The embodiments relate to a method for improving the quality of data transmission in a packet-based communication network comprising a plurality of network nodes. Each network node has a number of ports with which at least one queue is associated respectively, and by which ports a communication connection to another network node may be produced. At least the queues of those ports that are arranged, in the network nodes, along respective communication paths that are formed in the communication network, are monitored for their queue length. A degree of overload of the affected port(s) is determined from the queue length, and a runtime delay and/or a delay variation in the data transmission may be inferred. The overload amount rises above a predetermined threshold value for at least one of the communication paths running across an overloaded port.