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Network Working Group J. Case Request for Comments: 1443 SNMP Research, Inc. K. McCloghrie Hughes LAN Systems M. Rose Dover Beach Consulting, Inc. S. Waldbusser Carnegie Mellon University April 1993 Textual Conventions for version 2 of the Simple Network Management Protocol (SNMPv2) Status of this Memo This RFC specifes an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited. Table of Contents 1 Introduction .......................................... 2 1.1 A Note on Terminology ............................... 3 2 Definitions ........................................... 4 3 Mapping of the TEXTUAL-CONVENTION macro ............... 22 3.1 Mapping of the DISPLAY-HINT clause .................. 22 3.2 Mapping of the STATUS clause ........................ 24 3.3 Mapping of the DESCRIPTION clause ................... 24 3.4 Mapping of the REFERENCE clause ..................... 24 3.5 Mapping of the SYNTAX clause ........................ 24 4 Acknowledgements ...................................... 26 5 References ............................................ 30 6 Security Considerations ............................... 31 7 Authors' Addresses .................................... 31 Case, McCloghrie, Rose & Waldbusser [Page 1] RFC 1443 Textual Conventions for SNMPv2 April 1993 1. Introduction A network management system contains: several (potentially many) nodes, each with a processing entity, termed an agent, which has access to management instrumentation; at least one management station; and, a management protocol, used to convey management information between the agents and management stations. Operations of the protocol are carried out under an administrative framework which defines both authentication and authorization policies. Network management stations execute management applications which monitor and control network elements. Network elements are devices such as hosts, routers, terminal servers, etc., which are monitored and controlled through access to their management information. Management information is viewed as a collection of managed objects, residing in a virtual information store, termed the Management Information Base (MIB). Collections of related objects are defined in MIB modules. These modules are written using a subset of OSI's Abstract Syntax Notation One (ASN.1) [1], termed the Structure of Management Information (SMI) [2]. When designing a MIB module, it is often useful to new define types similar to those defined in the SMI. In comparison to a type defined in the SMI, each of these new types has a different name, a similar syntax, but a more precise semantics. These newly defined types are termed textual conventions, and are used for the convenience of humans reading the MIB module. It is the purpose of this document to define the initial set of textual conventions available to all MIB modules. Objects defined using a textual convention are always encoded by means of the rules that define their primitive type. However, textual conventions often have special semantics associated with them. As such, an ASN.1 macro, TEXTUAL- CONVENTION, is used to concisely convey the syntax and semantics of a textual convention. For all textual conventions defined in an information module, the name shall be unique and mnemonic, and shall not exceed 64 characters in length. All names used for the textual conventions defined in all "standard" information modules Case, McCloghrie, Rose & Waldbusser [Page 2] RFC 1443 Textual Conventions for SNMPv2 April 1993 shall be unique. 1.1. A Note on Terminology For the purpose of exposition, the original Internet-standard Network Management Framework, as described in RFCs 1155, 1157, and 1212, is termed the SNMP version 1 framework (SNMPv1). The current framework is termed the SNMP version 2 framework (SNMPv2). Case, McCloghrie, Rose & Waldbusser [Page 3] RFC 1443 Textual Conventions for SNMPv2 April 1993 2. Definitions SNMPv2-TC DEFINITIONS ::= BEGIN IMPORTS ObjectSyntax, Integer32, TimeTicks FROM SNMPv2-SMI; -- definition of textual conventions TEXTUAL-CONVENTION MACRO ::= BEGIN TYPE NOTATION ::= DisplayPart "STATUS" Status "DESCRIPTION" Text ReferPart "SYNTAX" type(Syntax) VALUE NOTATION ::= value(VALUE Syntax) DisplayPart ::= "DISPLAY-HINT" Text | empty Status ::= "current" | "deprecated" | "obsolete" ReferPart ::= "REFERENCE" Text | empty -- uses the NVT ASCII character set Text ::= """" string """" END Case, McCloghrie, Rose & Waldbusser [Page 4] RFC 1443 Textual Conventions for SNMPv2 April 1993 DisplayString ::= TEXTUAL-CONVENTION DISPLAY-HINT "255a" STATUS current DESCRIPTION "Represents textual information taken from the NVT ASCII character set, as defined in pages 4, 10-11 of RFC 854. Any object defined using this syntax may not exceed 255 characters in length." SYNTAX OCTET STRING (SIZE (0..255)) PhysAddress ::= TEXTUAL-CONVENTION DISPLAY-HINT "1x:" STATUS current DESCRIPTION "Represents media- or physical-level addresses." SYNTAX OCTET STRING MacAddress ::= TEXTUAL-CONVENTION DISPLAY-HINT "1x:" STATUS current DESCRIPTION "Represents an 802 MAC address represented in the 'canonical' order defined by IEEE 802.1a, i.e., as if it were transmitted least significant bit first, even though 802.5 (in contrast to other 802.x protocols) requires MAC addresses to be transmitted most significant bit first." SYNTAX OCTET STRING (SIZE (6)) TruthValue ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "Represents a boolean value." SYNTAX INTEGER { true(1), false(2) } Case, McCloghrie, Rose & Waldbusser [Page 5] RFC 1443 Textual Conventions for SNMPv2 April 1993 TestAndIncr ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "Represents integer-valued information used for atomic operations. When the management protocol is used to specify that an object instance having this syntax is to be modified, the new value supplied via the management protocol must precisely match the value presently held by the instance. If not, the management protocol set operation fails with an error of 'inconsistentValue'. Otherwise, if the current value is the maximum value of 2^31-1 (2147483647 decimal), then the value held by the instance is wrapped to zero; otherwise, the value held by the instance is incremented by one. (Note that regardless of whether the management protocol set operation succeeds, the variable-binding in the request and response PDUs are identical.) The value of the ACCESS clause for objects having this syntax is either 'read-write' or 'read- create'. When an instance of a columnar object having this syntax is created, any value may be supplied via the management protocol." SYNTAX INTEGER (0..2147483647) Case, McCloghrie, Rose & Waldbusser [Page 6] RFC 1443 Textual Conventions for SNMPv2 April 1993 AutonomousType ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "Represents an independently extensible type identification value. It may, for example, indicate a particular sub-tree with further MIB definitions, or define a particular type of protocol or hardware." SYNTAX OBJECT IDENTIFIER InstancePointer ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "A pointer to a specific instance of a conceptual row of a MIB table in the managed device. By convention, it is the name of the particular instance of the first columnar object in the conceptual row." SYNTAX OBJECT IDENTIFIER Case, McCloghrie, Rose & Waldbusser [Page 7] RFC 1443 Textual Conventions for SNMPv2 April 1993 RowStatus ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "The RowStatus textual convention is used to manage the creation and deletion of conceptual rows, and is used as the value of the SYNTAX clause for the status column of a conceptual row (as described in Section 7.7.1 of [2].) The status column has six defined values: - 'active', which indicates that the conceptual row is available for use by the managed device; - 'notInService', which indicates that the conceptual row exists in the agent, but is unavailable for use by the managed device (see NOTE below); - 'notReady', which indicates that the conceptual row exists in the agent, but is missing information necessary in order to be available for use by the managed device; - 'createAndGo', which is supplied by a management station wishing to create a new instance of a conceptual row and to have it available for use by the managed device; - 'createAndWait', which is supplied by a management station wishing to create a new instance of a conceptual row but not to have it available for use by the managed device; and, - 'destroy', which is supplied by a management station wishing to delete all of the instances associated with an existing conceptual row. Whereas five of the six values (all except 'notReady') may be specified in a management protocol set operation, only three values will be returned in response to a management protocol Case, McCloghrie, Rose & Waldbusser [Page 8] RFC 1443 Textual Conventions for SNMPv2 April 1993 retrieval operation: 'notReady', 'notInService' or 'active'. That is, when queried, an existing conceptual row has only three states: it is either available for use by the managed device (the status column has value 'active'); it is not available for use by the managed device, though the agent has sufficient information to make it so (the status column has value 'notInService'); or, it is not available for use by the managed device, because the agent lacks sufficient information (the status column has value 'notReady'). NOTE WELL This textual convention may be used for a MIB table, irrespective of whether the values of that table's conceptual rows are able to be modified while it is active, or whether its conceptual rows must be taken out of service in order to be modified. That is, it is the responsibility of the DESCRIPTION clause of the status column to specify whether the status column must be 'notInService' in order for the value of some other column of the same conceptual row to be modified. Case, McCloghrie, Rose & Waldbusser [Page 9] RFC 1443 Textual Conventions for SNMPv2 April 1993 To summarize the effect of having a conceptual row with a status column having a SYNTAX clause value of RowStatus, consider the following state diagram: STATE +--------------+-----------+-------------+------------- | A | B | C | D | |status col.|status column| |status column | is | is |status column ACTION |does not exist| notReady | notInService| is active --------------+--------------+-----------+-------------+------------- set status |noError ->D|inconsist- |inconsistent-|inconsistent- column to | or | entValue| Value| Value createAndGo |inconsistent- | | | | Value| | | --------------+--------------+-----------+-------------+------------- set status |noError see 1|inconsist- |inconsistent-|inconsistent- column to | or | entValue| Value| Value createAndWait |wrongValue | | | --------------+--------------+-----------+-------------+------------- set status |inconsistent- |inconsist- |noError |noError column to | Value| entValue| | active | | | | | | or | | | | | | | |see 2 ->D| ->D| ->D --------------+--------------+-----------+-------------+------------- set status |inconsistent- |inconsist- |noError |noError ->C column to | Value| entValue| | notInService | | | | | | or | | or | | | | | |see 3 ->C| ->C|wrongValue --------------+--------------+-----------+-------------+------------- set status |noError |noError |noError |noError column to | | | | destroy | ->A| ->A| ->A| ->A --------------+--------------+-----------+-------------+------------- set any other |see 4 |noError |noError |noError column to some| | | | value | ->A| see 1| ->C| ->D --------------+--------------+-----------+-------------+------------- Case, McCloghrie, Rose & Waldbusser [Page 10] RFC 1443 Textual Conventions for SNMPv2 April 1993 (1) goto B or C, depending on information available to the agent. (2) if other variable bindings included in the same PDU, provide values for all columns which are missing but required, then return noError and goto D. (3) if other variable bindings included in the same PDU, provide values for all columns which are missing but required, then return noError and goto C. (4) at the discretion of the agent, either noError or inconsistentValue may be returned. NOTE: Other processing of the set request may result in a response other than noError being returned, e.g., wrongValue, noCreation, etc. Conceptual Row Creation There are four potential interactions when creating a conceptual row: selecting an instance- identifier which is not in use; creating the conceptual row; initializing any objects for which the agent does not supply a default; and, making the conceptual row available for use by the managed device. Interaction 1: Selecting an Instance-Identifier The algorithm used to select an instance- identifier varies for each conceptual row. In some cases, the instance-identifier is semantically significant, e.g., the destination address of a route, and a management station selects the instance-identifier according to the semantics. In other cases, the instance-identifier is used solely to distinguish conceptual rows, and a management station without specific knowledge of the conceptual row might examine the instances Case, McCloghrie, Rose & Waldbusser [Page 11] RFC 1443 Textual Conventions for SNMPv2 April 1993 present in order to determine an unused instance- identifier. (This approach may be used, but it is often highly sub-optimal; however, it is also a questionable practice for a naive management station to attempt conceptual row creation.) Alternately, the MIB module which defines the conceptual row might provide one or more objects which provide assistance in determining an unused instance-identifier. For example, if the conceptual row is indexed by an integer-value, then an object having an integer-valued SYNTAX clause might be defined for such a purpose, allowing a management station to issue a management protocol retrieval operation. In order to avoid unnecessary collisions between competing management stations, 'adjacent' retrievals of this object should be different. Finally, the management station could select a pseudo-random number to use as the index. In the event that this index was already in use and an inconsistentValue was returned in response to the management protocol set operation, the management station should simply select a new pseudo-random number and retry the operation. A MIB designer should choose between the two latter algorithms based on the size of the table (and therefore the efficiency of each algorithm). For tables in which a large number of entries are expected, it is recommended that a MIB object be defined that returns an acceptable index for creation. For tables with small numbers of entries, it is recommended that the latter pseudo-random index mechanism be used. Interaction 2: Creating the Conceptual Row Once an unused instance-identifier has been selected, the management station determines if it wishes to create and activate the conceptual row in one transaction or in a negotiated set of interactions. Case, McCloghrie, Rose & Waldbusser [Page 12] RFC 1443 Textual Conventions for SNMPv2 April 1993 Interaction 2a: Creating and Activating the Conceptual Row The management station must first determine the column requirements, i.e., it must determine those columns for which it must or must not provide values. Depending on the complexity of the table and the management station's knowledge of the agent's capabilities, this determination can be made locally by the management station. Alternately, the management station issues a management protocol get operation to examine all columns in the conceptual row that it wishes to create. In response, for each column, there are three possible outcomes: - a value is returned, indicating that some other management station has already created this conceptual row. We return to interaction 1. - the exception 'noSuchInstance' is returned, indicating that the agent implements the object-type associated with this column, and that this column in at least one conceptual row would be accessible in the MIB view used by the retrieval were it to exist. For those columns to which the agent provides read- create access, the 'noSuchInstance' exception tells the management station that it should supply a value for this column when the conceptual row is to be created. - the exception 'noSuchObject' is returned, indicating that the agent does not implement the object-type associated with this column or that there is no conceptual row for which this column would be accessible in the MIB view used by the retrieval. As such, the management station can not issue any management protocol set operations to create an instance of this column. Once the column requirements have been determined, a management protocol set operation is accordingly Case, McCloghrie, Rose & Waldbusser [Page 13] RFC 1443 Textual Conventions for SNMPv2 April 1993 issued. This operation also sets the new instance of the status column to 'createAndGo'. When the agent processes the set operation, it verifies that it has sufficient information to make the conceptual row available for use by the managed device. The information available to the agent is provided by two sources: the management protocol set operation which creates the conceptual row, and, implementation-specific defaults supplied by the agent (note that an agent must provide implementation-specific defaults for at least those objects which it implements as read-only). If there is sufficient information available, then the conceptual row is created, a 'noError' response is returned, the status column is set to 'active', and no further interactions are necessary (i.e., interactions 3 and 4 are skipped). If there is insufficient information, then the conceptual row is not created, and the set operation fails with an error of 'inconsistentValue'. On this error, the management station can issue a management protocol retrieval operation to determine if this was because it failed to specify a value for a required column, or, because the selected instance of the status column already existed. In the latter case, we return to interaction 1. In the former case, the management station can re-issue the set operation with the additional information, or begin interaction 2 again using 'createAndWait' in order to negotiate creation of the conceptual row. Case, McCloghrie, Rose & Waldbusser [Page 14] RFC 1443 Textual Conventions for SNMPv2 April 1993 NOTE WELL Regardless of the method used to determine the column requirements, it is possible that the management station might deem a column necessary when, in fact, the agent will not allow that particular columnar instance to be created or written. In this case, the management protocol set operation will fail with an error such as 'noCreation' or 'notWritable'. In this case, the management station decides whether it needs to be able to set a value for that particular columnar instance. If not, the management station re-issues the management protocol set operation, but without setting a value for that particular columnar instance; otherwise, the management station aborts the row creation algorithm. Interaction 2b: Negotiating the Creation of the Conceptual Row The management station issues a management protocol set operation which sets the desired instance of the status column to 'createAndWait'. If the agent is unwilling to process a request of this sort, the set operation fails with an error of 'wrongValue'. (As a consequence, such an agent must be prepared to accept a single management protocol set operation, i.e., interaction 2a above, containing all of the columns indicated by its column requirements.) Otherwise, the conceptual row is created, a 'noError' response is returned, and the status column is immediately set to either 'notInService' or 'notReady', depending on whether it has sufficient information to make the conceptual row available for use by the managed device. If there is sufficient information available, then the status column is set to 'notInService'; otherwise, if there is insufficient information, then the status column is set to 'notReady'. Regardless, we proceed to interaction 3. Case, McCloghrie, Rose & Waldbusser [Page 15] RFC 1443 Textual Conventions for SNMPv2 April 1993 Interaction 3: Initializing non-defaulted Objects The management station must now determine the column requirements. It issues a management protocol get operation to examine all columns in the created conceptual row. In the response, for each column, there are three possible outcomes: - a value is returned, indicating that the agent implements the object-type associated with this column and had sufficient information to provide a value. For those columns to which the agent provides read- create access, a value return tells the management station that it may issue additional management protocol set operations, if it desires, in order to change the value associated with this column. - the exception 'noSuchInstance' is returned, indicating that the agent implements the object-type associated with this column, and that this column in at least one conceptual row would be accessible in the MIB view used by the retrieval were it to exist. However, the agent does not have sufficient information to provide a value, and until a value is provided, the conceptual row may not be made available for use by the managed device. For those columns to which the agent provides read-create access, the 'noSuchInstance' exception tells the management station that it must issue additional management protocol set operations, in order to provide a value associated with this column. - the exception 'noSuchObject' is returned, indicating that the agent does not implement the object-type associated with this column or that there is no conceptual row for which this column would be accessible in the MIB view used by the retrieval. As such, the management station can not issue any management protocol set operations to create Case, McCloghrie, Rose & Waldbusser [Page 16] RFC 1443 Textual Conventions for SNMPv2 April 1993 an instance of this column. If the value associated with the status column is 'notReady', then the management station must first deal with all 'noSuchInstance' columns, if any. Having done so, the value of the status column becomes 'notInService', and we proceed to interaction 4. Interaction 4: Making the Conceptual Row Available Once the management station is satisfied with the values associated with the columns of the conceptual row, it issues a management protocol set operation to set the status column to 'active'. If the agent has sufficient information to make the conceptual row available for use by the managed device, the management protocol set operation succeeds (a 'noError' response is returned). Otherwise, the management protocol set operation fails with an error of 'inconsistentValue'. NOTE WELL A conceptual row having a status column with value 'notInService' or 'notReady' is unavailable to the managed device. As such, it is possible for the managed device to create its own instances during the time between the management protocol set operation which sets the status column to 'createAndWait' and the management protocol set operation which sets the status column to 'active'. In this case, when the management protocol set operation is issued to set the status column to 'active', the values held in the agent supersede those used by the managed device. If the management station is prevented from setting the status column to 'active' (e.g., due to management station or network failure) the conceptual row will be left in the 'notInService' or 'notReady' state, consuming resources Case, McCloghrie, Rose & Waldbusser [Page 17] RFC 1443 Textual Conventions for SNMPv2 April 1993 indefinitely. The agent must detect conceptual rows that have been in either state for an abnormally long period of time and remove them. This period of time should be long enough to allow for human response time (including 'think time') between the creation of the conceptual row and the setting of the status to 'active'. It is suggested that this period be approximately 5 minutes in length. Conceptual Row Suspension When a conceptual row is 'active', the management station may issue a management protocol set operation which sets the instance of the status column to 'notInService'. If the agent is unwilling to do so, the set operation fails with an error of 'wrongValue'. Otherwise, the conceptual row is taken out of service, and a 'noError' response is returned. It is the responsibility of the the DESCRIPTION clause of the status column to indicate under what circumstances the status column should be taken out of service (e.g., in order for the value of some other column of the same conceptual row to be modified). Conceptual Row Deletion For deletion of conceptual rows, a management protocol set operation is issued which sets the instance of the status column to 'destroy'. This request may be made regardless of the current value of the status column (e.g., it is possible to delete conceptual rows which are either 'notReady', 'notInService' or 'active'.) If the operation succeeds, then all instances associated with the conceptual row are immediately removed." Case, McCloghrie, Rose & Waldbusser [Page 18] RFC 1443 Textual Conventions for SNMPv2 April 1993 SYNTAX INTEGER { -- the following two values are states: -- these values may be read or written active(1), notInService(2), -- the following value is a state: -- this value may be read, but not written notReady(3), -- the following three values are -- actions: these values may be written, -- but are never read createAndGo(4), createAndWait(5), destroy(6) } Case, McCloghrie, Rose & Waldbusser [Page 19] RFC 1443 Textual Conventions for SNMPv2 April 1993 TimeStamp ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "The value of MIB-II's sysUpTime object at which a specific occurrence happened. The specific occurrence must be defined in the description of any object defined using this type." SYNTAX TimeTicks TimeInterval ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION "A period of time, measured in units of 0.01 seconds." SYNTAX INTEGER (0..2147483647) Case, McCloghrie, Rose & Waldbusser [Page 20] RFC 1443 Textual Conventions for SNMPv2 April 1993 DateAndTime ::= TEXTUAL-CONVENTION DISPLAY-HINT "2d-1d-1d,1d:1d:1d.1d,1a1d:1d" STATUS current DESCRIPTION "A date-time specification. field octets contents range ----- ------ -------- ----- 1 1-2 year 0..65536 2 3 month 1..12 3 4 day 1..31 4 5 hour 0..23 5 6 minutes 0..59 6 7 seconds 0..60 (use 60 for leap-second) 7 8 deci-seconds 0..9 8 9 direction from UTC '+' / '-' 9 10 hours from UTC 0..11 10 11 minutes from UTC 0..59 For example, Tuesday May 26, 1992 at 1:30:15 PM EDT would be displayed as: 1992-5-26,13:30:15.0,-4:0 Note that if only local time is known, then timezone information (fields 8-10) is not present." SYNTAX OCTET STRING (SIZE (8 | 11)) END Case, McCloghrie, Rose & Waldbusser [Page 21] RFC 1443 Textual Conventions for SNMPv2 April 1993 3. Mapping of the TEXTUAL-CONVENTION macro The TEXTUAL-CONVENTION macro is used to convey the syntax and semantics associated with a textual convention. It should be noted that the expansion of the TEXTUAL-CONVENTION macro is something which conceptually happens during implementation and not during run-time. For all descriptors appearing in an information module, the descriptor shall be unique and mnemonic, and shall not exceed 64 characters in length. Further, the hyphen is not allowed as a character in the name of any textual convention. 3.1. Mapping of the DISPLAY-HINT clause The DISPLAY-HINT clause, which need not be present, gives a hint as to how the value of an instance of an object with the syntax defined using this textual convention might be displayed. The DISPLAY-HINT clause may only be present when the syntax has an underlying primitive type of INTEGER or OCTET STRING. When the syntax has an underlying primitive type of INTEGER, the hint consists of a single character suggesting a display format, either: 'x' for hexadecimal, 'd' for decimal, or 'o' for octal, or 'b' for binary. When the syntax has an underlying primitive type of OCTET STRING, the hint consists of one or more octet-format specifications. Each specification consists of five parts, with each part using and removing zero or more of the next octets from the value and producing the next zero or more characters to be displayed. The octets within the value are processed in order of significance, most significant first. The five parts of a octet-format specification are: (1) the (optional) repeat indicator; if present, this part is a '*', and indicates that the current octet of the value is to be used as the repeat count. The repeat count is an unsigned integer (which may be zero) which specifies how many times the remainder of this octet-format specification should be successively applied. If the repeat indicator is not present, the repeat count is one. Case, McCloghrie, Rose & Waldbusser [Page 22] RFC 1443 Textual Conventions for SNMPv2 April 1993 (2) the octet length: one or more decimal digits specifying the number of octets of the value to be used and formatted by this octet-specification. Note that the octet length can be zero. If less than this number of octets remain in the value, then the lesser number of octets are used. (3) the display format, either: 'x' for hexadecimal, 'd' for decimal, 'o' for octal, or 'a' for ascii. If the octet length part is greater than one, and the display format part refers to a numeric format, then network-byte ordering (big-endian encoding) is used interpreting the octets in the value. (4) the (optional) display separator character; if present, this part is a single character which is produced for display after each application of this octet- specification; however, this character is not produced for display if it would be immediately followed by the display of the repeat terminator character for this octet-specification. This character can be any character other than a decimal digit and a '*'. (5) the (optional) repeat terminator character, which can be present only if the display separator character is present and this octet-specification begins with a repeat indicator; if present, this part is a single character which is produced after all the zero or more repeated applications (as given by the repeat count) of this octet-specification. This character can be any character other than a decimal digit and a '*'. Output of a display separator character or a repeat terminator character is suppressed if it would occur as the last character of the display. If the octets of the value are exhausted before all the octet-format specification have been used, then the excess specifications are ignored. If additional octets remain in the value after interpreting all the octet-format specifications, then the last octet-format specification is re-interpreted to process the additional octets, until no octets remain in the value. Case, McCloghrie, Rose & Waldbusser [Page 23] RFC 1443 Textual Conventions for SNMPv2 April 1993 3.2. Mapping of the STATUS clause The STATUS clause, which must be present, indicates whether this definition is current or historic. The values "current", and "obsolete" are self-explanatory. The "deprecated" value indicates that the textual convention is obsolete, but that an implementor may wish to support that object to foster interoperability with older implementations. 3.3. Mapping of the DESCRIPTION clause The DESCRIPTION clause, which must be present, contains a textual definition of the textual convention, which provides all semantic definitions necessary for implementation, and should embody any information which would otherwise be communicated in any ASN.1 commentary annotations associated with the object. Note that, in order to conform to the ASN.1 syntax, the entire value of this clause must be enclosed in double quotation marks, and therefore cannot itself contain double quotation marks, although the value may be multi-line. 3.4. Mapping of the REFERENCE clause The REFERENCE clause, which need not be present, contains a textual cross-reference to a related item defined in some other published work. 3.5. Mapping of the SYNTAX clause The SYNTAX clause, which must be present, defines abstract data structure corresponding to the textual convention. The data structure must be one of the alternatives defined in the ObjectSyntax CHOICE [2]. Full ASN.1 sub-typing is allowed, as appropriate to the underingly ASN.1 type, primarily as an aid to implementors in understanding the meaning of the textual convention. Of course, sub-typing is not allowed for textual conventions derived from either the Counter32 or Counter64 types, but is Case, McCloghrie, Rose & Waldbusser [Page 24] RFC 1443 Textual Conventions for SNMPv2 April 1993 allowed for textual conventions derived from the Gauge32 type. Case, McCloghrie, Rose & Waldbusser [Page 25] RFC 1443 Textual Conventions for SNMPv2 April 1993 4. Acknowledgements PhysAddress (and textual conventions) originated in RFC 1213. MacAddress originated in RFCs 1230 and 1231. TruthValue originated in RFC 1253. AutonomousType and InstancePointer originated in RFC 1316. RowStatus originated in RFC 1271. A special thanks to Bancroft Scott of Open Systems Solutions, Inc., for helping in the definition of the TEXTUAL-CONVENTIONS macro. Finally, the comments of the SNMP version 2 working group are gratefully acknowledged: Beth Adams, Network Management Forum Steve Alexander, INTERACTIVE Systems Corporation David Arneson, Cabletron Systems Toshiya Asaba Fred Baker, ACC Jim Barnes, Xylogics, Inc. Brian Bataille Andy Bierman, SynOptics Communications, Inc. Uri Blumenthal, IBM Corporation Fred Bohle, Interlink Jack Brown Theodore Brunner, Bellcore Stephen F. Bush, GE Information Services Jeffrey D. Case, University of Tennessee, Knoxville John Chang, IBM Corporation Szusin Chen, Sun Microsystems Robert Ching Chris Chiotasso, Ungermann-Bass Bobby A. Clay, NASA/Boeing John Cooke, Chipcom Tracy Cox, Bellcore Juan Cruz, Datability, Inc. David Cullerot, Cabletron Systems Cathy Cunningham, Microcom James R. (Chuck) Davin, Bellcore Michael Davis, Clearpoint Case, McCloghrie, Rose & Waldbusser [Page 26] RFC 1443 Textual Conventions for SNMPv2 April 1993 Mike Davison, FiberCom Cynthia DellaTorre, MITRE Taso N. Devetzis, Bellcore Manual Diaz, DAVID Systems, Inc. Jon Dreyer, Sun Microsystems David Engel, Optical Data Systems Mike Erlinger, Lexcel Roger Fajman, NIH Daniel Fauvarque, Sun Microsystems Karen Frisa, CMU Shari Galitzer, MITRE Shawn Gallagher, Digital Equipment Corporation Richard Graveman, Bellcore Maria Greene, Xyplex, Inc. Michel Guittet, Apple Robert Gutierrez, NASA Bill Hagerty, Cabletron Systems Gary W. Haney, Martin Marietta Energy Systems Patrick Hanil, Nokia Telecommunications Matt Hecht, SNMP Research, Inc. Edward A. Heiner, Jr., Synernetics Inc. Susan E. Hicks, Martin Marietta Energy Systems Geral Holzhauer, Apple John Hopprich, DAVID Systems, Inc. Jeff Hughes, Hewlett-Packard Robin Iddon, Axon Networks, Inc. David Itusak Kevin M. Jackson, Concord Communications, Inc. Ole J. Jacobsen, Interop Company Ronald Jacoby, Silicon Graphics, Inc. Satish Joshi, SynOptics Communications, Inc. Frank Kastenholz, FTP Software Mark Kepke, Hewlett-Packard Ken Key, SNMP Research, Inc. Zbiginew Kielczewski, Eicon Jongyeoi Kim Andrew Knutsen, The Santa Cruz Operation Michael L. Kornegay, VisiSoft Deirdre C. Kostik, Bellcore Cheryl Krupczak, Georgia Tech Mark S. Lewis, Telebit David Lin David Lindemulder, AT&T/NCR Ben Lisowski, Sprint David Liu, Bell-Northern Research Case, McCloghrie, Rose & Waldbusser [Page 27] RFC 1443 Textual Conventions for SNMPv2 April 1993 John Lunny, The Wollongong Group Robert C. Lushbaugh Martin, Marietta Energy Systems Michael Luufer, BBN Carl Madison, Star-Tek, Inc. Keith McCloghrie, Hughes LAN Systems Evan McGinnis, 3Com Corporation Bill McKenzie, IBM Corporation Donna McMaster, SynOptics Communications, Inc. John Medicke, IBM Corporation Doug Miller, Telebit Dave Minnich, FiberCom Mohammad Mirhakkak, MITRE Rohit Mital, Protools George Mouradian, AT&T Bell Labs Patrick Mullaney, Cabletron Systems Dan Myers, 3Com Corporation Rina Nathaniel, Rad Network Devices Ltd. Hien V. Nguyen, Sprint Mo Nikain Tom Nisbet William B. Norton, MERIT Steve Onishi, Wellfleet Communications, Inc. David T. Perkins, SynOptics Communications, Inc. Carl Powell, BBN Ilan Raab, SynOptics Communications, Inc. Richard Ramons, AT&T Venkat D. Rangan, Metric Network Systems, Inc. Louise Reingold, Sprint Sam Roberts, Farallon Computing, Inc. Kary Robertson, Concord Communications, Inc. Dan Romascanu, Lannet Data Communications Ltd. Marshall T. Rose, Dover Beach Consulting, Inc. Shawn A. Routhier, Epilogue Technology Corporation Chris Rozman Asaf Rubissa, Fibronics Jon Saperia, Digital Equipment Corporation Michael Sapich Mike Scanlon, Interlan Sam Schaen, MITRE John Seligson, Ultra Network Technologies Paul A. Serice, Corporation for Open Systems Chris Shaw, Banyan Systems Timon Sloane Robert Snyder, Cisco Systems Joo Young Song Case, McCloghrie, Rose & Waldbusser [Page 28] RFC 1443 Textual Conventions for SNMPv2 April 1993 Roy Spitier, Sprint Einar Stefferud, Network Management Associates John Stephens, Cayman Systems, Inc. Robert L. Stewart, Xyplex, Inc. (chair) Kaj Tesink, Bellcore Dean Throop, Data General Ahmet Tuncay, France Telecom-CNET Maurice Turcotte, Racal Datacom Warren Vik, INTERACTIVE Systems Corporation Yannis Viniotis Steven L. Waldbusser, Carnegie Mellon Universitty Timothy M. Walden, ACC Alice Wang, Sun Microsystems James Watt, Newbridge Luanne Waul, Timeplex Donald E. Westlake III, Digital Equipment Corporation Gerry White Bert Wijnen, IBM Corporation Peter Wilson, 3Com Corporation Steven Wong, Digital Equipment Corporation Randy Worzella, IBM Corporation Daniel Woycke, MITRE Honda Wu Jeff Yarnell, Protools Chris Young, Cabletron Kiho Yum, 3Com Corporation Case, McCloghrie, Rose & Waldbusser [Page 29] RFC 1443 Textual Conventions for SNMPv2 April 1993 5. References [1] Information processing systems - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1), International Organization for Standardization. International Standard 8824, (December, 1987). [2] Case, J., McCloghrie, K., Rose, M., and Waldbusser, S., "Structure of Management Information for version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1442, SNMP Research, Inc., Hughes LAN Systems, Dover Beach Consulting, Inc., Carnegie Mellon University, April 1993. Case, McCloghrie, Rose & Waldbusser [Page 30] RFC 1443 Textual Conventions for SNMPv2 April 1993 6. Security Considerations Security issues are not discussed in this memo. 7. Authors' Addresses Jeffrey D. Case SNMP Research, Inc. 3001 Kimberlin Heights Rd. Knoxville, TN 37920-9716 US Phone: +1 615 573 1434 Email: case@snmp.com Keith McCloghrie Hughes LAN Systems 1225 Charleston Road Mountain View, CA 94043 US Phone: +1 415 966 7934 Email: kzm@hls.com Marshall T. Rose Dover Beach Consulting, Inc. 420 Whisman Court Mountain View, CA 94043-2186 US Phone: +1 415 968 1052 Email: mrose@dbc.mtview.ca.us Steven Waldbusser Carnegie Mellon University 4910 Forbes Ave Pittsburgh, PA 15213 US Phone: +1 412 268 6628 Email: waldbusser@cmu.edu Case, McCloghrie, Rose & Waldbusser [Page 31]