YANG

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Yet Another Next Generation (YANG, /jæŋ/, which rhymes with "hang")^[1][2][3] is a data modeling language for the definition of data sent over network management protocols such as the NETCONF^[4] and RESTCONF.^[5] The YANG data modeling language is maintained by the NETMOD ^[6] working group in the Internet Engineering Task Force (IETF) and initially was published as RFC 6020 in October 2010, with an update in August 2016 (RFC 7950). The data modeling language can be used to model both configuration data as well as state data of network elements. Furthermore, YANG can be used to define the format of event notifications emitted by network elements and it allows data modelers to define the signature of remote procedure calls that can be invoked on network elements via the NETCONF protocol. The language, being protocol independent, can then be converted into any encoding format, e.g. XML or JSON, that the network configuration protocol supports.

YANG is a modular language representing data structures in an XML tree format. The data modeling language comes with a number of built-in data types. Additional application specific data types can be derived from the built-in data types. More complex reusable data structures can be represented as groupings. YANG data models can use XPATH expressions to define constraints on the elements of a YANG data model.