rfc1303.txt

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RFC 1303         Convention for Describing SNMP Agents     February 1992


3.2.4.2.2.  Mapping of the WRITE-SYNTAX clause

   The WRITE-SYNTAX clause, which need not be present, is used to
   provide a refined SYNTAX for the object named in the correspondent
   VARIATION clause when instances of that object are written.

   Consult Section 3.3 for more information on refined syntax.

3.2.4.2.3.  Mapping of the ACCESS clause

   The ACCESS clause, which need not be present, is used to provide a
   refined ACCESS for the object named in the correspondent VARIATION
   clause.

3.2.4.2.4.  Mapping of the CREATION-REQUIRES clause

   The CREATION-REQUIRES clause, which need not be present, is used to
   name the columnar objects of a conceptual row to which values must be
   explicitly assigned, by a SNMP Set operation, before the agent will
   create new instances of objects in that row.  This clause must not be
   present unless the object named in the correspondent VARIATION clause
   is a conceptual row, i.e., has a syntax which resolves to a SEQUENCE
   containing columnar objects.  The objects named in the value of this
   clause usually will refer to columnar objects in that row.  However,
   objects unrelated to the conceptual row may also be specified.

   The absence of this clause for a particular conceptual row indicates
   that the agent does not support the creation, via SNMP operations, of
   new object instances in that row.

3.2.4.2.5.  Mapping of the DEFVAL clause

   The DEFVAL clause, which need not be present, is used to provide a
   refined DEFVAL value for the object named in the correspondent
   VARIATION clause.  The semantics of this value are identical to those
   of the OBJECT-TYPE macro's DEFVAL clause [2].

3.2.4.2.6.  Mapping of the DESCRIPTION clause

   The DESCRIPTION clause, which must be present for each use of the
   VARIATION clause, contains a textual description of the variant or
   refined implementation.

3.3.  Refined Syntax

   The SYNTAX and WRITE-SYNTAX clauses allow an object's Syntax to be
   refined.  However, not all refinements of syntax are appropriate.  In
   particular,



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RFC 1303         Convention for Describing SNMP Agents     February 1992


   (1)  the object's primitive or application type (as defined in
        the SMI [1]) must not be changed;

   (2)  an object defined with an SMI type of OBJECT IDENTIFIER,
        IpAddress, Counter, or TimeTicks cannot be refined; and,

   (3)  an object defined to have a specific set of values (e.g.,
        an INTEGER with named values) cannot have additional
        values defined for it.

3.4.  Usage Example

   Consider how one might document the 4BSD/ISODE "Secure" SNMP
   agent:

   FourBSD-ISODE   DEFINITIONS ::= BEGIN

   IMPORTS
       MODULE-CONFORMANCE
           FROM RFC-1303
       -- everything --
           FROM RFCxxxx-MIB
       -- everything --
           FROM RFC1213-MIB
       -- everything --
           FROM UNIX-MIB
       -- everything --
           FROM EVAL-MIB;

   fourBSD-isode-support MODULE-CONFORMANCE
       LAST-UPDATED        "9201252354Z"
       PRODUCT-RELEASE     "ISODE 7.0 + 'Secure' SNMP
                            upgrade for SunOS 4.1"
       DESCRIPTION         "4BSD/ISODE 'Secure' SNMP"

       SUPPORTS            RFCxxxx-MIB -- SNMP Party MIB --
           INCLUDES        { partyPublic, partyPrivate }

       SUPPORTS            RFC1213-MIB
           INCLUDES        { system, interfaces, at, ip, icmp,
                             tcp, udp, snmp }

           VARIATION       atEntry
               CREATION-REQUIRES { atPhysAddress }
               DESCRIPTION "Address mappings on 4BSD require
                            both protocol and media addresses"

           VARIATION       ifAdminStatus



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RFC 1303         Convention for Describing SNMP Agents     February 1992


               SYNTAX      INTEGER { up(1), down(2) }
               DESCRIPTION "Unable to set test mode on 4BSD"

           VARIATION       ifOperStatus
               SYNTAX      INTEGER { up(1), down(2) }
               DESCRIPTION "Information limited on 4BSD"

           VARIATION       ipDefaultTTL
               SYNTAX      INTEGER { maxttl(255) }
               DESCRIPTION "Hard-wired on 4BSD"

           VARIATION       ipInAddrErrors
               ACCESS      not-accessible
               DESCRIPTION "Information not available on 4BSD"

           VARIATION       ipInDiscards
               ACCESS      not-accessible
               DESCRIPTION "Information not available on 4BSD"

           VARIATION       ipRouteEntry
               CREATION-REQUIRES { ipRouteNextHop }
               DESCRIPTION "Routes on 4BSD require both
                            destination and next-hop"

           VARIATION       ipRouteType
               SYNTAX       INTEGER { direct(3), indirect(4) }
               WRITE-SYNTAX INTEGER { invalid(2), direct(3),
                                      indirect(4) }
               DESCRIPTION "Information limited on 4BSD"

           VARIATION       ipRouteProto
               SYNTAX      INTEGER { other(1), icmp (4) }
               DESCRIPTION "Information limited on 4BSD"

           VARIATION       ipRouteAge
               ACCESS      not-accessible
               DESCRIPTION "Information not available on 4BSD"

           VARIATION       ipNetToMediaEntry
               CREATION-REQUIRES { ipNetToMediaPhysAddress }
               DESCRIPTION "Address mappings on 4BSD require
                            both protocol and media addresses"

           VARIATION       ipNetToMediaType
               SYNTAX       INTEGER { dynamic(3), static(4) }
               WRITE-SYNTAX INTEGER { invalid(2), dynamic(3),
                                      static(4) }
               DESCRIPTION "Information limited on 4BSD"



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RFC 1303         Convention for Describing SNMP Agents     February 1992


           VARIATION       tcpConnState
               ACCESS      read-only
               DESCRIPTION "Unable to set this on 4BSD"

           VARIATION       tcpInErrs
               ACCESS      not-accessible
               DESCRIPTION "Information not available on 4BSD"

           VARIATION       tcpOutRsts
               ACCESS      not-accessible
               DESCRIPTION "Information not available on 4BSD"

       SUPPORTS            UNIX-MIB
           INCLUDES        { agents, mbuf, netstat }

       SUPPORTS            EVAL-MIB
           INCLUDES        { functions, expressions }

       ::= { fourBSD-isode 6 6 }

   END

   According to this invocation, an agent with a sysObjectID of

        { fourBSD-isode 6 6 }

   supports four MIB modules.

   From the SNMP Party MIB, all the objects contained in the partyPublic
   and partyPrivate groups are supported, without variation.

   From MIB-II, all groups except the egp group are supported.  However,
   the objects

        ipInAddrErrors
        ipInDiscards
        ipRouteAge
        tcpInErrs
        tcpOutRsts

   are not available, whilst the objects

        ifAdminStatus
        ifOperStatus
        ipDefaultTTL
        ipRouteType
        ipRouteProto
        ipNetToMediaType



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RFC 1303         Convention for Describing SNMP Agents     February 1992


   have a restricted syntax, and the object

        tcpConnState

   is available only for reading.  Note that in the case of the objects

        ipRouteType
        ipNetToMediaType

   the set of values which may be read is different than the set of
   values which may be written.  Finally, when creating a new row in the
   atTable, the set-request must create an instance of atPhysAddress.
   Similarly, when creating a new row in the ipRouteTable, the set-
   request must create an instance of ipRouteNextHop.  Similarly, when
   creating a new row in the ipNetToMediaTable, the set-request must
   create an instance of ipNetToMediaPhysAddress.

   From the UNIX-MIB, all the objects contained in the agents, mbuf, and
   netstat groups are supported, without variation.

   From the EVAL-MIB, all the objects contained in the functions and
   expressions groups are supported, without variation.

4.  Acknowledgements

   The authors gratefully acknowledge the comments of Mark van der Pol
   of Hughes LAN Systems, and David T. Perkins of SynOptics
   Communications.

5.  References

   [1]  Rose M., and K. McCloghrie, "Structure and Identification of
        Management Information for TCP/IP-based internets", RFC 1155,
        Performance Systems International, Hughes LAN Systems, May 1990.

   [2]  Rose, M., and K. McCloghrie, Editors, "Concise MIB Definitions",
        RFC 1212, Performance Systems International, Hughes LAN Systems,
        March 1991.

   [3]  McCloghrie K., and M. Rose, Editors, "Management Information
        Base forNetwork Management of TCP/IP-based internets", RFC 1213,
        Performance Systems International, March 1991.

   [4]  Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple
        Network Management Protocol (SNMP), RFC 1157, SNMP Research,
        Performance Systems International, Performance Systems
        International, MIT Laboratory for Computer Science, May 1990.




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RFC 1303         Convention for Describing SNMP Agents     February 1992


   [5]  Information processing systems - Open Systems Interconnection -
        Specification of Abstract Syntax Notation One (ASN.1),
        International Organization for Standardization, International
        Standard 8824, December 1987.

   [6]  Rose, M., "SNMP MUX Protocol and MIB", RFC 1227, Performance
        Systems International, May 1991.

6.  Security Considerations

   Security issues are not discussed in this memo.

7.  Authors' Addresses

   Keith McCloghrie
   Hughes LAN Systems
   1225 Charleston Road
   Mountain View, CA 94043

   Phone: [phone]
   EMail: [e-mail]


   Marshall T. Rose
   Dover Beach Consulting, Inc.
   420 Whisman Court
   Mountain View, CA  94043-2112

   Phone: [phone]
   EMail: [e-mail]





















McCloghrie & Rose                                              [Page 12]