ABSTRACT
This chapter focuses on the bidirectional data transmissions of a connection, in which Transmission Control Protocol (TCP) and acknowledgment (ACK) packets are flowing together but in opposite directions. It discusses the performance of FAST TCP in a bidirectional transmission scenario. The chapter investigates the network utility maximization (NUM) theory in the two-way flow scenario. The modelling and solution lead to some straightforward discoveries of a critical problem with network bandwidth allocation and performance optimization in the NUM framework to account for the impact of ACK packet flow. In most flow control models, the ACK packet flow is also simplified to feedback signals. However, an ACK is a packet with several bytes, and the network must handle ACKs. The behaviour of bidirectional TCP flows in a rate-controlled network is different from that of unidirectional TCP flows. The NUM model of bidirectional TCP flows in a network is different from that of unidirectional ones.
