End-user perspectives of Internet connectivity problems

Network connectivity problems often create severe issues to end users, ranging from malfunction of applications (e.g., WWW and email) to complete loss of connectivity. This paper seeks to characterize these problems and discover the most efficient ways to improve network connectivity from the perspective of end users. Over a period of 7 months, we monitor network connection failures from 103 hosts used daily by end users. We find that more than 60% of downtime involves misconfigurations in the end hosts. These errors occur for various reasons, such as subtle interactions between end-host applications and routers, inconsistent network policies, and software bugs. Solving these problems can require an excessive amount of time, for expert and non-expert users alike. In contrast, problems occurring in network cores and servers are less visible to end users. For example, certain routing problems in network cores are much less likely to be seen than they are reported previously (i.e., persistent forwarding loops comprise roughly 0.02% of the observed downtime, contrary to ∼2.5%, as reported in previous studies). Our results show that, although a single error in a network core or a server might affect a number of end users, the accumulated impact of errors near end hosts is much larger than that of errors in network cores and servers. We thus believe that by focusing on the problems that occur at or near end systems, we can significantly improve network availability for end users.