Wireless Sensor Network (WSN) enables pervasive, ubiquitous, and seamless communication with the physical world. This paper investigates an optimal cross-layer optimization for WSN with periodic application. A joint energy efficient routing with minimum delay scheduling optimization model is proposed in this paper. The problem is formulated as an Integer Linear Program (ILP) model. The proposed ILP model has multi objectives cost function. The main objective of the proposed model is to maximize network lifetime and to minimize delay. The proposed ILP model represents the operation of Energy-Efficient Distributed Schedule-Based (EEDS) protocol. The ILP model is solved for different network configurations. The solution obtained by solving the proposed ILP model is compared with EEDS simulation results. Although the two solutions show similar behavior, the ILP solution outperforms the solution obtained by EEDS simulation by 28.3%. Moreover, the optimal solutions assuming different objectives are compared together.