RFC 2864
The Inverted Stack Table Extension to the Interfaces Group MIB
The Inverted Stack Table Extension to the Interfaces Group MIB 💖
- RFC: 2864 🎀
- Authors: K. McCloghrie (Cisco Systems) and G. Hanson (ADC Telecommunications) 🫶
- Category: Standards Track 👑
- Date: June 2000 🌸
- Obsoletes and updates: the title block doesn't list anything this RFC obsoletes or updates ✨
Status of This Memo ✨
okay so this document is an Internet standards track protocol for the Internet community, and it's giving "please discuss and suggest improvements" 💅 Distribution of this memo is unlimited 🌈. If you want the standardization state and status of this protocol, check the current edition of the "Internet Official Protocol Standards" (STD 1). That's the source of truth, bestie 📚
Copyright Notice 🦋
Copyright (C) The Internet Society (2000). All Rights Reserved. No cap, that's the whole notice 💜
Table of Contents 🧚
1 Introduction .................................................. 1
2 The SNMP Network Management Framework ......................... 1
3 Interface Sub-Layers and the ifStackTable ..................... 3
4 Definitions ................................................... 4
5 Acknowledgements .............................................. 7
6 References .................................................... 7
7 Security Considerations ....................................... 8
8 Authors' Addresses ............................................ 9
9 Notice on Intellectual Property ............................... 10
10 Full Copyright Statement ..................................... 111. Introduction ✨
This memo defines a portion of the Management Information Base (MIB) for use with network management protocols in the Internet community 🌸 The main vibe: it describes managed objects that give you an inverted mapping of the interface stack table, which is what you use to manage network interfaces 🔥
2. The SNMP Network Management Framework 💖
okay so the SNMP Management Framework has five major components, and I'm obsessed with how they fit together 😭
- An overall architecture, described in RFC 2571 [1].
- 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 is described in STD 16, RFC 1155 [2], STD 16, RFC 1212 [3] and RFC 1215 [4]. The second version, called SMIv2, is described in STD 58, which is made up of RFC 2578 [5], RFC 2579 [6] and RFC 2580 [7].
- Message protocols for transferring management information. The first version of the SNMP message protocol is called SNMPv1 and is described in STD 15, RFC 1157 [8]. A second version of the SNMP message protocol, which is not an Internet standards track protocol, is called SNMPv2c and is described in RFC 1901 [9] and RFC 1906 [10]. The third version of the message protocol is called SNMPv3 and is described in RFC 1906 [10], RFC 2572 [11] and RFC 2574 [12].
- Protocol operations for accessing management information. The first set of protocol operations and associated PDU formats is described in STD 15, RFC 1157 [8]. A second set of protocol operations and associated PDU formats is described in RFC 1905 [13].
- A set of fundamental applications described in RFC 2573 [14], and the view-based access control mechanism described in RFC 2575 [15].
If you want a more detailed intro to the current SNMP Management Framework, go check RFC 2570 [18] 🧚
Managed objects are accessed via a virtual information store called the Management Information Base, or MIB. Objects in the MIB are defined using the mechanisms defined in the SMI 🎀
This memo specifies a MIB module that is compliant to the SMIv2. A MIB conforming to the SMIv1 can be produced through the appropriate translations. The resulting translated MIB must be semantically equivalent, except where objects or events are omitted because no translation is possible (e.g., use of Counter64). Some machine readable information in SMIv2 will be converted into textual descriptions in SMIv1 during the translation process. However, this loss of machine readable information is not considered to change the semantics of the MIB 🦋
3. Interface Sub-Layers and the ifStackTable 🌈
MIB-II [16] defines objects for managing network interfaces. It gives you a generic interface definition, plus the ability to define media-specific extensions. The generic objects are known as the 'interfaces' group 💜
Experience with defining media-specific extensions showed the need to tell apart the multiple sub-layers beneath the internetwork-layer. Picture an interface with PPP running over an HDLC link that uses an RS232-like connector. Each of those sub-layers has its own media-specific MIB module 🍓
The latest definition of the 'interfaces' group in the IF-MIB [17] handles this by giving each sub-layer its own conceptual row in the ifTable. It also defines an extra MIB table, the ifStackTable, which identifies the "superior" and "subordinate" sub-layers through ifIndex "pointers" to the right conceptual rows in the ifTable ✨
Each conceptual row in the ifStackTable represents a relationship between two interfaces. In that relationship, the "higher-layer" interface runs "on top" of the "lower-layer" interface. For example, if a PPP module operated directly over a serial interface, the PPP module would be the "higher layer" and the serial interface would be the "lower layer" 💅 This concept of "higher-layer" and "lower-layer" is the same one embodied in the definitions of the ifTable's packet counters 🔥
The ifStackTable is INDEX-ed by the ifIndex values of the two interfaces involved in the relationship. By necessity, one of those ifIndex values has to come first. The IF-MIB chose to put the higher-layer interface first and the lower-layer interface second 🎀 Because of this, it's straightforward for a Network Management application to read a subset of the ifStackTable and figure out which interfaces run underneath a particular interface 🫶 But if you want to know which interfaces run on top of a particular interface, the application has no alternative but to read the whole table. That's super inefficient when you're querying a device with lots of interfaces and lots of conceptual rows in its ifStackTable 😭
So this MIB provides an inverted Interfaces Stack Table, the ifInvStackTable. It holds no information beyond what's already in the ifStackTable. The difference is that the ifInvStackTable has its ifIndex values in its INDEX clause in reverse order: the lower-layer interface comes first and the higher-layer interface second 🧚 That makes the ifInvStackTable an inverted version of the same information in the ifStackTable. So it gives a Network Management application an efficient way to read a subset of the ifStackTable and figure out which interfaces run on top of a particular interface 💖
4. Definitions 🍓
The MIB module is below. I'm keeping every line exactly as written, since implementers rely on it 🫶
IF-INVERTED-STACK-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-TYPE, mib-2 FROM SNMPv2-SMI
RowStatus FROM SNMPv2-TC
MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF
ifStackGroup2,
ifStackHigherLayer, ifStackLowerLayer FROM IF-MIB;
ifInvertedStackMIB MODULE-IDENTITY
LAST-UPDATED "200006140000Z"
ORGANIZATION "IETF Interfaces MIB Working Group"
CONTACT-INFO
" Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
US
408-526-5260
kzm@cisco.com"
DESCRIPTION
"The MIB module which provides the Inverted Stack Table for
interface sub-layers."
REVISION "200006140000Z"
DESCRIPTION
"Initial revision, published as RFC 2864"
::= { mib-2 77 }
ifInvMIBObjects OBJECT IDENTIFIER ::= { ifInvertedStackMIB 1 }
--
-- The Inverted Interface Stack Group
--
ifInvStackTable OBJECT-TYPE
SYNTAX SEQUENCE OF IfInvStackEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A table containing information on the relationships between
the multiple sub-layers of network interfaces. In
particular, it contains information on which sub-layers run
'underneath' which other sub-layers, where each sub-layer
corresponds to a conceptual row in the ifTable. For
example, when the sub-layer with ifIndex value x runs
underneath the sub-layer with ifIndex value y, then this
table contains:
ifInvStackStatus.x.y=active
For each ifIndex value, z, which identifies an active
interface, there are always at least two instantiated rows
in this table associated with z. For one of these rows, z
is the value of ifStackHigherLayer; for the other, z is the
value of ifStackLowerLayer. (If z is not involved in
multiplexing, then these are the only two rows associated
with z.)
For example, two rows exist even for an interface which has
no others stacked on top or below it:
ifInvStackStatus.z.0=active
ifInvStackStatus.0.z=active
This table contains exactly the same number of rows as the
ifStackTable, but the rows appear in a different order."
REFERENCE
"ifStackTable of RFC 2863"
::= { ifInvMIBObjects 1 }
ifInvStackEntry OBJECT-TYPE
SYNTAX IfInvStackEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"Information on a particular relationship between two sub-
layers, specifying that one sub-layer runs underneath the
other sub-layer. Each sub-layer corresponds to a conceptual
row in the ifTable."
INDEX { ifStackLowerLayer, ifStackHigherLayer }
::= { ifInvStackTable 1 }
IfInvStackEntry ::=
SEQUENCE {
ifInvStackStatus RowStatus
}
ifInvStackStatus OBJECT-TYPE
SYNTAX RowStatus
MAX-ACCESS read-only
STATUS current
DESCRIPTION
"The status of the relationship between two sub-layers.
An instance of this object exists for each instance of the
ifStackStatus object, and vice versa. For example, if the
variable ifStackStatus.H.L exists, then the variable
ifInvStackStatus.L.H must also exist, and vice versa. In
addition, the two variables always have the same value.
However, unlike ifStackStatus, the ifInvStackStatus object
is NOT write-able. A network management application wishing
to change a relationship between sub-layers H and L cannot
do so by modifying the value of ifInvStackStatus.L.H, but
must instead modify the value of ifStackStatus.H.L. After
the ifStackTable is modified, the change will be reflected
in this table."
::= { ifInvStackEntry 1 }
-- conformance information
ifInvConformance OBJECT IDENTIFIER ::= { ifInvMIBObjects 2 }
ifInvGroups OBJECT IDENTIFIER ::= { ifInvConformance 1 }
ifInvCompliances OBJECT IDENTIFIER ::= { ifInvConformance 2 }
-- compliance statements🧚 part 1 ends right here, bestie! the compliance statements, the rest of the MIB and the remaining sections are coming up in part 2 💖
Okay bestie, the compliance statement is basically the checklist for who gets to say "yep, I support this MIB" 💅 Let's see what it asks for 🎀
ifInvCompliance MODULE-COMPLIANCE
STATUS current
DESCRIPTION
"The compliance statement for SNMP entities which provide
inverted information on the layering of network interfaces."
MODULE -- this module
MANDATORY-GROUPS { ifInvStackGroup }
OBJECT ifInvStackStatus
SYNTAX INTEGER { active(1) }
DESCRIPTION
"Support is only required for 'active'."
MODULE IF-MIB
MANDATORY-GROUPS { ifStackGroup2 }
::= { ifInvCompliances 1 }
-- units of conformance
ifInvStackGroup OBJECT-GROUP
OBJECTS { ifInvStackStatus }
STATUS current
DESCRIPTION
"A collection of objects providing inverted information on
the layering of MIB-II interfaces."
::= { ifInvGroups 1 }
ENDNgl the big takeaway is that ifInvStackStatus only needs to support active(1). That's it. Lowkey iconic 🦋
5. Acknowledgements 🌸
This memo was made by the IETF's Interfaces MIB working-group, so shoutout to them 🫶
6. References 📚
[1] Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for Describing SNMP Management Frameworks", RFC 2571, January 1998.
[2] Rose, M. and K. McCloghrie, "Structure and Identification of Management Information for TCP/IP-based Internets", STD 16, RFC 1155, May 1990.
[3] Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16, RFC 1212, March 1991.
[4] Rose, M., "A Convention for Defining Traps for use with the SNMP", RFC 1215, March 1991.
[5] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Structure of Management Information Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
[6] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999.
[7] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M. and S. Waldbusser, "Conformance Statements for SMIv2", STD 58, RFC 2580, April 1999.
[8] Case, J., Fedor, M., Schoffstall, M. and J. Davin, "Simple Network Management Protocol", STD 15, RFC 1157, May 1990.
[9] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Introduction to Community-based SNMPv2", RFC 1901, January 1996.
[10] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport Mappings for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1906, January 1996.
[11] Case, J., Harrington D., Presuhn R. and B. Wijnen, "Message Processing and Dispatching for the Simple Network Management Protocol (SNMP)", RFC 2572, January 1998.
[12] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)", RFC 2574, January 1998.
[13] SNMPv2 Working Group, Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Protocol Operations for Version 2 of the Simple Network Management Protocol (SNMPv2)", RFC 1905, January 1996.
[14] Levi, D., Meyer, P. and B. Stewart, "SNMP Applications", RFC 2573, January 1998.
[15] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access Control Model (VACM) for the Simple Network Management Protocol (SNMP)", RFC 2575, January 1998.
[16] McCloghrie, K. and M. Rose, "Management Information Base for Network Management of TCP/IP-based internets - MIB-II", STD 17, RFC 1213, March 1991.
[17] McCloghrie, K. and F. Kastenholz, "The Interface Group MIB", RFC 2863, June 2000.
[18] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction to Version 3 of the Internet-standard Network Management Framework", RFC 2570, April 1999.
7. Security Considerations 💀
Okay this section is SERIOUS, so read it twice 😭 There are no management objects in this MIB that have a MAX-ACCESS clause of read-write and/or read-create. So if this MIB is implemented correctly, there's no risk that an intruder can alter or create any management objects of this MIB through direct SNMP SET operations.
SNMPv1 by itself is not a secure environment. Even if the network itself is secure (for example by using IPSec), there is still no control over who on that secure network is allowed to access and GET/SET (read/change/create/delete) the objects in this MIB. Main character danger, fr fr 🙈
The implementers are recommended to consider the security features provided by the SNMPv3 framework. Specifically, the use of the User-based Security Model RFC 2574 [12] and the View-based Access Control Model RFC 2575 [15] is recommended. Lowkey the best move 🔥
It is then a customer/user responsibility to make sure that the SNMP entity giving access to an instance of this MIB is properly configured, so access to the objects is only given to those principals (users) who have legitimate rights to GET or SET (change/create/delete) them. Periodt 💅
8. Authors' Addresses 🧚
Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
Phone: 408-526-5260
EMail: kzm@cisco.com
Gary Hanson
ADC Telecommunications
14375 NW Science Park Drive
Portland, Oregon, 97229
Phone: (800)733-5511 x6333
EMail: gary_hanson@adc.com9. Notice on Intellectual Property 🦋
The IETF doesn't take a position on whether any intellectual property or other rights that might be claimed to apply to the technology in this document are valid or in scope, or whether any license under those rights might or might not be available. It also doesn't say it has tried to find any such rights. Info on the IETF's procedures for rights in standards-track and standards-related documents can be found in BCP-11. Copies of claimed rights that were made available for publication, any assurances of licenses that will be made available, or the result of an attempt to get a general license or permission for implementers or users to use those proprietary rights 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 send that information to the IETF Executive Director. Bestie, speak up if you know something 🫶
10. Full Copyright Statement 🌈
Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards, in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English.
The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Acknowledgement ✨
Funding for the RFC Editor function is currently provided by the Internet Society. Thank you to them for keeping the lights on 💖
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