_______________________________________________ This work was supported in part by the U.K. EPSRC, grant number 06R00456 Department of Computer Systems, P.O. Box 325, S-751 05 Uppsala, Sweden (E-mail: ken@docs.uu.se) Abstract The increasing use of communication networks in time critical applications presents engineers with fundamental problems with the determination of response times of communicating distributed processes. Although there has been some work on the analysis of communication protocols, most of this is for idealised networks. Experience with single processor scheduling analysis has shown that models which abstract away from implementation details are at best very pessimistic and at worst lead to unschedulable system being deemed schedulable. In this paper, we derive idealised scheduling analysis for the CAN network, and then study two actual interface chips to see how the analysis can be applied.