Low-Power and Lossy networks are an integral part of the IoT ecosystem. These networks are defined by their shared features such as having limited resources and high occurrence of packet loss. A routing protocol for such networks called Routing Protocol for Low-Power and Lossy Networks (RPL) was proposed in 2012. Even though RPL is now standardized and well-accepted by the community, it still has areas to be improved such as load balancing, stability, and support for mobility. This study focuses particularly on approaches proposed for the load balancing problem in RPL. In the literature, many researchers aimed to tackle this problem by creating different routing metrics that handle different objectives. This review makes a thorough assessment of these works, their strengths and shortcomings, and provides future directions on the issue.

低功耗和有损网络是物联网生态系统不可或缺的一部分。这些网络由它们的共享功能（例如资源有限和丢包率很高）来定义。2012年提出了针对此类网络的路由协议，称为“低功耗有损网络路由协议（RPL）”。尽​​管RPL已经标准化并得到了社区的广泛认可，但仍需要改进一些领域，例如负载平衡，稳定性，以及对机动性的支持。这项研究特别关注针对RPL中的负载平衡问题提出的方法。在文献中，许多研究人员旨在通过创建处理不同目标的不同路由度量来解决此问题。这篇综述对这些作品，它们的优缺点进行了全面的评估，并就此问题提供了未来的方向。