module IRTF-NMRG-SMING-TYPES {

//

// $RCSfile: IRTF-NMRG-SMING-TYPES,v $

// $Revision: 7606 $

// $Author: schoenw $

// $Date: 2008-01-22 13:38:03 +0100 (Tue, 22 Jan 2008) $

//

    organization    "IRTF Network Management Research Group (NMRG),

                     Network Management Group, TU Braunschweig";

    contact         "        Frank Strauss

                     Postal: TU Braunschweig

                             Bueltenweg 74/75

                             38106 Braunschweig

                             Germany

                      Phone: +49 531 391-3266

                      EMail: strauss@ibr.cs.tu-bs.de";

    description     "Core type definitions for SMIng.";

    revision {

        date        "2000-10-19";

        description "Special semantics and default value of 8 or 11

		     zero bytes for the DateAndTime type.";

    };

    revision {

        date        "2000-02-13";

        description "SMIng grammar dropped module identity objects.";

    };

    revision {

        date        "1999-05-07";

        description "Initial Revision.";

    };

    typedef Gauge32 {

        type        Unsigned32;

        description

           "The Gauge32 type represents a non-negative integer,

            which may increase or decrease, but shall never

            exceed a maximum value, nor fall below a minimum

            value.  The maximum value can not be greater than

            2^32-1 (4294967295 decimal), and the minimum value

            can not be smaller than 0.  The value of a Gauge32

            has its maximum value whenever the information

            being modeled is greater than or equal to its

            maximum value, and has its minimum value whenever

            the information being modeled is smaller than or

            equal to its minimum value.  If the information

            being modeled subsequently decreases below

            (increases above) the maximum (minimum) value, the

            Gauge32 also decreases (increases).  (Note that

            despite of the use of the term `latched' in the

            original definition of this type, it does not

            become `stuck' at its maximum or minimum value.)";

        reference

           "RFC 2578, Sections 2. and 7.1.7.";

    };

    typedef Counter32 {

        type        Unsigned32;

        description

           "The Counter32 type represents a non-negative integer

            which monotonically increases until it reaches a

            maximum value of 2^32-1 (4294967295 decimal), when it

            wraps around and starts increasing again from zero.

            Counters have no defined `initial' value, and thus, a

            single value of a Counter has (in general) no

            information content.  Discontinuities in the

            monotonically increasing value normally occur at

            re-initialization of the management system, and at

            other times as specified in the description of an

            object using this type.  If such other times can

            occur, for example, the creation of an object

            instance at times other than re-initialization, then

            a corresponding object should be defined, with an

            appropriate type, to indicate the last discontinuity.

            Examples of appropriate types include: TimeStamp,

            DateAndTime or TimeTicks (other types defined in this

            module).

            The value of the access statement for objects with a

            type value of Counter32 should be either `readonly'

            or `notifyonly'.

            A default statement should not be used for objects

            with a type value of Counter32.";

        reference

           "RFC 2578, Sections 2. and 7.1.6.";

    };

    typedef Gauge64 {

        type        Unsigned64;

        description

           "The Gauge64 type represents a non-negative integer,

            which may increase or decrease, but shall never

            exceed a maximum value, nor fall below a minimum

            value.  The maximum value can not be greater than

            2^64-1 (18446744073709551615), and the minimum value

            can not be smaller than 0.  The value of a Gauge64

            has its maximum value whenever the information

            being modeled is greater than or equal to its

            maximum value, and has its minimum value whenever

            the information being modeled is smaller than or

            equal to its minimum value.  If the information

            being modeled subsequently decreases below

            (increases above) the maximum (minimum) value, the

            Gauge64 also decreases (increases).  (Note that

            despite of the use of the term `latched' in the

            original definition of this type, it does not

            become `stuck' at its maximum or minimum value.)";

    };

    typedef Counter64 {

        type        Unsigned64;

        description

           "The Counter64 type represents a non-negative integer

            which monotonically increases until it reaches a

            maximum value of 2^64-1 (18446744073709551615), when

            it wraps around and starts increasing again from zero.

            Counters have no defined `initial' value, and thus, a

            single value of a Counter has (in general) no

            information content.  Discontinuities in the

            monotonically increasing value normally occur at

            re-initialization of the management system, and at

            other times as specified in the description of an

            object using this type.  If such other times can

            occur, for example, the creation of an object

            instance at times other than re-initialization, then

            a corresponding object should be defined, with an

            appropriate type, to indicate the last discontinuity.

            Examples of appropriate types include: TimeStamp,

            DateAndTime or TimeTicks (other types defined in this

            module).

            The value of the access statement for objects with a

            type value of Counter64 should be either `readonly'

            or `notifyonly'.

            A default statement should not be used for objects

            with a type value of Counter64.";

        reference

           "RFC 2578, Sections 2. and 7.1.10.";

    };

    typedef Opaque {

        type        OctetString;

        description

           "The Opaque type is provided solely for

            backward-compatibility, and shall not be used for

            newly-defined object types.

            The Opaque type supports the capability to pass

            arbitrary ASN.1 syntax.  A value is encoded using

            the ASN.1 Basic Encoding Rules into a string of

            octets.  This, in turn, is encoded as an

            OctetString, in effect `double-wrapping' the

            original ASN.1 value.

            Note that a conforming implementation need only be

            able to accept and recognize opaquely-encoded data.

            It need not be able to unwrap the data and then

            interpret its contents.

            A requirement on `standard' MIB modules is that no

            object may have a type value of Opaque.";

        reference

           "RFC 2578, Sections 2. and 7.1.9.";

    };

    typedef IpAddress {

        type        OctetString (4);

        status      deprecated;

        description

           "******* THIS TYPE DEFINITION IS DEPRECATED *******

            The IpAddress type represents a 32-bit internet

            IPv4 address.  It is represented as an OctetString

            of length 4, in network byte-order.

            Note that the IpAddress type is present for

            historical reasons. IPv4 and IPv6 addresses should

            be represented using the IpAddr type. Generic

            Network addresses should be represented using a

            pair of TDomain and TAddress types (all defined in

            this module).";

        reference

           "RFC 2578, Sections 2. and 7.1.5.";

    };

    typedef TimeTicks {

        type        Unsigned32;

        description

           "The TimeTicks type represents a non-negative

            integer which represents the time, modulo 2^32

            (4294967296 decimal), in hundredths of a second

            between two epochs.  When objects are defined which

            use this type, the description of the object

            identifies both of the reference epochs.

            For example, the TimeStamp type (defined in this

            module) is based on the TimeTicks type.

            With a TimeStamp, the first reference epoch is

            defined as the time when SNMPv2-MIB::sysUpTime was

            zero, and the second reference epoch is defined as

            the current value of sysUpTime.

            The TimeTicks type should not be sub-typed.";

        reference

           "RFC 2578, Sections 2. and 7.1.8.";

    };

    //

    //  The following type definitions are

    //  conversions of the textual conventions from

    //  the SNMPv2-TC module (RFC 2579), except for

    //  TAddressOrZero, which is not present in

    //  SNMPv2-TC.

    //

    typedef DisplayString {

        type        OctetString (0..255);

        format      "255a";

        description 

        "Represents textual information taken from the NVT ASCII

         character set, as defined in pages 4, 10-11 of RFC 854.

         To summarize RFC 854, the NVT ASCII repertoire specifies:

          - the use of character codes 0-127 (decimal)

          - the graphics characters (32-126) are interpreted as

            US ASCII

          - NUL, LF, CR, BEL, BS, HT, VT and FF have the special

            meanings specified in RFC 854

          - the other 25 codes have no standard interpretation

          - the sequence 'CR LF' means newline

          - the sequence 'CR NUL' means carriage-return

          - an 'LF' not preceded by a 'CR' means moving to the

            same column on the next line.

          - the sequence 'CR x' for any x other than LF or NUL is

            illegal.  (Note that this also means that a string may

            end with either 'CR LF' or 'CR NUL', but not with CR.)

         Any object defined using this syntax may not exceed 255

         characters in length.";

    };

    typedef PhysAddress {

        type        OctetString;

        format      "1x:";

        description 

        "Represents media- or physical-level addresses.";

    };

    typedef MacAddress {

        type        OctetString (6);

        format      "1x:";

        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.";

    };

    typedef TruthValue {

        type        Enumeration (true(1), false(2));

        description 

        "Represents a boolean value.";

    };

    typedef TestAndIncr {

        type        Integer32 (0..2147483647);

        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.

         When the network management portion of the system is re-

         initialized, the value of every object instance having this

         syntax must either be incremented from its value prior to

         the re-initialization, or (if the value prior to the re-

         initialization is unknown) be set to a pseudo-randomly

         generated value.";

    };

    typedef AutonomousType {

        type        ObjectIdentifier;

        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.";

    };

    typedef InstancePointer {

        type        ObjectIdentifier;

        status      obsolete;

        description 

        "A pointer to either a specific instance of a MIB object or

         a conceptual row of a MIB table in the managed device.  In

         the latter case, by convention, it is the name of the

         particular instance of the first accessible columnar object

         in the conceptual row.

         The two uses of this textual convention are replaced by

         VariablePointer and RowPointer, respectively.";

    };

    typedef VariablePointer {

        type        ObjectIdentifier;

        description 

        "A pointer to a specific object instance.  For example,

         sysContact.0 or ifInOctets.3.";

    };

    typedef RowPointer {

        type        ObjectIdentifier;

        description 

        "Represents a pointer to a conceptual row.  The value is the

         name of the instance of the first accessible columnar object

         in the conceptual row.

         For example, ifIndex.3 would point to the 3rd row in the

         ifTable (note that if ifIndex were not-accessible, then

         ifDescr.3 would be used instead).";

    };

    typedef RowStatus {

        type        Enumeration (active(1), notInService(2), 

                        notReady(3), createAndGo(4), 

                        createAndWait(5), destroy(6));

        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 its status automatically set

             to active, making 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 make 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 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, and an attempt to make it so

         would fail because the agent has insufficient information

         (the state 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

             not be `active' in order for the value of some other

             column of the same conceptual row to be modified.  If

             such a specification is made, affected columns may be

             changed by an SNMP set PDU if the RowStatus would not

             be equal to `active' either immediately before or after

             processing the PDU.  In other words, if the PDU also

             contained a varbind that would change the RowStatus

             value, the column in question may be changed if the

             RowStatus was not equal to `active' as the PDU was

             received, or if the varbind sets the status to a value

             other than 'active'.

         Also note that whenever any elements of a row exist, the

         RowStatus column must also exist.

         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|see 8     ->D|          ->D

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

set status    |inconsistent- |inconsist- |noError      |noError   ->C

column to     |         Value|   entValue|             |

notInService  |              |           |             |

              |              |     or    |             |      or

              |              |           |             |

              |              |see 3   ->C|          ->C|see 6

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

set status    |noError       |noError    |noError      |noError   ->A

column to     |              |           |             |      or

destroy       |           ->A|        ->A|          ->A|see 7

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

set any other |see 4         |noError    |noError      |see 5

column to some|              |           |             |

value         |              |      see 1|          ->C|          ->D

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

         (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, the return value may be

         either:

             inconsistentName: because the agent does not choose to

             create such an instance when the corresponding

             RowStatus instance does not exist, or

             inconsistentValue: if the supplied value is

             inconsistent with the state of some other MIB object's

             value, or

             noError: because the agent chooses to create the

             instance.

         If noError is returned, then the instance of the status

         column must also be created, and the new state is B or C,

         depending on the information available to the agent.  If

         inconsistentName or inconsistentValue is returned, the row

         remains in state A.

         (5) depending on the MIB definition for the column/table,

         either noError or inconsistentValue may be returned.

         (6) the return value can indicate one of the following

         errors:

             wrongValue: because the agent does not support

             createAndWait, or

             inconsistentValue: because the agent is unable to take

             the row out of service at this time, perhaps because it

             is in use and cannot be de-activated.

         (7) the return value can indicate the following error:

             inconsistentValue: because the agent is unable to

             remove the row at this time, perhaps because it is in

             use and cannot be de-activated.

         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 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.

         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 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.

                                 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.

         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 (and for which the agent allows their values to

             be changed after their creation), 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 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

         indefinitely.  The agent must detect conceptual rows that

         have been in either state for an abnormally long period of

         time and remove them.  It is the responsibility of the

         DESCRIPTION clause of the status column to indicate what an

         abnormally long period of time would be.  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'.

         In the absence of such information in the DESCRIPTION

         clause,

         it is suggested that this period be approximately 5 minutes

         in length.  This removal action applies not only to newly-

         created rows, but also to previously active rows which are

         set to, and left in, the notInService state for a prolonged

         period exceeding that which is considered normal for such a

         conceptual row.

                         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' or `inconsistentValue'.

         Otherwise, the conceptual row is taken out of service, and a

         `noError' response is returned.  It is the responsibility of

         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.";

    };

    typedef TimeStamp {

        type        TimeTicks;

        description 

        "The value of the sysUpTime object at which a specific

         occurrence happened.  The specific occurrence must be

         defined in the description of any object defined using this

         type.  When the specific occurrence occurred prior to the

         last time sysUpTime was zero, then the TimeStamp value is

         zero.  Note that this requires all TimeStamp values to be

         reset to zero when the value of sysUpTime reaches 497+ days

         and wraps around to zero.";

    };

    typedef TimeInterval {

        type        Integer32 (0..2147483647);

        description 

        "A period of time, measured in units of 0.01 seconds.";

    };

    typedef DateAndTime {

        type        OctetString (8 | 11);

	default     0x0000000000000000000000;

        format      "2d-1d-1d,1d:1d:1d.1d,1a1d:1d";

        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..13

         10      11    minutes from UTC          0..59

         * Notes:

         - the value of year is in big-endian encoding

         - daylight saving time in New Zealand is +13

         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