**2. Utilization of optical resources in cloud/fog computing environment**

In order to handle real-time and bandwidth-intensive applications, fog leverages the computing resources of the SDN-based optical network. **Figure 1** shows that the Optical-Fog layer [7] uses ONUs in the middleware of the cloud and IoT layer. In a typical PON channel with multiple OLTs, each OLT is connected with multiple ONUs (16–256) [8]. The Optical-Fog layer is designed by using their residual processing, storage, and interconnection capabilities. It can enable fast service provisioning, dynamic service restoration, network automation, and network optimization at different layers of the underlying network infrastructure. It makes optical network

**171**

**Table 1.** *List of acronyms.*

*Role of Optical Network in Cloud/Fog Computing DOI: http://dx.doi.org/10.5772/intechopen.84404*

**2.1 SDN-based optical network**

centralized, intelligent, and controlled (real time) which can serve application-level services efficiently in the heterogeneous IoT, machine learning, big data, and cloud computing paradigms. The acronyms used in this paper are defined in **Table 1**.

Presently, SDN is supporting wide area network to deal with many more technologies for delivering several benefits. It has adopted a hierarchical approach in which domain controllers collect information and delegate the control (real time) over the network layers and geographic clusters to support applications and provide higher levels of service orchestrations. Initially, SDN was used in data centers for separating the data plane, control plane, and management plane from each other [9]. The interface like OpenFlow is used by the centralized controller to deliver computing infrastructure for making better communication. While applying this concept to the optical network, optical domain controller (ODC) plays an important role. As shown in **Figure 2**, it provides a more programmatic and abstract view of the underlying optical network through the northbound interface [10]. The programming feature of SDN makes it capable of fulfilling customized demands for manipulating network infrastructure. To handle real-time, bandwidth-intensive applications, fog uses the computing resources of the SDN-based optical network. The SDN-based optical network infrastructure fulfills the demand of increasingly high-performance and network-based applications with flexibility and efficiency. The key security issues in fog/cloud computing over optical network lies at both downstream and upstream channels of PON. PON uses broadcasting in the downstream channel which is prone to eavesdropping attacks where an attacker can modify the behavior of ONUs at its media access control (MAC) layer. On the other hand, the traffic in the upstream channel is only visible to the OLT rather than other ONUs that can also be exploited for attacks. In PON network, OLT uses time division multiplexing access (TDMA) that provides sharing of the upstream channel among

PON Passive optical network OLT Optical line terminal ONU Optical network unit CPS Cyber physical systems

EEG Electroencephalogram QoE Quality of experience QoS Quality of service

ONV Optical network virtualization SDN Social-defined network FAR Free available resource

TDMA Time division multiplexing access MPCP Multipoint control protocol ODC Optical domain controller MAC Media access control

VR Virtual reality

**Figure 1.** *Utilization of optical resources in cloud/fog computing environment.*

centralized, intelligent, and controlled (real time) which can serve application-level services efficiently in the heterogeneous IoT, machine learning, big data, and cloud computing paradigms. The acronyms used in this paper are defined in **Table 1**.
