The Potential of End-to-End Observations in Trouble Localization and Quality Control of Network Links

Algorithms for the use of Origin-to-Destination (Endto-End) observations for the monitoring of direct network links (direct finals or primary high usage groups) were previously proposed and analyzed. In this paper a theoretical framework intended to shed insight on the potential for also monitoring non-direct network links is developed. In particular, a maximum likelihood based approach is applied to an idealized network model with fixed routing probability structure and point-to-point loads. This approach allows sufficient conditions for the identifiability (estimation) of a fixed set of per link call failure probabilities to be developed, indicating that identifiability problems can be resolved by the addition of observations on selected links from tandems. Because of the dynamically changing character of network loads and hence routing probabilities, the extension appears thus attractive to implement only for limited portions of the network. Through the proposed scheme, unnecessary complexity in the minicomputer network that realizes the quality control of the network links is avoided.