Service Level Agreements require a monitoring system that checks that no party violates the agreement. Current monitoring techniques either have a high performance overhead or are not reliable enough. This paper proposes a new hybrid monitoring system that we call
. It tries to balance the disadvantages of established monitoring techniques, in particular online and offline monitoring. Online monitoring has a relatively high performance overhead and offline monitoring does not identify all possible violations.
Reactive monitoring combines online monitoring, which is used for reactively checking continuous SLA properties with a new
passive monitoring scheme
. This scheme is used for monitoring discrete SLA properties. It is based on cryptographic primitives that provide proof that either a certain stage in an interaction has been reached correctly with all participants in compliance of the service level agreements or that a violation has occurred. In the latter case the violating party can be identified.
A theoretical analysis shows that in the worst case scenario this new approach has the same overhead as online monitoring techniques and in most cases the overhead will be significantly lower.