RFC 6933
Entity MIB (Version 4)
Internet Engineering Task Force (IETF) A. Bierman Request for Comments: 6933 YumaWorks, Inc. Obsoletes: 4133 D. Romascanu Category: Standards Track Avaya ISSN: 2070-1721 J. Quittek NEC Europe Ltd. M. Chandramouli Cisco Systems, Inc. May 2013 Entity MIB (Version 4)Abstract
This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community. In particular, it describes managed objects used for managing multiple logical and physical entities managed by a single Simple Network Management Protocol (SNMP) agent. This document specifies version 4 of the Entity MIB. This memo obsoletes version 3 of the Entity MIB module published as RFC 4133. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc6933. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.Table of Contents
1. The SNMP Management Framework ...................................3 2. Overview ........................................................3 2.1. Terms ......................................................5 2.2. Relationship to Community Strings ..........................6 2.3. Relationship to SNMP Contexts ..............................6 2.4. Relationship to Proxy Mechanisms ...........................6 2.5. Relationship to a Chassis MIB ..............................7 2.6. Relationship to the Interfaces MIB .........................7 2.7. Relationship to the Other MIB Modules ......................7 2.8. Relationship to Naming Scopes ..............................7 2.9. Multiple Instances of the Entity MIB .......................8 2.10. Re-Configuration of Entities ..............................9 2.11. Textual Convention Change .................................9 2.12. MIB Structure .............................................9 2.12.1. entityPhysical Group ..............................10 2.12.2. entityLogical Group ...............................12 2.12.3. entityMapping Group ...............................12 2.12.4. entityGeneral Group ...............................13 2.12.5. entityNotifications Group .........................13 2.13. Multiple Agents ..........................................13 2.14. Changes Since RFC 2037 ...................................14 2.14.1. Textual Conventions ...............................14 2.14.2. New entPhysicalTable Objects ......................14 2.14.3. New entLogicalTable Objects .......................14 2.14.4. Bug Fixes .........................................14 2.15. Changes Since RFC 2737 ...................................15 2.15.1. Textual Conventions ...............................15 2.15.2. New Objects .......................................15 2.15.3. Bug Fixes .........................................15 2.16. Changes Since RFC 4133 ...................................15 2.16.1. MIB Module Addition ...............................15 2.16.2. Modification to Some of the MIB Objects ...........15 2.16.3. New TC for Universally Unique Identifier ..........16 3. MIB Definitions ................................................16 3.1. ENTITY-MIB ................................................16 3.2. IANA-ENTITY-MIB ...........................................50 3.3. UUID-TC-MIB ...............................................53 4. Usage Examples .................................................55 4.1. Router/Bridge .............................................55 4.2. Repeaters .................................................62 4.3. EMAN Example ..............................................69 5. Security Considerations ........................................70
6. IANA Considerations ............................................72 7. Acknowledgements ...............................................73 8. References .....................................................73 8.1. Normative References ......................................73 8.2. Informative References ....................................741. The SNMP Management Framework
For a detailed overview of the documents that describe the current Internet-Standard Management Framework, please refer to section 7 of 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]. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].2. Overview
There is a need for a standardized way of representing a single agent, which supports multiple instances of one MIB module. This is presently true for at least 3 standard MIB modules and is likely to become true for more and more MIB modules as time passes. For example: - multiple instances of a bridge supported within a single device that has a single agent; - multiple repeaters supported by a single agent; and - multiple OSPF backbone areas, each operating as part of its own Autonomous System and each identified by the same area-id (e.g., 0.0.0.0), supported inside a single router with one agent. The single agent present in each of these cases implies a relationship binds these entities. Effectively, there is some "overall" physical entity that houses the sum of the things managed by that one agent, i.e., there are multiple "logical" entities within a single physical entity. Sometimes, the overall physical entity
contains multiple (smaller) physical entities, and each logical entity is associated with a particular physical entity. Sometimes, the overall physical entity is a "compound" of multiple physical entities (e.g., a stack of stackable hubs). What is needed is a way to determine exactly which logical entities are managed by the agent (with some version of SNMP) in order to communicate with the agent about a particular logical entity. When different logical entities are associated with different physical entities within the overall physical entity, it is also useful to be able to use this information to distinguish between logical entities. In these situations, there is no need for varbinds for multiple logical entities to be referenced in the same SNMP message (although that might be useful in the future). Rather, it is sufficient, and in some situations preferable, to have the context/community in the message identify the logical entity to which the varbinds apply. Version 2 of this MIB addresses new requirements that have emerged since the publication of the first Entity MIB [RFC2037]. There is a need for a standardized way of providing non-volatile, administratively assigned identifiers for physical components represented with the Entity MIB. There is also a need to align the Entity MIB with the SNMPv3 administrative framework (STD 62, [RFC3411]). Implementation experience has shown that additional physical component attributes are also desirable. Version 3 of this MIB addresses new requirements that have emerged since the publication of the second Entity MIB [RFC2737]. There is a need to identify physical entities that are central processing units (CPUs) and a need to provide a Textual Convention (TC) that identifies an entPhysicalIndex value or zero, where the value zero has application-specific semantics. Two new objects have been added to the entPhysicalTable to identify the manufacturing date and provide additional URIs for a particular physical entity. Version 4 of this MIB addresses new requirements that have emerged since the publication of the third version of the Entity MIB [RFC4133]. There is a need to add new enumerated values for entity physical classes, a need to provide identification information for physical entities using a Universally Unique Identifier (UUID) format, and a need to have compliant implementations of the Entity MIB with a smaller subsets of MIB objects for devices with constrained resources. The PhysicalClass TEXTUAL-CONVENTION was deprecated, and a new IANAPhysicalClass TC (maintained by IANA) was created. A new TC, UUIDorZero, was created to represent a UUID, and a new MIB object was
added to the entPhysicalTable to identify an entity. A new compliance statement, entity4CRCompliance, has been added for possible implementation of a selected subset of MIB objects by entities with constrained resources.2.1. Terms
The following terms are used throughout this document: - Naming Scope A "naming scope" represents the set of information that may be potentially accessed through a single SNMP operation. All instances within the naming scope share the same unique identifier space. For SNMPv1, a naming scope is identified by the value of the associated entLogicalCommunity instance. For SNMPv3, the term "context" is used instead of "naming scope". The complete definition of an SNMP context can be found in Section 3.3.1 of RFC 3411 [RFC3411]. - Multi-Scoped Object A MIB object for which identical instance values identify different managed information in different naming scopes is called a "multi- scoped" MIB object. - Single-Scoped Object A MIB object for which identical instance values identify the same managed information in different naming scopes is called a "single- scoped" MIB object. - Logical Entity A managed system contains one or more "logical entities", each represented by at most one instantiation of each of a particular set of MIB objects. A set of management functions is associated with each logical entity. Examples of logical entities include routers, bridges, print-servers, etc. - Physical Entity A "physical entity" or "physical component" represents an identifiable physical resource within a managed system. Zero or more logical entities may utilize a physical resource at any given time. Determining which physical components are represented by an agent in the EntPhysicalTable is an implementation-specific matter. Typically, physical resources (e.g., communications ports, backplanes, sensors, daughter-cards, power supplies, and the overall chassis), which can be managed via functions associated with one or more logical entities, are included in the MIB.
- Containment Tree
Each physical component may be modeled as 'contained' within
another physical component. A "containment-tree" is the conceptual
sequence of entPhysicalIndex values that uniquely specifies the
exact physical location of a physical component within the managed
system. It is generated by 'following and recording' each
entPhysicalContainedIn instance 'up the tree towards the root'
until a value of zero, indicating no further containment, is found.
2.2. Relationship to Community Strings
For community-based SNMP, differentiating logical entities is one
(but not the only) purpose of the community string [RFC1157]. This
is accommodated by representing each community string as a logical
entity.
Note that different logical entities may share the same naming scope
and, therefore, the same values of entLogicalCommunity. This is
possible, providing they have no need for the same instance of a MIB
object to represent different managed information.
2.3. Relationship to SNMP Contexts
Version 2 of the Entity MIB contains support for associating SNMPv3
contexts with logical entities. Two new MIB objects, defining an
SnmpEngineID and ContextName pair, are used together to identify an
SNMP context associated with a logical entity. This context can be
used (in conjunction with the entLogicalTAddress and
entLogicalTDomain MIB objects) to send SNMPv3 messages on behalf of a
particular logical entity.
2.4. Relationship to Proxy Mechanisms
The Entity MIB is designed to allow functional component discovery.
The administrative relationships between different logical entities
are not visible in any Entity MIB tables. A Network Management
System (NMS) cannot determine whether MIB instances in different
naming scopes are realized locally or remotely (e.g., via some proxy
mechanism) by examining any particular Entity MIB objects.
The management of administrative framework functions is not an
explicit goal of the Entity MIB WG at this time. This new area of
functionality may be revisited after some operational experience with
the Entity MIB is gained.
Note that for community-based versions of SNMP, a network administrator will likely be able to associate community strings with naming scopes that have proprietary mechanisms, as a matter of configuration. There are no mechanisms for managing naming scopes defined in this MIB.2.5. Relationship to a Chassis MIB
Some readers may recall that a previous IETF working group attempted to define a Chassis MIB. No consensus was reached by that working group, possibly because its scope was too broad. As such, it is not the purpose of the ENTITY-MIB module to be a "Chassis MIB replacement", nor is it within the scope of the ENTITY-MIB module to contain all the information that might be necessary to manage a "chassis". On the other hand, the entities represented by an implementation of the ENTITY-MIB module might well be contained in a chassis.2.6. Relationship to the Interfaces MIB
The Entity MIB contains a mapping table identifying physical components that have 'external values' (e.g., ifIndex) associated with them within a given naming scope. This table can be used to identify the physical location of each interface in the ifTable [RFC2863]. Because ifIndex values in different contexts are not related to one another, the interface-to-physical-component associations are relative to the same logical entity within the agent. The Entity MIB also contains entPhysicalName and entPhysicalAlias objects, which approximate the semantics of the ifName and ifAlias objects (respectively) from the Interfaces MIB [RFC2863] for all types of physical components.2.7. Relationship to the Other MIB Modules
The Entity MIB contains a mapping table identifying physical components that have identifiers from other standard MIB modules associated with them. For example, this table can be used along with the physical mapping table to identify the physical location of each repeater port in the rptrPortTable or each interface in the ifTable.2.8. Relationship to Naming Scopes
There is some question as to which MIB objects may be returned within a given naming scope. MIB objects that are not multi-scoped within a managed system are likely to ignore context information in
implementation. In such a case, it is likely such objects will be returned in all naming scopes (e.g., not just the 'default' naming scope or the SNMPv3 default context). For example, a community string used to access the management information for logical device 'bridge2' may allow access to all the non-bridge-related objects in the 'default' naming scope, as well as a second instance of the Bridge MIB [RFC4188]. The isolation of single-scoped MIB objects by the agent is an implementation-specific matter. An agent may wish to limit the objects returned in a particular naming scope to only the multi- scoped objects in that naming scope (e.g., system group and the Bridge MIB). In this case, all single-scoped management information would belong to a common naming scope (e.g., 'default'), which itself may contain some multi-scoped objects (e.g., system group).2.9. Multiple Instances of the Entity MIB
It is possible that more than one agent may exist in a managed system. In such cases, multiple instances of the Entity MIB (representing the same managed objects) may be available to an NMS. In order to reduce complexity for agent implementation, multiple instances of the Entity MIB are not required to be equivalent or even consistent. An NMS may be able to 'align' instances returned by different agents by examining the columns of each table, but vendor- specific identifiers and (especially) index values are likely to be different. Each agent may be managing different subsets of the entire chassis as well. When all of a physically modular device is represented by a single agent, the entry (for which entPhysicalContainedIn has the value zero) would likely have 'chassis' as the value of its entPhysicalClass. Alternatively, for an agent on a module where the agent represents only the physical entities on that module (not those on other modules), the entry (for which entPhysicalContainedIn has the value zero) would likely have 'module' as the value of its entPhysicalClass. An agent implementation of the entLogicalTable is not required to contain information about logical entities managed primarily by other agents. That is, the entLogicalTAddress and entLogicalTDomain objects in the entLogicalTable are provided to support a historical multiplexing mechanism, not to identify other SNMP agents. Note that the Entity MIB is a single-scoped MIB, in the event an agent represents the MIB in different naming scopes.
2.10. Re-Configuration of Entities
Most of the MIB objects defined in this MIB have, at most, a read- only MAX-ACCESS clause. This is a conscious decision by the working group to limit this MIB's scope. The second version of the Entity MIB allows a network administrator to configure some common attributes of physical components.2.11. Textual Convention Change
Version 1 of the Entity MIB contains three MIB objects defined with the (now obsolete) DisplayString TEXTUAL-CONVENTION. In version 2 of the Entity MIB, the syntax for these objects has been updated to use the (now preferred) SnmpAdminString TEXTUAL-CONVENTION. The ENTMIB working group (which was in charge of the document at that point) realized that this change is not strictly supported by SMIv2. In their judgment, the alternative of deprecating the old objects and defining new objects would have had a more adverse impact on backward compatibility and interoperability, given the particular semantics of these objects.2.12. MIB Structure
The Entity MIB contains five groups of MIB objects: - entityPhysical group Describes the physical entities managed by a single agent. - entityLogical group Describes the logical entities managed by a single agent. - entityMapping group Describes the associations between the physical entities, logical entities, interfaces, and non-interface ports managed by a single agent. - entityGeneral group Describes general system attributes shared by potentially all types of entities managed by a single agent. - entityNotifications group Contains status indication notifications.
2.12.1. entityPhysical Group
This group contains a single table to identify physical system components, called the entPhysicalTable. The entPhysicalTable contains one row per physical entity and must always contain at least one row for an "overall" physical entity, which should have an entPhysicalClass value of 'stack(11)', 'chassis(3)', or 'module(9)'. Each row is indexed by an arbitrary, small integer and contains a description and type of the physical entity. It also optionally contains the index number of another entPhysicalEntry, indicating a containment relationship between the two. Version 2 of the Entity MIB provides additional MIB objects for each physical entity. Some common read-only attributes have been added, as well as three writable string objects. - entPhysicalAlias This string can be used by an NMS as a non-volatile identifier for the physical component. Maintaining a non-volatile string for every physical component represented in the entPhysicalTable can be costly and unnecessary. An agent may algorithmically generate entPhysicalAlias strings for particular entries (e.g., based on the entPhysicalClass value). - entPhysicalAssetID This string is provided to store a user-specific asset identifier for removable physical components. In order to reduce the non- volatile storage needed by a particular agent, a network administrator should only assign asset identifiers to physical entities that are field-replaceable (i.e., not permanently contained within another physical entity). - entPhysicalSerialNum This string is provided to store a vendor-specific serial number string for physical components. This writable object is used when an agent cannot identify the serial numbers of all installed physical entities and a network administrator wishes to configure the non-volatile serial number strings manually (via an NMS application).
Version 3 of the Entity MIB provides two additional MIB objects for
each physical entity:
- entPhysicalMfgDate
This object contains the date of manufacturing of the managed
entity. If the manufacturing date is unknown or not supported the
object is not instantiated. The special value '0000000000000000'H
may also be returned in this case.
- entPhysicalUris
This object provides additional identification information about
the physical entity.
This object contains one or more Uniform Resource Identifiers
(URIs); therefore, the syntax of this object must conform to
[RFC3986], Section 3. Uniform Resource Names (URNs) [RFC3406] are
resource identifiers with the specific requirements for enabling
location-independent identification of a resource, as well as
longevity of reference. URNs are part of the larger URI family
with the specific goal of providing persistent naming of resources.
URI schemes and URN namespaces are registered by IANA (see
http://www.iana.org/assignments/uri-schemes and
http://www.iana.org/assignments/urn-namespaces).
For example, the entPhysicalUris object may be used to encode a URI
containing a Common Language Equipment Identifier (CLEI) URN for
the managed physical entity. The URN namespace for CLEIs is
defined in [RFC4152], and the CLEI format is defined in [T1.213]
and [T1.213a]. For example, an entPhysicalUris instance may have
the value of:
URN:CLEI:D4CE18B7AA
[RFC3986] and [RFC4152] identify this as a URI in the CLEI URN
namespace. The specific CLEI code, D4CE18B7AA, is based on the
example provided in [T1.213a].
Multiple URIs may be present and are separated by white space
characters. Leading and trailing white space characters are
ignored.
If no additional identification information is known about the
physical entity or supported, the object is not instantiated.
Version 4 of the Entity MIB module provides an additional MIB
object for each physical entity.
- entPhysicalUUID
This object provides an unique identification about the physical
entity. This object contains a globally unique identifier for the
physical entity with the format defined in RFC 4122 [RFC4122].
To support the existing implementations of ENTITY-MIB version 3
[RFC4133], entPhysicalUris object should be used to store the UUID
value of the physical entity as well in URN format. This
duplication of information enables backward compatibility. Note
that entPhysicalUris allows write access while entPhysicalUUID is
read-only.
2.12.2. entityLogical Group
This group contains a single table to identify logical entities,
called the entLogicalTable.
The entLogicalTable contains one row per logical entity. Each row is
indexed by an arbitrary, small integer and contains a name,
description, and type of the logical entity. It also contains
information to allow access to the MIB information for the logical
entity. This includes SNMP versions that use a community name (with
some form of implied context representation) and SNMP versions that
use the SNMP ARCH [RFC3411] method of context identification.
If an agent represents multiple logical entities with this MIB, then
this group must be implemented for all logical entities known to the
agent.
If an agent represents a single logical entity, or multiple logical
entities within a single naming scope, then implementation of this
group may be omitted by the agent.
2.12.3. entityMapping Group
This group contains three tables to identify associations between
different system components.
- entLPMappingTable
This table contains mappings between entLogicalIndex values
(logical entities) and entPhysicalIndex values (the physical
components supporting that entity). A logical entity can map to
more than one physical component, and more than one logical entity
can map to (share) the same physical component. If an agent
represents a single logical entity, or multiple logical entities
within a single naming scope, then implementation of this table may
be omitted by the agent.
- entAliasMappingTable
This table contains mappings between entLogicalIndex,
entPhysicalIndex pairs, and 'alias' object identifier values. This
allows resources managed with other MIB modules (e.g., repeater
ports, bridge ports, physical and logical interfaces) to be
identified in the physical entity hierarchy. Note that each alias
identifier is only relevant in a particular naming scope. If an
agent represents a single logical entity, or multiple logical
entities within a single naming scope, then implementation of this
table may be omitted by the agent.
- entPhysicalContainsTable
This table contains simple mappings between entPhysicalContainedIn
values for each container/'containee' relationship in the managed
system. The indexing of this table allows an NMS to quickly
discover the entPhysicalIndex values for all children of a given
physical entity.
2.12.4. entityGeneral Group
This group contains general information relating to the other object
groups.
At this time, the entGeneral group contains a single scalar object
(entLastChangeTime), which represents the value of sysUpTime when any
part of the Entity MIB configuration last changed.
2.12.5. entityNotifications Group
This group contains notification definitions relating to the overall
status of the Entity MIB instantiation.
2.13. Multiple Agents
Even though a primary motivation for this MIB is to represent the
multiple logical entities supported by a single agent, another
motivation is to represent multiple logical entities supported by
multiple agents (in the same "overall" physical entity). Indeed, it
is implicit in the SNMP architecture that the number of agents is
transparent to a network management station.
However, there is no agreement at this time as to the degree of
cooperation that should be expected for agent implementations.
Therefore, multiple agents within the same managed system are free to
implement the Entity MIB independently. (For more information, refer
to Section 2.9, "Multiple Instances of the Entity MIB".)
2.14. Changes Since RFC 2037
2.14.1. Textual Conventions
The PhysicalClass TC text has been clarified, and a new enumeration to support 'stackable' components has been added. The SnmpEngineIdOrNone TC has been added to support SNMPv3.2.14.2. New entPhysicalTable Objects
The entPhysicalHardwareRev, entPhysicalFirmwareRev, and entPhysicalSoftwareRev objects have been added for revision identification. The entPhysicalSerialNum, entPhysicalMfgName, entPhysicalModelName, and entPhysicalIsFRU objects have been added for better vendor identification for physical components. In the event the agent cannot identify this information, the entPhysicalSerialNum object can be set by a management station. The entPhysicalAlias and entPhysicalAssetID objects have been added for better user component identification. These objects are intended to be set by a management station and preserved by the agent across restarts.2.14.3. New entLogicalTable Objects
The entLogicalContextEngineID and entLogicalContextName objects have been added to provide an SNMP context for SNMPv3 access on behalf of a logical entity.2.14.4. Bug Fixes
A bug was fixed in the entLogicalCommunity object. The subrange was incorrect (1..255) and is now correct (0..255). The description clause has also been clarified. This object is now deprecated. The entLastChangeTime object description has been changed to generalize the events that cause an update to the last change timestamp. The syntax was changed from DisplayString to SnmpAdminString for the entPhysicalDescr, entPhysicalName, and entLogicalDescr objects.
2.15. Changes Since RFC 2737
2.15.1. Textual Conventions
The PhysicalIndexOrZero TC has been added to allow objects to reference an entPhysicalIndex value or zero. The PhysicalClass TC has been extended to support a new enumeration for central processing units.2.15.2. New Objects
The entPhysicalMfgDate object has been added to the entPhysicalTable to provide the date of manufacturing of the managed entity. The entPhysicalUris object has been added to the entPhysicalTable to provide additional identification information about the physical entity, such as a Common Language Equipment Identifier (CLEI) URN.2.15.3. Bug Fixes
The syntax was changed from INTEGER to Integer32 for the entPhysicalParentRelPos, entLogicalIndex, and entAliasLogicalIndexOrZero objects, and from INTEGER to PhysicalIndexOrZero for the entPhysicalContainedIn object.2.16. Changes Since RFC 4133
2.16.1. MIB Module Addition
Over time, there may be the need to add new enumerated values to the PhysicalClass TEXTUAL-CONVENTION. To allow for such additions without requiring re-issuing of this MIB module, a new MIB module called IANA-ENTITY-MIB that provides the IANA-maintained TEXTUAL- CONVENTION IANAPhysicalClass has been created. The PhysicalClass TC has been deprecated.2.16.2. Modification to Some of the MIB Objects
A new MIB object has been added to the entPhysicalTable, entPhysicalUUID. In comparison to entPhysicalUris, the new object is read-only and restricted to a fixed size to allow only for RFC 4122 [RFC4122] compliant values. The PhysicalClass TEXTUAL-CONVENTION was deprecated, and a new IANAPhysicalClass TC (maintained by IANA) has been created.
Two new MODULE-COMPLIANCE modules have been created: entity4Compliance for full compliance with version 4 of the Entity MIB, and entity4CRCompliance for devices with constrained resources like batteries that might require a limited number of objects to be supported (entPhysicalClass, entPhysicalName, and entPhysicalUUID).2.16.3. New TC for Universally Unique Identifier
A new TEXTUAL-CONVENTION, UUIDorZero, was created to represent a Universally Unique Identifier (UUID) with a syntax that conforms to [RFC4122], Section 4.1. Defining it as a TC will allow for future reuse in other MIB modules that will import the TC. This Textual Convention is included in the UUID-TC-MIB module.
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