The NETCONF protocol architecture is conceptually divided into four layers. When a NETCONF client sends a request to a server, it utilizes both the operations and messages layers.

The operations layer defines the set of base protocol operations, such as or , which are invoked as Remote Procedure Call (RPC) methods. The client selects an operation from this layer to define the action it wants the server to perform.

The messages layer provides the framing mechanism for the request. It encodes the chosen operation within an element, creating a well-formed message that can be sent to the server. Therefore, both layers are used to construct and send an RPC.

A. A NETCONF client sends RPCs and receives messages. The server receives RPCs. The messages layer is for framing, not the act of receiving.

C. The operations layer defines the methods invoked by an RPC; it does not handle the reception of the message itself.

1. Juniper Networks Official Documentation, "NETCONF XML Management Protocol Overview": This document outlines the four conceptual layers of NETCONF. It states, "The messages layer provides a mechanism for encoding RPCs...within ...elements." It also states, "The operations layer defines a set of base protocol operations that are invoked as RPC methods," listing examples like and . This supports that both layers are used to construct and send an RPC. (Source: Juniper TechLibrary, Automation, NETCONF XML Management Protocol Overview)

2. RFC 6241, "Network Configuration Protocol (NETCONF)", Section 1.1. NETCONF Layers: This RFC defines the standard. It describes the Messages Layer as providing "a simple, transport-independent framing mechanism for encoding RPCs" and the Operations Layer as defining "a set of base protocol operations invoked as RPC methods". This confirms that a client uses the operations layer to define the method and the messages layer to frame it for sending.