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RFC2271 - An Architecture for Describing SNMP Management Frameworks

王朝other·作者佚名  2008-05-31
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Network Working Group D. Harrington

Request for Comments: 2271 Cabletron Systems, Inc.

Obsoletes: 2261 R. Presuhn

Category: Standards Track BMC Software, Inc.

B. Wijnen

IBM T. J. Watson Research

January 1998

An Architecture for Describing

SNMP Management Frameworks

Status of this Memo

This document specifies an Internet standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "Internet

Official Protocol Standards" (STD 1) for the standardization state

and status of this protocol. Distribution of this memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1998). All Rights Reserved.

IANA Note

Due to a clerical error in the assignment of the snmpModules in this

memo, this RFCprovides the corrected number assignment for this

protocol. This memo obsoletes RFC2261.

Abstract

This document describes an architecture for describing SNMP

Management Frameworks. The architecture is designed to be modular to

allow the evolution of the SNMP protocol standards over time. The

major portions of the architecture are an SNMP engine containing a

Message Processing Subsystem, a Security Subsystem and an Access

Control Subsystem, and possibly multiple SNMP applications which

provide specific functional processing of management data.

Table of Contents

1. IntrodUCtion ................................................ 3

1.1. Overview .................................................. 3

1.2. SNMP ...................................................... 4

1.3. Goals of this Architecture ................................ 5

1.4. Security Requirements of this Architecture ................ 6

1.5. Design Decisions .......................................... 7

2. Documentation Overview ...................................... 8

2.1. Document Roadmap .......................................... 10

2.2. Applicability Statement ................................... 10

2.3. Coexistence and Transition ................................ 10

2.4. Transport Mappings ........................................ 11

2.5. Message Processing ........................................ 11

2.6. Security .................................................. 11

2.7. Access Control ............................................ 11

2.8. Protocol Operations ....................................... 12

2.9. Applications .............................................. 12

2.10. Structure of Management Information ...................... 12

2.11. Textual Conventions ...................................... 13

2.12. Conformance Statements ................................... 13

2.13. Management Information Base Modules ...................... 13

2.13.1. SNMP Instrumentation MIBs .............................. 13

2.14. SNMP Framework Documents ................................. 13

3. Elements of the Architecture ................................ 14

3.1. The Naming of Entities .................................... 14

3.1.1. SNMP engine ............................................. 15

3.1.1.1. snmpEngineID .......................................... 16

3.1.1.2. Dispatcher ............................................ 16

3.1.1.3. Message Processing Subsystem .......................... 16

3.1.1.3.1. Message Processing Model ............................ 17

3.1.1.4. Security Subsystem .................................... 17

3.1.1.4.1. Security Model ...................................... 17

3.1.1.4.2. Security Protocol ................................... 18

3.1.2. Access Control Subsystem ................................ 18

3.1.2.1. Access Control Model .................................. 18

3.1.3. Applications ............................................ 18

3.1.3.1. SNMP Manager .......................................... 19

3.1.3.2. SNMP Agent ............................................ 20

3.2. The Naming of Identities .................................. 21

3.2.1. Principal ............................................... 21

3.2.2. securityName ............................................ 21

3.2.3. Model-dependent security ID ............................. 22

3.3. The Naming of Management Information ...................... 22

3.3.1. An SNMP Context ......................................... 23

3.3.2. contextEngineID ......................................... 24

3.3.3. contextName ............................................. 24

3.3.4. scopedPDU ............................................... 25

3.4. Other Constructs .......................................... 25

3.4.1. maxSizeResponseScopedPDU ................................ 25

3.4.2. Local Configuration Datastore ........................... 25

3.4.3. securityLevel ........................................... 25

4. Abstract Service Interfaces ................................. 26

4.1. Dispatcher Primitives ..................................... 26

4.1.1. Generate Outgoing Request or Notification ............... 26

4.1.2. Process Incoming Request or Notification PDU ............ 26

4.1.3. Generate Outgoing Response .............................. 27

4.1.4. Process Incoming Response PDU ........................... 27

4.1.5. Registering Responsibility for Handling SNMP PDUs ....... 28

4.2. Message Processing Subsystem Primitives ................... 28

4.2.1. Prepare Outgoing SNMP Request or Notification Message ... 28

4.2.2. Prepare an Outgoing SNMP Response Message ............... 29

4.2.3. Prepare Data Elements from an Incoming SNMP Message ..... 29

4.3. Access Control Subsystem Primitives ....................... 30

4.4. Security Subsystem Primitives ............................. 30

4.4.1. Generate a Request or Notification Message .............. 30

4.4.2. Process Incoming Message ................................ 31

4.4.3. Generate a Response Message ............................. 31

4.5. Common Primitives ......................................... 32

4.5.1. Release State Reference Information ..................... 32

4.6. Scenario Diagrams ......................................... 32

4.6.1. Command Generator or Notification Originator ............ 32

4.6.2. Scenario Diagram for a Command Responder Application .... 33

5. Managed Object Definitions for SNMP Management Frameworks ... 35

6. Intellectual Property ....................................... 44

7. Acknowledgements ............................................ 45

8. Security Considerations ..................................... 46

9. References .................................................. 46

10. Editors' Addresses ......................................... 48

A. Guidelines for Model Designers .............................. 49

A.1. Security Model Design Requirements ........................ 49

A.1.1. Threats ................................................. 49

A.1.2. Security Processing ..................................... 50

A.1.3. Validate the security-stamp in a received message ....... 51

A.1.4. Security MIBs ........................................... 51

A.1.5. Cached Security Data .................................... 51

A.2. Message Processing Model Design Requirements .............. 52

A.2.1. Receiving an SNMP Message from the Network .............. 52

A.2.2. Sending an SNMP Message to the Network .................. 52

A.3. Application Design Requirements ........................... 53

A.3.1. Applications that Initiate Messages ..................... 53

A.3.2. Applications that Receive Responses ..................... 54

A.3.3. Applications that Receive Asynchronous Messages ......... 54

A.3.4. Applications that Send Responses ........................ 54

A.4. Access Control Model Design Requirements .................. 55

B. Full Copyright Statement .................................... 56

1. Introduction

1.1. Overview

This document defines a vocabulary for describing SNMP Management

Frameworks, and an architecture for describing the major portions of

SNMP Management Frameworks.

This document does not provide a general introduction to SNMP. Other

documents and books can provide a much better introduction to SNMP.

Nor does this document provide a history of SNMP. That also can be

found in books and other documents.

Section 1 describes the purpose, goals, and design decisions of this

architecture.

Section 2 describes various types of documents which define SNMP

Frameworks, and how they fit into this architecture. It also provides

a minimal road map to the documents which have previously defined

SNMP frameworks.

Section 3 details the vocabulary of this architecture and its pieces.

This section is important for understanding the remaining sections,

and for understanding documents which are written to fit within this

architecture.

Section 4 describes the primitives used for the abstract service

interfaces between the various subsystems, models and applications

within this architecture.

Section 5 defines a collection of managed objects used to instrument

SNMP entities within this architecture.

Sections 6, 7, 8, and 9 are administrative in nature.

Appendix A contains guidelines for designers of Models which are

eXPected to fit within this 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 [RFC2119].

1.2. SNMP

An SNMP management system contains:

- several (potentially many) nodes, each with an SNMP entity

containing command responder and notification originator

applications, which have access to management instrumentation

(traditionally called agents);

- at least one SNMP entity containing command generator and/or

notification receiver applications (traditionally called a

manager) and,

- a management protocol, used to convey management information

between the SNMP entities.

SNMP entities executing command generator and notification receiver

applications monitor and control managed elements. Managed elements

are devices such as hosts, routers, terminal servers, etc., which are

monitored and controlled via access to their management information.

It is the purpose of this document to define an architecture which

can evolve to realize effective management in a variety of

configurations and environments. The architecture has been designed

to meet the needs of implementations of:

- minimal SNMP entities with command responder and/or

notification originator applications (traditionally called SNMP

agents),

- SNMP entities with proxy forwarder applications (traditionally

called SNMP proxy agents),

- command line driven SNMP entities with command generator and/or

notification receiver applications (traditionally called SNMP

command line managers),

- SNMP entities with command generator and/or notification

receiver, plus command responder and/or notification originator

applications (traditionally called SNMP mid-level managers or

dual-role entities),

- SNMP entities with command generator and/or notification

receiver and possibly other types of applications for managing

a potentially very large number of managed nodes (traditionally

called (network) management stations).

1.3. Goals of this Architecture

This architecture was driven by the following goals:

- Use existing materials as much as possible. It is heavily based

on previous work, informally known as SNMPv2u and SNMPv2*.

- Address the need for secure SET support, which is considered

the most important deficiency in SNMPv1 and SNMPv2c.

- Make it possible to move portions of the architecture forward

in the standards track, even if consensus has not been reached

on all pieces.

- Define an architecture that allows for longevity of the SNMP

Frameworks that have been and will be defined.

- Keep SNMP as simple as possible.

- Make it relatively inexpensive to deploy a minimal conforming

implementation.

- Make it possible to upgrade portions of SNMP as new approaches

become available, without disrupting an entire SNMP framework.

- Make it possible to support features required in large

networks, but make the expense of supporting a feature directly

related to the support of the feature.

1.4. Security Requirements of this Architecture

Several of the classical threats to network protocols are applicable

to the management problem and therefore would be applicable to any

Security Model used in an SNMP Management Framework. Other threats

are not applicable to the management problem. This section discusses

principal threats, secondary threats, and threats which are of lesser

importance.

The principal threats against which any Security Model used within

this architecture SHOULD provide protection are:

Modification of Information

The modification threat is the danger that some unauthorized SNMP

entity may alter in-transit SNMP messages generated on behalf of

an authorized principal in such a way as to effect unauthorized

management operations, including falsifying the value of an

object.

Masquerade

The masquerade threat is the danger that management operations not

authorized for some principal may be attempted by assuming the

identity of another principal that has the appropriate

authorizations.

Message Stream Modification

The SNMP protocol is typically based upon a connectionless

transport service which may operate over any subnetwork service.

The re-ordering, delay or replay of messages can and does occur

through the natural operation of many such subnetwork services.

The message stream modification threat is the danger that messages

may be maliciously re-ordered, delayed or replayed to an extent

which is greater than can occur through the natural operation of a

subnetwork service, in order to effect unauthorized management

operations.

Disclosure

The disclosure threat is the danger of eavesdropping on the

exchanges between SNMP engines. Protecting against this threat

may be required as a matter of local policy.

There are at least two threats against which a Security Model within

this architecture need not protect.

Denial of Service

A Security Model need not attempt to address the broad range of

attacks by which service on behalf of authorized users is denied.

Indeed, such denial-of-service attacks are in many cases

indistinguishable from the type of network failures with which any

viable management protocol must cope as a matter of course.

Traffic Analysis

A Security Model need not attempt to address traffic analysis

attacks. Many traffic patterns are predictable - entities may be

managed on a regular basis by a relatively small number of

management stations - and therefore there is no significant

advantage afforded by protecting against traffic analysis.

1.5. Design Decisions

Various design decisions were made in support of the goals of the

architecture and the security requirements:

- Architecture

An architecture should be defined which identifies the

conceptual boundaries between the documents. Subsystems should

be defined which describe the abstract services provided by

specific portions of an SNMP framework. Abstract service

interfaces, as described by service primitives, define the

abstract boundaries between documents, and the abstract

services that are provided by the conceptual subsystems of an

SNMP framework.

- Self-contained Documents

Elements of procedure plus the MIB objects which are needed for

processing for a specific portion of an SNMP framework should

be defined in the same document, and as much as possible,

should not be referenced in other documents. This allows pieces

to be designed and documented as independent and self-contained

parts, which is consistent with the general SNMP MIB module

approach. As portions of SNMP change over time, the documents

describing other portions of SNMP are not directly impacted.

This modularity allows, for example, Security Models,

authentication and privacy mechanisms, and message formats to

be upgraded and supplemented as the need arises. The self-

contained documents can move along the standards track on

different time-lines.

- Threats

The Security Models in the Security Subsystem SHOULD protect

against the principal threats: modification of information,

masquerade, message stream modification and disclosure. They

do not need to protect against denial of service and traffic

analysis.

- Remote Configuration

The Security and Access Control Subsystems add a whole new set

of SNMP configuration parameters. The Security Subsystem also

requires frequent changes of secrets at the various SNMP

entities. To make this deployable in a large operational

environment, these SNMP parameters must be able to be remotely

configured.

- Controlled Complexity

It is recognized that producers of simple managed devices want

to keep the resources used by SNMP to a minimum. At the same

time, there is a need for more complex configurations which can

spend more resources for SNMP and thus provide more

functionality. The design tries to keep the competing

requirements of these two environments in balance and allows

the more complex environments to logically extend the simple

environment.

2. Documentation Overview

The following figure shows the set of documents that fit within the

SNMP Architecture.

+------------------------- Document Set ----------------------------+

+------------+ +-----------------+ +----------------+

Document * Applicability * Coexistence *

Roadmap Statement & Transition

+------------+ +-----------------+ +----------------+

+---------------------------------------------------------------+

Message Handling

+----------------+ +-----------------+ +-----------------+

Transport Message Security

Mappings Processing and

Dispatcher

+----------------+ +-----------------+ +-----------------+

+---------------------------------------------------------------+

+---------------------------------------------------------------+

PDU Handling

+----------------+ +-----------------+ +-----------------+

Protocol Applications Access

Operations Control

+----------------+ +-----------------+ +-----------------+

+---------------------------------------------------------------+

+---------------------------------------------------------------+

Information Model

+--------------+ +--------------+ +---------------+

Structure of Textual Conformance

Management Conventions Statements

Information

+--------------+ +--------------+ +---------------+

+---------------------------------------------------------------+

+---------------------------------------------------------------+

MIBs

+-------------+ +-------------+ +----------+ +----------+

Standard v1 Standard v1 Historic Draft v2

RFC1157 RFC1212 RFC14XX RFC19XX

format format format format

+-------------+ +-------------+ +----------+ +----------+

+---------------------------------------------------------------+

+-------------------------------------------------------------------+

Note: RFC14XX means RFCs 1442, 1443, and 1444. RFC19XX means RFCs

1902, 1903, and 1904.

Those marked with an asterisk (*) are expected to be written in the

future. Each of these documents may be replaced or supplemented.

This Architecture document specifically describes how new documents

fit into the set of documents in the area of Message and PDU

handling.

2.1. Document Roadmap

One or more documents may be written to describe how sets of

documents taken together form specific Frameworks. The configuration

of document sets might change over time, so the "road map" should be

maintained in a document separate from the standards documents

themselves.

2.2. Applicability Statement

SNMP is used in networks that vary widely in size and complexity, by

organizations that vary widely in their requirements of management.

Some models will be designed to address specific problems of

management, such as message security.

One or more documents may be written to describe the environments to

which certain versions of SNMP or models within SNMP would be

appropriately applied, and those to which a given model might be

inappropriately applied.

2.3. Coexistence and Transition

The purpose of an evolutionary architecture is to permit new models

to replace or supplement existing models. The interactions between

models could result in incompatibilities, security "holes", and other

undesirable effects.

The purpose of Coexistence documents is to detail recognized

anomalies and to describe required and recommended behaviors for

resolving the interactions between models within the architecture.

Coexistence documents may be prepared separately from model

definition documents, to describe and resolve interaction anomalies

between a model definition and one or more other model definitions.

Additionally, recommendations for transitions between models may also

be described, either in a coexistence document or in a separate

document.

2.4. Transport Mappings

SNMP messages are sent over various transports. It is the purpose of

Transport Mapping documents to define how the mapping between SNMP

and the transport is done.

2.5. Message Processing

A Message Processing Model document defines a message format, which

is typically identified by a version field in an SNMP message header.

The document may also define a MIB module for use in message

processing and for instrumentation of version-specific interactions.

An SNMP engine includes one or more Message Processing Models, and

thus may support sending and receiving multiple versions of SNMP

messages.

2.6. Security

Some environments require secure protocol interactions. Security is

normally applied at two different stages:

- in the transmission/receipt of messages, and

- in the processing of the contents of messages.

For purposes of this document, "security" refers to message-level

security; "access control" refers to the security applied to protocol

operations.

Authentication, encryption, and timeliness checking are common

functions of message level security.

A security document describes a Security Model, the threats against

which the model protects, the goals of the Security Model, the

protocols which it uses to meet those goals, and it may define a MIB

module to describe the data used during processing, and to allow the

remote configuration of message-level security parameters, such as

passwords.

An SNMP engine may support multiple Security Models concurrently.

2.7. Access Control

During processing, it may be required to control access to managed

objects for operations.

An Access Control Model defines mechanisms to determine whether

access to a managed object should be allowed. An Access Control

Model may define a MIB module used during processing and to allow the

remote configuration of access control policies.

2.8. Protocol Operations

SNMP messages encapsulate an SNMP Protocol Data Unit (PDU). It is the

purpose of a Protocol Operations document to define the operations of

the protocol with respect to the processing of the PDUs.

An application document defines which Protocol Operations documents

are supported by the application.

2.9. Applications

An SNMP entity normally includes a number of applications.

Applications use the services of an SNMP engine to accomplish

specific tasks. They coordinate the processing of management

information operations, and may use SNMP messages to communicate with

other SNMP entities.

Applications documents describe the purpose of an application, the

services required of the associated SNMP engine, and the protocol

operations and informational model that the application uses to

perform management operations.

An application document defines which set of documents are used to

specifically define the structure of management information, textual

conventions, conformance requirements, and operations supported by

the application.

2.10. Structure of Management Information

Management information is viewed as a collection of managed objects,

residing in a virtual information store, termed the Management

Information Base (MIB). Collections of related objects are defined in

MIB modules.

It is the purpose of a Structure of Management Information document

to establish the syntax for defining objects, modules, and other

elements of managed information.

2.11. Textual Conventions

When designing a MIB module, it is often useful to define new types

similar to those defined in the SMI, but with more precise semantics,

or which have special semantics associated with them. These newly

defined types are termed textual conventions, and may defined in

separate documents, or within a MIB module.

2.12. Conformance Statements

It may be useful to define the acceptable lower-bounds of

implementation, along with the actual level of implementation

achieved. It is the purpose of Conformance Statements to define the

notation used for these purposes.

2.13. Management Information Base Modules

MIB documents describe collections of managed objects which

instrument some ASPect of a managed node.

2.13.1. SNMP Instrumentation MIBs

An SNMP MIB document may define a collection of managed objects which

instrument the SNMP protocol itself. In addition, MIB modules may be

defined within the documents which describe portions of the SNMP

architecture, such as the documents for Message processing Models,

Security Models, etc. for the purpose of instrumenting those Models,

and for the purpose of allowing remote configuration of the Model.

2.14. SNMP Framework Documents

This architecture is designed to allow an orderly evolution of

portions of SNMP Frameworks.

Throughout the rest of this document, the term "subsystem" refers to

an abstract and incomplete specification of a portion of a Framework,

that is further refined by a model specification.

A "model" describes a specific design of a subsystem, defining

additional constraints and rules for conformance to the model. A

model is sufficiently detailed to make it possible to implement the

specification.

An "implementation" is an instantiation of a subsystem, conforming to

one or more specific models.

SNMP version 1 (SNMPv1), is the original Internet-standard Network

Management Framework, as described in RFCs 1155, 1157, and 1212.

SNMP version 2 (SNMPv2), is the SNMPv2 Framework as derived from the

SNMPv1 Framework. It is described in RFCs 1902-1907. SNMPv2 has no

message definition.

The Community-based SNMP version 2 (SNMPv2c), is an experimental SNMP

Framework which supplements the SNMPv2 Framework, as described in

RFC1901. It adds the SNMPv2c message format, which is similar to the

SNMPv1 message format.

SNMP version 3 (SNMPv3), is an extensible SNMP Framework which

supplements the SNMPv2 Framework, by supporting the following:

- a new SNMP message format,

- Security for Messages, and

- Access Control.

Other SNMP Frameworks, i.e., other configurations of implemented

subsystems, are expected to also be consistent with this

architecture.

3. Elements of the Architecture

This section describes the various elements of the architecture and

how they are named. There are three kinds of naming:

1) the naming of entities,

2) the naming of identities, and

3) the naming of management information.

This architecture also defines some names for other constructs that

are used in the documentation.

3.1. The Naming of Entities

An SNMP entity is an implementation of this architecture. Each such

SNMP entity consists of an SNMP engine and one or more associated

applications.

The following figure shows details about an SNMP entity and the

components within it.

+-------------------------------------------------------------------+

SNMP entity

+-------------------------------------------------------------+

SNMP engine (identified by snmpEngineID)

+------------+ +------------+ +-----------+ +-----------+

Dispatcher Message Security Access

Processing Subsystem Control

Subsystem Subsystem

+------------+ +------------+ +-----------+ +-----------+

+-------------------------------------------------------------+

+-------------------------------------------------------------+

Application(s)

+-------------+ +--------------+ +--------------+

Command Notification Proxy

Generator Receiver Forwarder

+-------------+ +--------------+ +--------------+

+-------------+ +--------------+ +--------------+

Command Notification Other

Responder Originator

+-------------+ +--------------+ +--------------+

+-------------------------------------------------------------+

+-------------------------------------------------------------------+

3.1.1. SNMP engine

An SNMP engine provides services for sending and receiving messages,

authenticating and encrypting messages, and controlling access to

managed objects. There is a one-to-one association between an SNMP

engine and the SNMP entity which contains it.

The engine contains:

1) a Dispatcher,

2) a Message Processing Subsystem,

3) a Security Subsystem, and

4) an Access Control Subsystem.

3.1.1.1. snmpEngineID

Within an administrative domain, an snmpEngineID is the unique and

unambiguous identifier of an SNMP engine. Since there is a one-to-one

association between SNMP engines and SNMP entities, it also uniquely

and unambiguously identifies the SNMP entity.

3.1.1.2. Dispatcher

There is only one Dispatcher in an SNMP engine. It allows for

concurrent support of multiple versions of SNMP messages in the SNMP

engine. It does so by:

- sending and receiving SNMP messages to/from the network,

- determining the version of an SNMP message and interacting with

the corresponding Message Processing Model,

- providing an abstract interface to SNMP applications for

delivery of a PDU to an application.

- providing an abstract interface for SNMP applications that

allows them to send a PDU to a remote SNMP entity.

3.1.1.3. Message Processing Subsystem

The Message Processing Subsystem is responsible for preparing

messages for sending, and extracting data from received messages.

The Message Processing Subsystem potentially contains multiple

Message Processing Models as shown in the next figure.

* One or more Message Processing Models may be present.

+------------------------------------------------------------------+

Message Processing Subsystem

+------------+ +------------+ +------------+ +------------+

* * * *

SNMPv3 SNMPv1 SNMPv2c Other

Message Message Message Message

Processing Processing Processing Processing

Model Model Model Model

+------------+ +------------+ +------------+ +------------+

+------------------------------------------------------------------+

3.1.1.3.1. Message Processing Model

Each Message Processing Model defines the format of a particular

version of an SNMP message and coordinates the preparation and

extraction of each such version-specific message format.

3.1.1.4. Security Subsystem

The Security Subsystem provides security services such as the

authentication and privacy of messages and potentially contains

multiple Security Models as shown in the following figure

* One or more Security Models may be present.

+------------------------------------------------------------------+

Security Subsystem

+----------------+ +-----------------+ +-------------------+

* * *

User-Based Other Other

Security Security Security

Model Model Model

+----------------+ +-----------------+ +-------------------+

+------------------------------------------------------------------+

3.1.1.4.1. Security Model

A Security Model defines the threats against which it protects, the

goals of its services, and the security protocols used to provide

security services such as authentication and privacy.

3.1.1.4.2. Security Protocol

A Security Protocol defines the mechanisms, procedures, and MIB data

used to provide a security service such as authentication or privacy.

3.1.2. Access Control Subsystem

The Access Control Subsystem provides authorization services by means

of one or more Access Control Models.

+------------------------------------------------------------------+

Access Control Subsystem

+---------------+ +-----------------+ +------------------+

* * *

View-Based Other Other

Access Access Access

Control Control Control

Model Model Model

+---------------+ +-----------------+ +------------------+

+------------------------------------------------------------------+

3.1.2.1. Access Control Model

An Access Control Model defines a particular access decision function

in order to support decisions regarding access rights.

3.1.3. Applications

There are several types of applications, including:

- command generators, which monitor and manipulate management

data,

- command responders, which provide access to management data,

- notification originators, which initiate asynchronous messages,

- notification receivers, which process asynchronous messages,

and

- proxy forwarders, which forward messages between entities.

These applications make use of the services provided by the SNMP

engine.

3.1.3.1. SNMP Manager

An SNMP entity containing one or more command generator and/or

notification receiver applications (along with their associated SNMP

engine) has traditionally been called an SNMP manager. * One or more

models may be present.

(traditional SNMP manager)

+-------------------------------------------------------------------+

+--------------+ +--------------+ +--------------+ SNMP entity

NOTIFICATION NOTIFICATION COMMAND

ORIGINATOR RECEIVER GENERATOR

applications applications applications

+--------------+ +--------------+ +--------------+

^ ^ ^

v v v

+-------+--------+-----------------+

^

+---------------------+ +----------------+

Message Processing Security

Dispatcher v Subsystem Subsystem

+-------------------+ +------------+

PDU Dispatcher +-> v1MP * <---> +------------+

+------------+ Other

+------------+ Security

+-> v2cMP * <---> Model

Message +------------+ +------------+

Dispatcher <--------->+

+------------+ +------------+

+-> v3MP * <---> User-based

Transport +------------+ Security

Mapping +------------+ Model

(e.g RFC1906) +-> otherMP * <---> +------------+

+-------------------+ +------------+

^ +---------------------+ +----------------+

v

+-------------------------------------------------------------------+

+-----+ +-----+ +-------+

UDP IPX . . . other

+-----+ +-----+ +-------+

^ ^ ^

v v v

+------------------------------+

Network

+------------------------------+

3.1.3.2. SNMP Agent

An SNMP entity containing one or more command responder and/or

notification originator applications (along with their associated

SNMP engine) has traditionally been called an SNMP agent.

+------------------------------+

Network

+------------------------------+

^ ^ ^

v v v

+-----+ +-----+ +-------+

UDP IPX . . . other

+-----+ +-----+ +-------+ (traditional SNMP agent)

+-------------------------------------------------------------------+

^

+---------------------+ +----------------+

Message Processing Security

Dispatcher v Subsystem Subsystem

+-------------------+ +------------+

Transport +-> v1MP * <---> +------------+

Mapping +------------+ Other

(e.g. RFC1906) +------------+ Security

+-> v2cMP * <---> Model

Message +------------+ +------------+

Dispatcher <---------> +------------+ +------------+

+-> v3MP * <---> User-based

+------------+ Security

PDU Dispatcher +------------+ Model

+-------------------+ +-> otherMP * <---> +------------+

^ +------------+

+---------------------+ +----------------+

v

+-------+-------------------------+---------------+

^ ^ ^

v v v

+-------------+ +---------+ +--------------+ +-------------+

COMMAND ACCESS NOTIFICATION PROXY *

RESPONDER <-> CONTROL <-> ORIGINATOR FORWARDER

application applications application

+-------------+ +---------+ +--------------+ +-------------+

^ ^

v v

+----------------------------------------------+

MIB instrumentation SNMP entity

+-------------------------------------------------------------------+

3.2. The Naming of Identities

principal

^

+-----------------------------------------+

SNMP engine v

+--------------+

+----------------- securityName ---+

Security Model

+--------------+

^

v

+------------------------------+

Model

Dependent

Security ID

+------------------------------+

^

+-----------------------------------+

+-----------------------------------------+

v

network

3.2.1. Principal

A principal is the "who" on whose behalf services are provided or

processing takes place.

A principal can be, among other things, an individual acting in a

particular role; a set of individuals, with each acting in a

particular role; an application or a set of applications; and

combinations thereof.

3.2.2. securityName

A securityName is a human readable string representing a principal.

It has a model-independent format, and can be used outside a

particular Security Model.

3.2.3. Model-dependent security ID

A model-dependent security ID is the model-specific representation of

a securityName within a particular Security Model.

Model-dependent security IDs may or may not be human readable, and

have a model-dependent syntax. Examples include community names, user

names, and parties.

The transformation of model-dependent security IDs into securityNames

and vice versa is the responsibility of the relevant Security Model.

3.3. The Naming of Management Information

Management information resides at an SNMP entity where a Command

Responder Application has local access to potentially multiple

contexts. This application uses a contextEngineID equal to the

snmpEngineID of its associated SNMP engine.

+-----------------------------------------------------------------+

SNMP entity (identified by snmpEngineID, example: abcd)

+------------------------------------------------------------+

SNMP engine (identified by snmpEngineID)

+-------------+ +------------+ +-----------+ +-----------+

Dispatcher Message Security Access

Processing Subsystem Control

Subsystem Subsystem

+-------------+ +------------+ +-----------+ +-----------+

+------------------------------------------------------------+

+------------------------------------------------------------+

Command Responder Application

(contextEngineID, example: abcd)

example contextNames:

"bridge1" "bridge2" "" (default)

--------- --------- ------------

+---------------------------------------------------------+

+---------------------------------------------------------+

MIB instrumentation

+---v------------+ +---v------------+ +----v-----------+

context context context

+------------+ +------------+ +------------+

bridge MIB bridge MIB other MIB

+------------+ +------------+ +------------+

+------------+

some MIB

+------------+

+-----------------------------------------------------------------+

3.3.1. An SNMP Context

An SNMP context, or just "context" for short, is a collection of

management information accessible by an SNMP entity. An item of

management information may exist in more than one context. An SNMP

entity potentially has access to many contexts.

Typically, there are many instances of each managed object type

within a management domain. For simplicity, the method for

identifying instances specified by the MIB module does not allow each

instance to be distinguished amongst the set of all instances within

a management domain; rather, it allows each instance to be identified

only within some scope or "context", where there are multiple such

contexts within the management domain. Often, a context is a

physical device, or perhaps, a logical device, although a context can

also encompass multiple devices, or a subset of a single device, or

even a subset of multiple devices, but a context is always defined as

a subset of a single SNMP entity. Thus, in order to identify an

individual item of management information within the management

domain, its contextName and contextEngineID must be identified in

addition to its object type and its instance.

For example, the managed object type ifDescr [RFC1573], is defined as

the description of a network interface. To identify the description

of device-X's first network interface, four pieces of information are

needed: the snmpEngineID of the SNMP entity which provides access to

the management information at device-X, the contextName (device-X),

the managed object type (ifDescr), and the instance ("1").

Each context has (at least) one unique identification within the

management domain. The same item of management information can exist

in multiple contexts. An item of management information may have

multiple unique identifications. This occurs when an item of

management information exists in multiple contexts, and this also

occurs when a context has multiple unique identifications.

The combination of a contextEngineID and a contextName unambiguously

identifies a context within an administrative domain; note that there

may be multiple unique combinations of contextEngineID and

contextName that unambiguously identify the same context.

3.3.2. contextEngineID

Within an administrative domain, a contextEngineID uniquely

identifies an SNMP entity that may realize an instance of a context

with a particular contextName.

3.3.3. contextName

A contextName is used to name a context. Each contextName MUST be

unique within an SNMP entity.

3.3.4. scopedPDU

A scopedPDU is a block of data containing a contextEngineID, a

contextName, and a PDU.

The PDU is an SNMP Protocol Data Unit containing information named in

the context which is unambiguously identified within an

administrative domain by the combination of the contextEngineID and

the contextName. See, for example, RFC1905 for more information about

SNMP PDUs.

3.4. Other Constructs

3.4.1. maxSizeResponseScopedPDU

The maxSizeResponseScopedPDU is the maximum size of a scopedPDU to be

included in a response message. Note that the size of a scopedPDU

does not include the size of the SNMP message header.

3.4.2. Local Configuration Datastore

The subsystems, models, and applications within an SNMP entity may

need to retain their own sets of configuration information.

Portions of the configuration information may be accessible as

managed objects.

The collection of these sets of information is referred to as an

entity's Local Configuration Datastore (LCD).

3.4.3. securityLevel

This architecture recognizes three levels of security:

- without authentication and without privacy (noAuthNoPriv)

- with authentication but without privacy (authNoPriv)

- with authentication and with privacy (authPriv)

These three values are ordered such that noAuthNoPriv is less than

authNoPriv and authNoPriv is less than authPriv.

Every message has an associated securityLevel. All Subsystems

(Message Processing, Security, Access Control) and applications are

required to either supply a value of securityLevel or to abide by the

supplied value of securityLevel while processing the message and its

contents.

4. Abstract Service Interfaces

Abstract service interfaces have been defined to describe the

conceptual interfaces between the various subsystems within an SNMP

entity.

These abstract service interfaces are defined by a set of primitives

that define the services provided and the abstract data elements that

are to be passed when the services are invoked. This section lists

the primitives that have been defined for the various subsystems.

4.1. Dispatcher Primitives

The Dispatcher typically provides services to the SNMP applications

via its PDU Dispatcher. This section describes the primitives

provided by the PDU Dispatcher.

4.1.1. Generate Outgoing Request or Notification

The PDU Dispatcher provides the following primitive for an

application to send an SNMP Request or Notification to another SNMP

entity:

statusInformation = -- sendPduHandle if success

-- errorIndication if failure

sendPdu(

IN transportDomain -- transport domain to be used

IN transportAddress -- transport address to be used

IN messageProcessingModel -- typically, SNMP version

IN securityModel -- Security Model to use

IN securityName -- on behalf of this principal

IN securityLevel -- Level of Security requested

IN contextEngineID -- data from/at this entity

IN contextName -- data from/in this context

IN pduVersion -- the version of the PDU

IN PDU -- SNMP Protocol Data Unit

IN expectResponse -- TRUE or FALSE

)

4.1.2. Process Incoming Request or Notification PDU

The PDU Dispatcher provides the following primitive to pass an

incoming SNMP PDU to an application:

processPdu( -- process Request/Notification PDU

IN messageProcessingModel -- typically, SNMP version

IN securityModel -- Security Model in use

IN securityName -- on behalf of this principal

IN securityLevel -- Level of Security

IN contextEngineID -- data from/at this SNMP entity

IN contextName -- data from/in this context

IN pduVersion -- the version of the PDU

IN PDU -- SNMP Protocol Data Unit

IN maxSizeResponseScopedPDU -- maximum size of the Response PDU

IN stateReference -- reference to state information

) -- needed when sending a response

4.1.3. Generate Outgoing Response

The PDU Dispatcher provides the following primitive for an

application to return an SNMP Response PDU to the PDU Dispatcher:

returnResponsePdu(

IN messageProcessingModel -- typically, SNMP version

IN securityModel -- Security Model in use

IN securityName -- on behalf of this principal

IN securityLevel -- same as on incoming request

IN contextEngineID -- data from/at this SNMP entity

IN contextName -- data from/in this context

IN pduVersion -- the version of the PDU

IN PDU -- SNMP Protocol Data Unit

IN maxSizeResponseScopedPDU -- maximum size of the Response PDU

IN stateReference -- reference to state information

-- as presented with the request

IN statusInformation -- success or errorIndication

) -- error counter OID/value if error

4.1.4. Process Incoming Response PDU

The PDU Dispatcher provides the following primitive to pass an

incoming SNMP Response PDU to an application:

processResponsePdu( -- process Response PDU

IN messageProcessingModel -- typically, SNMP version

IN securityModel -- Security Model in use

IN securityName -- on behalf of this principal

IN securityLevel -- Level of Security

IN contextEngineID -- data from/at this SNMP entity

IN contextName -- data from/in this context

IN pduVersion -- the version of the PDU

IN PDU -- SNMP Protocol Data Unit

IN statusInformation -- success or errorIndication

IN sendPduHandle -- handle from sendPdu

)

4.1.5. Registering Responsibility for Handling SNMP PDUs

Applications can register/unregister responsibility for a specific

contextEngineID, for specific pduTypes, with the PDU Dispatcher

according to the following primitives. The list of particular

pduTypes that an application can register for is determined by the

Message Processing Model(s) supported by the SNMP entity that

contains the PDU Dispatcher.

statusInformation = -- success or errorIndication

registerContextEngineID(

IN contextEngineID -- take responsibility for this one

IN pduType -- the pduType(s) to be registered

)

unregisterContextEngineID(

IN contextEngineID -- give up responsibility for this one

IN pduType -- the pduType(s) to be unregistered

)

Note that realizations of the registerContextEngineID and

unregisterContextEngineID abstract service interfaces may provide

implementation-specific ways for applications to register/deregister

responsiblity for all possible values of the contextEngineID or

pduType parameters.

4.2. Message Processing Subsystem Primitives

The Dispatcher interacts with a Message Processing Model to process a

specific version of an SNMP Message. This section describes the

primitives provided by the Message Processing Subsystem.

4.2.1. Prepare Outgoing SNMP Request or Notification Message

The Message Processing Subsystem provides this service primitive for

preparing an outgoing SNMP Request or Notification Message:

statusInformation = -- success or errorIndication

prepareOutgoingMessage(

IN transportDomain -- transport domain to be used

IN transportAddress -- transport address to be used

IN messageProcessingModel -- typically, SNMP version

IN securityModel -- Security Model to use

IN securityName -- on behalf of this principal

IN securityLevel -- Level of Security requested

IN contextEngineID -- data from/at this entity

IN contextName -- data from/in this context

IN pduVersion -- the version of the PDU

IN PDU -- SNMP Protocol Data Unit

IN expectResponse -- TRUE or FALSE

IN sendPduHandle -- the handle for matching

-- incoming responses

OUT destTransportDomain -- destination transport domain

OUT destTransportAddress -- destination transport address

OUT outgoingMessage -- the message to send

OUT outgoingMessageLength -- its length

)

4.2.2. Prepare an Outgoing SNMP Response Message

The Message Processing Subsystem provides this service primitive for

preparing an outgoing SNMP Response Message:

result = -- SUCCESS or FAILURE

prepareResponseMessage(

IN messageProcessingModel -- typically, SNMP version

IN securityModel -- same as on incoming request

IN securityName -- same as on incoming request

IN securityLevel -- same as on incoming request

IN contextEngineID -- data from/at this SNMP entity

IN contextName -- data from/in this context

IN pduVersion -- the version of the PDU

IN PDU -- SNMP Protocol Data Unit

IN maxSizeResponseScopedPDU -- maximum size of the Response PDU

IN stateReference -- reference to state information

-- as presented with the request

IN statusInformation -- success or errorIndication

-- error counter OID/value if error

OUT destTransportDomain -- destination transport domain

OUT destTransportAddress -- destination transport address

OUT outgoingMessage -- the message to send

OUT outgoingMessageLength -- its length

)

4.2.3. Prepare Data Elements from an Incoming SNMP Message

The Message Processing Subsystem provides this service primitive for

preparing the abstract data elements from an incoming SNMP message:

result = -- SUCCESS or errorIndication

prepareDataElements(

IN transportDomain -- origin transport domain

IN transportAddress -- origin transport address

IN wholeMsg -- as received from the network

IN wholeMsgLength -- as received from the network

OUT messageProcessingModel -- typically, SNMP version

OUT securityModel -- Security Model to use

OUT securityName -- on behalf of this principal

OUT securityLevel -- Level of Security requested

OUT contextEngineID -- data from/at this entity

OUT contextName -- data from/in this context

OUT pduVersion -- the version of the PDU

OUT PDU -- SNMP Protocol Data Unit

OUT pduType -- SNMP PDU type

OUT sendPduHandle -- handle for matched request

OUT maxSizeResponseScopedPDU -- maximum size of the Response PDU

OUT statusInformation -- success or errorIndication

-- error counter OID/value if error

OUT stateReference -- reference to state information

-- to be used for possible Response

)

4.3. Access Control Subsystem Primitives

Applications are the typical clients of the service(s) of the Access

Control Subsystem.

The following primitive is provided by the Access Control Subsystem

to check if access is allowed:

statusInformation = -- success or errorIndication

isAccessAllowed(

IN securityModel -- Security Model in use

IN securityName -- principal who wants to access

IN securityLevel -- Level of Security

IN viewType -- read, write, or notify view

IN contextName -- context containing variableName

IN variableName -- OID for the managed object

)

4.4. Security Subsystem Primitives

The Message Processing Subsystem is the typical client of the

services of the Security Subsystem.

4.4.1. Generate a Request or Notification Message

The Security Subsystem provides the following primitive to generate a

Request or Notification message:

statusInformation =

generateRequestMsg(

IN messageProcessingModel -- typically, SNMP version

IN globalData -- message header, admin data

IN maxMessageSize -- of the sending SNMP entity

IN securityModel -- for the outgoing message

IN securityEngineID -- authoritative SNMP entity

IN securityName -- on behalf of this principal

IN securityLevel -- Level of Security requested

IN scopedPDU -- message (plaintext) payload

OUT securityParameters -- filled in by Security Module

OUT wholeMsg -- complete generated message

OUT wholeMsgLength -- length of the generated message

)

4.4.2. Process Incoming Message

The Security Subsystem provides the following primitive to process an

incoming message:

statusInformation = -- errorIndication or success

-- error counter OID/value if error

processIncomingMsg(

IN messageProcessingModel -- typically, SNMP version

IN maxMessageSize -- of the sending SNMP entity

IN securityParameters -- for the received message

IN securityModel -- for the received message

IN securityLevel -- Level of Security

IN wholeMsg -- as received on the wire

IN wholeMsgLength -- length as received on the wire

OUT securityEngineID -- identification of the principal

OUT securityName -- identification of the principal

OUT scopedPDU, -- message (plaintext) payload

OUT maxSizeResponseScopedPDU -- maximum size of the Response PDU

OUT securityStateReference -- reference to security state

) -- information, needed for response

4.4.3. Generate a Response Message

The Security Subsystem provides the following primitive to generate a

Response message:

statusInformation =

generateResponseMsg(

IN messageProcessingModel -- typically, SNMP version

IN globalData -- message header, admin data

IN maxMessageSize -- of the sending SNMP entity

IN securityModel -- for the outgoing message

IN securityEngineID -- authoritative SNMP entity

IN securityName -- on behalf of this principal

IN securityLevel -- for the outgoing message

IN scopedPDU -- message (plaintext) payload

IN securityStateReference -- reference to security state

-- information from original request

OUT securityParameters -- filled in by Security Module

OUT wholeMsg -- complete generated message

OUT wholeMsgLength -- length of the generated message

)

4.5. Common Primitives

These primitive(s) are provided by multiple Subsystems.

4.5.1. Release State Reference Information

All Subsystems which pass stateReference information also provide a

primitive to release the memory that holds the referenced state

information:

stateRelease(

IN stateReference -- handle of reference to be released

)

4.6. Scenario Diagrams

4.6.1. Command Generator or Notification Originator

This diagram shows how a Command Generator or Notification Originator

application requests that a PDU be sent, and how the response is

returned (asynchronously) to that application.

Command Dispatcher Message Security

Generator Processing Model

Model

sendPdu

------------------->

prepareOutgoingMessage

: ----------------------->

: generateRequestMsg

: -------------------->

:

: <--------------------

:

: <-----------------------

:

: ------------------+

: Send SNMP

: Request Message

: to Network

: v

: : : : :

: : : : :

: : : : :

:

: Receive SNMP

: Response Message

: from Network

: <-----------------+

:

: prepareDataElements

: ----------------------->

: processIncomingMsg

: -------------------->

:

: <--------------------

:

: <-----------------------

processResponsePdu

<-------------------

4.6.2. Scenario Diagram for a Command Responder Application

This diagram shows how a Command Responder or Notification Receiver

application registers for handling a pduType, how a PDU is dispatched

to the application after a SNMP message is received, and how the

Response is (asynchronously) send back to the network.

Command Dispatcher Message Security

Responder Processing Model

Model

registerContextEngineID

------------------------>

<------------------------

Receive SNMP

: Message

: from Network

: <-------------+

:

: prepareDataElements

: ------------------->

: processIncomingMsg

: ------------------->

:

: <-------------------

:

: <-------------------

processPdu

<------------------------

: : : :

: : : :

returnResponsePdu

------------------------>

: prepareResponseMsg

: ------------------->

: generateResponseMsg

: ------------------->

:

: <-------------------

:

: <-------------------

:

: --------------+

: Send SNMP

: Message

: to Network

: v

5. Managed Object Definitions for SNMP Management Frameworks

SNMP-FRAMEWORK-MIB DEFINITIONS ::= BEGIN

IMPORTS

MODULE-IDENTITY, OBJECT-TYPE,

OBJECT-IDENTITY,

snmpModules FROM SNMPv2-SMI

TEXTUAL-CONVENTION FROM SNMPv2-TC

MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF;

snmpFrameworkMIB MODULE-IDENTITY

LAST-UPDATED "9711200000Z" -- 20 November 1997

ORGANIZATION "SNMPv3 Working Group"

CONTACT-INFO "WG-email: snmpv3@tis.com

Subscribe: majordomo@tis.com

In message body: subscribe snmpv3

Chair: Russ Mundy

Trusted Information Systems

postal: 3060 Washington Rd

Glenwood MD 21738

USA

email: mundy@tis.com

phone: +1 301-854-6889

Co-editor Dave Harrington

Cabletron Systems, Inc.

postal: Post Office Box 5005

Mail Stop: Durham

35 Industrial Way

Rochester, NH 03867-5005

USA

email: dbh@ctron.com

phone: +1 603-337-7357

Co-editor Randy Presuhn

BMC Software, Inc.

postal: 1190 Saratoga Avenue

Suite 130

San Jose, CA 95129

USA

email: rpresuhn@bmc.com

phone: +1 408-556-0720

Co-editor: Bert Wijnen

IBM T.J. Watson Research

postal: Schagen 33

3461 GL Linschoten

Netherlands

email: wijnen@vnet.ibm.com

phone: +31 348-432-794

"

DESCRIPTION "The SNMP Management Architecture MIB"

::= { snmpModules 10 }

-- Textual Conventions used in the SNMP Management Architecture ***

SnmpEngineID ::= TEXTUAL-CONVENTION

STATUS current

DESCRIPTION "An SNMP engine's administratively-unique identifier.

The value for this object may not be all zeros or

all 'ff'H or the empty (zero length) string.

The initial value for this object may be configured

via an operator console entry or via an algorithmic

function. In the latter case, the following

example algorithm is recommended.

In cases where there are multiple engines on the

same system, the use of this algorithm is NOT

appropriate, as it would result in all of those

engines ending up with the same ID value.

1) The very first bit is used to indicate how the

rest of the data is composed.

0 - as defined by enterprise using former methods

that existed before SNMPv3. See item 2 below.

1 - as defined by this architecture, see item 3

below.

Note that this allows existing uses of the

engineID (also known as AgentID [RFC1910]) to

co-exist with any new uses.

2) The snmpEngineID has a length of 12 octets.

The first four octets are set to the binary

equivalent of the agent's SNMP management

private enterprise number as assigned by the

Internet Assigned Numbers Authority (IANA).

For example, if Acme Networks has been assigned

{ enterprises 696 }, the first four octets would

be assigned '000002b8'H.

The remaining eight octets are determined via

one or more enterprise-specific methods. Such

methods must be designed so as to maximize the

possibility that the value of this object will

be unique in the agent's administrative domain.

For example, it may be the IP address of the SNMP

entity, or the MAC address of one of the

interfaces, with each address suitably padded

with random octets. If multiple methods are

defined, then it is recommended that the first

octet indicate the method being used and the

remaining octets be a function of the method.

3) The length of the octet strings varies.

The first four octets are set to the binary

equivalent of the agent's SNMP management

private enterprise number as assigned by the

Internet Assigned Numbers Authority (IANA).

For example, if Acme Networks has been assigned

{ enterprises 696 }, the first four octets would

be assigned '000002b8'H.

The very first bit is set to 1. For example, the

above value for Acme Networks now changes to be

'800002b8'H.

The fifth octet indicates how the rest (6th and

following octets) are formatted. The values for

the fifth octet are:

0 - reserved, unused.

1 - IPv4 address (4 octets)

lowest non-special IP address

2 - IPv6 address (16 octets)

lowest non-special IP address

3 - MAC address (6 octets)

lowest IEEE MAC address, canonical

order

4 - Text, administratively assigned

Maximum remaining length 27

5 - Octets, administratively assigned

Maximum remaining length 27

6-127 - reserved, unused

127-255 - as defined by the enterprise

Maximum remaining length 27

"

SYNTAX OCTET STRING (SIZE(1..32))

SnmpSecurityModel ::= TEXTUAL-CONVENTION

STATUS current

DESCRIPTION "An identifier that uniquely identifies a

securityModel of the Security Subsystem within the

SNMP Management Architecture.

The values for securityModel are allocated as

follows:

- The zero value is reserved.

- Values between 1 and 255, inclusive, are reserved

for standards-track Security Models and are

managed by the Internet Assigned Numbers Authority

(IANA).

- Values greater than 255 are allocated to

enterprise-specific Security Models. An

enterprise-specific securityModel value is defined

to be:

enterpriseID * 256 + security model within

enterprise

For example, the fourth Security Model defined by

the enterprise whose enterpriseID is 1 would be

260.

This scheme for allocation of securityModel

values allows for a maximum of 255 standards-

based Security Models, and for a maximum of

255 Security Models per enterprise.

It is believed that the assignment of new

securityModel values will be rare in practice

because the larger the number of simultaneously

utilized Security Models, the larger the

chance that interoperability will suffer.

Consequently, it is believed that such a range

will be sufficient. In the unlikely event that

the standards committee finds this number to be

insufficient over time, an enterprise number

can be allocated to oBTain an additional 255

possible values.

Note that the most significant bit must be zero;

hence, there are 23 bits allocated for various

organizations to design and define non-standard

securityModels. This limits the ability to

define new proprietary implementations of Security

Models to the first 8,388,608 enterprises.

It is worthwhile to note that, in its encoded

form, the securityModel value will normally

require only a single byte since, in practice,

the leftmost bits will be zero for most messages

and sign extension is suppressed by the encoding

rules.

As of this writing, there are several values

of securityModel defined for use with SNMP or

reserved for use with supporting MIB objects.

They are as follows:

0 reserved for 'any'

1 reserved for SNMPv1

2 reserved for SNMPv2c

3 User-Based Security Model (USM)

"

SYNTAX INTEGER(0..2147483647)

SnmpMessageProcessingModel ::= TEXTUAL-CONVENTION

STATUS current

DESCRIPTION "An identifier that uniquely identifies a Message

Processing Model of the Message Processing

Subsystem within a SNMP Management Architecture.

The values for messageProcessingModel are

allocated as follows:

- Values between 0 and 255, inclusive, are

reserved for standards-track Message Processing

Models and are managed by the Internet Assigned

Numbers Authority (IANA).

- Values greater than 255 are allocated to

enterprise-specific Message Processing Models.

An enterprise messageProcessingModel value is

defined to be:

enterpriseID * 256 +

messageProcessingModel within enterprise

For example, the fourth Message Processing Model

defined by the enterprise whose enterpriseID

is 1 would be 260.

This scheme for allocation of securityModel

values allows for a maximum of 255 standards-

based Message Processing Models, and for a

maximum of 255 Message Processing Models per

enterprise.

It is believed that the assignment of new

messageProcessingModel values will be rare

in practice because the larger the number of

simultaneously utilized Message Processing Models,

the larger the chance that interoperability

will suffer. It is believed that such a range

will be sufficient. In the unlikely event that

the standards committee finds this number to be

insufficient over time, an enterprise number

can be allocated to obtain an additional 256

possible values.

Note that the most significant bit must be zero;

hence, there are 23 bits allocated for various

organizations to design and define non-standard

messageProcessingModels. This limits the ability

to define new proprietary implementations of

Message Processing Models to the first 8,388,608

enterprises.

It is worthwhile to note that, in its encoded

form, the securityModel value will normally

require only a single byte since, in practice,

the leftmost bits will be zero for most messages

and sign extension is suppressed by the encoding

rules.

As of this writing, there are several values of

messageProcessingModel defined for use with SNMP.

They are as follows:

0 reserved for SNMPv1

1 reserved for SNMPv2c

2 reserved for SNMPv2u and SNMPv2*

3 reserved for SNMPv3

"

SYNTAX INTEGER(0..2147483647)

SnmpSecurityLevel ::= TEXTUAL-CONVENTION

STATUS current

DESCRIPTION "A Level of Security at which SNMP messages can be

sent or with which operations are being processed;

in particular, one of:

noAuthNoPriv - without authentication and

without privacy,

authNoPriv - with authentication but

without privacy,

authPriv - with authentication and

with privacy.

These three values are ordered such that

noAuthNoPriv is less than authNoPriv and

authNoPriv is less than authPriv.

"

SYNTAX INTEGER { noAuthNoPriv(1),

authNoPriv(2),

authPriv(3)

}

SnmpAdminString ::= TEXTUAL-CONVENTION

DISPLAY-HINT "255a"

STATUS current

DESCRIPTION "An octet string containing administrative

information, preferably in human-readable form.

To facilitate internationalization, this

information is represented using the ISO/IEC

IS 10646-1 character set, encoded as an octet

string using the UTF-8 transformation format

described in [RFC2044].

Since additional code points are added by

amendments to the 10646 standard from time

to time, implementations must be prepared to

encounter any code point from 0x00000000 to

0x7fffffff.

The use of control codes should be avoided.

When it is necessary to represent a newline,

the control code sequence CR LF should be used.

The use of leading or trailing white space should

be avoided.

For code points not directly supported by user

interface hardware or software, an alternative

means of entry and display, such as hexadecimal,

may be provided.

For information encoded in 7-bit US-ASCII,

the UTF-8 encoding is identical to the

US-ASCII encoding.

Note that when this TC is used for an object that

is used or envisioned to be used as an index, then

a SIZE restriction must be specified so that the

number of sub-identifiers for any object instance

does not exceed the limit of 128, as defined by

[RFC1905].

"

SYNTAX OCTET STRING (SIZE (0..255))

-- Administrative assignments ***************************************

snmpFrameworkAdmin

OBJECT IDENTIFIER ::= { snmpFrameworkMIB 1 }

snmpFrameworkMIBObjects

OBJECT IDENTIFIER ::= { snmpFrameworkMIB 2 }

snmpFrameworkMIBConformance

OBJECT IDENTIFIER ::= { snmpFrameworkMIB 3 }

-- the snmpEngine Group ********************************************

snmpEngine OBJECT IDENTIFIER ::= { snmpFrameworkMIBObjects 1 }

snmpEngineID OBJECT-TYPE

SYNTAX SnmpEngineID

MAX-ACCESS read-only

STATUS current

DESCRIPTION "An SNMP engine's administratively-unique identifier.

"

::= { snmpEngine 1 }

snmpEngineBoots OBJECT-TYPE

SYNTAX INTEGER (1..2147483647)

MAX-ACCESS read-only

STATUS current

DESCRIPTION "The number of times that the SNMP engine has

(re-)initialized itself since its initial

configuration.

"

::= { snmpEngine 2 }

snmpEngineTime OBJECT-TYPE

SYNTAX INTEGER (0..2147483647)

MAX-ACCESS read-only

STATUS current

DESCRIPTION "The number of seconds since the SNMP engine last

incremented the snmpEngineBoots object.

"

::= { snmpEngine 3 }

snmpEngineMaxMessageSize OBJECT-TYPE

SYNTAX INTEGER (484..2147483647)

MAX-ACCESS read-only

STATUS current

DESCRIPTION "The maximum length in octets of an SNMP message

which this SNMP engine can send or receive and

process, determined as the minimum of the maximum

message size values supported among all of the

transports available to and supported by the engine.

"

::= { snmpEngine 4 }

-- Registration Points for Authentication and Privacy Protocols **

snmpAuthProtocols OBJECT-IDENTITY

STATUS current

DESCRIPTION "Registration point for standards-track

authentication protocols used in SNMP Management

Frameworks.

"

::= { snmpFrameworkAdmin 1 }

snmpPrivProtocols OBJECT-IDENTITY

STATUS current

DESCRIPTION "Registration point for standards-track privacy

protocols used in SNMP Management Frameworks.

"

::= { snmpFrameworkAdmin 2 }

-- Conformance information ******************************************

snmpFrameworkMIBCompliances

OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 1}

snmpFrameworkMIBGroups

OBJECT IDENTIFIER ::= {snmpFrameworkMIBConformance 2}

-- compliance statements

snmpFrameworkMIBCompliance MODULE-COMPLIANCE

STATUS current

DESCRIPTION "The compliance statement for SNMP engines which

implement the SNMP Management Framework MIB.

"

MODULE -- this module

MANDATORY-GROUPS { snmpEngineGroup }

::= { snmpFrameworkMIBCompliances 1 }

-- units of conformance

snmpEngineGroup OBJECT-GROUP

OBJECTS {

snmpEngineID,

snmpEngineBoots,

snmpEngineTime,

snmpEngineMaxMessageSize

}

STATUS current

DESCRIPTION "A collection of objects for identifying and

determining the configuration and current timeliness

values of an SNMP engine.

"

::= { snmpFrameworkMIBGroups 1 }

END

6. Intellectual Property

The IETF takes no position regarding the validity or scope of any

intellectual property or other rights that might be claimed to

pertain to the implementation or use of the technology described in

this document or the extent to which any license under such rights

might or might not be available; neither does it represent that it

has made any effort to identify any such rights. Information on the

IETF's procedures with respect to rights in standards-track and

standards-related documentation can be found in BCP-11. Copies of

claims of rights made available for publication and any assurances of

licenses to be made available, or the result of an attempt made to

obtain a general license or permission for the use of such

proprietary rights by implementors or users of this specification can

be obtained from the IETF Secretariat.

The IETF invites any interested party to bring to its attention any

copyrights, patents or patent applications, or other proprietary

rights which may cover technology that may be required to practice

this standard. Please address the information to the IETF Executive

Director.

7. Acknowledgements

This document is the result of the efforts of the SNMPv3 Working

Group. Some special thanks are in order to the following SNMPv3 WG

members:

Dave Battle (SNMP Research, Inc.)

Uri Blumenthal (IBM T.J. Watson Research Center)

Jeff Case (SNMP Research, Inc.)

John Curran (BBN)

T. Max Devlin (Hi-TECH Connections)

John Flick (Hewlett Packard)

David Harrington (Cabletron Systems Inc.)

N.C. Hien (IBM T.J. Watson Research Center)

Dave Levi (SNMP Research, Inc.)

Louis A Mamakos (UUNET Technologies Inc.)

Paul Meyer (Secure Computing Corporation)

Keith McCloghrie (Cisco Systems)

Russ Mundy (Trusted Information Systems, Inc.)

Bob Natale (ACE*COMM Corporation)

Mike O'Dell (UUNET Technologies Inc.)

Dave Perkins (DeskTalk)

Peter Polkinghorne (Brunel University)

Randy Presuhn (BMC Software, Inc.)

David Reid (SNMP Research, Inc.)

Shawn Routhier (Epilogue)

Juergen Schoenwaelder (TU Braunschweig)

Bob Stewart (Cisco Systems)

Bert Wijnen (IBM T.J. Watson Research Center)

The document is based on recommendations of the IETF Security and

Administrative Framework Evolution for SNMP Advisory Team. Members

of that Advisory Team were:

David Harrington (Cabletron Systems Inc.)

Jeff Johnson (Cisco Systems)

David Levi (SNMP Research Inc.)

John Linn (Openvision)

Russ Mundy (Trusted Information Systems) chair

Shawn Routhier (Epilogue)

Glenn Waters (Nortel)

Bert Wijnen (IBM T. J. Watson Research Center)

As recommended by the Advisory Team and the SNMPv3 Working Group

Charter, the design incorporates as much as practical from previous

RFCs and drafts. As a result, special thanks are due to the authors

of previous designs known as SNMPv2u and SNMPv2*:

Jeff Case (SNMP Research, Inc.)

David Harrington (Cabletron Systems Inc.)

David Levi (SNMP Research, Inc.)

Keith McCloghrie (Cisco Systems)

Brian O'Keefe (Hewlett Packard)

Marshall T. Rose (Dover Beach Consulting)

Jon Saperia (BGS Systems Inc.)

Steve Waldbusser (International Network Services)

Glenn W. Waters (Bell-Northern Research Ltd.)

8. Security Considerations

This document describes how an implementation can include a Security

Model to protect management messages and an Access Control Model to

control access to management information.

The level of security provided is determined by the specific Security

Model implementation(s) and the specific Access Control Model

implementation(s) used.

Applications have access to data which is not secured. Applications

should take reasonable steps to protect the data from disclosure.

It is the responsibility of the purchaser of an implementation to

ensure that:

1) an implementation complies with the rules defined by this

architecture,

2) the Security and Access Control Models utilized satisfy the

security and access control needs of the organization,

3) the implementations of the Models and Applications comply with

the model and application specifications,

4) and the implementation protects configuration secrets from

inadvertent disclosure.

9. References

[RFC1155] Rose, M. and K. McCloghrie, "Structure and Identification

of Management Information for TCP/IP-based internets", STD 16, RFC

1155, May 1990.

[RFC1157] Case, J., Fedor, M., Schoffstall, M. and J. Davin, "The

Simple Network Management Protocol", STD 15, RFC1157, May 1990.

[RFC1212] Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD

16, RFC1212, March 1991.

[RFC1901] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

"Introduction to Community-based SNMPv2", RFC1901, January 1996.

[RFC1902] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

"Structure of Management Information for Version 2 of the Simple

Network Management Protocol (SNMPv2)", RFC1902, January 1996.

[RFC1905] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

"Protocol Operations for Version 2 of the Simple Network

Management Protocol (SNMPv2)", RFC1905, January 1996.

[RFC1906] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

"Transport Mappings for Version 2 of the Simple Network Management

Protocol (SNMPv2)", RFC1906, January 1996.

[RFC1907] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

"Management Information Base for Version 2 of the Simple Network

Management Protocol (SNMPv2)", RFC1907 January 1996.

[RFC1908] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,

"Coexistence between Version 1 and Version 2 of the Internet-

standard Network Management Framework", RFC1908, January 1996.

[RFC1909] McCloghrie, K., Editor, "An Administrative Infrastructure

for SNMPv2", RFC1909, February 1996.

[RFC1910] Waters, G., Editor, "User-based Security Model for SNMPv2",

RFC1910, February 1996.

[RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in

the IETF Standards Process", BCP 11, RFC2028, October 1996.

[RFC2044] Yergeau, F., "UTF-8, a transformation format of Unicode and

ISO 10646", RFC2044, October 1996.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate

Requirement Levels", BCP 14, RFC2119, March 1997.

[RFC2272] Case, J., Harrington, D., Presuhn, R., and B. Wijnen,

"Message Processing and Dispatching for the Simple Network

Management Protocol (SNMP)", RFC2272, January 1998.

[RFC2274] Blumenthal, U., and B. Wijnen, "The User-Based

Security Model for Version 3 of the Simple Network Management

Protocol (SNMPv3)", RFC2274, January 1998.

[RFC2275] Wijnen, B., Presuhn, R., and K. McCloghrie,

"View-based Access Control Model for the Simple Network Management

Protocol (SNMP)", RFC2275, January 1998.

[RFC2273] Levi, D., Meyer, P., and B. Stewart, "SNMPv3

Applications", RFC2273, January 1998.

10. Editors' Addresses

Bert Wijnen

IBM T.J. Watson Research

Schagen 33

3461 GL Linschoten

Netherlands

Phone: +31 348-432-794

EMail: wijnen@vnet.ibm.com

Dave Harrington

Cabletron Systems, Inc

Post Office Box 5005

Mail Stop: Durham

35 Industrial Way

Rochester, NH 03867-5005

USA

Phone: +1 603-337-7357

EMail: dbh@ctron.com

Randy Presuhn

BMC Software, Inc.

1190 Saratoga Avenue

Suite 130

San Jose, CA 95129

USA

Phone: +1 408-556-0720

EMail: rpresuhn@bmc.com

APPENDIX A

A. Guidelines for Model Designers

This appendix describes guidelines for designers of models which are

expected to fit into the architecture defined in this document.

SNMPv1 and SNMPv2c are two SNMP frameworks which use communities to

provide trivial authentication and access control. SNMPv1 and SNMPv2c

Frameworks can coexist with Frameworks designed according to this

architecture, and modified versions of SNMPv1 and SNMPv2c Frameworks

could be designed to meet the requirements of this architecture, but

this document does not provide guidelines for that coexistence.

Within any subsystem model, there should be no reference to any

specific model of another subsystem, or to data defined by a specific

model of another subsystem.

Transfer of data between the subsystems is deliberately described as

a fixed set of abstract data elements and primitive functions which

can be overloaded to satisfy the needs of multiple model definitions.

Documents which define models to be used within this architecture

SHOULD use the standard primitives between subsystems, possibly

defining specific mechanisms for converting the abstract data

elements into model-usable formats. This constraint exists to allow

subsystem and model documents to be written recognizing common

borders of the subsystem and model. Vendors are not constrained to

recognize these borders in their implementations.

The architecture defines certain standard services to be provided

between subsystems, and the architecture defines abstract service

interfaces to request these services.

Each model definition for a subsystem SHOULD support the standard

service interfaces, but whether, or how, or how well, it performs the

service is dependent on the model definition.

A.1. Security Model Design Requirements

A.1.1. Threats

A document describing a Security Model MUST describe how the model

protects against the threats described under "Security Requirements

of this Architecture", section 1.4.

A.1.2. Security Processing

Received messages MUST be validated by a Model of the Security

Subsystem. Validation includes authentication and privacy processing

if needed, but it is explicitly allowed to send messages which do not

require authentication or privacy.

A received message contains a specified securityLevel to be used

during processing. All messages requiring privacy MUST also require

authentication.

A Security Model specifies rules by which authentication and privacy

are to be done. A model may define mechanisms to provide additional

security features, but the model definition is constrained to using

(possibly a subset of) the abstract data elements defined in this

document for transferring data between subsystems.

Each Security Model may allow multiple security protocols to be used

concurrently within an implementation of the model. Each Security

Model defines how to determine which protocol to use, given the

securityLevel and the security parameters relevant to the message.

Each Security Model, with its associated protocol(s) defines how the

sending/receiving entities are identified, and how secrets are

configured.

Authentication and Privacy protocols supported by Security Models are

uniquely identified using Object Identifiers. IETF standard protocols

for authentication or privacy should have an identifier defined

within the snmpAuthProtocols or the snmpPrivProtocols subtrees.

Enterprise specific protocol identifiers should be defined within the

enterprise subtree.

For privacy, the Security Model defines what portion of the message

is encrypted.

The persistent data used for security should be SNMP-manageable, but

the Security Model defines whether an instantiation of the MIB is a

conformance requirement.

Security Models are replaceable within the Security Subsystem.

Multiple Security Model implementations may exist concurrently within

an SNMP engine. The number of Security Models defined by the SNMP

community should remain small to promote interoperability.

A.1.3. Validate the security-stamp in a received message

A Message Processing Model requests that a Security Model:

- verifies that the message has not been altered,

- authenticates the identification of the principal for whom the

message was generated.

- decrypts the message if it was encrypted.

Additional requirements may be defined by the model, and additional

services may be provided by the model, but the model is constrained

to use the following primitives for transferring data between

subsystems. Implementations are not so constrained.

A Message Processing Model uses the processMsg primitive as described

in section 4.5.

A.1.4. Security MIBs

Each Security Model defines the MIB module(s) required for security

processing, including any MIB module(s) required for the security

protocol(s) supported. The MIB module(s) SHOULD be defined

concurrently with the procedures which use the MIB module(s). The

MIB module(s) are subject to normal access control rules.

The mapping between the model-dependent security ID and the

securityName MUST be able to be determined using SNMP, if the model-

dependent MIB is instantiated and if access control policy allows

access.

A.1.5. Cached Security Data

For each message received, the Security Model caches the state

information such that a Response message can be generated using the

same security information, even if the Local Configuration Datastore

is altered between the time of the incoming request and the outgoing

response.

A Message Processing Model has the responsibility for explicitly

releasing the cached data if such data is no longer needed. To enable

this, an abstract securityStateReference data element is passed from

the Security Model to the Message Processing Model.

The cached security data may be implicitly released via the

generation of a response, or explicitly released by using the

stateRelease primitive, as described in section 4.1.

A.2. Message Processing Model Design Requirements

An SNMP engine contains a Message Processing Subsystem which may

contain multiple Message Processing Models.

The Message Processing Model MUST always (conceptually) pass the

complete PDU, i.e., it never forwards less than the complete list of

varBinds.

A.2.1. Receiving an SNMP Message from the Network

Upon receipt of a message from the network, the Dispatcher in the

SNMP engine determines the version of the SNMP message and interacts

with the corresponding Message Processing Model to determine the

abstract data elements.

A Message Processing Model specifies the SNMP Message format it

supports and describes how to determine the values of the abstract

data elements (like msgID, msgMaxSize, msgFlags,

msgSecurityParameters, securityModel, securityLevel etc). A Message

Processing Model interacts with a Security Model to provide security

processing for the message using the processMsg primitive, as

described in section 4.5.

A.2.2. Sending an SNMP Message to the Network

The Dispatcher in the SNMP engine interacts with a Message Processing

Model to prepare an outgoing message. For that it uses the following

primitives:

- for requests and notifications: prepareOutgoingMessage, as

described in section 4.4

- for response messages: prepareResponseMessage, as described in

section 4.4

A Message Processing Model, when preparing an Outgoing SNMP Message,

interacts with a Security Model to secure the message. For that it

uses the following primitives:

- for requests and notifications: generateRequestMsg, as

described in section 4.5.

- for response messages: generateResponseMsg as described in

section 4.5.

Once the SNMP message is prepared by a Message Processing Model,

the Dispatcher sends the message to the desired address using the

appropriate transport.

A.3. Application Design Requirements

Within an application, there may be an explicit binding to a specific

SNMP message version, i.e., a specific Message Processing Model, and

to a specific Access Control Model, but there should be no reference

to any data defined by a specific Message Processing Model or Access

Control Model.

Within an application, there should be no reference to any specific

Security Model, or any data defined by a specific Security Model.

An application determines whether explicit or implicit access control

should be applied to the operation, and, if access control is needed,

which Access Control Model should be used.

An application has the responsibility to define any MIB module(s)

used to provide application-specific services.

Applications interact with the SNMP engine to initiate messages,

receive responses, receive asynchronous messages, and send responses.

A.3.1. Applications that Initiate Messages

Applications may request that the SNMP engine send messages

containing SNMP commands or notifications using the sendPdu primitive

as described in section 4.2.

If it is desired that a message be sent to multiple targets, it is

the responsibility of the application to provide the iteration.

The SNMP engine assumes necessary access control has been applied to

the PDU, and provides no access control services.

The SNMP engine looks at the "expectResponse" parameter, and if a

response is expected, then the appropriate information is cached such

that a later response can be associated to this message, and can then

be returned to the application. A sendPduHandle is returned to the

application so it can later correspond the response with this message

as well.

A.3.2. Applications that Receive Responses

The SNMP engine matches the incoming response messages to outstanding

messages sent by this SNMP engine, and forwards the response to the

associated application using the processResponsePdu primitive, as

described in section 4.2.

A.3.3. Applications that Receive Asynchronous Messages

When an SNMP engine receives a message that is not the response to a

request from this SNMP engine, it must determine to which application

the message should be given.

An Application that wishes to receive asynchronous messages registers

itself with the engine using the primitive registerContextEngineID as

described in section 4.2.

An Application that wishes to stop receiving asynchronous messages

should unregister itself with the SNMP engine using the primitive

unregisterContextEngineID as described in section 4.2.

Only one registration per combination of PDU type and contextEngineID

is permitted at the same time. Duplicate registrations are ignored.

An errorIndication will be returned to the application that attempts

to duplicate a registration.

All asynchronously received messages containing a registered

combination of PDU type and contextEngineID are sent to the

application which registered to support that combination.

The engine forwards the PDU to the registered application, using the

processPdu primitive, as described in section 4.2.

A.3.4. Applications that Send Responses

Request operations require responses. An application sends a

response via the returnResponsePdu primitive, as described in section

4.2.

The contextEngineID, contextName, securityModel, securityName,

securityLevel, and stateReference parameters are from the initial

processPdu primitive. The PDU and statusInformation are the results

of processing.

A.4. Access Control Model Design Requirements

An Access Control Model determines whether the specified securityName

is allowed to perform the requested operation on a specified managed

object. The Access Control Model specifies the rules by which access

control is determined.

The persistent data used for access control should be manageable

using SNMP, but the Access Control Model defines whether an

instantiation of the MIB is a conformance requirement.

The Access Control Model must provide the primitive isAccessAllowed.

B. Full Copyright Statement

Copyright (C) The Internet Society (1998). All Rights Reserved.

This document and translations of it may be copied and furnished to

others, and derivative works that comment on or otherwise explain it

or assist in its implementation may be prepared, copied, published

and distributed, in whole or in part, without restriction of any

kind, provided that the above copyright notice and this paragraph are

included on all such copies and derivative works. However, this

document itself may not be modified in any way, such as by removing

the copyright notice or references to the Internet Society or other

Internet organizations, except as needed for the purpose of

developing Internet standards in which case the procedures for

copyrights defined in the Internet Standards process must be

followed, or as required to translate it into languages other than

English.

The limited permissions granted above are perpetual and will not be

revoked by the Internet Society or its successors or assigns.

This document and the information contained herein is provided on an

"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING

TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING

BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION

HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF

MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

 
 
 
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