Which of the following HTTP methods are NOT supported in REST and RESTCONF?

REST (Representational State Transfer) and the RESTCONF protocol (RFC 8040) utilize a standard set of HTTP methods to perform CRUD (Create, Read, Update, Delete) operations on managed resources. The supported methods include GET (to retrieve data), PUT (to create or replace a resource), POST (to create a resource), DELETE (to remove a resource), and PATCH (to partially update a resource). The method 'ADD' is not a standard HTTP method defined in the relevant IETF RFCs (such as RFC 7231 or RFC 5789 for PATCH) and is therefore not supported by REST or RESTCONF. Operations that might be conceptually described as "adding" are handled by the standard POST or PUT methods.

A. GET: This is a fundamental method used to retrieve (read) a resource and is fully supported in both REST and RESTCONF.
B. PUT: This method is used to create a new resource or completely replace an existing one and is a standard supported method.
C. DELETE: This method is used to remove a resource and is a standard supported method in both REST and RESTCONF.
E. PATCH: This method is used for partial modification of a resource and is explicitly supported by RESTCONF as defined in RFC 8040.

1. IETF RFC 8040: RESTCONF Protocol. This document is the standard that defines RESTCONF. Section 4, "RESTCONF Methods," explicitly lists the supported HTTP methods: GET, POST, PUT, PATCH, DELETE, OPTIONS, and HEAD. The 'ADD' method is not included in this list.

Reference: Section 4, Page 21. (https://datatracker.ietf.org/doc/html/rfc8040#section-4)

2. Nokia SR OS System Management Guide, Release 22.10.R1. This official vendor documentation details the RESTCONF implementation on Nokia devices. The "RESTCONF operations" section provides examples and descriptions for standard HTTP methods like GET, PUT, POST, PATCH, and DELETE, confirming their support. There is no mention of a non-standard 'ADD' method.

Reference: Part: Programmability and Automation, Section: "RESTCONF".

3. Fielding, R. T. (2000). Architectural Styles and the Design of Network-based Software Architectures. Doctoral dissertation, University of California, Irvine. This is the foundational text on REST. Chapter 5, "Representational State Transfer (REST)," describes the uniform interface constraint, which relies on a standard, limited set of methods (e.g., GET, PUT, DELETE).

Reference: Chapter 5, Section 5.2.1 "Methods". (https://www.ics.uci.edu/~fielding/pubs/dissertation/restarchstyle.htm#sec521)