Multiple Path Transmission Control Protocols (MPTCPs) allow flows to explore path diversity of datacenter networks and multihoming to improve throughput, reliability, and network resource utilization. However, the existing MPTCPs are largely empirical by design and fall short of achieving satisfactory tradeoffs among responsiveness, TCP fairness and throughput. By leveraging the TCP utility and a network-utility-maximization (NUM) solution for concave utilities, in this paper, we derive and implement in Linux kernels two distinct families of NUM-optimal MPTCP protocols, EUTCP ($\gamma$), a function of a rate-scaling vector of the sub-flow rate-scaling coefficients,$\gamma$, and WUTCP ($\omega$), a function of a utility weight vector of the sub-flow weights,$\omega$, respectively. While the former allows resource pooling, the latter does not. We then show that the Semicoupled algorithm and EWTCP are in fact EUTCP(1) and WUTCP$(1/m^{2})$, where$m$is the number of sub-flow paths, and hence, are NUM-optimal. The performance of the two families with equal weight and equal rate-scaling coefficient for all sub-flows when coexisting with TCP is also analyzed based on experiments in a testbed. In particular, the test results demonstrate that the family members of EUTCP ($\gamma$) with rate-scaling coefficient in the range of [1, 1.1] outperform three well-known MPTCPs with resource pooling capability, including LIA, OLIA and Balia, in terms of achieving satisfactory tradeoffs among responsiveness, fairness and throughput. Finally, the effectiveness of the proposed algorithms compared to the existing ones is further confirmed by simulation in a fat-tree datacenter network topology running both long and short flows.

In this paper, we put forward a HOListic traffic control framework for datacenter NETworks (HOLNET). HOLNET reformulates the network utility maximization (NUM) framework into a HOLNET NUM framework that fully harnesses the potential of the existing NUM-based solutions to allow large families of traffic control protocols of various degrees of sophistication to be developed, i.e., host-based, single or multiple Class-of-Service (CoS) enabled, single or multi-path congestion control, with or without in-network load balancing. Unlike the existing solutions that are largely empirical and point by design, HOLNET is a principled, systematic framework. All the protocols in a family developed under HOLNET share a common, user-defined global optimization objective and fairness criterion. As a result, the protocols in a family can be fairly compared and carefully selected to fully explore the performance, scalability and design complexity tradeoffs. Case studies, based on both a single and a multi-path host-based solutions, demonstrate the viability and flexibility in HOLNET design space exploration. To further test the backward compatibility and performance with respect to some existing lightweight solutions, we develop HOLNET-UTA, an integrated congestion control and load balancing protocol, achieving TCP-fair resource allocation. HOLNET-UTA is found by simulation to improve the average flow completion time (FCT) by more than 20%, compared to DRILL with DCTCP.