The router automatically assigns a default queue-limit value. The calculated value varies with the queueing method and with the platform. Importantly, the queue limit needs to be small enough to avoid introducing latency due to queueing, but large enough to avoid drops and a resulting impact to TCP-based flows. Specifically, the queue limit is determined by the maximum delay of 500ms with an average packet size of 250 bytes. For example, a class with 1 MB of bandwidth is given a queue limit of 1000000 / (250 x 8 x 2) = 250.
