Network Working Group J. Schoenwaelder Internet-Draft TU Braunschweig Expires April 2000 22. October 1999 Operation-Types for SMIv2 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Distribution of this document is unlimited. Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. Abstract This document defines an extension for the SMIv2 which allows to define operations. Operations can among other things be used to define install/remove operations on conceptual MIB tables. This can result in simpler and more efficient implementations of configuration management systems. Warning This document has not been written in order to specify a solution. Instead, this document has been written to stimulate (controversial) discussions within the NMRG (and elsewhere). Schoenwaelder [Page 1] Internet-Draft Operation-Types for SMIv2 October 1999 Table of Contents 1 Introduction ................................................. 3 2 Definitions .................................................. 4 3 Mapping of the OPERATION-TYPE macro .......................... 5 3.1 Mapping of the ARGUMENTS clause ............................ 6 3.2 Mapping of the ERRORS clause ............................... 6 3.3 Mapping of the RESULTS clause .............................. 6 3.4 Mapping of the CREATES clause .............................. 6 3.5 Mapping of the DELETES clause .............................. 7 3.6 Mapping of the STATUS clause ............................... 7 3.7 Mapping of the DESCRIPTION clause .......................... 7 3.8 Mapping of the REFERENCE clause ............................ 7 3.9 Mapping of the OPERATION-TYPE value ........................ 8 3.10 Usage Examples ............................................ 9 4 Revising Operation Type Definitions .......................... 10 5 Open Issues .................................................. 11 6 Security Considerations ...................................... 12 7 Authors' Address ............................................. 12 8 References ................................................... 12 9 Full Copyright Statement ..................................... 13 Schoenwaelder [Page 2] Internet-Draft Operation-Types for SMIv2 October 1999 1. Introduction Management information is viewed as a collection of managed objects, residing in a virtual information store, termed the Management Information Base (MIB). Collections of related objects are defined in MIB modules. These modules are written using an adapted subset of OSI's Abstract Syntax Notation One, ASN.1 (1988) [ASN1], termed the Structure of Management Information (SMI) [RFC2578]. When designing a MIB module, it is often useful to define operations on collections of related objects. Operations go beyond what is available with normal read and write access to individual objects: - Operations have a defined name which makes it easier to communicate complex operations on MIB objects. - Operations have well defined input and output parameters with ordering constraints which reduces variability and simplifies implementations. - Operations can raise operation specific errors during their invocation. - Operations define whether they create or delete rows in conceptual tables. - The defined signatures of operations allow to implement tools that generate APIs and stub procedures for command responder as well as command generator applications. Operations can be defined on arbitrary collections of objects. However, it is expected that operations will normally be defined only on closely related objects (e.g. objects contained in a single conceptual row) since this simplifies implementation in extensible agent environments. Schoenwaelder [Page 3] Internet-Draft Operation-Types for SMIv2 October 1999 2. Definitions SNMPv2-OPS DEFINITIONS ::= BEGIN IMPORTS ObjectName FROM SNMPv2-SMI; OPERATION-TYPE MACRO ::= BEGIN TYPE NOTATION ::= ArgumentsPart ErrorsPart ResultsPart CreatesPart DeletesPart "STATUS" Status "DESCRIPTION" Text ReferPart VALUE NOTATION ::= value(VALUE ObjectName) ArgumentsPart ::= "ARGUMENTS" "{" Parameters "}" | empty ErrorsPart ::= "ERRORS" "{" NamedNumbers "}" -- INTEGER enumerations | empty ResultsPart ::= "RESULTS" "{" Parameters "}" | empty CreatesPart ::= "CREATES" "{" Rows "}" | empty DeletesPart ::= "DELETES" "{" Rows "}" | empty Parameters ::= Parameter | Parameters "," Parameter Parameter ::= identifier Syntax Syntax ::= type Schoenwaelder [Page 4] Internet-Draft Operation-Types for SMIv2 October 1999 | "BITS" "{" NamedBits "}" NamedBits ::= NamedBit | NamedBits "," NamedBit NamedBit ::= identifier "(" number ")" -- number is nonnegative NamedNumbers ::= NamedNumber | NamedNumbers "," NamedNumber NamedNumber ::= identifier "(" number ")" Rows ::= Row | Rows "," Row Row ::= value(ObjectName) Status ::= "current" | "deprecated" | "obsolete" ReferPart ::= "REFERENCE" Text | empty -- a character string as defined in [RFC2578] Text ::= value(IA5String) END END 3. Mapping of the OPERATION-TYPE macro The OPERATION-TYPE macro is used to define an operation. An operation has a defined signature which consists of the operation name, the types and names of the arguments, the types and names of the results and the operation specific errors that can occur while invoking the operation. Operations can create or delete rows in conceptual tables. The optional CREATES and DELETES clauses of the OPERATION-TYPE macro identify the tables in which rows are created or deleted. It should be noted that the expansion of the OPERATION-TYPE macro is something which conceptually happens during implementation and not during run- time. Schoenwaelder [Page 5] Internet-Draft Operation-Types for SMIv2 October 1999 3.1. Mapping of the ARGUMENTS clause The ARGUMENTS clause, which need not be present, defines an ordered sequence of the types and names that form the arguments of the operation. The operation's DESCRIPTION clause must specify the information/meaning conveyed by each argument listed in the ARGUMENTS clause. The name of an argument must consist of one or more letters or digits, and its initial character must be a lower-case letter. Argument names must be unique across all arguments and results defined in a single invocation of an OPERATION-TYPE macro. 3.2. Mapping of the ERRORS clause The ERRORS clause, which need not be present, defines the operation specific errors that can occur while invoking the operation. Errors are represented as integer-valued named-number enumerations. Note that although it is recommended that error values start at 1 and be numbered contiguously, any valid value for an INTEGER in the range (1 to 2147483647 decimal) is allowed for an error value and, further, error values need not be contiguously assigned. The no error case does not need to be enumerated. A label for a named-number enumeration within the ERRORS clause must consist of one or more letters or digits, up to a maximum of 64 characters, and the initial character must be a lower-case letter. (However, labels longer than 32 characters are not recommended.) Note that hyphens are not allowed. 3.3. Mapping of the RESULTS clause The RESULTS clause, which need not be present, defines an ordered sequence of the types and names that form the results of the operation. The operation's DESCRIPTION clause must specify the information/meaning conveyed by each result listed in the RESULTS clause. The name of a result parameter must consist of one or more letters or digits, and its initial character must be a lower-case letter. Result names must be unique across all arguments and results defined in a single invocation of an OPERATION-TYPE macro. 3.4. Mapping of the CREATES clause The CREATES clause, which need not be present, defines the conceptual table rows that will be created by invoking the operation. Rows are Schoenwaelder [Page 6] Internet-Draft Operation-Types for SMIv2 October 1999 identified by the descriptor which refers to a conceptual row, i.e. has a syntax which resolves to a SEQUENCE containing columnar objects. The operation's DESCRIPTION clause must specify how an implementation determines the instance identifier(s) of the row(s) created by the operation. 3.5. Mapping of the DELETES clause The DELETES clause, which need not be present, defines the conceptual table rows that will be deleted by invoking the operation. Rows are identified by the descriptor which refers to a conceptual row, i.e. has a syntax which resolves to a SEQUENCE containing columnar objects. The operation's DESCRIPTION clause must specify how an implementation determines the instance identifier(s) of the row(s) deleted by the operation. 3.6. Mapping of the STATUS clause The STATUS clause, which must be present, indicates whether this definition is current or historic. The value "current" means that the definition is current and valid. The value "obsolete" means the definition is obsolete and should not be implemented and/or can be removed if previously implemented. While the value "deprecated" also indicates an obsolete definition, it permits new/continued implementation in order to foster interoperability with older/existing implementations. 3.7. Mapping of the DESCRIPTION clause The DESCRIPTION clause, which must be present, contains a textual definition of the operation type which provides all semantic definitions necessary for implementation and use, and should embody any information which would otherwise be communicated in any ASN.1 commentary annotations associated with the object. 3.8. Mapping of the REFERENCE clause The REFERENCE clause, which need not be present, contains a textual cross-reference to some other document, either another information module or some other document which provides additional information relevant to this definition. Schoenwaelder [Page 7] Internet-Draft Operation-Types for SMIv2 October 1999 3.9. Mapping of the OPERATION-TYPE value The value of an invocation of the OPERATION-TYPE macro is the name of the operation type, which is an OBJECT IDENTIFIER, an administratively assigned name. Schoenwaelder [Page 8] Internet-Draft Operation-Types for SMIv2 October 1999 3.10. Usage Examples The first example shows an operation which creates or allocates a new entry in the vacmSecurityToGroupTable [RFC2575]. vacmCreateSTGEntry OPERATION-TYPE ARGUMENTS { securityModel SnmpSecurityModel (1..2147483647), securityName SnmpAdminString (SIZE(1..32)), groupName SnmpAdminString (SIZE(1..32)), storageType StorageType { volatile(2), nonVolatile(3) } } ERRORS { rowAlreadyExists(1) } CREATES { vacmSecurityToGroupEntry } DESCRIPTION "This operation installs and activates a new entry in the vacmSecurityToGroupTable. The new entry is identified by the securityModel and securityName parameters. Implementations that do not support the creation of new rows but which have permanent rows that are currently notInService are expected to allocate and activate one of these notInService rows. The value of the storageType parameter is ignored in this case. The rowAlreadyExists(1) error is returned if the row identified by securityModel and securityName already exists." ::= { vacmOperations 1 } The second example shows the definition of an operation that can be used to remove a row from the vacmSecurityToGroupTable. vacmRemoveSTGEntry OPERATION-TYPE ARGUMENTS { securityModel SnmpSecurityModel (1..2147483647), securityName SnmpAdminString (SIZE(1..32)) } ERRORS { rowDoesNotExist(1), readOnlyStorageType(2) } DELETES { vacmSecurityToGroupEntry } DESCRIPTION "This operation removes an entry identified by the securityModel and securityName parameters from the vacmSecurityToGroupTable. Entries which can not be removed (e.g. the value Schoenwaelder [Page 9] Internet-Draft Operation-Types for SMIv2 October 1999 of vacmSecurityToGroupStorageType is permanent) will be disabled by changing the RowStatus column vacmSecurityToGroupStatus to notInService. The rowDoesNotExist(1) error is returned if the row identified by the securityModel and securityName parameters does not exist. The readOnlyStorageType(2) error is returned if the row cannot be removed or disabled since it is stored in ROM." ::= { vacmOperations 2 } The third example shows the definition of an operation which deletes zero or more entries from the vacmSecurityToGroupTable. The argument of the operation contains a pattern which is matched against all vacmGroupName instances. vacmRemoveSTGEntryByGroupName OPERATION-TYPE ARGUMENTS { pattern SnmpAdminString (SIZE(1..32)) } RESULTS { numberRemoved Unsigned32 } DELETES { vacmSecurityToGroupEntry } DESCRIPTION "This operation removes all entries from the vacmSecurityToGroupTable where the vacmGroupName matches the pattern parameter. The comparison is an exact match where each byte must match exactly (no wildcarding). Entries that can not be removed (e.g. the value of vacmSecurityToGroupStorageType is permanent) will be disabled by changing the RowStatus column vacmSecurityToGroupStatus to notInService. Entries that can not be disabled (e.g. the value of vacmSecurityToGroupStorageType is readOnly) will be ignored. The operation returns the number of entries that were actually removed from or disabled in the vacmSecurityToGroupTable." ::= { vacmOperations 3 } 4. Revising Operation Type Definitions An operation definition may be revised in any of the following ways: (1) The ERRORS clause may have new enumerations added. Schoenwaelder [Page 10] Internet-Draft Operation-Types for SMIv2 October 1999 (2) A STATUS clause value of "current" may be revised as "deprecated" or "obsolete". Similarly, a STATUS clause value of "deprecated" may be revised as "obsolete". When making such a change, the DESCRIPTION clause should be updated to explain the rationale. (3) A REFERENCE clause may be added or updated. (4) Clarifications and additional information may be included in the DESCRIPTION clause. (5) Entirely new operations may be defined, named with previously unassigned OBJECT IDENTIFIER values. Otherwise, if the semantics of any previously defined operation are changed (i.e., if a non-editorial change is made to any clause other than those specifically allowed above), then the OBJECT IDENTIFIER value associated with that operation must also be changed. Note that changing the descriptor associated with an existing operation is considered a semantic change, as these strings may be used in fielded implementations and APIs derived from the operation type definition. 5. Open Issues 1. The current version supports three different ways to define a parameter. There are valid reasons for all three alternatives. First, there is a need to have input parameters for operations that do not exactly match an existing object. It would be a burdon to require that all parameters be defined as objects since many would end up with a write-only access (which does not exist) anyway. Second, there is a need to refer to types that are implicitely defined as part of an object definition. A good example is ifAdminStatus, which is an implicitly defined enumeration without a proper name. Third, it is necessary to assign names to parameters in order to solve problems when a single type of implicit type shows up in a arguments or result clause more than once. 2. It is currently not allowed to return vectors as a result. There are several issues to consider in this case. The most important reason to allow vectors is that you can have an operation which itself returns a sequence of operations to recreate the current Schoenwaelder [Page 11] Internet-Draft Operation-Types for SMIv2 October 1999 state. But the details how this would work are not yet fully worked out. 6. Security Considerations This document defines the means to define operations on collections of MIB objects. The definition of operations has no direct security impact on the Internet. 7. Authors' Address Juergen Schoenwaelder TU Braunschweig Bueltenweg 74/75 38106 Braunschweig Germany Phone: +49 531 391-3283 EMail: schoenw@ibr.cs.tu-bs.de 8. References [ASN1] Information processing systems - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1), International Organization for Standardization. International Standard 8824, December, 1987 [RFC2575] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)", RFC 2575, April 1999 [RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M., and S. Waldbusser, "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999 [RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M., and S. Waldbusser, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999 Schoenwaelder [Page 12] Internet-Draft Operation-Types for SMIv2 October 1999 9. Full Copyright Statement Copyright (C) The Internet Society (1999). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Schoenwaelder [Page 13]