The proposed AC algorithm (3/5)
ÙProbing Stage – Estimation of the impact of a new flow
ØEvery QoS metric can be considered as a value which increases as the “traffic load” increases. The addition of a new connection will increase the load of the paths it may be using, and therefore it is assumed that the value taken by the QoS metrics will increase.
ØLet us consider some link (i,j). A small increase x in the load that is obtained in a controlled manner, generates an estimate of the manner in which the QoS metric q varies around the current load point Y.
ØThe impact of a new flow with total traffic rate X can then be evaluated by using the measured derivative without having to know the initial load  Y.
, e.g. by sending probe packets at rate x
 Contrary to most existing schemes that use probing, it is not required to send the probe packets at the requested rate. We can have an accurate estimation by sending at much lower rates, so that the probing process will not contribute significantly to the network's congestion.