# Video Streaming Adaptive QoS Routing with Resource Reservation (VQoSRR) Model for SDN Networks
## 1 Introduction  
With the explosive growth of the Internet, video streaming driven by providers of streaming media services is already a large portion of Internet traffic today and is predicted to continue growing. Another ongoing trend that feeds this growth is the increasing number of smartphone devices, social media users, and the advancement of networks technologies, such as Wi-Fi and 5G connections. According to the Cisco Global Forecast Highlights report [1], video traffic will account for 80% of global Internet traffic by 2021. This increasing demand for high-quality online video requires network operators and media service providers to adopt new strategies and technologies. In this regard, QoS-based routing has emerged to enable the routing layer to enhance traffic performance and overallquality of service (QoS) by meeting multiple users' QoS requirements. However, its routing decisions depend on multiple metrics, and finding a path that meets the composed multiple metrics of delay, cost, packet loss probability, and jitter is an NP-complete problem [2]. Due to the special characteristics of video streaming and its applications, the networks must be managed to provide a convenient and guaranteed level of QoS and QoE. However, the QoS model in the traditional Internet faced unresolved problems such as bounded visibility of the global topology, per-hop decisions, and the difficulty of providing different levels of QoS for different applications flows. Furthermore, some of the existing IP short path routings algorithms cannot verify the link QoS required to adapt to the requested requirements of QoS for the flow, since it is unaware of the available QoS over the path [3]. In contrast, IP link-state protocols provide QBR by flooding updates to exchanging routing information and reflecting an up-to-date view of the network in order to calculate new routes. However, the frequent flooding process can impose significant communication overhead on forwarding devices, and repeatedly changing the routing paths can increase the delay experienced by the end-users [3;4]. Another aspect of the shortest path routing is that it allows the using of multiple equal-cost paths as alternatives to redirect traffic from one path to another when a better one is available. The router will redirect the traffic even if the existing route has an acceptable but non-optimal cost that can meet the service requirements of the already-existing traffic. Along with the short path routing issues described above, the Internet best effort service led to an insufficient QoS implementation. In addition, Internet video streams with higher resolution definitions have become more popular recently. The Cisco study also estimates that the standard-definition (SD) video traffic will decrease to 24.5% in 2021 compared to 61.4% in 2016. In contrast, high-definition (HD) video traffic will rise to 56.3% in 2021, up from 36.4% in 2016; and ultra-high-definition (UHD) or 4K will be 19.2% of Internet video traffic in 2021, up from 2.2% in 2016 [1]. The video resolution is one of the video content characteristics that impact the video quality of experience (QoE) because it indicates the level of detail in a video frame. Displaying videos at a higher definition will maximize user-perceived quality; however, increasing the video resolution will make more visible those problems that may occur during the video delivery, causing different levels of degradation for the user QoE. As a result, it requires a good level of network QoS [5] because QoS parameters, such as jitter, delay, lost packets, etc., influence video QoE [6]. Additionally, video traffic is resource-intensive and consumes a lot of network bandwidth, especially high-resolution videos, and videos with a high bit rate; therefore, any planned model for videos streaming must provide resource reservation capabilities. Additionally, it must balance between these resource allocation techniques and QoS-based routing methods to avoid affecting network QoS, in turn avoiding affecting video QoE.