# SDN-Based Survivability Analysis for V2I Communications
## 1 Introduction
Due to that, MPTCP is one of the most important candidate protocols to improve end-to-end (E2E) communication reliability, elasticity, and bandwidth efficiency in 5G mobile networks. The authors in Reference [5] introduced the applications of MPTCP to LTE networks in detail. In Reference [6], the MPTCP congestion control extension algorithm for LTE networks is proposed with the goal of aggregating the available bandwidth of multiple paths, as well as that it can avoid the common single-path TCP transmission of shared paths attack behavior. In addition, the combination of MPTCP and SDN in V2I networks within the vehicle short-distance communication is proposed in Reference [7], where the connectivity between the vehicle and Wi-Fi, vehicle and RSU are simulated by using Mininet-WiFi. Moreover, the connectivity performance is also measured from three indexes: packet loss rate, round-trip time, and average throughput, respectively. In Reference [8], the authors proposed the use of MPTCP to communicate reliably on the Internet of Vehicles (IoV). It is worth noting that, in this paper, the survivability refers to the service quality of the system to complete the key tasks in time when the software and hardware fail, which not only pays attention to the overall security of the network system but also ensures the timely and effective transmission of the key information. On the basis of this, the study of survivability has been applied in various networks, such as information systems [9], wavelength division multiplexing (WDM) fiber optic networks [10; 11], asynchronous transfer mode (ATM) networks [12], internet [13], military communications networks [14], satellite communications networks [15], wireless sensor networks [16; 17; 18], and vehicular ad-hoc networks (VANETs) [19]. Moreover, the research on survivability mainly includes the definition of survivability, the model of survivability, and the method of survivability analysis. The definition of survivability varies according to the application environment [20; 21; 22; 23; 24; 25]. The present survivability models are mainly the Markov model, Markov reward model, semi-Markov model, and stochastic graph model [21; 24; 25; 26; 27; 28; 29; 30]. To further improve the communication link survivability when the network fails, some effective modeling methods are introduced in the literature [31; 32; 33; 34; 35]. In addition, survivability analysis mainly includes quantitative analysis, in which quantitative analysis is presented in a numerical form and the performance is more intuitive. Most of the present researches on the improvement of the network performance method are mainly to evaluate the network operations from the point of view of a theoretical algorithm and simulation. To the best of our acknowledge, few studies focus on the research and applications of SDN- and MPTCP-based vehicle networks, especially for V2I network communications. Moreover, as one of the evaluation indexes of the network performance, survivability is less applied in the vehicle network, which refers to the ability of the network to still transmit tasks (or continuous service) after the failure and has a certain research value in certain kinds of vehicle networks. Therefore, it is necessary to study vehicle network survivability in the process of a random dynamic change of vehicle network topology and the failure of vehicle network links caused by various uncertain factors. With the above observations, our motivation is to analyze and evaluate the survivability in different vehicle network communication models and propose effective survivability models to provide the vehicle network survivability in abnormal situations. This paper proposes to use the probabilistic checking method to accurately analyze and evaluate the survivability of a SDN-based vehicle network from the point of view of network link failure (including software and hardware failure) and recovery.