution can balance load of each transit switch in the data center network, improve a bandwidth resource utilization rate, and reduce a transmission delay.