  Video streaming is dominating the Internet. To compete with the performance
of traditional cable and satellite options, content providers outsource the
content delivery to third-party content distribution networks and brokers.
However, no existing monitoring mechanism offers a multilateral view of a
streaming service's performance. In other words, no auditing mechanism reflects
the mutual agreement of content providers, content distributors and end-users
alike about how well, or not, a service performs.
  In this paper, we present UgoVor, a system for monitoring multilateral
streaming contracts, that is enforceable descriptions of mutual agreements
among content providers, content distributors and end-users. Our key insight is
that real-time multilateral micro-monitoring -- capable of accounting for every
re-buffering event and the resolution of every video chunk in a stream -- is
not only feasible, but an Internet-scalable task. To demonstrate this claim we
evaluate UgoVor in the context of a 10-month long experiment, corresponding to
over 25 years of streaming data, including over 430,000 streaming sessions with
clients from over 1,300 unique ASes. Our measurements confirm that UgoVor can
provide an accurate distributed performance consensus for Internet streaming,
and can help radically advance existing performance-agnostic pricing model
towards novel and transparent pay-what-you-experience ones.
