IEEE 802.1Q networks with extensions for time-sensitive networking aim to enable converged networks. Converged networks support hard-real time communication services in addition to the currently supported services classes. Real-time communication in these networks requires routes and schedules for the real-time transmissions. We present a formulation in the integer linear programming (ILP) framework which models the joint routing and scheduling problem for flows of periodic real-time transmissions in converged TSN networks. In the joint routing and scheduling problem, both routes and schedules for real-time transmissions are computed in one step, i.e. we do not schedule over predefined routes. We explore the practical limitations of this approach by evaluating the runtime of problem instances with widely varying parameters with a state-of-the-art ILP solver. The observed solver runtimes indicate the qualitative impact of the number of real-time flows, the size of the network, the transmission frequency of real-time transmissions, and the network topology.