The effect of layer-2 store-and-forward devices on per-hop capacity estimation

— Tools such as pathchar, clink, and pchar attempt to measure the capacity of every Layer-3 (L3) hop in a network path. These tools use the same underlying measurement methodology, which we refer to as Variable Packet Size (VPS) probing. The key assumption in VPS is that each L3 hop along a path increases the delay of a packet by a “serialization latency”, which is the ratio of the packet size over that hop’s capacity. Unfortunately, the capacity estimates of VPS tools are sometimes wrong. In this paper, we investigate the source of these errors, and show that the presence of Layer-2 (L2) store-and-forward devices, such as Ethernet switches, have a detrimental effect on the accuracy of VPS tools. Specifically, each L2 store-andforward device introduces an additional serialization latency in a packet’s delay, which results in consistent underestimation of that L3 hop’s capacity. We analyze this negative effect, deriving the measured capacity of an L3 hop as a function of th...

• Type: Conference
• Year: 2003
• Where: INFOCOM
• Authors: Ravi Prasad, Constantinos Dovrolis, Bruce A. Mah
• Keywords: Communications, Hop’s Capacity, INFOCOM 2003, L3 Hop, VPS Tools