Literature review on standards for data structuring in physical layer of optical network.

With the increase of users and the popularization of the internet, the needs of users have changed, business needs have become more and more complex, and conventional network architecture has become increasingly unable to meet the needs of both users and businesses. International research organizations and individuals have launched the research on the new network architecture. SDN also emerged at this time. As a new network innovation architecture scheme, SDN has burned a research boom in the industry since its birth. Software-defined networking (SDN) separates the control plane from the data forwarding plane, which is presented as a new kind of architecture of networking control and management. SDN is designed to separate the control plane from the data forwarding plane, support the centralized network state control, which shows the transplant view from the underlying network devices to the upper layer applications. And SND has flexible programming capability, and the emergence of SDN has effectively improved the automated control and management of networking. This article, firstly mainly introduce and summarize the functionality and significance of SDN architecture, and its most important part -Open Daylight, which serves as the core controller of SDN.  Then specifically introduce YANG modeling language, which is extensively used in SDN architecture, we mainly summarize syntax, semantic, and functions of YANG modeling language, and also pave the way for the subsequent introduction of SDN-based network protocols. Finally, we mainly summarize the two types of SDN-based network protocols, NETCONF and RESTCONF. Both NETCONF and RESTCONF are also based on YANG modeling language. We summarize the operation methods and functionality of NETCONF and RESTCONF at length. On the other hand, the emergence of NETCONF has greatly simplified the process of a network configuration for clients. In like manner, RESTCONF has also advantages such as flexibility, simple application, scalability, and others. In this article, we researched RESTCONF in detail, focusing on its resource access, information communication, and CRUD operation mechanisms. This article is basically a literature review, main purpose is to summarize the current hot topic in the fast-expanding field of optical networking.