draft-ietf-isms-tmsm-04.txt   draft-ietf-isms-tmsm-05.txt 
Network Working Group D. Harrington Network Working Group D. Harrington
Internet-Draft Huawei Technologies (USA) Internet-Draft Huawei Technologies (USA)
Intended status: Informational J. Schoenwaelder Intended status: Standards Track J. Schoenwaelder
Expires: April 14, 2007 International University Bremen Expires: June 16, 2007 International University Bremen
October 11, 2006 December 13, 2006
Transport Subsystem for the Simple Network Management Protocol (SNMP) Transport Subsystem for the Simple Network Management Protocol (SNMP)
draft-ietf-isms-tmsm-04.txt draft-ietf-isms-tmsm-05
Status of This Memo Status of This Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 35 skipping to change at page 1, line 35
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 14, 2007. This Internet-Draft will expire on June 16, 2007.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The IETF Trust (2006).
Abstract Abstract
This document describes a Transport Subsystem, extending the Simple This document describes a Transport Subsystem, extending the Simple
Network Management Protocol (SNMP) architecture defined in RFC 3411. Network Management Protocol (SNMP) architecture defined in RFC 3411.
This document describes a subsystem to contain transport models, This document describes a subsystem to contain transport models,
comparable to other subsystems in the RFC3411 architecture. As work comparable to other subsystems in the RFC3411 architecture. As work
is being done to expand the transport to include secure transport is being done to expand the transport to include secure transport
such as SSH and TLS, using a subsystem will enable consistent design such as SSH and TLS, using a subsystem will enable consistent design
and modularity of such transport models. This document identifies and modularity of such transport models. This document identifies
and discusses some key aspects that need to be considered for any and discusses some key aspects that need to be considered for any
transport model for SNMP. transport model for SNMP.
This memo also defines a portion of the Management Information Base
(MIB) for managing models in the Transport Subsystem.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. The Internet-Standard Management Framework . . . . . . . . 4 1.1. The Internet-Standard Management Framework . . . . . . . . 3
1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Requirements of a Transport Model . . . . . . . . . . . . . . 6
2. Requirements of a Transport Model . . . . . . . . . . . . . . 6 3.1. Message Security Requirements . . . . . . . . . . . . . . 6
2.1. Message Security Requirements . . . . . . . . . . . . . . 6 3.1.1. Security Protocol Requirements . . . . . . . . . . . . 6
2.1.1. Security Protocol Requirements . . . . . . . . . . . . 6 3.2. SNMP Requirements . . . . . . . . . . . . . . . . . . . . 7
2.2. SNMP Requirements . . . . . . . . . . . . . . . . . . . . 7 3.2.1. Architectural Modularity Requirements . . . . . . . . 7
2.2.1. Architectural Modularity Requirements . . . . . . . . 7 3.2.2. Access Control Requirements . . . . . . . . . . . . . 11
2.2.2. Access Control Requirements . . . . . . . . . . . . . 14 3.2.3. Security Parameter Passing Requirements . . . . . . . 12
2.2.3. Security Parameter Passing Requirements . . . . . . . 16 3.3. Session Requirements . . . . . . . . . . . . . . . . . . . 14
2.3. Session Requirements . . . . . . . . . . . . . . . . . . . 17 3.3.1. Session Establishment Requirements . . . . . . . . . . 14
2.3.1. Session Establishment Requirements . . . . . . . . . . 18 3.3.2. Session Maintenance Requirements . . . . . . . . . . . 16
2.3.2. Session Maintenance Requirements . . . . . . . . . . . 19 3.3.3. Message security versus session security . . . . . . . 16
2.3.3. Message security versus session security . . . . . . . 19 4. Scenario Diagrams for the Transport Subsystem . . . . . . . . 17
3. Scenario Diagrams for the Transport Subsystem . . . . . . . . 21 4.1. Command Generator or Notification Originator . . . . . . . 17
3.1. Command Generator or Notification Originator . . . . . . . 21 4.2. Command Responder . . . . . . . . . . . . . . . . . . . . 18
3.2. Command Responder . . . . . . . . . . . . . . . . . . . . 22 5. Cached Information and References . . . . . . . . . . . . . . 19
4. Cached Information and References . . . . . . . . . . . . . . 23 5.1. securityStateReference . . . . . . . . . . . . . . . . . . 20
4.1. securityStateReference . . . . . . . . . . . . . . . . . . 24 5.2. tmStateReference . . . . . . . . . . . . . . . . . . . . . 21
4.2. tmStateReference . . . . . . . . . . . . . . . . . . . . . 25 6. Abstract Service Interfaces . . . . . . . . . . . . . . . . . 21
5. Abstract Service Interfaces . . . . . . . . . . . . . . . . . 25 6.1. Generating an Outgoing SNMP Message . . . . . . . . . . . 22
5.1. Generating an Outgoing SNMP Message . . . . . . . . . . . 26 6.2. Processing for an Outgoing Message . . . . . . . . . . . . 23
5.2. Processing for an Outgoing Message . . . . . . . . . . . . 27 6.3. Processing an Incoming SNMP Message . . . . . . . . . . . 23
5.3. Processing an Incoming SNMP Message . . . . . . . . . . . 28 6.3.1. Processing an Incoming Message . . . . . . . . . . . . 23
5.3.1. Processing an Incoming Message . . . . . . . . . . . . 28 6.3.2. Prepare Data Elements from Incoming Messages . . . . . 23
5.3.2. Prepare Data Elements from Incoming Messages . . . . . 28 6.3.3. Processing an Incoming Message . . . . . . . . . . . . 24
5.3.3. Processing an Incoming Message . . . . . . . . . . . . 29 7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
6. The Transport-Subsystem-MIB Module . . . . . . . . . . . . . . 30 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
6.1. Structure of the MIB Module . . . . . . . . . . . . . . . 31 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
6.1.1. The tmsmStats Subtree . . . . . . . . . . . . . . . . 31 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
6.2. Relationship to Other MIB Modules . . . . . . . . . . . . 31 10.1. Normative References . . . . . . . . . . . . . . . . . . . 26
6.2.1. Textual Conventions . . . . . . . . . . . . . . . . . 31 10.2. Informative References . . . . . . . . . . . . . . . . . . 27
6.2.2. MIB Modules Required for IMPORTS . . . . . . . . . . . 31 Appendix A. Parameter Table . . . . . . . . . . . . . . . . . . . 28
6.3. Definitions . . . . . . . . . . . . . . . . . . . . . . . 31 A.1. ParameterList.csv . . . . . . . . . . . . . . . . . . . . 28
7. Security Considerations . . . . . . . . . . . . . . . . . . . 36 Appendix B. Why tmStateReference? . . . . . . . . . . . . . . . . 29
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 B.1. Define an Abstract Service Interface . . . . . . . . . . . 29
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 37 B.2. Using an Encapsulating Header . . . . . . . . . . . . . . 30
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38 B.3. Modifying Existing Fields in an SNMP Message . . . . . . . 30
10.1. Normative References . . . . . . . . . . . . . . . . . . . 38 B.4. Using a Cache . . . . . . . . . . . . . . . . . . . . . . 30
10.2. Informative References . . . . . . . . . . . . . . . . . . 39 Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . . 31
Appendix A. Parameter Table . . . . . . . . . . . . . . . . . . . 39 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 31
A.1. ParameterList.csv . . . . . . . . . . . . . . . . . . . . 39
Appendix B. Why tmStateReference? . . . . . . . . . . . . . . . . 41
B.1. Define an Abstract Service Interface . . . . . . . . . . . 41
B.2. Using an Encapsulating Header . . . . . . . . . . . . . . 41
B.3. Modifying Existing Fields in an SNMP Message . . . . . . . 42
B.4. Using a Cache . . . . . . . . . . . . . . . . . . . . . . 42
Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . . . 42
Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 42
1. Introduction 1. Introduction
This document describes a Transport Subsystem, extending the Simple This document describes a Transport Subsystem, extending the Simple
Network Management Protocol (SNMP) architecture defined in [RFC3411]. Network Management Protocol (SNMP) architecture defined in [RFC3411].
This document identifies and discusses some key aspects that need to This document identifies and discusses some key aspects that need to
be considered for any transport model for SNMP. be considered for any transport model for SNMP.
1.1. The Internet-Standard Management Framework 1.1. The Internet-Standard Management Framework
For a detailed overview of the documents that describe the current For a detailed overview of the documents that describe the current
Internet-Standard Management Framework, please refer to section 7 of Internet-Standard Management Framework, please refer to section 7 of
RFC 3410 [RFC3410]. RFC 3410 [RFC3410].
Managed objects are accessed via a virtual information store, termed
the Management Information Base or MIB. MIB objects are generally
accessed through the Simple Network Management Protocol (SNMP).
Objects in the MIB are defined using the mechanisms defined in the
Structure of Management Information (SMI). This memo specifies a MIB
module that is compliant to the SMIv2, which is described in STD 58,
RFC 2578 [RFC2578], STD 58, RFC 2579 [RFC2579] and STD 58, RFC 2580
[RFC2580].
1.2. Conventions 1.2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Some points requiring further WG research and discussion are 2. Motivation
identified by [discuss] markers in the text. Some points requiring
further editing by the editors are marked [todo] in the text.
1.3. Acronyms
This section contains a list of acronyms used within the document and
references to where in the document the acronym is defined, for easy
lookup.
o [todo]
1.4. Motivation
There are multiple ways to secure one's home or business, in a There are multiple ways to secure one's home or business, in a
continuum of alternatives. Let's consider three general approaches. continuum of alternatives. Let's consider three general approaches.
In the first approach, an individual could buy a gun, learn to use In the first approach, an individual could buy a gun, learn to use
it, and sit on your front porch waiting for intruders. In the second it, and sit on your front porch waiting for intruders. In the second
approach, one could hire an employee with a gun, schedule the approach, one could hire an employee with a gun, schedule the
employee, position the employee to guard what you want protected, employee, position the employee to guard what you want protected,
hire a second guard to cover if the first gets sick, and so on. In hire a second guard to cover if the first gets sick, and so on. In
the third approach, you could hire a security company, tell them what the third approach, you could hire a security company, tell them what
you want protected, and they could hire employees, train them, buy you want protected, and they could hire employees, train them, buy
the guns, position the guards, schedule the guards, send a the guns, position the guards, schedule the guards, send a
replacement when a guard cannot make it, etc., thus providing the replacement when a guard cannot make it, etc., thus providing the
security you want, with no significant effort on your part other than security you want, with no significant effort on your part other than
identifying requirements and verifying the quality of the service identifying requirements and verifying the quality of the service
being provided. being provided.
The User-based Security Model (USM) as defined in [RFC3414] largely The User-based Security Model (USM) as defined in [RFC3414] largely
uses the first approach - it provides its own security. It utilizes uses the first approach - it provides its own security. It utilizes
existing mechanisms (MD5=the gun), but provides all the coordination. existing mechanisms (SHA=the gun), but provides all the coordination.
USM provides for the authentication of a principal, message USM provides for the authentication of a principal, message
encryption, data integrity checking, timeliness checking, etc. encryption, data integrity checking, timeliness checking, etc.
USM was designed to be independent of other existing security USM was designed to be independent of other existing security
infrastructures. USM therefore requires a separate principal and key infrastructures. USM therefore requires a separate principal and key
management infrastructure. Operators have reported that deploying management infrastructure. Operators have reported that deploying
another principal and key management infrastructure in order to use another principal and key management infrastructure in order to use
SNMPv3 is a deterrent to deploying SNMPv3. It is possible but SNMPv3 is a deterrent to deploying SNMPv3. It is possible but
difficult to define external mechanisms that handle the distribution difficult to define external mechanisms that handle the distribution
of keys for use by the USM approach. of keys for use by the USM approach.
skipping to change at page 6, line 6 skipping to change at page 4, line 33
[RFC4422], and SSH [RFC4251]. [RFC4422], and SSH [RFC4251].
From an operational perspective, it is highly desirable to use From an operational perspective, it is highly desirable to use
security mechanisms that can unify the administrative security security mechanisms that can unify the administrative security
management for SNMPv3, command line interfaces (CLIs) and other management for SNMPv3, command line interfaces (CLIs) and other
management interfaces. The use of security services provided by management interfaces. The use of security services provided by
lower layers is the approach commonly used for the CLI, and is also lower layers is the approach commonly used for the CLI, and is also
the approach being proposed for NETCONF [I-D.ietf-netconf-ssh]. the approach being proposed for NETCONF [I-D.ietf-netconf-ssh].
This document describes a Transport Subsystem extension to the This document describes a Transport Subsystem extension to the
RFC3411 architecture, that allows security to be provided by an RFC3411 architecture.
external protocol connected to the SNMP engine through an SNMP
transport-model [RFC3417]. Such a transport model would then enable +-------------------------------------------------------------------+
the use of existing security mechanisms such as (TLS) [RFC4366] or | SNMP entity |
SSH [RFC4251] within the RFC3411 architecture. | |
| +-------------------------------------------------------------+ |
| | SNMP engine (identified by snmpEngineID) | |
| | | |
| | +------------+ | |
| | | Transport | | |
| | | Subsystem | | |
| | +------------+ | |
| | | |
| | +------------+ +------------+ +-----------+ +-----------+ | |
| | | Dispatcher | | Message | | Security | | Access | | |
| | | | | Processing | | Subsystem | | Control | | |
| | | | | Subsystem | | | | Subsystem | | |
| | +------------+ +------------+ +-----------+ +-----------+ | |
| +-------------------------------------------------------------+ |
| |
| +-------------------------------------------------------------+ |
| | Application(s) | |
| | | |
| | +-------------+ +--------------+ +--------------+ | |
| | | Command | | Notification | | Proxy | | |
| | | Generator | | Receiver | | Forwarder | | |
| | +-------------+ +--------------+ +--------------+ | |
| | | |
| | +-------------+ +--------------+ +--------------+ | |
| | | Command | | Notification | | Other | | |
| | | Responder | | Originator | | | | |
| | +-------------+ +--------------+ +--------------+ | |
| +-------------------------------------------------------------+ |
| |
+-------------------------------------------------------------------+
This extension allows security to be provided by an external protocol
connected to the SNMP engine through an SNMP transport-model
[RFC3417]. Such a transport model would then enable the use of
existing security mechanisms such as (TLS) [RFC4366] or SSH [RFC4251]
within the RFC3411 architecture.
There are a number of Internet security protocols and mechanisms that There are a number of Internet security protocols and mechanisms that
are in wide spread use. Many of them try to provide a generic are in wide spread use. Many of them try to provide a generic
infrastructure to be used by many different application layer infrastructure to be used by many different application layer
protocols. The motivation behind the transport subsystem is to protocols. The motivation behind the transport subsystem is to
leverage these protocols where it seems useful. leverage these protocols where it seems useful.
There are a number of challenges to be addressed to map the security There are a number of challenges to be addressed to map the security
provided by a secure transport into the SNMP architecture so that provided by a secure transport into the SNMP architecture so that
SNMP continues to work without any surprises. These challenges are SNMP continues to work without any surprises. These challenges are
discussed in detail in this document. For some key issues, design discussed in detail in this document. For some key issues, design
choices are discussed that may be made to provide a workable solution choices are discussed that may be made to provide a workable solution
that meets operational requirements and fits into the SNMP that meets operational requirements and fits into the SNMP
architecture defined in [RFC3411]. architecture defined in [RFC3411].
2. Requirements of a Transport Model 3. Requirements of a Transport Model
2.1. Message Security Requirements 3.1. Message Security Requirements
Transport security protocols SHOULD ideally provide the protection Transport security protocols SHOULD ideally provide the protection
against the following message-oriented threats [RFC3411]: against the following message-oriented threats [RFC3411]:
1. modification of information 1. modification of information
2. masquerade 2. masquerade
3. message stream modification 3. message stream modification
4. disclosure 4. disclosure
According to [RFC3411], it is not required to protect against denial According to [RFC3411], it is not required to protect against denial
of service or traffic analysis. of service or traffic analysis.
2.1.1. Security Protocol Requirements 3.1.1. Security Protocol Requirements
There are a number of standard protocols that could be proposed as There are a number of standard protocols that could be proposed as
possible solutions within the transport subsystem. Some factors possible solutions within the transport subsystem. Some factors
should be considered when selecting a protocol. should be considered when selecting a protocol.
Using a protocol in a manner for which it was not designed has Using a protocol in a manner for which it was not designed has
numerous problems. The advertised security characteristics of a numerous problems. The advertised security characteristics of a
protocol may depend on its being used as designed; when used in other protocol may depend on its being used as designed; when used in other
ways, it may not deliver the expected security characteristics. It ways, it may not deliver the expected security characteristics. It
is recommended that any proposed model include a discussion of the is recommended that any proposed model include a discussion of the
applicability statement of the protocols to be used. applicability of the transport model.
A transport model should require no modifications to the underlying A transport model should require no modifications to the underlying
protocol. Modifying the protocol may change its security protocol. Modifying the protocol may change its security
characteristics in ways that would impact other existing usages. If characteristics in ways that would impact other existing usages. If
a change is necessary, the change should be an extension that has no a change is necessary, the change should be an extension that has no
impact on the existing usages. It is recommended that any transport impact on the existing usages. It is recommended that any transport
model include a discussion of potential impact on other usages of the model include a discussion of potential impact on other usages of the
protocol. protocol.
It has been a long-standing requirement that SNMP be able to work It has been a long-standing requirement that SNMP be able to work
skipping to change at page 7, line 31 skipping to change at page 7, line 17
troubleshoot and repair unstable networks. troubleshoot and repair unstable networks.
There has been discussion of ways SNMP could be extended to better There has been discussion of ways SNMP could be extended to better
support management/monitoring needs when a network is running just support management/monitoring needs when a network is running just
fine. Use of a TCP transport, for example, could enable larger fine. Use of a TCP transport, for example, could enable larger
message sizes and more efficient table retrievals. message sizes and more efficient table retrievals.
Transport models MUST be able to coexist with other transport models, Transport models MUST be able to coexist with other transport models,
and may be designed to utilize either TCP or UDP or SCTP. and may be designed to utilize either TCP or UDP or SCTP.
2.2. SNMP Requirements 3.2. SNMP Requirements
2.2.1. Architectural Modularity Requirements 3.2.1. Architectural Modularity Requirements
SNMP version 3 (SNMPv3) is based on a modular architecture (described SNMP version 3 (SNMPv3) is based on a modular architecture (described
in [RFC3411] section 3) to allow the evolution of the SNMP protocol in [RFC3411] section 3) to allow the evolution of the SNMP protocol
standards over time, and to minimize side effects between subsystems standards over time, and to minimize side effects between subsystems
when changes are made. when changes are made.
The RFC3411 architecture includes a security subsystem for enabling The RFC3411 architecture includes a security subsystem for enabling
different methods of providing security services, a messaging different methods of providing security services, a messaging
subsystem permitting different message versions to be handled by a subsystem permitting different message versions to be handled by a
single engine, an application subsystem to support different types of single engine, an application subsystem to support different types of
skipping to change at page 8, line 27 skipping to change at page 8, line 14
Parameters have been provided in the ASIs to pass model-independent Parameters have been provided in the ASIs to pass model-independent
information about the authentication that has been provided. These information about the authentication that has been provided. These
parameters include a model-independent identifier of the security parameters include a model-independent identifier of the security
"principal", the security model used to perform the authentication, "principal", the security model used to perform the authentication,
and which SNMP-specific security features were applied to the message and which SNMP-specific security features were applied to the message
(authentication and/or privacy). (authentication and/or privacy).
Parameters have been provided in the ASIs to pass model-independent Parameters have been provided in the ASIs to pass model-independent
transport address information. These parameters utilize the transport address information. These parameters utilize the
TransportType and TransportAddress transportDomain and transportAddress
The design of a transport subsystem must abide the goals of the The design of a transport subsystem must abide the goals of the
RFC3411 architecture defined in [RFC3411]. To that end, this RFC3411 architecture defined in [RFC3411]. To that end, this
transport subsystem proposal uses a modular design that will permit transport subsystem proposal uses a modular design that will permit
transport models to be advanced through the standards process transport models to be advanced through the standards process
independently of other transport models, and independent of other independently of other transport models, and independent of other
modular SNMP components as much as possible. modular SNMP components as much as possible.
IETF standards typically require one mandatory to implement solution, IETF standards typically require one mandatory to implement solution,
with the capability of adding new mechanisms in the future. Part of with the capability of adding new mechanisms in the future. Part of
skipping to change at page 10, line 22 skipping to change at page 9, line 22
| +--------------------------------------------------+ | | +--------------------------------------------------+ |
| | Transport Subsystem | | | | Transport Subsystem | |
| | +-----+ +-----+ +-----+ +-----+ +-------+ | | | | +-----+ +-----+ +-----+ +-----+ +-------+ | |
| | | UDP | | TCP | | SSH | | TLS | . . . | other | | | | | | UDP | | TCP | | SSH | | TLS | . . . | other | | |
| | +-----+ +-----+ +-----+ +-----+ +-------+ | | | | +-----+ +-----+ +-----+ +-----+ +-------+ | |
| +--------------------------------------------------+ | | +--------------------------------------------------+ |
| ^ | | ^ |
| | | | | |
| Dispatcher v | | Dispatcher v |
| +-------------------+ +---------------------+ +----------------+ | | +-------------------+ +---------------------+ +----------------+ |
| | | | Message Processing | | Security | | | | Transport | | Message Processing | | Security | |
| | | | Subsystem | | Subsystem | | | | Dispatch | | Subsystem | | Subsystem | |
| | | | +------------+ | | +------------+ | | | | | | +------------+ | | +------------+ | |
| | | | +->| v1MP * |<--->| | USM * | | | | | | | +->| v1MP * |<--->| | USM * | | |
| | | | | +------------+ | | +------------+ | | | | | | | +------------+ | | +------------+ | |
| | | | | +------------+ | | +------------+ | | | | | | | +------------+ | | +------------+ | |
| | | | +->| v2cMP * |<--->| | Transport* | | | | | | | +->| v2cMP * |<--->| | Transport* | | |
| | Message | | | +------------+ | | | Security | | | | | Message | | | +------------+ | | | Security | | |
| | Dispatcher <--------->| +------------+ | | | Model | | | | | Dispatch <--------->| +------------+ | | | Model | | |
| | | | +->| v3MP * |<--->| +------------+ | | | | | | +->| v3MP * |<--->| +------------+ | |
| | | | | +------------+ | | +------------+ | | | | | | | +------------+ | | +------------+ | |
| | PDU Dispatcher | | | +------------+ | | | Other * | | | | | PDU Dispatch | | | +------------+ | | | Other * | | |
| +-------------------+ | +->| otherMP * |<--->| | Model(s) | | | | +-------------------+ | +->| otherMP * |<--->| | Model(s) | | |
| ^ | +------------+ | | +------------+ | | | ^ | +------------+ | | +------------+ | |
| | +---------------------+ +----------------+ | | | +---------------------+ +----------------+ |
| v | | v |
| +-------+-------------------------+---------------+ | | +-------+-------------------------+---------------+ |
| ^ ^ ^ | | ^ ^ ^ |
| | | | | | | | | |
| v v v | | v v v |
| +-------------+ +---------+ +--------------+ +-------------+ | | +-------------+ +---------+ +--------------+ +-------------+ |
| | COMMAND | | ACCESS | | NOTIFICATION | | PROXY | | | | COMMAND | | ACCESS | | NOTIFICATION | | PROXY | |
| | RESPONDER |<->| CONTROL |<->| ORIGINATOR | | FORWARDER | | | | RESPONDER |<->| CONTROL |<->| ORIGINATOR | | FORWARDER | |
| | application | | | | applications | | application | | | | application | | | | applications | | application | |
| +-------------+ +---------+ +--------------+ +-------------+ | | +-------------+ +---------+ +--------------+ +-------------+ |
| ^ ^ | | ^ ^ |
| | | | | | | |
| v v | | v v |
| +----------------------------------------------+ | | +----------------------------------------------+ |
| | MIB instrumentation | SNMP entity | | | MIB instrumentation | SNMP entity |
+-------------------------------------------------------------------+ +-------------------------------------------------------------------+
2.2.1.1. USM and the RFC3411 Architecture 3.2.1.1. USM and the RFC3411 Architecture
The following diagrams illustrate the difference in the security The following diagrams illustrate the difference in the security
processing done by the USM model and the security processing processing done by the USM model and the security processing
potentially done by a transport model. potentially done by a transport model.
The USM security model is encapsulated by the messaging model, The USM security model is encapsulated by the messaging model,
because the messaging model needs to perform the following steps (for because the messaging model needs to perform the following steps (for
incoming messages) incoming messages)
1) decode the ASN.1 (messaging model) 1) decode the ASN.1 (messaging model)
2) determine the SNMP security model and parameters (messaging model) 2) determine the SNMP security model and parameters (messaging model)
3) decrypt the encrypted portions of the message (security model) 3) decrypt the encrypted portions of the message (security model)
4) translate parameters to model-independent parameters (security 4) translate parameters to model-independent parameters (security
model) model)
5) determine which application should get the decrypted portions 5) determine which application should get the decrypted portions
(messaging model), and (messaging model), and
6) pass on the decrypted portions with model-independent parameters. 6) pass on the decrypted portions with model-independent parameters.
The USM approach uses SNMP-specific message security and parameters. The USM approach uses SNMP-specific message security and parameters.
| -----------------------------------------------| 3.2.1.2. Transport Subsystem and the RFC3411 Architecture
| transport layer |
| -----------------------------------------------|
^
|
v
--------------------------------------------------
| -----------------------------------------------|
| | transport mapping |
| -----------------------------------------------|
| ^
| |
| v
| --------------------------------------------- |
| --------------------- ------------------ |
| SNMP messaging <--> | decryption + | |
| | translation | |
| --------------------- ------------------ |
| ^
| |
| v
| --------------------- ------------------ |
| | SNMP applications | <--> | access control | |
| --------------------- ------------------ |
| --------------------------------------------- |
2.2.1.2. Transport Subsystem and the RFC3411 Architecture
With the Transport Subsystem, the order of the steps may differ and With the Transport Subsystem, the order of the steps may differ and
may be handled by different subsystems: may be handled by different subsystems:
1) decrypt the encrypted portions of the message (transport layer) 1) decrypt the encrypted portions of the message (transport layer)
2*) translate parameters to model-independent parameters (transport 2*) translate parameters to model-independent parameters (transport
model) model)
3) determine the SNMP security model and parameters (messaging model) 3) determine the SNMP security model and parameters (transport model)
4) decode the ASN.1 (messaging model) 4) decode the ASN.1 (messaging model)
5) determine which application should get the decrypted portions 5) determine which application should get the decrypted portions
(messaging model) (messaging model)
7) pass on the decrypted portions with model-independent security 7) pass on the decrypted portions with model-independent security
parameters parameters
If a message is secured using non-SNMP-specific message security and If a message is secured using non-SNMP-specific message security and
parameters, then the transport model should provide the translation parameters, then the transport model should provide the translation
from e.g., an SSH user name to the securityName in step 3, from the authenticated identity (e.g., an SSH user name) to the
| -----------------------------------------------| securityName in step 3.
| ------------------ |
| transport layer <--> | decryption | |
| ------------------ |
| -----------------------------------------------|
^
|
v
--------------------------------------------------
| -----------------------------------------------|
| ------------------ |
| transport model <--> | translation | |
| ------------------ |
| -----------------------------------------------|
| ^
| |
| v
| --------------------------------------------- |
| |
| message model |
| |
| -----------------------------------------------|
| ^
| |
| v
| --------------------------------------------- |
| |
| security model |
| |
| -----------------------------------------------|
| ^
| |
| v
| --------------------- ------------------ |
| | SNMP applications | <--> | access control | |
| --------------------- ------------------ |
| --------------------------------------------- |
2.2.1.3. Passing Information between Engines 3.2.1.3. Passing Information between Engines
A secure transport model will establish an encrypted tunnel between A secure transport model will establish an encrypted tunnel between
the transport models of two SNMP engines. One transport model the transport models of two SNMP engines. One transport model
instance encrypts all messages, and the other transport model instance encrypts all messages, and the other transport model
instance decrypts the messages. instance decrypts the messages.
After a transport layer tunnel is established, then SNMP messages can After a transport layer tunnel is established, then SNMP messages can
conceptually be sent through the tunnel from one SNMP engine to conceptually be sent through the tunnel from one SNMP engine to
another SNMP engine. Once the tunnel is established, multiple SNMP another SNMP engine. Once the tunnel is established, multiple SNMP
messages may be able to be passed through the same tunnel. messages may be able to be passed through the same tunnel.
2.2.2. Access Control Requirements 3.2.2. Access Control Requirements
2.2.2.1. securityName Binding 3.2.2.1. securityName Binding
For SNMP access control to function properly, security processing For SNMP access control to function properly, security processing
must establish a securityModel identifier, a securityLevel, and a must establish a securityModel identifier, a securityLevel, and a
securityName, which is the security model independent identifier for securityName, which is the security model independent identifier for
a principal. The message processing subsystem relies on a security a principal. The message processing subsystem relies on a security
model, such as USM, to play a role in security that goes beyond model, such as USM, to play a role in security that goes beyond
protecting the message - it provides a mapping between the USM- protecting the message - it provides a mapping between the USM-
specific principal to a security-model independent securityName which specific principal to a security-model independent securityName which
can be used for subsequent processing, such as for access control. can be used for subsequent processing, such as for access control.
The securityName MUST be bound to the mechanism-specific The securityName MUST be bound to the mechanism-specific
authenticated identity, and this mapping MUST be done for incoming authenticated identity, and this mapping MUST be done for incoming
messages before the security model passes securityName to the message messages before the security model passes securityName to the message
processing model via the processIncoming() ASI. This translation processing model via the processIncoming() ASI. This translation
from a mechanism-specific authenticated identity to a securityName from a mechanism-specific authenticated identity to a securityName
MAY be done by the transport model, and the securityname is then MAY be done by the transport model, and the securityname is then
provided to the security model to be passed to the message processing provided to the security model to be passed to the message processing
model.. model.
If the type of authentication provided by the transport layer (e.g. If the type of authentication provided by the transport layer (e.g.
TLS) is considered adequate to secure and/or encrypt the message, but TLS) is considered adequate to secure and/or encrypt the message, but
inadequate to provide the desired granularity of access control (e.g. inadequate to provide the desired granularity of access control (e.g.
user-based), then a second authentication (e.g., one provided via a user-based), then a second authentication (e.g., one provided via a
RADIUS server) MAY be used to provide the authentication identity RADIUS server) MAY be used to provide the authentication identity
which is bound to the securityName. This approach would require a which is bound to the securityName. This approach would require a
good analysis of the potential for man-in-the-middle attacks or good analysis of the potential for man-in-the-middle attacks or
masquerade possibilities. masquerade possibilities.
2.2.2.2. Separation of Authentication and Authorization 3.2.2.2. Separation of Authentication and Authorization
A transport model that provides security services should take care to A transport model that provides security services should take care to
not violate the separation of authentication and authorization in the not violate the separation of authentication and authorization in the
RFC3411 architecture. The isAccessAllowed() primitive is used for RFC3411 architecture. The isAccessAllowed() primitive is used for
passing security-model independent parameters between the subsystems passing security-model independent parameters between the subsystems
of the architecture. of the architecture.
Mapping of (securityModel, securityName) to an access control policy Mapping of (securityModel, securityName) to an access control policy
should be handled within the access control subsystem, not the should be handled within the access control subsystem, not the
transport or security subsystems, to be consistent with the transport or security subsystems, to be consistent with the
skipping to change at page 16, line 5 skipping to change at page 12, line 47
otherwise made available to the access control subsystem, e.g., via a otherwise made available to the access control subsystem, e.g., via a
MIB table similar to the vacmSecurityToGroupTable, so the access MIB table similar to the vacmSecurityToGroupTable, so the access
control subsystem can create an appropriate binding between the control subsystem can create an appropriate binding between the
model-independent securityModel and securityName and a model-specific model-independent securityModel and securityName and a model-specific
access control policy. This may be highly undesirable, however, if access control policy. This may be highly undesirable, however, if
it creates a dependency between a transport model or a security model it creates a dependency between a transport model or a security model
and an access control model, just as it is undesirable for a and an access control model, just as it is undesirable for a
transport model to create a dependency between an SNMP message transport model to create a dependency between an SNMP message
version and the security provided by a transport model. version and the security provided by a transport model.
2.2.3. Security Parameter Passing Requirements 3.2.3. Security Parameter Passing Requirements
RFC3411 section 4 describes primitives to describe the abstract data RFC3411 section 4 describes primitives to describe the abstract data
flows between the various subsystems, models and applications within flows between the various subsystems, models and applications within
the architecture. Abstract Service Interfaces describe the flow of the architecture. Abstract Service Interfaces describe the flow of
data between subsystems within an engine. The ASIs generally pass data between subsystems within an engine. The ASIs generally pass
model-independent information. model-independent information.
Within an engine using a transport model, outgoing SNMP messages are Within an engine using a transport model, outgoing SNMP messages are
passed unencrypted from the message dispatcher to the transport passed unencrypted from the message dispatcher to the transport
model, and incoming messages are passed unencrypted from the model, and incoming messages are passed unencrypted from the
skipping to change at page 17, line 17 skipping to change at page 14, line 12
This document describes a cache mechanism, into which the transport This document describes a cache mechanism, into which the transport
model puts information about the transport and security parameters model puts information about the transport and security parameters
applied to a transport connection or an incoming message, and a applied to a transport connection or an incoming message, and a
security model MAY extract that information from the cache. A security model MAY extract that information from the cache. A
tmStateReference is passed as an extra parameter in the ASIs of the tmStateReference is passed as an extra parameter in the ASIs of the
transport subsystem and the messaging and security subsystems, to transport subsystem and the messaging and security subsystems, to
identify the relevant cache. identify the relevant cache.
This approach of passing a model-independent reference is consistent This approach of passing a model-independent reference is consistent
with the securityStateReference cache already being passed around in with the securityStateReference cache already being passed around in
the RFC3411 ASIs. [todo: can we avoid dependencies?] the RFC3411 ASIs.
2.3. Session Requirements 3.3. Session Requirements
Throughout this document, the term session is used. Some underlying Some secure transports may have a notion of sessions, while other
secure transports will have a notion of session. Some underlying secure transports might provide channels or other session-like thing.
secure transports might enable the use of channels or other session- Throughout this document, the term session is used in a broad sense
like thing. In this document the term session refers to an to cover sessions, channels, and session-like things. Session refers
association between two SNMP engines that permits the secure to an association between two SNMP engines that permits the
transmission of one or more SNMP messages within the lifetime of the transmission of one or more SNMP messages within the lifetime of the
session. How the session is actually established, opened, closed, or session. How the session is actually established, opened, closed, or
maintained is specific to a particular transport model. maintained is specific to a particular transport model.
Sessions are not part of the SNMP architecture described in Sessions are not part of the SNMP architecture described in
[RFC3411], but are considered desirable because the cost of [RFC3411], but are considered desirable because the cost of
authentication can be amortized over potentially many transactions. authentication can be amortized over potentially many transactions.
It is important to note that the architecture described in [RFC3411] It is important to note that the architecture described in [RFC3411]
does not include a session selector in the Abstract Service does not include a session selector in the Abstract Service
skipping to change at page 18, line 5 skipping to change at page 14, line 47
usage, including how to establish/open a transport session (i.e., how usage, including how to establish/open a transport session (i.e., how
it maps to the concepts of session-like things of the underlying it maps to the concepts of session-like things of the underlying
protocol), how to behave when a session cannot be established, how to protocol), how to behave when a session cannot be established, how to
close a session properly, how to behave when a session is closed close a session properly, how to behave when a session is closed
improperly, the session security properties, session establishment improperly, the session security properties, session establishment
overhead, and session maintenance overhead. overhead, and session maintenance overhead.
To reduce redundancy, this document will discuss aspects that are To reduce redundancy, this document will discuss aspects that are
expected to be common to all transport model sessions. expected to be common to all transport model sessions.
2.3.1. Session Establishment Requirements 3.3.1. Session Establishment Requirements
SNMP applications must provide the transport type, transport address, SNMP applications must provide the transport type, transport address,
securityName, securityModel, and securityLevel to be used for a securityName, securityModel, and securityLevel to be used for a
session. session.
SNMP Applications typically have no knowledge of whether the session SNMP Applications typically have no knowledge of whether the session
that will be used to carry commands was initially established as a that will be used to carry commands was initially established as a
notification session, or a request-response session, and SHOULD NOT notification session, or a request-response session, and SHOULD NOT
make any assumptions based on knowing the direction of the session. make any assumptions based on knowing the direction of the session.
If an administrator or transport model designer wants to If an administrator or transport model designer wants to
skipping to change at page 18, line 44 skipping to change at page 15, line 38
currently established connection that can be used to send the currently established connection that can be used to send the
notification. For a client-server security protocol, this may notification. For a client-server security protocol, this may
require provisioning authentication credentials on the agent, either require provisioning authentication credentials on the agent, either
statically or dynamically, so the client/agent can successfully statically or dynamically, so the client/agent can successfully
authenticate to a notification receiver. authenticate to a notification receiver.
A transport model must be able to determine whether a session does or A transport model must be able to determine whether a session does or
does not exist, and must be able to determine which session has the does not exist, and must be able to determine which session has the
appropriate security characteristics (transport type, transport appropriate security characteristics (transport type, transport
address, securityName, securityModel, and securityLevel) for an address, securityName, securityModel, and securityLevel) for an
outgoing message. [discuss: does the transport model have insight outgoing message.
into the securityModel?]
A transport model implementation MAY reuse an already established A transport model implementation MAY reuse an already established
session with the appropriate transport type, transport address, session with the appropriate transport type, transport address,
securityName, securityModel, and securityLevel characteristics for securityName, securityModel, and securityLevel characteristics for
delivery of a message originated by a different type of application delivery of a message originated by a different type of application
than originally caused the session to be created. For example, an than originally caused the session to be created. For example, an
implementation that has an existing session originally established to implementation that has an existing session originally established to
receive a request may use that session to send an outgoing receive a request may use that session to send an outgoing
notification, and may use a session that was originally established notification, and may use a session that was originally established
to send a notification to send a request. Responses are expected to to send a notification to send a request. Responses are expected to
be returned using the same session that carried the corresponding be returned using the same session that carried the corresponding
request message. Reuse of sessions is not required for conformance. request message. Reuse of sessions is not required for conformance.
If a session can be reused for a different type of message, but a If a session can be reused for a different type of message, but a
receiver is not prepared to accept different message types over the receiver is not prepared to accept different message types over the
same session, then the message MAY be dropped by the receiver. This same session, then the message MAY be dropped by the receiver. This
may strongly affect the usefulness of session reuse. may strongly affect the usefulness of session reuse, and transport
models should define a standard behavior for this circumstance.
2.3.2. Session Maintenance Requirements 3.3.2. Session Maintenance Requirements
A transport model can tear down sessions as needed. It may be A transport model can tear down sessions as needed. It may be
necessary for some implementations to tear down sessions as the necessary for some implementations to tear down sessions as the
result of resource constraints, for example. result of resource constraints, for example.
The decision to tear down a session is implementation-dependent. The decision to tear down a session is implementation-dependent.
While it is possible for an implementation to automatically tear down While it is possible for an implementation to automatically tear down
each session once an operation has completed, this is not recommended each session once an operation has completed, this is not recommended
for anticipated performance reasons. How an implementation for anticipated performance reasons. How an implementation
determines that an operation has completed, including all potential determines that an operation has completed, including all potential
error paths, is implementation-dependent. error paths, is implementation-dependent.
Implementations should be careful to not tear down a session between
the time a request is received and the time the response is sent.
The elements of procedure for transport models should be sure to
describe the expected behavior when no session exists for a response.
[todo: do we already say that the message should be discarded, or is
that just in the ssh transport model?]
The elements of procedure may discuss when cached information can be The elements of procedure may discuss when cached information can be
discarded, and the timing of cache cleanup may have security discarded, and the timing of cache cleanup may have security
implications, but cache memory management is an implementation issue. implications, but cache memory management is an implementation issue.
If a transport model defines MIB module objects to maintain session If a transport model defines MIB module objects to maintain session
state information, then the transport model MUST describe what state information, then the transport model MUST describe what
happens to the objects when a related session is torn down, since happens to the objects when a related session is torn down, since
this will impact interoperability of the MIB module. this will impact interoperability of the MIB module.
2.3.3. Message security versus session security 3.3.3. Message security versus session security
A transport model session is associated with state information that A transport model session is associated with state information that
is maintained for its lifetime. This state information allows for is maintained for its lifetime. This state information allows for
the application of various security services to multiple messages. the application of various security services to multiple messages.
Cryptographic keys established at the beginning of the session SHOULD Cryptographic keys established at the beginning of the session SHOULD
be used to provide authentication, integrity checking, and encryption be used to provide authentication, integrity checking, and encryption
services for data that is communicated during the session. The services for data that is communicated during the session. The
cryptographic protocols used to establish keys for a transport model cryptographic protocols used to establish keys for a transport model
session SHOULD ensure that fresh new session keys are generated for session SHOULD ensure that fresh new session keys are generated for
each session. If each session uses new session keys, then messages each session. If each session uses new session keys, then messages
cannot be replayed from one session to another. In addition sequence cannot be replayed from one session to another. In addition sequence
information MAY be maintained in the session which can be used to information MAY be maintained in the session which can be used to
prevent the replay and reordering of messages within a session. prevent the replay and reordering of messages within a session.
A transport model session will typically have a single transport A transport model session will typically have a single transport
type, ransport address, securityModel, securityName and securityLevel type, transport address, securityModel, securityName and
associated with it. If an exchange between communicating engines securityLevel associated with it. If an exchange between
would require a different securityLevel or would be on behalf of a communicating engines requires a different securityLevel or is on
different securityName, or to use a different securityModel, then behalf of a different securityName, or uses a different
another session would be needed. An immediate consequence of this is securityModel, then another session would be needed. An immediate
that implementations should be able to maintain some reasonable consequence of this is that implementations should be able to
number of concurrent sessions. maintain some reasonable number of concurrent sessions.
For transport models, securityName is typically specified during For transport models, securityName is typically specified during
session setup, and associated with the session identifier. session setup, and associated with the session identifier.
SNMPv3 was designed to support multiple levels of security, SNMPv3 was designed to support multiple levels of security,
selectable on a per-message basis by an SNMP application, because selectable on a per-message basis by an SNMP application, because
there is not much value in using encryption for a Commander Generator there is not much value in using encryption for a Commander Generator
to poll for non-sensitive performance data on thousands of interfaces to poll for non-sensitive performance data on thousands of interfaces
every ten minutes; the encryption adds significant overhead to every ten minutes; the encryption may add significant overhead to
processing of the messages. processing of the messages.
Some transport models MAY support only specific authentication and Some transport models MAY support only specific authentication and
encryption services, such as requiring all messages to be carried encryption services, such as requiring all messages to be carried
using both authentication and encryption, regardless of the security using both authentication and encryption, regardless of the security
level requested by an SNMP application. level requested by an SNMP application. A transport model MAY
upgrade the requested security level, i.e. noAuth/noPriv and auth/
Some transport models may use an underlying transport that provides a noPriv MAY be sent over an authenticated and encrypted session.
per-message requested level of authentication and encryption
services. For example, if a session is created as 'authPriv', then
keys for encryption could still be negotiated once at the beginning
of the session. But if a message is presented to the session with a
security level of authNoPriv, then that message could simply be
authenticated and not encrypted within the same transport session.
Whether this is possible depends on the transport model and the
secure transport used.
If the underlying transport layer security is configurable on a per-
message basis, a transport model could have a transport-model MIB
module with configurable maxSecurityLevel and a minSecurityLevel
objects to identify the range of possible levels. A session's
maxSecurityLevel would identify the maximum security it could
provide, and a session created with a minSecurityLevel of authPriv
would reject an attempt to send an authNoPriv message. The elements
of procedure of the transport model would need to describe the
procedures to enable this determination. [discuss: this is a feature
I find questionable. It can be developed as a feature of a specific
transport model. Do we need this discussion here?]
For transport models that do not support variable security services
in one session, multiple sessions could be established with different
security levels, and for every packet the SNMP engine could select
the appropriate session based on the requested securityLevel. Some
SNMP entities are resource-constrained. Adding sessions increases
the need for resources, but so does encrypting unnecessarily.
Designers of transport models should consider the trade offs for
resource-constrained devices.
3. Scenario Diagrams for the Transport Subsystem 4. Scenario Diagrams for the Transport Subsystem
RFC3411 section 4.6 provides scenario diagrams to illustrate how an RFC3411 section 4.6 provides scenario diagrams to illustrate how an
outgoing message is created, and how an incoming message is outgoing message is created, and how an incoming message is
processed. Both diagrams are incomplete, however. In section 4.6.1, processed. Both diagrams are incomplete, however. In section 4.6.1,
the diagram doesn't show the ASI for sending an SNMP request to the the diagram doesn't show the ASI for sending an SNMP request to the
network or receiving an SNMP response message from the network. In network or receiving an SNMP response message from the network. In
section 4.6.2, the diagram doesn't illustrate the interfaces required section 4.6.2, the diagram doesn't illustrate the interfaces required
to receive an SNMP message from the network, or to send an SNMP to receive an SNMP message from the network, or to send an SNMP
message to the network. message to the network.
3.1. Command Generator or Notification Originator 4.1. Command Generator or Notification Originator
This diagram from RFC3411 4.6.1 shows how a Command Generator or This diagram from RFC3411 4.6.1 shows how a Command Generator or
Notification Originator application [RFC3413] requests that a PDU be Notification Originator application [RFC3413] requests that a PDU be
sent, and how the response is returned (asynchronously) to that sent, and how the response is returned (asynchronously) to that
application. application.
Command Dispatcher Message Security Command Dispatcher Message Security
Generator | Processing Model Generator | Processing Model
| | Model | | | Model |
| sendPdu | | | | sendPdu | | |
skipping to change at page 22, line 45 skipping to change at page 18, line 45
: | | processIncomingMsg | : | | processIncomingMsg |
: | |-------------------->| : | |-------------------->|
: | | | : | | |
: | |<--------------------| : | |<--------------------|
: | | | : | | |
: |<-----------------------| | : |<-----------------------| |
| processResponsePdu | | | | processResponsePdu | | |
|<-------------------| | | |<-------------------| | |
| | | | | | | |
3.2. Command Responder 4.2. Command Responder
This diagram shows how a Command Responder or Notification Receiver This diagram shows how a Command Responder or Notification Receiver
application registers for handling a pduType, how a PDU is dispatched application registers for handling a pduType, how a PDU is dispatched
to the application after an SNMP message is received, and how the to the application after an SNMP message is received, and how the
Response is (asynchronously) send back to the network. Response is (asynchronously) send back to the network.
Command Dispatcher Message Security Command Dispatcher Message Security
Responder | Processing Model Responder | Processing Model
| | Model | | | Model |
| | | | | | | |
skipping to change at page 23, line 47 skipping to change at page 19, line 47
: | |<-------------------| : | |<-------------------|
: | | | : | | |
: |<-------------------| | : |<-------------------| |
: | | | : | | |
: |--------------+ | | : |--------------+ | |
: | Send SNMP | | | : | Send SNMP | | |
: | Message | | | : | Message | | |
: | to Network | | | : | to Network | | |
: | v | | : | v | |
4. Cached Information and References 5. Cached Information and References
The RFC3411 architecture uses caches to store dynamic model-specific The RFC3411 architecture uses caches to store dynamic model-specific
information, and uses references in the ASIs to indicate in a model- information, and uses references in the ASIs to indicate in a model-
independent manner which cached information must flow between independent manner which cached information must flow between
subsystems. subsystems.
There are two levels of state that may need to be maintained: the There are two levels of state that may need to be maintained: the
security state in a request-response pair, and potentially long-term security state in a request-response pair, and potentially long-term
state relating to transport and security. state relating to transport and security.
This state is maintained in caches and a Local Configuration This state is maintained in caches. To simplify the elements of
Datastore (LCD). To simplify the elements of procedure, the release procedure, the release of state information is not always explicitly
of state information is not always explicitly specified. As a specified. As a general rule, if state information is available when
general rule, if state information is available when a message being a message being processed gets discarded, the state related to that
processed gets discarded, the state related to that message should message should also be discarded, and if state information is
also be discarded, and if state information is available when a available when a relationship between engines is severed, such as the
relationship between engines is severed, such as the closing of a closing of a transport session, the state information for that
transport session, the state information for that relationship might relationship might also be discarded.
also be discarded.
This document differentiates the tmStateReference from the This document differentiates the tmStateReference from the
securityStateReference. This document does not specify an securityStateReference. This document does not specify an
implementation strategy, only an abstract discussion of the data that implementation strategy, only an abstract discussion of the data that
must flow between subsystems. An implementation MAY use one cache must flow between subsystems. An implementation MAY use one cache
and one reference to serve both functions, but an implementer must be and one reference to serve both functions, but an implementer must be
aware of the cache-release issues to prevent the cache from being aware of the cache-release issues to prevent the cache from being
released before a security or transport model has had an opportunity released before a security or transport model has had an opportunity
to extract the information it needs. to extract the information it needs.
4.1. securityStateReference 5.1. securityStateReference
From RFC3411: "For each message received, the Security Model caches From RFC3411: "For each message received, the Security Model caches
the state information such that a Response message can be generated the state information such that a Response message can be generated
using the same security information, even if the Local Configuration using the same security information, even if the Local Configuration
Datastore is altered between the time of the incoming request and the Datastore is altered between the time of the incoming request and the
outgoing response. outgoing response.
A Message Processing Model has the responsibility for explicitly A Message Processing Model has the responsibility for explicitly
releasing the cached data if such data is no longer needed. To releasing the cached data if such data is no longer needed. To
enable this, an abstract securityStateReference data element is enable this, an abstract securityStateReference data element is
passed from the Security Model to the Message Processing Model. The passed from the Security Model to the Message Processing Model. The
cached security data may be implicitly released via the generation of cached security data may be implicitly released via the generation of
a response, or explicitly released by using the stateRelease a response, or explicitly released by using the stateRelease
primitive, as described in RFC3411 section 4.5.1." primitive, as described in RFC3411 section 4.5.1."
The information saved should include the model-independent parameters The information saved should include the model-independent parameters
(transportType, transportAddress, securityName, securityModel, and (transportDomain, transportAddress, securityName, securityModel, and
securityLevel), related security parameters, and other information securityLevel), related security parameters, and other information
needed to imatch the response with the request. The Message needed to imatch the response with the request. The Message
Processing Model has the responsibility for explicitly releasing the Processing Model has the responsibility for explicitly releasing the
securityStateReference when such data is no longer needed. The securityStateReference when such data is no longer needed. The
securityStateReference cached data may be implicitly released via the securityStateReference cached data may be implicitly released via the
generation of a response, or explicitly released by using the generation of a response, or explicitly released by using the
stateRelease primitive, as described in RFC 3411 section 4.5.1." stateRelease primitive, as described in RFC 3411 section 4.5.1."
If the transport model connection is closed between the time a If the transport model connection is closed between the time a
Request is received and a Response message is being prepared, then Request is received and a Response message is being prepared, then
the Response message MAY be discarded. the Response message MAY be discarded.
4.2. tmStateReference 5.2. tmStateReference
For each message or transport session, information about the message For each message or transport session, information about the message
security is stored in the Local Configuration Datastore (LCD), security is stored in a cache, which may inlcude model- and
supplemented with a cache, to pass model- and mechanism-specific mechanism-specific parameters. The tmStateReference is passed
parameters. The state referenced by tmStateReference may be saved between subsystems to provide a handle for the cache. A transport
across multiple messages, as compared to securityStateReference which model may store transport-specific parameters in the cache for
is only saved for the life of a request-response pair of messages. subsequent usage. Since the contents of a cache are meaningful only
within an implementation, and not on-the-wire, the format of the
The format of the cache and the LCD are implementation-specific. For cache is implementation-specific.
ease of explanation, this document defines a MIB module to
conceptually represent the LCD, but this is not meant to contrain
implementations from doing it differently.
It is expected that the LCD will allow lookup based on the
combination of transportType, transportAddress, securityName,
securityModel, and securityLevel. It is expected that the cache
contain these values or contain pointers/references to entries in the
LCD.
It is expected that a transport model may store transport-specific
parameters in the LCD for subsequent usage.
5. Abstract Service Interfaces The state referenced by tmStateReference may be saved in a Local
Configuration Datastore (LCD) to make it available across multiple
messages, as compared to securityStateReference which is designed to
be saved only for the life of a request-response pair of messages.
It is expected that an LCD will allow lookup based on the combination
of transportDomain, transportAddress, securityName, securityModel,
and securityLevel, and that the cache contain these values to
reference entries in the LCD.
[todo: the discussion of ASIs that are not directly related to the 6. Abstract Service Interfaces
transport or security models was added to the document because it was
difficult to understand what information was available at what
points, and who provided the information. The presence of this
expository text can make it hard to find the relevant ASIs for the
transport subsystem, and can be confusing because it talks about
things that the transport subsystem should not know about. This text
should be reduced.
Abstract service interfaces have been defined by RFC 3411 to describe Abstract service interfaces have been defined by RFC 3411 to describe
the conceptual data flows between the various subsystems within an the conceptual data flows between the various subsystems within an
SNMP entity. SNMP entity.
To simplify the elements of procedure, the release of state To simplify the elements of procedure, the release of state
information is not always explicitly specified. As a general rule, information is not always explicitly specified. As a general rule,
if state information is available when a message gets discarded, the if state information is available when a message gets discarded, the
message-state information should also be released, and if state message-state information should also be released, and if state
information is available when a session is closed, the session state information is available when a session is closed, the session state
information should also be released. information should also be released.
An error indication may return an OID and value for an incremented An error indication may return an OID and value for an incremented
counter and a value for securityLevel, and values for contextEngineID counter and a value for securityLevel, and values for contextEngineID
and contextName for the counter, and the securityStateReference if and contextName for the counter, and the securityStateReference if
the information is available at the point where the error is the information is available at the point where the error is
detected. detected.
5.1. Generating an Outgoing SNMP Message 6.1. Generating an Outgoing SNMP Message
This section describes the procedure followed by an RFC3411- This section describes the procedure followed by an RFC3411-
compatible system whenever it generates a message containing a compatible system whenever it generates a message containing a
management operation (such as a request, a response, a notification, management operation (such as a request, a response, a notification,
or a report) on behalf of a user. or a report) on behalf of a user.
statusInformation = -- success or errorIndication statusInformation = -- success or errorIndication
prepareOutgoingMessage( prepareOutgoingMessage(
IN transportDomain -- transport domain to be used IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used IN transportAddress -- transport address to be used
skipping to change at page 26, line 40 skipping to change at page 22, line 31
IN contextName -- data from/in this context IN contextName -- data from/in this context
IN pduVersion -- the version of the PDU IN pduVersion -- the version of the PDU
IN PDU -- SNMP Protocol Data Unit IN PDU -- SNMP Protocol Data Unit
IN expectResponse -- TRUE or FALSE IN expectResponse -- TRUE or FALSE
IN sendPduHandle -- the handle for matching IN sendPduHandle -- the handle for matching
incoming responses incoming responses
OUT destTransportDomain -- destination transport domain OUT destTransportDomain -- destination transport domain
OUT destTransportAddress -- destination transport address OUT destTransportAddress -- destination transport address
OUT outgoingMessage -- the message to send OUT outgoingMessage -- the message to send
OUT outgoingMessageLength -- its length OUT outgoingMessageLength -- its length
OUT tmStateReference OUT tmStateReference -- (NEW) reference to transport state
) )
Note that tmStateReference has been added to this ASI. Note that tmStateReference has been added to this ASI.
The IN parameters of the prepareOutgoingMessage() ASI are used to The IN parameters of the prepareOutgoingMessage() ASI are used to
pass information from the dispatcher (for the application subsystem) pass information from the dispatcher (from the application subsystem)
to the message processing subsystem. to the message processing subsystem.
The abstract service primitive from a Message Processing Model to a The abstract service primitive from a Message Processing Model to a
Security Model to generate the components of a Request message is Security Model to generate the components of a Request message is
generateRequestMsg(). generateRequestMsg().
The abstract service primitive from a Message Processing Model to a The abstract service primitive from a Message Processing Model to a
Security Model to generate the components of a Response message is Security Model to generate the components of a Response message is
generateResponseMsg(). generateResponseMsg().
Upon completion of processing, the Security Model returns Upon completion of processing, the Security Model returns
statusInformation. If the process was successful, the completed statusInformation. If the process was successful, the completed
message is returned. If the process was not successful, then an message is returned. If the process was not successful, then an
errorIndication is returned. errorIndication is returned.
The OUT parameters of the prepareOutgoingMessage() ASI are used to The OUT parameters of the prepareOutgoingMessage() ASI are used to
pass information from the message processing model to the dispatcher pass information from the message processing model to the dispatcher
and on to the transport model: and on to the transport model:
5.2. Processing for an Outgoing Message 6.2. Processing for an Outgoing Message
The sendMessage ASI is used to pass a message from the Dispatcher to The sendMessage ASI is used to pass a message from the Dispatcher to
the appropriate transport model for sending. the appropriate transport model for sending.
statusInformation = statusInformation =
sendMessage( sendMessage(
IN destTransportDomain -- transport domain to be used IN destTransportDomain -- transport domain to be used
IN destTransportAddress -- transport address to be used IN destTransportAddress -- transport address to be used
IN outgoingMessage -- the message to send IN outgoingMessage -- the message to send
IN outgoingMessageLength -- its length IN outgoingMessageLength -- its length
IN tmStateReference IN tmStateReference -- reference to transport state
)
The Transport Subsystem provides the following primitives to pass
data back and forth between the dispatcher and specific transport
models, which provide the interface to the underlying secure
transport service. Each transport model should define the elements
of procedure for the openSession() and closeSession() interfaces.
statusInformation =
openSession(
IN transportDomain -- transport domain to be used
IN transportAddress -- transport address to be used
IN tmStateReference
)
statusInformation =
closeSession(
IN tmStateReference
) )
5.3. Processing an Incoming SNMP Message 6.3. Processing an Incoming SNMP Message
5.3.1. Processing an Incoming Message 6.3.1. Processing an Incoming Message
If one does not exist, the Transport Model will need to create an If one does not exist, the Transport Model will need to create an
entry in a Local Configuration Datastore referenced by entry in a Local Configuration Datastore referenced by
tmStateReference. This information will include transportDomain, tmStateReference. This information will include transportDomain,
transportAddress, the securityModel, the securityLevel, and the transportAddress, the securityModel, the securityLevel, and the
securityName, plus any model or mechanism-specific details. How this securityName, plus any model or mechanism-specific details. How this
information is determined is model-specific. information is determined is model-specific.
The recvMessage ASI is used to pass a message from the transport The recvMessage ASI is used to pass a message from the transport
subsystem to the Dispatcher. subsystem to the Dispatcher.
statusInformation = statusInformation =
recvMessage( recvMessage(
IN destTransportDomain -- transport domain to be used IN transportDomain -- origin transport domain
IN destTransportAddress -- transport address to be used IN transportAddress -- origin transport address
IN incomingMessage -- the message received IN incomingMessage -- the message received
IN incomingMessageLength -- its length IN incomingMessageLength -- its length
IN tmStateReference IN tmStateReference -- reference to transport state
) )
5.3.2. Prepare Data Elements from Incoming Messages 6.3.2. Prepare Data Elements from Incoming Messages
The abstract service primitive from the Dispatcher to a Message The abstract service primitive from the Dispatcher to a Message
Processing Model for a received message is: Processing Model for a received message is:
result = -- SUCCESS or errorIndication result = -- SUCCESS or errorIndication
prepareDataElements( prepareDataElements(
IN transportDomain -- origin transport domain IN transportDomain -- origin transport domain
IN transportAddress -- origin transport address IN transportAddress -- origin transport address
IN wholeMsg -- as received from the network IN wholeMsg -- as received from the network
IN wholeMsgLength -- as received from the network IN wholeMsgLength -- as received from the network
IN tmStateReference -- from the transport model IN tmStateReference -- (NEW) from the transport model
OUT messageProcessingModel -- typically, SNMP version OUT messageProcessingModel -- typically, SNMP version
OUT securityModel -- Security Model to use OUT securityModel -- Security Model to use
OUT securityName -- on behalf of this principal OUT securityName -- on behalf of this principal
OUT securityLevel -- Level of Security requested OUT securityLevel -- Level of Security requested
OUT contextEngineID -- data from/at this entity OUT contextEngineID -- data from/at this entity
OUT contextName -- data from/in this context OUT contextName -- data from/in this context
OUT pduVersion -- the version of the PDU OUT pduVersion -- the version of the PDU
OUT PDU -- SNMP Protocol Data Unit OUT PDU -- SNMP Protocol Data Unit
OUT pduType -- SNMP PDU type OUT pduType -- SNMP PDU type
OUT sendPduHandle -- handle for matched request OUT sendPduHandle -- handle for matched request
OUT maxSizeResponseScopedPDU -- maximum size sender can accept OUT maxSizeResponseScopedPDU -- maximum size sender can accept
OUT statusInformation -- success or errorIndication OUT statusInformation -- success or errorIndication
-- error counter OID/value if error -- error counter OID/value if error
OUT stateReference -- reference to state information OUT stateReference -- reference to state information
-- to be used for possible Response -- to be used for possible Response
) )
Note that tmStateReference has been added to this ASI. Note that tmStateReference has been added to this ASI.
5.3.3. Processing an Incoming Message 6.3.3. Processing an Incoming Message
This section describes the procedure followed by the Security Model This section describes the procedure followed by the Security Model
whenever it receives an incoming message containing a management whenever it receives an incoming message containing a management
operation on behalf of a user from a Message Processing model. operation on behalf of a user from a Message Processing model.
The Message Processing Model extracts some information from the The Message Processing Model extracts some information from the
wholeMsg. The abstract service primitive from a Message Processing wholeMsg. The abstract service primitive from a Message Processing
Model to the Security Subsystem for a received message is:: Model to the Security Subsystem for a received message is:
statusInformation = -- errorIndication or success statusInformation = -- errorIndication or success
-- error counter OID/value if error -- error counter OID/value if error
processIncomingMsg( processIncomingMsg(
IN messageProcessingModel -- typically, SNMP version IN messageProcessingModel -- typically, SNMP version
IN maxMessageSize -- of the sending SNMP entity IN maxMessageSize -- of the sending SNMP entity
IN securityParameters -- for the received message IN securityParameters -- for the received message
IN securityModel -- for the received message IN securityModel -- for the received message
IN securityLevel -- Level of Security IN securityLevel -- Level of Security
IN wholeMsg -- as received on the wire IN wholeMsg -- as received on the wire
IN wholeMsgLength -- length as received on the wire IN wholeMsgLength -- length as received on the wire
IN tmStateReference -- from the transport model IN tmStateReference -- (NEW) from the transport model
OUT securityEngineID -- authoritative SNMP entity OUT securityEngineID -- authoritative SNMP entity
OUT securityName -- identification of the principal OUT securityName -- identification of the principal
OUT scopedPDU, -- message (plaintext) payload OUT scopedPDU, -- message (plaintext) payload
OUT maxSizeResponseScopedPDU -- maximum size sender can handle OUT maxSizeResponseScopedPDU -- maximum size sender can handle
OUT securityStateReference -- reference to security state OUT securityStateReference -- reference to security state
) -- information, needed for response ) -- information, needed for response
1) The securityEngineID is set to a value in a model-specific manner. 1) The securityEngineID is set to a value in a model-specific manner.
If the securityEngineID is not utilized by the specific model, then If the securityEngineID is not utilized by the specific model, then
it should be set to the local snmpEngineID, to satisfy the SNMPv3 it should be set to the local snmpEngineID, to satisfy the SNMPv3
skipping to change at page 30, line 41 skipping to change at page 25, line 41
3) The scopedPDU component is extracted from the wholeMsg. 3) The scopedPDU component is extracted from the wholeMsg.
4) The maxSizeResponseScopedPDU is calculated. This is the maximum 4) The maxSizeResponseScopedPDU is calculated. This is the maximum
size allowed for a scopedPDU for a possible Response message. size allowed for a scopedPDU for a possible Response message.
5)The security data is cached as cachedSecurityData, so that a 5)The security data is cached as cachedSecurityData, so that a
possible response to this message can and will use the same security possible response to this message can and will use the same security
parameters. Then securityStateReference is set for subsequent parameters. Then securityStateReference is set for subsequent
reference to this cached data. reference to this cached data.
4) The statusInformation is set to success and a return is made to 6) The statusInformation is set to success and a return is made to
the calling module passing back the OUT parameters as specified in the calling module passing back the OUT parameters as specified in
the processIncomingMsg primitive. the processIncomingMsg primitive.
6. The Transport-Subsystem-MIB Module
This memo defines a portion of the Management Information Base (MIB)
for statistics in the Transport Subsystem.
6.1. Structure of the MIB Module
Objects in this MIB module are arranged into subtrees. Each subtree
is organized as a set of related objects. The overall structure and
assignment of objects to their subtrees, and the intended purpose of
each subtree, is shown below.
6.1.1. The tmsmStats Subtree
This subtree contains security-model-independent counters which are
applicable to all security models based on the .Transport Subsystem.
This subtree provides information for identifying fault conditions
and performance degradation.
6.2. Relationship to Other MIB Modules
Some management objects defined in other MIB modules are applicable
to an entity implementing this MIB. In particular, it is assumed
that an entity implementing the Transport-Subsystem-MIB module will
also implement the SNMPv2-MIB [RFC3418].
This MIB module is expected to be used with the MIB modules defined
for managing specific transport models within the transport
subsystem. This MIB module is designed to be transport-model
independent and security-model independent, and contains objects
useful for managing common aspects of any transport model. Specific
transport models may define a MIB module to contain transport-model
dependent information.
6.2.1. Textual Conventions
Generic and Common Textual Conventions used in this document can be
found summarized at http://www.ops.ietf.org/mib-common-tcs.html
6.2.2. MIB Modules Required for IMPORTS
The. following MIB module imports items from [RFC2578], [RFC2579],
[RFC2580], [RFC3411], and [RFC3419]
6.3. Definitions
Transport-Subsystem-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE,
mib-2, Integer32, Unsigned32, Gauge32
FROM SNMPv2-SMI
TestAndIncr, StorageType, RowStatus
FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP
FROM SNMPv2-CONF
SnmpSecurityModel,
SnmpAdminString, SnmpSecurityLevel, SnmpEngineID
FROM SNMP-FRAMEWORK-MIB
TransportAddress, TransportAddressType
FROM TRANSPORT-ADDRESS-MIB
;
tmsMIB MODULE-IDENTITY
LAST-UPDATED "200610060000Z"
ORGANIZATION "ISMS Working Group"
CONTACT-INFO "WG-EMail: isms@lists.ietf.org
Subscribe: isms-request@lists.ietf.org
Chairs:
Juergen Quittek
NEC Europe Ltd.
Network Laboratories
Kurfuersten-Anlage 36
69115 Heidelberg
Germany
+49 6221 90511-15
quittek@netlab.nec.de
Juergen Schoenwaelder
International University Bremen
Campus Ring 1
28725 Bremen
Germany
+49 421 200-3587
j.schoenwaelder@iu-bremen.de
Editor:
David Harrington
FutureWei Technologies
1700 Alma Drive, Suite 100
Plano, Texas 75075
USA
+1 603-436-8634
dharrington@huawei.com
"
DESCRIPTION "The Transport Subsystem MIB Module
Copyright (C) The Internet Society (2006). This
version of this MIB module is part of RFC XXXX;
see the RFC itself for full legal notices.
-- NOTE to RFC editor: replace XXXX with actual RFC number
-- for this document and remove this note
"
DESCRIPTION "The initial version, published in RFC XXXX.
-- NOTE to RFC editor: replace XXXX with actual RFC number
-- for this document and remove this note
"
::= { mib-2 xxxx }
-- RFC Ed.: replace xxxx with IANA-assigned number and
-- remove this note
-- ---------------------------------------------------------- --
-- subtrees in the Transport-Subsystem-MIB
-- ---------------------------------------------------------- --
tmsNotifications OBJECT IDENTIFIER ::= { tmsMIB 0 }
tmsObjects OBJECT IDENTIFIER ::= { tmsMIB 1 }
tmsConformance OBJECT IDENTIFIER ::= { tmsMIB 2 }
-- -------------------------------------------------------------
-- Objects
-- -------------------------------------------------------------
-- Textual Conventions
SnmpTransportModel ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION "An identifier that uniquely identifies a
Transport Model of the Transport Subsystem within
the SNMP Management Architecture.
The values for transportModel are allocated as
follows:
- The zero value does not identify any particular
transport model.
- Values between 1 and 255, inclusive, are reserved
for standards-track Transport Models and are
managed by the Internet Assigned Numbers Authority
(IANA).
- Values greater than 255 are allocated to
enterprise-specific Transport Models. An
enterprise-specific transportModel value is defined
to be:
enterpriseID * 256 + transport model within
enterprise
For example, the fourth Transport Model defined by
the enterprise whose enterpriseID is 1 would be
260.
This scheme for allocation of transportModel
values allows for a maximum of 255 standards-
based Transport Models, and for a maximum of
256 Transport Models per enterprise.
It is believed that the assignment of new
transportModel values will be rare in practice
because the larger the number of simultaneously
utilized Transport 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 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
transportModels. This limits the ability to
define new proprietary implementations of Transport
Models to the first 8,388,608 enterprises.
It is worthwhile to note that, in its encoded
form, the transportModel 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 transportModel defined for use with SNMP or
reserved for use with supporting MIB objects.
They are as follows:
0 reserved for 'any'
1 reserved for UDP
2 reserved for TCP
3 SSH Transport Model
"
SYNTAX INTEGER(0 .. 2147483647)
-- Notifications for the Transport Subsystem
-- Statistics for the Transport Subsystem
tmsStats OBJECT IDENTIFIER ::= { tmsObjects 1 }
-- -------------------------------------------------------------
-- Conformance Information
-- -------------------------------------------------------------
tmsGroups OBJECT IDENTIFIER ::= { tmsConformance 1 }
tmsCompliances OBJECT IDENTIFIER ::= { tmsConformance 2 }
-- -------------------------------------------------------------
-- Units of conformance
-- -------------------------------------------------------------
tmsGroup OBJECT-GROUP
OBJECTS {
}
STATUS current
DESCRIPTION "A collection of objects for maintaining session
information of an SNMP engine which implements the
Transport subsystem.
"
::= { tmsGroups 2 }
-- -------------------------------------------------------------
-- Compliance statements
-- -------------------------------------------------------------
tmsCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for SNMP engines that support the
Transport-Subsystem-MIB"
MODULE
MANDATORY-GROUPS { tmsGroup }
::= { tmsCompliances 1 }
END
7. Security Considerations 7. Security Considerations
This document describes an architectural approach and multiple This document describes an architectural approach that would permit
proposed configurations that would permit SNMP to utilize transport SNMP to utilize transport layer security services. Each proposed
layer security services. Each section containing a proposal should transport model should discuss the security considerations of the
discuss the security considerations. transport model.
It is considered desirable by some industry segments that SNMP It is considered desirable by some industry segments that SNMP
transport models should utilize transport layer security that transport models should utilize transport layer security that
addresses perfect forward secrecy at least for encryption keys. addresses perfect forward secrecy at least for encryption keys.
Perfect forward secrecy guarantees that compromise of long term Perfect forward secrecy guarantees that compromise of long term
secret keys does not result in disclosure of past session keys. secret keys does not result in disclosure of past session keys. The
editors recommend that each proposed transport model include a
There are no management objects defined in this MIB module that have discussion in its security considerations of whether perfect forward
a MAX-ACCESS clause of read-write and/or read-create. So, if this security is appropriate for the transport model.
MIB module is implemented correctly, then there is no risk that an
intruder can alter or create any management objects of this MIB
module via direct SNMP SET operations.
Some of the readable objects in this MIB module (i.e., objects with a
MAX-ACCESS other than not-accessible) may be considered sensitive or
vulnerable in some network environments. It is thus important to
control even GET and/or NOTIFY access to these objects and possibly
to even encrypt the values of these objects when sending them over
the network via SNMP. These are the tables and objects and their
sensitivity/vulnerability:
o [todo] list the tables and objects and state why they are
sensitive.
SNMP versions prior to SNMPv3 did not include adequate security.
Even if the network itself is secure (for example by using IPSec),
even then, there is no control as to who on the secure network is
allowed to access and GET/SET (read/change/create/delete) the objects
in this MIB module.
It is RECOMMENDED that implementers consider the security features as
provided by the SNMPv3 framework (see [RFC3410], section 8),
including full support for the SNMPv3 cryptographic mechanisms (for
authentication and privacy).
Further, deployment of SNMP versions prior to SNMPv3 is NOT Since the cache and LCD will contain security-related parameters,
RECOMMENDED. Instead, it is RECOMMENDED to deploy SNMPv3 and to they should be kept in protected storage.
enable cryptographic security. It is then a customer/operator
responsibility to ensure that the SNMP entity giving access to an
instance of this MIB module is properly configured to give access to
the objects only to those principals (users) that have legitimate
rights to indeed GET or SET (change/create/delete) them.
8. IANA Considerations 8. IANA Considerations
IANA is requested to create a new registry in the Simple Network This document requires no action by IANA.
Management Protocol (SNMP) Number Spaces for SnmpTransportModels, as
described in the Transport-Subsystem-MIB defined in this document.
Values 0 through 255 are IANA-assigned by Standards Action, as
defined in RFC2434. Values above 255 are assigned by Hierarchical
allocation, using the algorithm defined in the definition of the
SnmpTransportModels TEXTUAL-CONVENTION in the Transport-Subsystem-MIB
in this document.
The MIB module in this document uses the following IANA-assigned
OBJECT IDENTIFIER values recorded in the SMI Numbers registry:
Descriptor OBJECT IDENTIFIER value
---------- -----------------------
Transport-Subsystem-MIB { mib-2 XXXX }
Editor's Note (to be removed prior to publication): the IANA is
requested to assign a value for "XXXX" under the 'mib-2' subtree
and to record the assignment in the SMI Numbers registry. When
the assignment has been made, the RFC Editor is asked to replace
"XXXX" (here and in the MIB module) with the assigned value and to
remove this note.
9. Acknowledgments 9. Acknowledgments
The Integrated Security for SNMP WG would like to thank the following The Integrated Security for SNMP WG would like to thank the following
people for their contributions to the process: people for their contributions to the process:
The authors of submitted security model proposals: Chris Elliot, Wes The authors of submitted security model proposals: Chris Elliot, Wes
Hardaker, Dave Harrington, Keith McCloghrie, Kaushik Narayan, Dave Hardaker, Dave Harrington, Keith McCloghrie, Kaushik Narayan, Dave
Perkins, Joseph Salowey, and Juergen Schoenwaelder. Perkins, Joseph Salowey, and Juergen Schoenwaelder.
The members of the Protocol Evaluation Team: Uri Blumenthal, The members of the Protocol Evaluation Team: Uri Blumenthal,
Lakshminath Dondeti, Randy Presuhn, and Eric Rescorla. Lakshminath Dondeti, Randy Presuhn, and Eric Rescorla.
WG members who committed to and performed detailed reviews: Jeffrey WG members who committed to and performed detailed reviews: Jeffrey
Hutzelman Hutzelman
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to
Requirement Levels", BCP 14, RFC 2119, March 1997. Indicate Requirement Levels", BCP 14,
RFC 2119, March 1997.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
and T. Wright, "Transport Layer Security (TLS)
Extensions", RFC 4366, April 2006.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J. [RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information Schoenwaelder, Ed., "Structure of Management
Version 2 (SMIv2)", STD 58, RFC 2578, April 1999. Information Version 2 (SMIv2)", STD 58,
RFC 2578, April 1999.
[RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Textual Conventions for SMIv2",
STD 58, RFC 2579, April 1999.
[RFC2580] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Conformance Statements for SMIv2", STD 58, RFC 2580,
April 1999.
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, June 2000.
[RFC3411] Harrington, D., Presuhn, R., and B. Wijnen, "An
Architecture for Describing Simple Network Management
Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
December 2002.
[RFC3412] Case, J., Harrington, D., Presuhn, R., and B. Wijnen,
"Message Processing and Dispatching for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3412,
December 2002.
[RFC3414] Blumenthal, U. and B. Wijnen, "User-based Security Model
(USM) for version 3 of the Simple Network Management
Protocol (SNMPv3)", STD 62, RFC 3414, December 2002.
[RFC3416] Presuhn, R., "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62,
RFC 3416, December 2002.
[RFC3417] Presuhn, R., "Transport Mappings for the Simple Network [RFC3411] Harrington, D., Presuhn, R., and B. Wijnen,
Management Protocol (SNMP)", STD 62, RFC 3417, "An Architecture for Describing Simple
December 2002. Network Management Protocol (SNMP) Management
Frameworks", STD 62, RFC 3411, December 2002.
[RFC3418] Presuhn, R., "Management Information Base (MIB) for the [RFC3412] Case, J., Harrington, D., Presuhn, R., and B.
Simple Network Management Protocol (SNMP)", STD 62, Wijnen, "Message Processing and Dispatching
RFC 3418, December 2002. for the Simple Network Management Protocol
(SNMP)", STD 62, RFC 3412, December 2002.
[RFC3419] Daniele, M. and J. Schoenwaelder, "Textual Conventions for [RFC3414] Blumenthal, U. and B. Wijnen, "User-based
Transport Addresses", RFC 3419, December 2002. Security Model (USM) for version 3 of the
Simple Network Management Protocol (SNMPv3)",
STD 62, RFC 3414, December 2002.
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH) [RFC3417] Presuhn, R., "Transport Mappings for the
Protocol Architecture", RFC 4251, January 2006. Simple Network Management Protocol (SNMP)",
STD 62, RFC 3417, December 2002.
10.2. Informative References 10.2. Informative References
[RFC2865] Rigney, C., Willens, S., Rubens, A., and W.
Simpson, "Remote Authentication Dial In User
Service (RADIUS)", RFC 2865, June 2000.
[RFC3410] Case, J., Mundy, R., Partain, D., and B. [RFC3410] Case, J., Mundy, R., Partain, D., and B.
Stewart, "Introduction and Applicability Stewart, "Introduction and Applicability
Statements for Internet-Standard Management Statements for Internet-Standard Management
Framework", RFC 3410, December 2002. Framework", RFC 3410, December 2002.
[RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple [RFC3413] Levi, D., Meyer, P., and B. Stewart, "Simple
Network Management Protocol (SNMP) Network Management Protocol (SNMP)
Applications", STD 62, RFC 3413, Applications", STD 62, RFC 3413,
December 2002. December 2002.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D.,
Mikkelsen, J., and T. Wright, "Transport
Layer Security (TLS) Extensions", RFC 4366,
April 2006.
[RFC4422] Melnikov, A. and K. Zeilenga, "Simple [RFC4422] Melnikov, A. and K. Zeilenga, "Simple
Authentication and Security Layer (SASL)", Authentication and Security Layer (SASL)",
RFC 4422, June 2006. RFC 4422, June 2006.
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell
(SSH) Protocol Architecture", RFC 4251,
January 2006.
[I-D.ietf-netconf-ssh] Wasserman, M. and T. Goddard, "Using the [I-D.ietf-netconf-ssh] Wasserman, M. and T. Goddard, "Using the
NETCONF Configuration Protocol over Secure NETCONF Configuration Protocol over Secure
Shell (SSH)", draft-ietf-netconf-ssh-06 (work Shell (SSH)", draft-ietf-netconf-ssh-06 (work
in progress), March 2006. in progress), March 2006.
Appendix A. Parameter Table Appendix A. Parameter Table
Following is a CSV formatted matrix useful for tracking data flows Following is a CSV formatted matrix useful for tracking data flows
into and out of the dispatcher, message, and security subsystems. into and out of the dispatcher, transport, message, and security
Import this into your favorite spreadsheet or other CSV compatible subsystems. Import this into your favorite spreadsheet or other CSV
application. You will need to remove lines feeds from the second and compatible application. You will need to remove lines feeds from the
third lines, which needed to be wrapped to fit into RFC limits. second, third, and fourth lines, which needed to be wrapped to fit
into RFC limits.
A.1. ParameterList.csv A.1. ParameterList.csv
,Dispatcher,,,,Messaging,,,Security,, ,Dispatcher,,,,Messaging,,,Security,,,Transport,
,sendPdu,returnResponse,processPdu,processResponse ,sendPDU,returnResponse,processPDU,processResponse,
,prepareOutgoingMessage,prepareResponseMessage,prepareDataElements
,generateRequest,processIncoming,generateResponse
transportDomain,In,,,,In,,In,,, prepareOutgoingMessage,prepareResponseMessage,prepareDataElements,
transportAddress,In,,,,In,,In,,,
destTransportDomain,,,,,Out,Out,,,, generateRequest,processIncoming,generateResponse,
destTransportAddress,,,,,Out,Out,,,, sendMessage,recvMessage
messageProcessingModel,In,In,In,In,In,In,Out,In,In,In transportDomain,In,,,,In,,In,,,,,In
securityModel,In,In,In,In,In,In,Out,In,In,In transportAddress,In,,,,In,,In,,,,,In
securityName,In,In,In,In,In,In,Out,In,Out,In destTransportDomain,,,,,Out,Out,,,,,In,
securityLevel,In,In,In,In,In,In,Out,In,In,In destTransportAddress,,,,,Out,Out,,,,,In,
contextEngineID,In,In,In,In,In,In,Out,,, messageProcessingModel,In,In,In,In,In,In,Out,In,In,In,,
contextName,In,In,In,In,In,In,Out,,, securityModel,In,In,In,In,In,In,Out,In,In,In,,
expectResponse,In,,,,In,,,,, securityName,In,In,In,In,In,In,Out,In,Out,In,,
PDU,In,In,In,In,In,In,Out,,, securityLevel,In,In,In,In,In,In,Out,In,In,In,,
pduVersion,In,In,In,In,In,In,Out,,, contextEngineID,In,In,In,In,In,In,Out,,,,,
statusInfo,Out,In,,In,,In,Out,Out,Out,Out contextName,In,In,In,In,In,In,Out,,,,,
errorIndication,Out,Out,,,,,Out,,, expectResponse,In,,,,In,,,,,,,
sendPduHandle,Out,,,In,In,,Out,,, PDU,In,In,In,In,In,In,Out,,,,,
maxSizeResponsePDU,,In,In,,,In,Out,,Out, pduVersion,In,In,In,In,In,In,Out,,,,,
stateReference,,In,In,,,In,Out,,, statusInfo,Out,In,,In,,In,Out,Out,Out,Out,,
errorIndication,Out,Out,,,,,Out,,,,,
wholeMessage,,,,,Out,Out,,Out,In,Out sendPduHandle,Out,,,In,In,,Out,,,,,
messageLength,,,,,Out,Out,,Out,In,Out maxSizeResponsePDU,,In,In,,,In,Out,,Out,,,
maxMessageSize,,,,,,,,In,In,In stateReference,,In,In,,,In,Out,,,,,
globalData,,,,,,,,In,,In wholeMessage,,,,,Out,Out,In,Out,In,Out,In,In
securityEngineID,,,,,,,,In,Out,In messageLength,,,,,Out,Out,In,Out,In,Out,In,In
scopedPDU,,,,,,,,In,Out,In maxMessageSize,,,,,,,,In,In,In,,
securityParameters,,,,,,,,Out,,Out globalData,,,,,,,,In,,In,,
securityStateReference,,,,,,,,,Out,In
pduType,,,,,,,Out,,, securityEngineID,,,,,,,,In,Out,In,,
tmStateReference,,,,,,Out,In,,In, scopedPDU,,,,,,,,In,Out,In,,
securityParameters,,,,,,,,Out,In,Out,,
securityStateReference,,,,,,,,,Out,In,,
pduType,,,,,,,Out,,,,,
tmStateReference,,,,,Out,Out,In,,In,,In,In
Appendix B. Why tmStateReference? Appendix B. Why tmStateReference?
This appendix considers why a cache-based approach was selected for This appendix considers why a cache-based approach was selected for
passing parameters. This section may be removed from subsequent passing parameters. This section may be removed from subsequent
revisions of the document. revisions of the document.
There are four approaches that could be used for passing information There are four approaches that could be used for passing information
between the Transport Model and an Security Model. between the Transport Model and an Security Model.
skipping to change at page 42, line 26 skipping to change at page 30, line 46
Transport Model will need to decode the ASN.1 message, modify the Transport Model will need to decode the ASN.1 message, modify the
fields, and re-encode the message in ASN.1 before passing the message fields, and re-encode the message in ASN.1 before passing the message
on to the message dispatcher or to the transport layer. This would on to the message dispatcher or to the transport layer. This would
require an intimate knowledge of the message format and message require an intimate knowledge of the message format and message
versions so the Transport Model knew which fields could be modified. versions so the Transport Model knew which fields could be modified.
This would seriously violate the modularity of the architecture. This would seriously violate the modularity of the architecture.
B.4. Using a Cache B.4. Using a Cache
This document describes a cache, into which the Transport Model puts This document describes a cache, into which the Transport Model puts
information about the security applied to an incoming message, and an information about the security applied to an incoming message, and a
Security Model extracts that information from the cache. Given that Security Model can extract that information from the cache. Given
there may be multiple TM-security caches, a tmStateReference is that there may be multiple TM-security caches, a tmStateReference is
passed as an extra parameter in the ASIs between the transport passed as an extra parameter in the ASIs between the transport
subsystem and the security subsystem, so the Security Model knows subsystem and the security subsystem, so the Security Model knows
which cache of information to consult. which cache of information to consult.
This approach does create dependencies between a specific Transport This approach does create dependencies between a specific Transport
Model and a corresponding specific Security Model. This approach of Model and a corresponding specific Security Model. However, the
passing a model-independent reference is consistent with the approach of passing a model-independent reference to a model-
securityStateReference cache already being passed around in the dependent cache is consistent with the securityStateReference already
RFC3411 ASIs. being passed around in the RFC3411 ASIs.
Appendix C. Open Issues Appendix C. Open Issues
Appendix D. Change Log Appendix D. Change Log
NOTE to RFC editor: Please remove this change log before publishing NOTE to RFC editor: Please remove this change log before publishing
this document as an RFC. this document as an RFC.
Changes from revision -04- to -05-
removed all objects from the MIB module.
changed document status to "Standard" rather than the xml2rfc
default of informational.
changed mention of MD5 to SHA
moved addressing style to TDomain and TAddress
modified the diagrams as requested
removed the "layered stack" diagrams that compared USM and a
Transport Model processing
removed discussion of speculative features that might exist in
future transport models
removed openSession() and closeSession() ASIs, since those are
model-dependent
removed the MIB module
removed the MIB boilerplate into (this memo defines a SMIv2 MIB
...)
removed IANA considerations related to the now-gone MIB module
removed security considerations related to the MIB module
removed references needed for the MIB module
changed recvMessage ASI to use origin transport domain/address
updated Parameter CSV appendix
Changes from revision -03- to -04- Changes from revision -03- to -04-
changed title from Transport Mapping Security Model Architectural changed title from Transport Mapping Security Model Architectural
Extension to Transport Subsystem Extension to Transport Subsystem
modified the abstract and introduction modified the abstract and introduction
changed TMSM to TMS changed TMSM to TMS
changed MPSP to simply Security Model changed MPSP to simply Security Model
changed SMSP to simply Security Model changed SMSP to simply Security Model
changed TMSP to Transport Model changed TMSP to Transport Model
removed MPSP and TMSP and SMSP from Acronyms section removed MPSP and TMSP and SMSP from Acronyms section
skipping to change at page 45, line 7 skipping to change at page 34, line 7
International University Bremen International University Bremen
Campus Ring 1 Campus Ring 1
28725 Bremen 28725 Bremen
Germany Germany
Phone: +49 421 200-3587 Phone: +49 421 200-3587
EMail: j.schoenwaelder@iu-bremen.de EMail: j.schoenwaelder@iu-bremen.de
Full Copyright Statement Full Copyright Statement
Copyright (C) The Internet Society (2006). Copyright (C) The IETF Trust (2006).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property Intellectual Property
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information made any independent effort to identify any such rights. Information
 End of changes. 116 change blocks. 
712 lines changed or deleted 307 lines changed or added

This html diff was produced by rfcdiff 1.33. The latest version is available from http://tools.ietf.org/tools/rfcdiff/