The big data plane of bDDN is responsible for data awareness, data storage, data analysis, and providing data services and intelligent services for network plane and management plane. For these functionality, the transmission of massive amounts of data is the basic capability of big data plane. This Recommendation specifies the data transmission mechanism in bDDN. It includes overview of data transmission in bDDN, data transmission mechanism within big data plane, as well as data transmission mechanism between big data plane and network plane, data transmission mechanism between big data plane and management plane, and security considerations.