Which function is available in NETCONF and unavailable is RESTCONF?

The NETCONF protocol defines a standard configuration datastore. This datastore acts as a staging area where configuration changes can be made and then validated for syntactical and semantic correctness using the operation before being applied to the running configuration via a operation. This provides a robust, transactional change mechanism. In contrast, the RESTCONF protocol, as defined in RFC 8040, does not include a standard candidate datastore. RESTCONF operations typically modify the datastore directly, lacking the built-in, standardized staging and validation capabilities inherent to NETCONF's candidate datastore.

A. Configuration changes are automatically activated. This is incorrect. NETCONF requires an explicit operation to activate changes from the candidate datastore to the running datastore; it is not automatic.
B. Uses the YANG data models to communicate. This is incorrect. Both NETCONF and RESTCONF are fundamentally designed to use YANG as the data modeling language for configuration and state data.
C. Support JSON and data encoding. This is incorrect. RESTCONF mandates support for both JSON and XML encoding. While XML is mandatory for NETCONF, JSON is an optional encoding.

1. IETF RFC 8040: RESTCONF Protocol.

Section 1.3

"Relationship to NETCONF": "The NETCONF protocol has a richer set of operations than RESTCONF... For example

NETCONF supports

and operations that are not available in RESTCONF."

Section 4.3

"Datastore Resources": "The 'candidate' datastore is not supported directly in RESTCONF."

2. IETF RFC 6241: Network Configuration Protocol (NETCONF).

Section 8.5

" Operation": "This operation allows the client to validate the contents of a specified configuration. The source of the configuration is a configuration datastore or a complete configuration contained within the RPC." This section explicitly defines the validation capability.

Section 5.1

"Datastores": This section defines the standard datastores

including

which is "a full configuration data set that can be manipulated without impacting the device's current configuration."

3. Cisco IOS XE Programmability Configuration Guide

Cisco IOS XE Bengaluru 17.6.x.

Chapter: RESTCONF Protocol

"RESTCONF and NETCONF" section: "RESTCONF does not support the candidate datastore. All configuration changes are applied to the running datastore." This official vendor documentation confirms the absence of the candidate datastore in their RESTCONF implementation

aligning with the RFC standard.