**3.3 Bandwidth measure**

Real-time applications require more bandwidth to process the extraordinarily huge volume of data. Thus, the traditional cloud system increases the overhead on communication bandwidth which results in increasing delay and poor QoE. To compute the communication bandwidth constraint, the traffic rate is assumed to be dispatched from the fog node *i* located at Edge-Fog layer to the server *j* located at cloud data center through the transmission path [17]. There is a limitation <sup>λ</sup>*i*,*<sup>j</sup> max* on the bandwidth capacity of each path which is computed as:

$$\mathbf{0} \le \lambda\_{i,j} \; \leq \; \lambda\_{i,j}^{\max} \; \forall \; i \; \mathbf{N}\_{\text{fog}} \; \mathbf{and} \; \forall \; \mathbf{e} \; M\_{\text{cloud}} \tag{6}$$

Here, *Nfog* represents the set of fog devices where *Mcloud* is the set of cloud data center servers. The optimum utilization of Optical-Fog network is more effective than the traditional cloud.
