A system for managing traffic between servers, the system may include first tier switches that are coupled to the servers; second tier switches that are coupled to the first tier switches and to third tier switches; and controllers. Wherein each first tier switch comprises first queues. Wherein each second tier switch comprises second queues. The controllers are configured to control a traffic between the first tier switches and the second tier switches attributed to the traffic between the servers, (a) on, at least, a queue granularity; (b) while controlling some first queues to provide buffer extension to some second queues, and (c) while controlling some second queues to provide buffer extension to some first queues.