In many respects, NETCONF and RESTCONF are similar. They both use the YANG data model and YANG development kits. They both are client/server based, with the controller being the client or the initiator and the server or receiver being the network element. They both use ietf-yang-library to either discover server capabilities (NETCONF) or list the features the server supports (RESTCONF). NETCONF and RESTCONF both use the concept of data stores, but RESTCONF uses the data stores defined in NETCONF.
Figure 12-11 shows a stack comparison of NETCONF and RESTCONF. As you can see, they have many similarities, especially in terms of YANG.

Figure 12-11 NETCONF and RESTCONF Stack Comparison
Let’s consider some of the differences between NETCONF and RESTCONF. NETCONF was developed first, in 2006, using XML encoding, and it uses SSH as a transport protocol. RESTCONF was developed approximately 10 years later to support both XML and JSON encoding, and it uses HTTP as a transport protocol. NETCONF can deploy across multiple devices by using a networkwide transaction. RESTCONF, on the other hand, has no concept of a transaction. A RESTCONF call uses HTTP PUT, POST, UPDATE, or DELETE methods to edit data resources represented by YANG data models. NETCONF includes the concept of a lock to stop operations while editing the configuration in the candidate data store; RESTCONF does not provide the concept of a lock; changes are directly applied.
Figure 12-12 illustrates the TCP/IP network frame format showing where NETCONF, RESTCONF, gRPC, and YANG are present within an IP packet.

Figure 12-12 TCP/IP Network Frame Format
IETF, OpenConfig, and Cisco YANG Models
YANG data models are developed by industry standards bodies such as the IETF and OpenConfig or specific vendors such as Cisco.
IETF
The Internet Engineering Task Force (IETF) is an Internet standards body that develops open standards through open processes. The IETF is a large international group of network designers, operators, vendors, and researchers who are focused on the evolution of Internet architecture. Their technical work within the IETF is done in working groups organized by topic into several areas. The YANG Model Coordination Group, for example, has been spending time on the inventory of YANG models in the industry, tooling aspects, training and education of NETCONF, YANG, pyang, and the model coordination for the IETF.
IETF data models are available on GitHub, at https://github.com/YangModels/yang.