The Controller Area Network (CAN) is a robust, low-cost, and simple event-triggered technology for connecting electronic control units in the manufacturing industry and vehicles. Today's real-time control systems are distributed over a multitude of CAN systems (domains) which are connected via embedded gateways. A failure or overload situation in the gateway can affect several domains. Furthermore, gateways often become bottlenecks between the domains and in the case of CAN buses they can pose further problems with respect to the priority-based network access method. Due to this access method and the limited resources (e.g., buffer capacity) embedded CAN-CAN gateways have to be dimensioned accurately. Otherwise, unacceptable processing delay and message loss within the gateway can occur. The main contribution of this paper is to investigate the optimized dimensioning of an embedded CAN-CAN gateway with regard to minimizing gateway resources in terms of processing and buffer capacity and decreasing message loss at the same time. For that purpose a CAN bus and a gateway model are described and used to investigate scenarios with two domains connected via a gateway.