Internet Draft Andy Bierman Cisco Systems, Inc. Keith McCloghrie Cisco Systems, Inc. Randy Presuhn BMC Software, Inc. 22 October 1999 SMI Extensions for Additional High Capacity Data Types Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [RFC2026]. 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. Please send comments to the authors. 1. Copyright Notice Copyright (C) The Internet Society (1999). All Rights Reserved. Internet-Draft High Capacity Data Types October 1999 2. Abstract This memo specifies clarifications to the Structure of Management Information [SMIv2] for the purpose of providing a broader range of data types for high capacity numbers. 3. Table of Contents 1 Copyright Notice ................................................ 1 2 Abstract ........................................................ 2 3 Table of Contents ............................................... 2 4 The SNMP Management Framework ................................... 2 5 Overview ........................................................ 3 5.1 New Data Types Needed ......................................... 3 5.2 Short Term and Long Term Objectives ........................... 3 5.3 Backward Compatibility with Counter64 ......................... 5 5.4 ASN.1 Vs. Textual Convention Approach ......................... 5 5.5 SMI Interpretation Supporting the TC Approach ................. 5 6 Definitions ..................................................... 7 7 Intellectual Property ........................................... 8 8 References ...................................................... 8 9 Security Considerations ......................................... 11 10 Authors' Addresses ............................................. 12 11 Full Copyright Statement ....................................... 13 4. The SNMP Management Framework The SNMP Management Framework presently consists of five major components: o An overall architecture, described in RFC 2571 [RFC2571]. o Mechanisms for describing and naming objects and events for the purpose of management. The first version of this Structure of Management Information (SMI) is called SMIv1 and described in RFC 1155 [RFC1155], RFC 1212 [RFC1212] and RFC 1215 [RFC1215]. The second version, called SMIv2, is described in RFC 2578 [RFC2578], RFC 2579 [RFC2579] and RFC 2580 [RFC2580]. o Message protocols for transferring management information. The first version of the SNMP message protocol is called SNMPv1 and described in RFC 1157 [RFC1157]. A second version of the SNMP message protocol, which is not an Internet standards track protocol, is called SNMPv2c and described in RFC 1901 [RFC1901] and RFC 1906 [RFC1906]. The third version of the message Expires April 2000 [Page 2] Internet-Draft High Capacity Data Types October 1999 protocol is called SNMPv3 and described in RFC 1906 [RFC1906], RFC 2572 [RFC2572] and RFC 2574 [RFC2574]. o Protocol operations for accessing management information. The first set of protocol operations and associated PDU formats is described in RFC 1157 [RFC1157]. A second set of protocol operations and associated PDU formats is described in RFC 1905 [RFC1905]. o A set of fundamental applications described in RFC 2573 [RFC2573] and the view-based access control mechanism described in RFC 2575 [RFC2575]. A more detailed introduction to the current SNMP Management Framework can be found in RFC 2570 [RFC2570]. Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the mechanisms defined in the SMI. This document does not define a MIB module. 5. Overview There is a need for a standardized way of representing different types of high capacity numbers in MIB modules, in a manner suitable for use with existing SNMP engines. The SMIv2 [RFC2578] currently contains support for high-speed counters (i.e., Counter64), but does not contain support for 64 bit gauges or (signed and unsigned) integers. 5.1. New Data Types Needed There are standards track MIBs in progress, which require 64 bit gauges and integers. There are some MIB features such as polling history or alarm thresholding, that are supported for 32-bit counters, but not strictly supported for 64-bit counters. The SMI does not provide the right base types or textual conventions for 64-bit data types. The SMI is also ambiguous regarding the semantics of a MIB object defined with a textual convention (TC), instead of a base type. 5.2. Short Term and Long Term Objectives In order to support Gigabit Ethernet and other high speed interfaces properly, the following new data types are needed: Expires April 2000 [Page 3] Internet-Draft High Capacity Data Types October 1999 - Gauge64 - Unsigned64 - Integer64 There is an immediate need to provide Gauge64 and Unsigned64 data types, similar in semantics to the Gauge32 and Unsigned32 data types. Signed integers can be stored in two MIB objects (sign and absolute value) as is done with the usrHistoryTable in the RMON-2 MIB [RFC2021], so there is not an immediate need for an Integer64 data type. A new ASN.1 tag for 64-bit integers should be added to the SMI as soon as possible. This document does not suggest a short-term solution for signed 64-bit integers. In the short term, textual conventions defining new unsigned 64-bit data types need to be defined in a document which augments, but does not invalidate anything contained in the existing SMI documents. Resolutions to the ambiguities regarding the use of textual conventions also needs to be resolved in the short-term. During IETF WG discussions about progressing the SNMPv2 specifications (RFCs 1902-1908) to a higher level of the standardization status, the issue of supporting new SMI data types was deferred to the future. One school of thought suggests that such future SMI capability should be a generalized solution for being able to transition to support any new data type. However, the definition of a generalized solution will take time, both to specify and to get implementations of it deployed. The updates to the SMIv2 specified in this memo are not intended to prejudice the argument about whether such a generalized solution is needed. Meanwhile, there is an immediate need to add data types for 64 bit unsigned numbers, and that these additions be done in a way that will be supportable by any underlying SNMP engine which already implements Counter64 MIB objects. The approach in this memo is motivated by the observation that the SMIv2 specification already specifies two base-level data types (Gauge32 and Unsigned32) which map onto the same underlying ASN.1 tag, and thus are indistinguishable when contained in an SNMP packet in transmission. So, why not have the additional high capacity data types map onto the same underlying ASN.1 tag as Counter64, so that they are similarly indistinguishable when contained in an SNMP packet? Expires April 2000 [Page 4] Internet-Draft High Capacity Data Types October 1999 5.3. Backward Compatibility with Counter64 In order to be backward compatible with existing implementations of Counter64, the encoding of Gauge64 and Unsigned64 objects needs to be identical to the encoding of Counter64 objects, i.e., identified by the [APPLICATION 6] ASN.1 tag. 5.4. ASN.1 Vs. Textual Convention Approach Defining new unsigned data types with textual conventions based on the Counter64 tag, instead of a new (or other existing) ASN.1 tag has some advantages and some limitations: - The MAX-ACCESS of the TC must be read-only, because the MAX-ACCESS of the underlying Counter64 type is read-only, (as established in RFC 2578 clause 7.1.10 [RFC2578]). - No sub-range can be specified on the TC-derived types, because sub- ranges are not allowed on Counter64 objects. - No DEFVAL clause can be specified for the TC-derived types, because DEFVALs are not allowed on read-only objects. - The TC-derived types cannot be used in an INDEX clause. This is not an important feature, and supporting it would have a significant impact on MIB compliers. - Enumerated integers cannot be defined with a value larger than 2147483647. This is not an important feature, and supporting it would have a significant impact on MIB compliers. - The ASN.1 tag should carry only encoding information, not encoding and semantic information. Semantic content should be determined entirely by the SYNTAX clause in the MIB object definition. 5.5. SMI Interpretation Supporting the TC Approach Clause 3.3 of RFC 2579, 'Mapping of the DESCRIPTION clause' states: 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. Expires April 2000 [Page 5] Internet-Draft High Capacity Data Types October 1999 Note the use of the word "all". Clause 3.5 of RFC 2579, 'Mapping of the SYNTAX clause' states: 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 or the BITS construct (see section 7.1 in [2]). Note that this means that the SYNTAX clause of a Textual Convention can not refer to a previously defined Textual Convention. An extended subset of the full capabilities of ASN.1 (1988) sub- typing is allowed, as appropriate to the underlying ASN.1 type. Any such restriction on size, range or enumerations specified in this clause represents the maximal level of support which makes "protocol sense". Restrictions on sub- typing are specified in detail in Section 9 and Appendix A of [2]. Note that no mention is made of any underlying data type semantics. Taken together, these two passages indicate that the unsigned 64-bit TCs are perfectly legal. There is a passage in RFC 2579 that hints otherwise is a slightly ambiguous passage in the introduction: When designing a MIB module, it is often useful to define new 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. ... The ambiguity depends on how one reads "more precise semantics". One could read it in the strict sense of a type hierarchy with inheritance of semantics, or one could read it in the spirit of clause 3.3, which states that ALL semantics are in the TC's DESCRIPTION clause. Therefore, the ambiguity is whether the semantics of the base type have to be inherited by a new TC based on that underlying type. I.e., whether a TC based on the Counter64 base type must inherit the 'delta-only' characteristics of Counter64, or whether the description of the TC can override that. The definitions in section 6 assume that a TC can override it. Expires April 2000 [Page 6] Internet-Draft High Capacity Data Types October 1999 6. Definitions The following textual conventions are defined to support unsigned 64-bit data types. SMIv2-HCNUM-EXT DEFINITIONS ::= BEGIN IMPORTS TEXTUAL-CONVENTION FROM SNMPv2-TC; Gauge64 ::= TEXTUAL-CONVENTION STATUS current 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 decimal), 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.)" SYNTAX Counter64 Unsigned64 ::= TEXTUAL-CONVENTION STATUS current DESCRIPTION The Unsigned64 type represents integer-valued information between 0 and 2^64-1 inclusive (0 to 18446744073709551615 decimal)." SYNTAX Counter64 END Expires April 2000 [Page 7] Internet-Draft High Capacity Data Types October 1999 7. Intellectual Property The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards- related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 8. References [RFC1155] Rose, M., and K. McCloghrie, "Structure and Identification of Management Information for TCP/IP-based Internets", RFC 1155, STD 16, Performance Systems International, Hughes LAN Systems, May 1990. [RFC1157] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network Management Protocol", RFC 1157, STD 15, SNMP Research, Performance Systems International, Performance Systems International, MIT Laboratory for Computer Science, May 1990. [RFC1212] Rose, M., and K. McCloghrie, "Concise MIB Definitions", RFC 1212, STD 16, Performance Systems International, Hughes LAN Systems, March 1991. [RFC1215] M. Rose, "A Convention for Defining Traps for use with the SNMP", RFC 1215, Performance Systems International, March 1991. Expires April 2000 [Page 8] Internet-Draft High Capacity Data Types October 1999 [RFC1901] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Introduction to Community-based SNMPv2", RFC 1901, SNMP Research, Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc., International Network Services, January 1996. [RFC1905] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Protocol Operations for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1905, SNMP Research, Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc., International Network Services, January 1996. [RFC1906] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport Mappings for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1906, SNMP Research, Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc., International Network Services, January 1996. [RFC2021] S. Waldbusser, "Remote Network Monitoring MIB (RMON-2)", RFC 2021, International Network Services, January 1997. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", RFC 2026, Harvard University, October, 1996. [RFC2570] Case, J., Mundy, R., Partain, D., and B. Stewart, "Introduction to Version 3 of the Internet-standard Network Management Framework", RFC 2570, SNMP Research, Inc., TIS Labs at Network Associates, Inc., Ericsson, Cisco Systems, April 1999. [RFC2571] Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for Describing SNMP Management Frameworks", RFC 2571, Cabletron Systems, Inc., BMC Software, Inc., IBM T. J. Watson Research, April 1999. [RFC2572] Case, J., Harrington D., Presuhn R., and B. Wijnen, "Message Processing and Dispatching for the Simple Network Management Protocol (SNMP)", RFC 2572, SNMP Research, Inc., Cabletron Systems, Inc., BMC Software, Inc., IBM T. J. Watson Research, April 1999. Expires April 2000 [Page 9] Internet-Draft High Capacity Data Types October 1999 [RFC2573] Levi, D., Meyer, P., and B. Stewart, "SNMPv3 Applications", RFC 2573, SNMP Research, Inc., Secure Computing Corporation, Cisco Systems, April 1999. [RFC2574] Blumenthal, U., and B. Wijnen, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)", RFC 2574, IBM T. J. Watson Research, April 1999. [RFC2575] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)", RFC 2575, IBM T. J. Watson Research, BMC Software, Inc., Cisco Systems, Inc., April 1999. [RFC2578] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M., and S. Waldbusser, "Structure of Management Information Version 2 (SMIv2)", RFC 2578, STD 58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research, First Virtual Holdings, International Network Services, April 1999. [RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M., and S. Waldbusser, "Textual Conventions for SMIv2", RFC 2579, STD 58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research, First Virtual Holdings, International Network Services, April 1999. [RFC2580] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M., and S. Waldbusser, "Conformance Statements for SMIv2", RFC 2580, STD 58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research, First Virtual Holdings, International Network Services, April 1999. Expires April 2000 [Page 10] Internet-Draft High Capacity Data Types October 1999 9. Security Considerations There are no security issues raised by this document. Expires April 2000 [Page 11] Internet-Draft High Capacity Data Types October 1999 10. Authors' Addresses Andy Bierman Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA Phone: +1 408-527-3711 Email: abierman@cisco.com Keith McCloghrie Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134 USA Phone: +1 408-526-5260 Email: kzm@cisco.com Randy Presuhn BMC Software, Inc. 1190 Saratoga Avenue Suite 130 San Jose, CA 95129 USA Phone: +1 408-556-0720 EMail: rpresuhn@bmc.com Expires April 2000 [Page 12] Internet-Draft High Capacity Data Types October 1999 11. 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. 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