An As-Level Study Of Internet Path Delay Characteristics

According to conventional wisdom, links connecting different Autonomous Systems (ASes) are the performance bottlenecks in the core of the Internet. This paper presents an empirical evaluation of delays across inter-AS links using hop-limited active probes. The measurements cover a diverse set of Internet paths starting from locations within three large transit Internet Service Providers (ISPs). We find that most inter-AS links on the Internet paths covered by this study do not contribute significantly to end-to-end delays. The few exceptions are long-haul links with large propagation delays. Furthermore, the delay estimates are fairly stable across days, making it possible for ISPs to choose inter-domain paths or perform traffic engineering based on delay measurement feedback. Our observations also suggest that a very large component of the end-to-end delay for the measured paths usually occurs within a single AS.