In some embodiments, the buffer state is a buffer fill level and the change of the buffer state is a change of the buffer fill level. Hence, the first network node 10 may comprise means 11 adapted to monitor the buffer fill level as well as means 12 adapted to determine the condition indicative of congestion in response to the buffer fill level exceeding the predetermined limit.

In some embodiments, the buffer state is a buffer change rate at which the buffer changes and the change of the buffer state is a change of the buffer change rate. Hence, the first network node 10 may comprise means 11 adapted to monitor the rate at which the buffer state changes and means 12 adapted to determine the condition indicative of congestion in response to said buffer change rate exceeding the predetermined limit. In one embodiment, the buffer change rate is a buffer fill rate at which the buffer fills and the buffer change rate is a buffer fill rate. Accordingly, the first network node 10 may be provided with means 11 adapted to monitor the rate at which the buffer state fills; and means 12 adapted to determine the condition indicative of congestion in response to said buffer fill rate exceeding the predetermined limit.