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1. Overview

This document describes five types of SNMP applications:

  • Applications which initiate SNMP Read-Class, and/or Write-Class requests, called 'command generators.'
  • Applications which respond to SNMP Read-Class, and/or Write-Class requests, called 'command responders.'
  • Applications which generate SNMP Notification-Class PDUs, called 'notification originators.'
  • Applications which receive SNMP Notification-Class PDUs, called 'notification receivers.'
  • Applications which forward SNMP messages, called 'proxy forwarders.'

Note that these application types are not mutually exclusive. A single SNMP entity may contain multiple types of applications. For example, an SNMP entity may contain a command responder application, a notification originator application, and a proxy forwarder application.

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 [RFC2119].

1.1 Command Generator Applications​

A command generator application initiates SNMP read or write requests, and processes responses received from command responder applications.

A command generator application may:

  • Generate GetRequest-PDU, GetNextRequest-PDU, GetBulkRequest-PDU, or SetRequest-PDU as defined in STD 62, RFC 3416 [RFC3416].
  • Process Response-PDU messages received from command responder applications.

1.2 Command Responder Applications​

A command responder application receives SNMP read or write requests from command generator applications and generates appropriate responses.

A command responder application may:

  • Process GetRequest-PDU, GetNextRequest-PDU, GetBulkRequest-PDU, or SetRequest-PDU messages received from command generator applications, as defined in STD 62, RFC 3416 [RFC3416].
  • Generate Response-PDU messages.

1.3 Notification Originator Applications​

A notification originator application generates SNMP notification messages (traps or inform requests). A notification originator may be configured to send notifications to one or more notification receiver applications.

A notification originator application may:

  • Generate SNMPv2-Trap-PDU or InformRequest-PDU as defined in STD 62, RFC 3416 [RFC3416].
  • If an InformRequest-PDU is generated, process Response-PDU messages received from notification receiver applications.

1.4 Notification Receiver Applications​

A notification receiver application receives SNMP notification messages from notification originator applications or proxy forwarder applications.

A notification receiver application may:

  • Process SNMPv2-Trap-PDU or InformRequest-PDU messages received from notification originator applications or proxy forwarder applications, as defined in STD 62, RFC 3416 [RFC3416].
  • If an InformRequest-PDU is received, generate a Response-PDU message.

1.5 Proxy Forwarder Applications​

A proxy forwarder application forwards SNMP messages between SNMP entities. A proxy forwarder may modify SNMP messages to accommodate different SNMP versions, security models, or management information views.

A proxy forwarder application may:

  • Forward command requests from command generator applications to command responder applications.
  • Forward command responses from command responder applications back to command generator applications.
  • Forward notifications from notification originator applications to notification receiver applications.

The operation of a proxy forwarder involves:

  1. Receiving an SNMP message from a command generator or notification originator.
  2. Determining the appropriate target management entity.
  3. Modifying message parameters as necessary (e.g., translating security parameters, modifying PDUs).
  4. Forwarding the modified message to the target.
  5. If a response is expected, receiving the response and forwarding it back to the original sender.

Proxy forwarders are particularly useful in scenarios involving:

  • Protocol Translation: Translating between different SNMP versions (SNMPv1, SNMPv2c, SNMPv3).
  • Security Translation: Translating between different security models or security levels.
  • Management Domain Bridging: Bridging between different management domains, each with potentially different security requirements or management information views.
  • Centralized Management: Allowing a centralized management system to access devices in multiple network segments through proxies.

The configuration of proxy forwarders is managed through the SNMP-PROXY-MIB module defined in this document.

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