Sampling and quantization in Networked Control Systems (NCS) are addressed in this paper. The NCS studied in this paper consists of a continuous time plant, a sensor network and a discrete time controller. The amount of network induces delay to the control system is a function of the sampling rate of the control system. An upper bound for the delay will be found using network calculus which is a theory for deterministic queuing. From the control side of view, we consider a delayed sampled data system and propose a method to study the effects of sampling and delay in a unified framework. We define the quality-of-control in the sense of a ${\mathcal{H}_\infty }$ norm of the system and we propose a method to minimize this norm. According to our result, the optimal solution may not corresponds to the lowest sampling rate and it depends on the dynamics of the system and parameters of the communication link. We also extend the result to investigate the effect of quantization by proposing a new finite level quantizer. Similar to the sampling rate, we show that a larger number of allocated bits for quantization does not necessarily result in a better quality-of-control.