Link buffer sizing: a new look at the old problem

We revisit the question of how much buffer an IP router should allocate for its droptail FIFO link. For a long time, setting the buffer size to the bitrate-delay product has been regarded as reasonable. Recent studies of interaction between queueing at IP routers and TCP congestion control offered alternative guidelines. First, we explore and reconcile contradictions between the existing rules. Then, we argue that the problem of link buffer sizing needs a new formulation: design a buffer sizing algorithm that accommodates needs of all Internet applications without engaging IP routers in any additional signaling. Our solution keeps network queues short: set the buffer size to 2L datagrams, where L is the number of input links. We also explain how end systems can utilize the network effectively despite such small buffering at routers.