1. Introduction

The Architecture for describing Internet Management Frameworks [RFC3411] describes that an SNMP engine is composed of:

1. a Dispatcher
2. a Message Processing Subsystem,
3. a Security Subsystem, and
4. an Access Control Subsystem.

Applications make use of the services of these subsystems.

It is important to understand the SNMP architecture and its terminology to understand where the Message Processing Subsystem and Dispatcher described in this document fit into the architecture and interact with other subsystems within the architecture. The reader is expected to have read and understood the description of the SNMP architecture, defined in [RFC3411].

The Dispatcher in the SNMP engine sends and receives SNMP messages. It also dispatches SNMP PDUs to SNMP applications. When an SNMP message needs to be prepared or when data needs to be extracted from an SNMP message, the Dispatcher delegates these tasks to a message version-specific Message Processing Model within the Message Processing Subsystem.

A Message Processing Model is responsible for processing an SNMP version-specific message and for coordinating the interaction with the Security Subsystem to ensure proper security is applied to the SNMP message being handled.

Interactions between the Dispatcher, the Message Processing Subsystem, and applications are modeled using abstract data elements and abstract service interface primitives defined by the SNMP architecture.

Similarly, interactions between the Message Processing Subsystem and the Security Subsystem are modeled using abstract data elements and abstract service interface primitives as defined by the SNMP architecture.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119.