With the advances in automotive industry and telecommunication technologies, more and more vehicles are connected which paves the pathway to future intelligent transportation system (ITS). The safety of both the passengers and pedestrians has been a major concern in ITS. Vehicular ad hoc network (VANET) is a promising technology that can provide a wide range of services, such as safety, convenience, and infotainment for the passengers and drivers. However, due to the dynamic nature of the vehicular environment, VANET has to deal with several challenges such as intermittent connectivity, provisioning of quality of service (QoS), and heterogeneity of applications. Moreover, the deployment of new services/protocols on a large-scale is a daunting task due to the inflexible architecture of VANET. The distinctive features of software-defined vehicular network (SDVN) such as programmability and flexibility leverages the vehicular network to satisfy the performance and management requirements of VANET. In this paper, we first present the taxonomy of SDVN architecture based on its modes of operation. Then we survey the state-of-the-art SDVN routing protocols and classify them based on different criteria. Finally, we highlight the challenges of current SDVNs.

随着汽车工业和电信技术的发展，越来越多的汽车被连接起来，这为未来的智能交通系统（ITS）铺平了道路。乘客和行人的安全一直是ITS的主要关注点。车载自组织网络（VANET）是一项很有前途的技术，可以为乘客和驾驶员提供广泛的服务，例如安全性，便利性和信息娱乐。但是，由于车辆环境的动态性质，VANET必须应对一些挑战，例如间歇性连接，服务质量（QoS）的提供和应用程序的异构性。此外，由于VANET的体系结构不灵活，因此大规模部署新服务/协议是一项艰巨的任务。软件定义的车载网络（SDVN）的独特功能（例如可编程性和灵活性）充分利用了车载网络来满足VANET的性能和管理要求。在本文中，我们首先根据其运行模式介绍SDVN体系结构的分类法。然后，我们调查最新的SDVN路由协议，并根据不同的标准对其进行分类。最后，我们重点介绍了当前SDVN的挑战。