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 complex data structure 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 .