We present a novel constrained flow control scheme for a class of large-scale networks, modelled by interconnected network resources with capacity and buffer size limitations. We first propose a decentralized sliding mode controller  to achieve asymptotic regulation of each individual network node in the presence of uncertain inter-node traffic, while network delays are omitted. We then incorporate network delays associated with inter-node transmissions and study both the delay-independent and the delay-dependent control designs, to investigate the delay robustness of the proposed flow control scheme. It is shown that the when network delays are small, asymptotic stability can be preserved under the decentralized, constrained control law, using the idea of delay-dependent design. A delay-independent regulation scheme is also presented to counteract arbitrary network delays.