End-to-end available bandwidth: Measurement methodology, dynamics, and relation with TCP throughput

TLDR

Available bandwidth is critical for congestion control, streaming, QoS, server selection, and overlay networks, yet persistent TCP connections can overestimate it by saturating the path and increasing delays. The study introduces SLoPS, an end‑to‑end method for measuring available bandwidth, and investigates its relationship with TCP throughput. SLoPS sends periodic packet streams and observes increasing one‑way delays when the sending rate exceeds available bandwidth; the method is implemented in the pathload tool and used to assess bandwidth dynamics. Pathload accurately measures available bandwidth without significantly affecting network traffic, and shows that bandwidth variability rises on heavily utilized or low‑capacity paths.

Abstract

The available bandwidth (avail-bw) in a network path is of major importance in congestion control, streaming applications, quality-of-service verification, server selection, and overlay networks. We describe an end-to-end methodology, called self-loading periodic streams (SLoPS), for measuring avail-bw. The basic idea in SLoPS is that the one-way delays of a periodic packet stream show an increasing trend when the stream's rate is higher than the avail-bw. We have implemented SLoPS in a tool called pathload. The accuracy of the tool has been evaluated with both simulations and experiments over real-world Internet paths. Pathload is nonintrusive, meaning that it does not cause significant increases in the network utilization, delays, or losses. We used pathload to evaluate the variability ("dynamics") of the avail-bw in Internet paths. The avail-bw becomes significantly more variable in heavily utilized paths, as well as in paths with limited capacity (probably due to a lower degree of statistical multiplexing). We finally examine the relation between avail-bw and TCP throughput. A persistent TCP connection can be used to measure roughly the avail-bw in a path, but TCP saturates the path and increases significantly the path delays and jitter.