# Stochastic Modeling for Intelligent Software-Defined Vehicular Networks: A Survey
## 5 Performance Evaluation of iSDVN
### Challenges of Multi-Service Provisioning of QoS for iSDVN and iSDHVN  
Multi-service provisioning refers to the ability of a network to support the delivery of multiple types of services, such as voice, video, and data, over a single infrastructure. With the increasing demand for new services, the ability to deliver multiple services efficiently and cost-effectively has become essential for network operators. Typically, it is achieved through the use of QoS mechanisms that ensure that different types of traffic are prioritized in accordance with their requirements. QoS mechanisms can help ensure that the network resources are used effectively, and the delivery of critical services is not compromised.  
In addition to QoS mechanisms, network operators can also use Service Level Agreements (SLAs) to guarantee service quality for specific applications or customers. SLAs can include specific requirements such as bandwidth, latency, and packet loss rates and can help ensure that critical services are delivered with the desired level of performance. Multi-service provisioning can be challenging for network operators, as different services may have different requirements for bandwidth, latency, and other metrics. This requires careful planning and management to ensure that the network is optimized for the delivery of multiple services. It is typically achieved through the use of QoS mechanisms and SLAs, which prioritize different types of traffic based on their requirements and guarantee service quality for specific applications or customers. Effective multi-service provisioning requires careful planning and management to optimize the network for the delivery of multiple services.  
The aim of this work was to improve the reliability of service provisioning in iSDVNs. We examined how SDN has evolved into new wired and wireless networking applications and end-user services. Multiple wireless network technologies are integrated into SDN to support and improve QoS. The iSDVN enables link reliability in V2V environments, especially in an SDVN controlled by a centralized server. To improve vehicular safety, queueing-based models are most appropriate for evaluating SDN controllers and switches. The utilization of resources, traffic flow, and queue management are optimized. As data traffic flows or services are provisioned, network management becomes feasible. The logically centralized management of an SDVN allows V2V communications to be conducted efficiently. In the control plane, high-priority messages can be sent through wired or wireless channels allocated to specific controllers and switches.  
A queueing-based model is found to be more effective for evaluating controllers and switches. The iSDVN system has been designed to balance high traffic loads and data services. A packet flow's service time is based on an exponential distribution in iSDVNs. In the queueing-based model, a path selection approach is used, queues are modeled with the controller, and traffic flow is controlled by switches. VNC (virtual network customization) can be increased with SDN. For using multi-service provisioning in an SDVN, we propose the multi-hop cooperative data dissemination approach to enhance data link reliability and stability and select the best route for packets from the source to the destination. Data traffic load balancing in vehicular networks is a significant problem that SDN heterogeneous vehicular networks can handle [138]. To minimize network management latency and maximize network utility, the iSDHVN controller controls events over the cellular network. Throughput and resource utilization are optimized with the proposed enhanced service reliability model, which also reduces resource consumption and minimizes response time.