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Draft Interfaces Group Evolution May 1993 Evolution of the Interfaces Group of MIB-II 1 June 1993 Keith McCloghrie Hughes LAN Systems kzm@hls.com Frank J. Kastenholz FTP Software kasten@ftp.com Status of this Memo This document is an Internet Draft. 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 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 a "work in progress". Expires November 1993 [Page 1] Draft Interfaces Group Evolution May 1993 1. Introduction MIB-II [3] is the core set of managed objects defined for use by network management of the Internet suite of protocols. MIB-II was defined using the SNMPv1 Network Management Framework. This memo discusses the 'interfaces' group of MIB-II, especially the experience gained from the definition of numerous media-specific MIB modules for use in conjunction with the 'interfaces' group for managing various sub-layers beneath the internetwork-layer. It proposes clarifications to, and extensions of, the architectural issues within the current model used for the 'interfaces' group. This memo also includes a MIB module. As well as including new experimental MIB definitions to support the architectural extensions, this MIB module also re-specifies the 'interfaces' group of MIB-II in a manner which is both compliant to the SNMPv2 SMI and semantically-identical to the existing SNMPv1- based definitions. Expires November 1993 [Page 2] Draft Interfaces Group Evolution May 1993 2. The SNMPv2 Network Management Framework The SNMPv2 Network Management Framework consists of four major components. They are: o RFC 1441 which defines the SMI, the mechanisms used for describing and naming objects for the purpose of management. o RFC 1213 defines MIB-II, the core set of managed objects for the Internet suite of protocols. o RFC 1445 which defines the administrative and other architectural aspects of the framework. o RFC 1448 which defines the protocol used for network access to managed objects. The Framework permits new objects to be defined for the purpose of experimentation and evaluation. 2.1. Object Definitions Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. Objects in the MIB are defined using the subset of Abstract Syntax Notation One (ASN.1) defined in the SMI. In particular, each object object type is named by an OBJECT IDENTIFIER, an administratively assigned name. The object type together with an object instance serves to uniquely identify a specific instantiation of the object. For human convenience, we often use a textual string, termed the descriptor, to refer to the object type. Expires November 1993 [Page 3] Draft Interfaces Group Evolution May 1993 3. Experience with the Interfaces Group One of the strengths of internetwork-layer protocols such as IP [6] is that they are designed to run over any network interface. In achieving this, IP considers any and all protocols it runs over as a single "network interface" layer. A similar view is be taken by other internetwork-layer protocols. This concept is represented in MIB-II by the 'interfaces' group which defines a generic set of managed objects such that any network interface can be managed in an interface-independent manner through these managed objects. The 'interfaces' group provides the means for additional managed objects specific to particular types of network interface (e.g., a specific medium such as Ethernet) to be defined as extensions to the 'interfaces' group for media- specific management. Since the standardization of MIB-II, many such media-specific MIB modules have been defined. Experience in defining these media-specific MIB modules has shown that the model defined by MIB-II is too simplistic and/or static for some types of media-specific management. As a result, some of these media-specific MIB modules have assumed an evolution/loosening of the model. This memo is a proposal to document/standardize the evolution of the model and to fill in the gaps caused by that evolution. 3.1. Areas of Clarification/Revision There are four areas for which experience indicates that clarification or revision of the model would be helpful. The next sections discuss these. 3.1.1. Interface Numbering MIB-II defines an object, ifNumber, whose value represents: "The number of network interfaces (regardless of their current state) present on this system." Each interface is identified by a unique value of the ifIndex object, and the description of ifIndex constrains its value as follows: Expires November 1993 [Page 4] Draft Interfaces Group Evolution May 1993 "Its value ranges between 1 and the value of ifNumber. The value for each interface must remain constant at least from one re-initialization of the entity's network management system to the next re-initialization." This constancy requirement on the value of ifIndex for a particular interface is vital for efficient management. However, an increasing number of devices allow for the dynamic addition/removal of network interfaces. One example of this is a dynamic ability to configure the use of SLIP/PPP over a character-oriented port. For such dynamic additions/removals, the combination of the constancy requirement and the restriction that the value of ifIndex is less than ifNumber is problematic. 3.1.2. Interface Sub-Layers Experience in defining media-specific management information has shown the need to distinguish between the multiple sub- layers beneath the internetwork-layer. In addition, there is a need to manage these sub-layers in devices (e.g., MAC-layer bridges) which are unaware of which, if any, internetwork protocols run over these sub-layers. As such, a model of having a single conceptual row in the interfaces table (MIB- II's ifTable) represent a whole interface underneath the internetwork-layer, and having a single associated media- specific MIB module (referenced by the ifSpecific object) is too simplistic. A further problem arises with the value of the ifType object which has enumerated values for each type of interface. Consider, for example, an interface with PPP running over an HDLC link which uses a RS232-like connector. Each of these sub-layers has its own media-specific MIB module. If all of this is represented by a single conceptual row in the ifTable, then an enumerated value for ifType is needed for that specific combination, and that row's ifSpecific variable can "point" to only one of the three media-specific MIB modules. Furthermore, even if there was a convention for deciding which MIB module is referenced by ifSpecific then there is still a lack of a method to describe the relationship of all the sub- layers of the MIB stack. An associated problem is that of upward and downward Expires November 1993 [Page 5] Draft Interfaces Group Evolution May 1993 multiplexing of the sub-layers. An example of upward multiplexing is MLP (Multi-Link) which provides load-sharing over several serial lines by appearing as a single point-to- point link to the sub-layer(s) above. An example of downward multiplexing would be several instances of PPP, each running over a Frame Relay virtual circuit, all of which run over the same ISDN B channel. The current MIB structure does not allow for these sorts of relationships to be described. 3.1.3. Virtual Circuits Several of the sub-layers for which media-specific MIB modules have been defined are connection oriented (e.g., Frame Relay, X.25). Experience has shown that each effort to define such a MIB module revisits the question of whether separate conceptual rows in the ifTable are needed for each virtual circuit. Most, if not all, of these efforts to date have decided to have all virtual circuits reference a single conceptual row in the ifTable. 3.1.4. Bit and Character Oriented Interfaces RS-232 is an example of a character-oriented sub-layer over which (e.g., through use of PPP) IP datagrams can be sent. Due to the packet-based nature of many of the objects in the ifTable, experience has shown that it is not appropriate to have a character-oriented sub-layer represented by a (whole) conceptual row in the ifTable. Experience has also shown that it is sometimes desirable to have some management information for bit-oriented interfaces, which are similarly difficult to represent by a (whole) conceptual row in the ifTable. For example, to manage the channels of a DS1 circuit, where only some of the channels are carrying packet-based data. 3.2. Clarifications/Revisions The following clarifications and/or revisions are proposed. Expires November 1993 [Page 6] Draft Interfaces Group Evolution May 1993 3.2.1. Interface Numbering One solution to the interface numbering problem would be to redefine ifNumber to be the largest value of ifIndex, but the utility of such an object is questionable, and such a re- definition would require ifNumber to be deprecated. Thus, an improvement would be to deprecate ifNumber and not replace it. However, the deprecation of ifNumber would require a change to that portion of ifIndex's definition which refers to ifNumber. So, since the definition of ifIndex must be changed anyway in order to solve the problem, changes to ifNumber do not benefit the solution. The solution adopted in this memo is just to delete the requirement that the value of ifIndex must be less than the value of ifNumber, and to retain ifNumber with its current definition. It could be argued that this is a change in the semantics of ifIndex; however, all existing implementations conform to this new definition, and in the interests of not requiring changes in existing implementations and in the many existing media-specific MIBs, it is proposed that this change does not require ifIndex to be deprecated. This solution also results in the possibility of "holes" in the ifTable, i.e., the ifIndex values of conceptual rows in the ifTable are not necessarily contiguous, but SNMP's GetNext (and SNMPv2's GetBulk) operation easily deals with such holes. The value of ifNumber still represents the number of conceptual rows, which increases/decreases as new interfaces are dynamically added/removed. The vital constancy requirement is met by requiring that after an interface is dynamically removed, its ifIndex value is not re-used (by another dynamically added interface) until after the following re-initialization of the network management system. This avoids the need for a priori assignment of ifIndex values for all possible interfaces which might be added dynamically. Because of the restriction of the value of ifIndex to be less than ifNumber, interfaces have been numbered with small integer values. This has led to the ability by humans to use the ifIndex values as (somewhat) user-friendly names for network interfaces (e.g., "interface number 3"). With the relaxation of the restriction on the value of ifIndex, there is now the possibility that ifIndex values could be assigned as very large numbers (e.g., memory addresses). Such numbers Expires November 1993 [Page 7] Draft Interfaces Group Evolution May 1993 would be much less user-friendly. Therefore, this memo recommends that ifIndex values still be assigned as small integer values starting at 1, even though the values in use at any one time are not necessarily contiguous. (Note that this makes it easy for agents which dynamically add new interfaces, to remember which values have been assigned.) 3.2.2. Interface Sub-Layers One possible but not recommended solution to the problem of representing multiple sub-layers would be to retain the concept of one conceptual row for all the sub-layers of an interface and have each media-specific MIB module identify its "superior" and "subordinate" sub-layers through OBJECT IDENTIFIER "pointers". The drawbacks of this scheme are: 1) that the superior/subordinate pointers are contained in the media-specific MIB modules, and thus, a manager could not learn the structure of an interface, without inspecting multiple pointers in different MIB modules; this is overly complex and only possible if the manager has knowledge of all the relevant media-specific MIB modules; 2) current MIB modules would all need to be retrofitted with these new "pointers"; 3) this scheme does not adequately address the problem of upward and downward multiplexing; and 4) enumerated values of ifType are needed for each combination of sub- layers. Another possible but not recommended scheme would be to retain the concept of one conceptual row for all the sub-layers of an interface and have a new separate MIB table to identify the "superior" and "subordinate" sub-layers and to contain OBJECT IDENTIFIER "pointers" to media-specific MIBs. Effectively, one conceptual row in the ifTable would represent each combination of sub-layers between the internetwork-layer and the wire. While this scheme has fewer drawbacks, it would deprecate the use of ifSpecific and it still does not support downward multiplexing, such as PPP over MLP: since MLP makes two (or more) serial lines appear to the layers above as a single physical interface, PPP over MLP should appear to the internetwork-layer as a single interface; this scheme, however, would result in two (or more) conceptual rows in the ifTable, both of which the internetwork-layer would run over. This scheme also requires enumerated values of ifType for each combination of sub-layers. Expires November 1993 [Page 8] Draft Interfaces Group Evolution May 1993 The solution adopted in this memo is to have an individual conceptual row in the ifTable to represent each sub-layer, and have a new separate MIB table (the ifStackTable, see section 4 of this memo) to identify the "superior" and "subordinate" sub-layers through INTEGER "pointers" to the appropriate conceptual rows in the ifTable. This solution supports both upward and downward multiplexing, allows the ifSpecific pointer in each conceptual row of the ifTable to point to the media-specific MIB module for that sub-layer, such that the new table need only be referenced to obtain information about layering, and it only requires enumerated values of ifType for each sub-layer, not for combinations of them. However, it does require that the descriptions of some objects in the ifTable (specifically, ifType, ifPhysAddress, ifInUcastPkts, and ifOutUcastPkts) be generalized so as to apply to any sub- layer (rather than only to a sub-layer immediately beneath the network layer, as at present), plus some (specifically, ifSpeed) which need to have appropriate values identified for use when a generalized definition does not apply to a particular sub-layer. In addition, this adopted solution makes no requirement that a device, in which a sub-layer is instrumented by a conceptual row of the ifTable, be aware of whether an internetwork protocol runs on top of (i.e., at some layer above) that sub- layer. 3.2.3. Virtual Circuits This memo recommends that, in general, connection-oriented sub-layers do not have a conceptual row in the ifTable for each virtual circuit. This avoids the proliferation of conceptual rows, especially those which have considerable redundant information. (Note, as a comparison, that connection-less sub-layers do not have conceptual rows for each remote address.) There may, however, be circumstances under which it is appropriate for a virtual circuit of a connection-oriented sub-layer to have its own conceptual row in the ifTable; an example of this might be PPP over a Frame Relay virtual circuit. The MIB in section 4 of this memo supports such circumstances. Expires November 1993 [Page 9] Draft Interfaces Group Evolution May 1993 3.2.4. Bit and Character Oriented Interfaces About half the objects in the ifTable are applicable to every type of interface: packet-oriented, character-oriented, and bit-oriented. Of the other half, two are applicable to both character-oriented and packet-oriented interfaces, and the rest are applicable only to packet-oriented interfaces. Thus, while it is desirable for consistency to be able to represent any/all types of interfaces in the ifTable, it is not possible to implement the full ifTable for bit- and character-oriented sub-layers. One possible but not recommended solution to this problem would be to split the ifTable into two (or more) new MIB tables, one of which would contain objects that are relevant only to packet-oriented interfaces (e.g. PPP), and another that may be used by all interfaces. This is highly undesirable since it would require changes in every agent implementing the ifTable (i.e., just about every existing SNMP agent). The solution adopted in this memo builds upon the fact that compliance statements in SNMPv2 (in contrast to SNMPv1) refer to object groups, where object groups are explicitly defined by listing the objects they contain. Thus, in SNMPv2, multiple compliance statements can be specified, one for all interfaces and additional ones for specific types of interfaces. The separate compliance statements can be based on separate object groups, where the object group for all interfaces can contain only those objects from the ifTable which are appropriate for every type of interfaces. Using this solution, every sub-layer can have its own conceptual row in the ifTable. Thus, the following section contains definitions of the objects of the existing 'interfaces' group of MIB-II, in a manner which is both SNMPv2-compliant and semantically- equivalent to the existing MIB-II definitions. With equivalent semantics, and with the BER ("on the wire") encodings unchanged, these definitions retain the same OBJECT IDENTIFIER values as assigned by MIB-II. Thus, no rewrite of existing agents is required. Three new object groups are defined: the ifGeneralGroup containing those objects applicable to all types of network Expires November 1993 [Page 10] Draft Interfaces Group Evolution May 1993 interfaces; the ifCharacterGroup containing those objects applicable to character-oriented (but not packet-oriented) network interfaces; and the ifPacketGroup containing those objects applicable only to packet-oriented network interfaces. Expires November 1993 [Page 11] Draft Interfaces Group Evolution May 1993 4. Definitions IF-MIB DEFINITIONS ::= BEGIN IMPORTS MODULE-IDENTITY, OBJECT-TYPE, Counter32, Gauge32, Integer32, TimeTicks, experimental FROM SNMPv2-SMI DisplayString, PhysAddress, RowStatus FROM SNMPv2-TC MODULE-COMPLIANCE, OBJECT-GROUP FROM SNMPv2-CONF mib-2, interfaces FROM RFC-1213; -- combining the experimental parts of this MIB with the -- existing ifExtensions MIB (RFC 1229) should be considered. -- ifExtensions is defined in RFC 1239 as { mib-2 12 } ifMIB MODULE-IDENTITY LAST-UPDATED "9305262355Z" ORGANIZATION "IETF Interfaces MIB Working Group" CONTACT-INFO " Keith McCloghrie Hughes LAN Systems 1225 Charleston Road Mountain View, Ca. 94043 Tel: 415-966-7934 Fax: 415-966-7980 E-mail: kzm@hls.com." DESCRIPTION "The MIB module to describe generic objects for network interface sub-layers. This MIB is an updated version of MIB-II's ifTable." ::= { experimental xx } ifMIBObjects OBJECT IDENTIFIER ::= { ifMIB 1 } Expires November 1993 [Page 12] Draft Interfaces Group Evolution May 1993 -- the Interfaces group ifNumber OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of network interfaces (regardless of their current state) present on this system." ::= { interfaces 1 } -- the Interfaces table -- The Interfaces table contains information on the entity's -- interfaces. Each sub-layer below the internetwork-layer -- of a network interface is considered to be an interface. ifTable OBJECT-TYPE SYNTAX SEQUENCE OF IfEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "A list of interface entries. The number of entries is given by the value of ifNumber." ::= { interfaces 2 } ifEntry OBJECT-TYPE SYNTAX IfEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "An entry containing management information applicable to a particular interface." INDEX { ifIndex } ::= { ifTable 1 } IfEntry ::= SEQUENCE { ifIndex Integer32, ifDescr DisplayString, ifType INTEGER, ifMtu Integer32, ifSpeed Gauge32, ifPhysAddress PhysAddress, Expires November 1993 [Page 13] Draft Interfaces Group Evolution May 1993 ifAdminStatus INTEGER, ifOperStatus INTEGER, ifLastChange TimeTicks, ifInOctets Counter32, ifInUcastPkts Counter32, ifInNUcastPkts Counter32, ifInDiscards Counter32, ifInErrors Counter32, ifInUnknownProtos Counter32, ifOutOctets Counter32, ifOutUcastPkts Counter32, ifOutNUcastPkts Counter32, ifOutDiscards Counter32, ifOutErrors Counter32, ifOutQLen Gauge32, ifSpecific OBJECT IDENTIFIER } ifIndex OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS read-only STATUS current DESCRIPTION "A unique value, greater than zero, for each interface. It is recommended that values are assigned contiguously starting from 1. The value for each interface sub-layer must remain constant at least from one re-initialization of the entity's network management system to the next re-initialization." ::= { ifEntry 1 } ifDescr OBJECT-TYPE SYNTAX DisplayString (SIZE (0..255)) MAX-ACCESS read-only STATUS current DESCRIPTION "A textual string containing information about the interface. This string should include the name of the manufacturer, the product name and the version of the hardware interface." ::= { ifEntry 2 } ifType OBJECT-TYPE SYNTAX INTEGER { Expires November 1993 [Page 14] Draft Interfaces Group Evolution May 1993 other(1), -- none of the following regular1822(2), hdh1822(3), ddn-x25(4), rfc877-x25(5), ethernet-csmacd(6), iso88023-csmacd(7), iso88024-tokenBus(8), iso88025-tokenRing(9), iso88026-man(10), starLan(11), proteon-10Mbit(12), proteon-80Mbit(13), hyperchannel(14), fddi(15), lapb(16), sdlc(17), ds1(18), -- T-1 e1(19), -- european equiv. of T-1 basicISDN(20), primaryISDN(21), -- proprietary serial propPointToPointSerial(22), ppp(23), softwareLoopback(24), eon(25), -- CLNP over IP [11] ethernet-3Mbit(26), nsip(27), -- XNS over IP slip(28), -- generic SLIP ultra(29), -- ULTRA technologies ds3(30), -- T-3 sip(31), -- SMDS frame-relay(32) } MAX-ACCESS read-only STATUS current DESCRIPTION "The type of interface." ::= { ifEntry 3 } ifMtu OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS read-only STATUS current DESCRIPTION "The size of the largest datagram which can be Expires November 1993 [Page 15] Draft Interfaces Group Evolution May 1993 sent/received on the interface, specified in octets. For interfaces that are used for transmitting network datagrams, this is the size of the largest network datagram that can be sent on the interface." ::= { ifEntry 4 } ifSpeed OBJECT-TYPE SYNTAX Gauge32 MAX-ACCESS read-only STATUS current DESCRIPTION "An estimate of the interface's current bandwidth in bits per second. For interfaces which do not vary in bandwidth or for those where no accurate estimation can be made, this object should contain the nominal bandwidth. For a sub-layer which has no concept of bandwidth, this object should be zero." ::= { ifEntry 5 } ifPhysAddress OBJECT-TYPE SYNTAX PhysAddress MAX-ACCESS read-only STATUS current DESCRIPTION "The interface's address at its protocol sub- layer. For interfaces which do not have such an address (e.g., a serial line), this object should contain an octet string of zero length." ::= { ifEntry 6 } ifAdminStatus OBJECT-TYPE SYNTAX INTEGER { up(1), -- ready to pass packets down(2), testing(3) -- in some test mode } MAX-ACCESS read-write STATUS current DESCRIPTION "The desired state of the interface. The testing(3) state indicates that no operational packets can be passed." ::= { ifEntry 7 } Expires November 1993 [Page 16] Draft Interfaces Group Evolution May 1993 ifOperStatus OBJECT-TYPE SYNTAX INTEGER { up(1), -- ready to pass packets down(2), testing(3) -- in some test mode } MAX-ACCESS read-only STATUS current DESCRIPTION "The current operational state of the interface. The testing(3) state indicates that no operational packets can be passed." ::= { ifEntry 8 } ifLastChange OBJECT-TYPE SYNTAX TimeTicks MAX-ACCESS read-only STATUS current DESCRIPTION "The value of sysUpTime at the time the interface entered its current operational state. If the current state was entered prior to the last re- initialization of the local network management subsystem, then this object contains a zero value." ::= { ifEntry 9 } ifInOctets OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The total number of octets received on the interface, including framing characters." ::= { ifEntry 10 } ifInUcastPkts OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of packets, delivered by this sub- layer to a higher-layer protocol, which were not addressed to a multicast or broadcast address at this sub-layer." Expires November 1993 [Page 17] Draft Interfaces Group Evolution May 1993 ::= { ifEntry 11 } ifInNUcastPkts OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of packets, delivered by this sub- layer to a higher-layer protocol, which were addressed to a multicast or broadcast address at this sub-layer." ::= { ifEntry 12 } ifInDiscards OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of inbound packets which were chosen to be discarded even though no errors had been detected to prevent their being deliverable to a higher-layer protocol. One possible reason for discarding such a packet could be to free up buffer space." ::= { ifEntry 13 } ifInErrors OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of inbound packets that contained errors preventing them from being deliverable to a higher-layer protocol." ::= { ifEntry 14 } ifInUnknownProtos OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of packets received via the interface which were discarded because of an unknown or unsupported protocol." ::= { ifEntry 15 } Expires November 1993 [Page 18] Draft Interfaces Group Evolution May 1993 ifOutOctets OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The total number of octets transmitted out of the interface, including framing characters." ::= { ifEntry 16 } ifOutUcastPkts OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The total number of packets that higher-level protocols requested be transmitted, and which were not addressed to a multicast or broadcast address at this sub-layer, including those that were discarded or not sent." ::= { ifEntry 17 } ifOutNUcastPkts OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The total number of packets that higher-level protocols requested be transmitted, and which were addressed to a multicast or broadcast address at this sub-layer, including those that were discarded or not sent." ::= { ifEntry 18 } ifOutDiscards OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of outbound packets which were chosen to be discarded even though no errors had been detected to prevent their being transmitted. One possible reason for discarding such a packet could be to free up buffer space." ::= { ifEntry 19 } Expires November 1993 [Page 19] Draft Interfaces Group Evolution May 1993 ifOutErrors OBJECT-TYPE SYNTAX Counter32 MAX-ACCESS read-only STATUS current DESCRIPTION "The number of outbound packets that could not be transmitted because of errors." ::= { ifEntry 20 } ifOutQLen OBJECT-TYPE SYNTAX Gauge32 MAX-ACCESS read-only STATUS current DESCRIPTION "The length of the output packet queue (in packets)." ::= { ifEntry 21 } ifSpecific OBJECT-TYPE SYNTAX OBJECT IDENTIFIER MAX-ACCESS read-only STATUS current DESCRIPTION "A reference to MIB definitions specific to the particular media being used to realize the interface. For example, if the interface is realized by an ethernet, then the value of this object refers to a document defining objects specific to ethernet. If this information is not present, its value should be set to the OBJECT IDENTIFIER { 0 0 }, which is a syntactically valid object identifier, and any conformant implementation of ASN.1 and BER must be able to generate and recognize this value." ::= { ifEntry 22 } Expires November 1993 [Page 20] Draft Interfaces Group Evolution May 1993 -- -- The Interface Stack Group -- -- Implementation of this group is mandatory for all systems ifStackTable OBJECT-TYPE SYNTAX SEQUENCE OF IfStackEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "The table containing information on the relationships between the multiple sub-layers of network interfaces. In particular, it contains information on which sub-layers run 'on top of' which other sub-layers. Each sub-layer corresponds to a conceptual row in the ifTable." ::= { ifMIBObjects 1 } ifStackEntry OBJECT-TYPE SYNTAX IfStackEntry MAX-ACCESS not-accessible STATUS current DESCRIPTION "Information on a particular relationship between two sub-layers, specifying that one sub-layer runs on 'top' of the other sub-layer. Each sub-layer corresponds to a conceptual row in the ifTable." INDEX { ifStackHigherLayer, ifStackLowerLayer } ::= { ifStackTable 1 } IfStackEntry ::= SEQUENCE { ifStackHigherLayer Integer32, ifStackLowerLayer Integer32, ifStackStatus RowStatus } ifStackHigherLayer OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS not-accessible STATUS current DESCRIPTION Expires November 1993 [Page 21] Draft Interfaces Group Evolution May 1993 "The value of ifIndex corresponding to the higher sub-layer of the relationship, i.e., the sub-layer which runs on 'top' of the sub-layer identified by the corresponding instance of ifStackLowerLayer. If there is no higher sub-layer (below the internetwork layer), then this object has the value 0." ::= { ifStackEntry 1 } ifStackLowerLayer OBJECT-TYPE SYNTAX Integer32 MAX-ACCESS not-accessible STATUS current DESCRIPTION "The value of ifIndex corresponding to the lower sub-layer of the relationship, i.e., the sub-layer which runs 'below' the sub-layer identified by the corresponding instance of ifStackHigherLayer. If there is no lower sub-layer, then this object has the value 0." ::= { ifStackEntry 2 } ifStackStatus OBJECT-TYPE SYNTAX RowStatus MAX-ACCESS read-write STATUS current DESCRIPTION "The status of the relationship between two sub- layers. Changing the value of this object from "active" to "notInService" or "destroy" will likely have consequences up and down the interface stack. Thus, write access to this object is likely to be inappropriate for some types of interfaces, and many implementations will choose not to support write-access for any type of interface." ::= { ifStackEntry 3 } Expires November 1993 [Page 22] Draft Interfaces Group Evolution May 1993 -- conformance information ifConformance OBJECT IDENTIFIER ::= { ifMIB 2 } ifGroups OBJECT IDENTIFIER ::= { ifConformance 1 } ifCompliances OBJECT IDENTIFIER ::= { ifConformance 2 } -- compliance statements ifCompliance MODULE-COMPLIANCE STATUS current DESCRIPTION "The compliance statement for SNMPv2 entities which have network interfaces." MODULE -- this module MANDATORY-GROUPS { ifGeneralGroup, ifStackGroup } GROUP ifCharacterGroup DESCRIPTION "This group is mandatory only for those network interfaces which are character-oriented or packet-oriented." GROUP ifPacketGroup DESCRIPTION "This group is mandatory only for those network interfaces which are packet-oriented." OBJECT ifStackStatus SYNTAX INTEGER { active(1) } -- subset of RowStatus MIN-ACCESS read-only DESCRIPTION "Write access is not required, and only one of the six enumerated values for the RowStatus textual convention need be supported, specifically: active(1)." ::= { ifCompliances 1 } Expires November 1993 [Page 23] Draft Interfaces Group Evolution May 1993 -- units of conformance ifGeneralGroup OBJECT-GROUP OBJECTS { ifDescr, ifType, ifSpeed, ifPhysAddress, ifAdminStatus, ifOperStatus, ifLastChange, ifSpecific } STATUS current DESCRIPTION "A collection of objects providing information applicable to all network interfaces." ::= { ifGroups 1 } ifCharacterGroup OBJECT-GROUP OBJECTS { ifInOctets, ifOutOctets } STATUS current DESCRIPTION "A collection of objects providing information specific to packet-oriented or character-oriented network interfaces." ::= { ifGroups 2 } ifPacketGroup OBJECT-GROUP OBJECTS { ifMtu, ifInUcastPkts, ifInNUcastPkts, ifInDiscards, ifInErrors, ifInUnknownProtos, ifOutUcastPkts, ifOutNUcastPkts, ifOutDiscards, ifOutErrors, ifOutQLen } STATUS current DESCRIPTION "A collection of objects providing information specific to packet-oriented network interfaces." ::= { ifGroups 3 } ifStackGroup OBJECT-GROUP OBJECTS { ifStackStatus } STATUS current DESCRIPTION "A collection of objects providing information on the layering of MIB-II interfaces." ::= { ifGroups 4 } END Expires November 1993 [Page 24] Draft Interfaces Group Evolution May 1993 5. Acknowledgements The proposals in this memo are the result of conversations and discussions with many people, including at least the following: Fred Baker, Ted Brunner, Chuck Davin, Jeremy Greene, Marshall Rose, Kaj Tesink, and Dean Throop. However, it does not necessarily represent any consensus among the above-mentioned. Expires November 1993 [Page 25] Draft Interfaces Group Evolution May 1993 6. References [1] M.T. Rose and K. McCloghrie, Structure and Identification of Management Information for TCP/IP-based internets, Request for Comments 1155. (May, 1990). [2] M. Rose and K. McCloghrie, Editors, Concise MIB Definitions, RFC 1212, March 1991. [3] K. McCloghrie and M.T. Rose, Management Information Base for Network Management of TCP/IP-based internets - MIB-2, Request for Comments 1213. (March, 1991). [4] J.D. Case, M.S. Fedor, M.L. Schoffstall, and J.R. Davin, Simple Network Management Protocol, Request for Comments 1157. (May, 1990). [5] International Organization for Standardization, Information processing systems - Open Systems Interconnection - Specification of Abstract Syntax Notation One (ASN.1), International Standard 8824, (December, 1987). [6] J. Postel, Internet Protocol, RFC791, September 1981. [7] K. McCloghrie, Extensions to the Generic-Interface MIB, RFC1229, May 1991. Expires November 1993 [Page 26] Draft Interfaces Group Evolution May 1993 7. Security Considerations Security issues are not discussed in this memo. 8. Authors' Address Keith McCloghrie Hughes LAN Systems 1225 Charleston Rd, Mountain View, Ca 94043 415-966-7934 kzm@hls.com Frank Kastenholz FTP Software 2 High Street North Andover, Mass. USA 01845 (508)685-4000 kasten@ftp.com Expires November 1993 [Page 27] Draft Interfaces Group Evolution May 1993 Table of Contents 1 Introduction .......................................... 2 2 The SNMPv2 Network Management Framework ............... 3 2.1 Object Definitions .................................. 3 3 Experience with the Interfaces Group .................. 4 3.1 Areas of Clarification/Revision ..................... 4 3.1.1 Interface Numbering ............................... 4 3.1.2 Interface Sub-Layers .............................. 5 3.1.3 Virtual Circuits .................................. 6 3.1.4 Bit and Character Oriented Interfaces ............. 6 3.2 Clarifications/Revisions ............................ 6 3.2.1 Interface Numbering ............................... 7 3.2.2 Interface Sub-Layers .............................. 8 3.2.3 Virtual Circuits .................................. 9 3.2.4 Bit and Character Oriented Interfaces ............. 10 4 Definitions ........................................... 12 5 Acknowledgements ...................................... 25 6 References ............................................ 26 7 Security Considerations ............................... 27 8 Authors' Address ...................................... 27 Expires November 1993 [Page 28]