Before revision:  Although the celebrated back-pressure algorithm maximizes throughput, it requires per-flow  information (which may be difficult to obtain and maintain), maintains per-flow (or per-destination) queues at each node, relies on constant exchange of queue length information among neighboring nodes to calculate link weights, and may result in poor delay performance  .
After revision:  Although the celebrated back-pressure algorithm maximizes throughput, it requires per-flow information (which may be difficult to obtain and maintain), maintains per-flow (or per-destination) queues at each node, relies on constant exchange of queue length information among neighboring nodes to calculate link weights, and may result in poor delay performance in certain scenarios .