A communication subsystem, method and computer program product preconfigure a size of a transport control protocol (TCP) buffer when connected to a master node using a first radio access technology (RAT) that supports during dual connectivity with a secondary node using a second RAT. A timer is started when the secondary node is available but not being used at least in part for data transfer. Until the timer expires, the TCP buffer is maintained in a size to efficiently provide both (i) support for data transfer using the first RAT via the master node only; and (ii) expedited setup of data transfer using at least the secondary node using the second RAT. When the timer expires without connecting to the secondary node, the controller reduces the size of the TCP buffer to release storage resources that are not needed for data transfer via only the master node.