| Rfc | 6643 |
|---|
| Title | Translation of Structure of Management Information Version 2 (SMIv2)
MIB Modules to YANG Modules |
|---|
| Author | J. Schoenwaelder |
|---|
| Date | July 2012 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Internet Engineering Task Force (IETF) J. Schoenwaelder
Request for Comments: 6643 Jacobs University
Category: Standards Track July 2012
ISSN: 2070-1721
Translation of Structure of Management Information Version 2 (SMIv2)
MIB Modules to YANG Modules
Abstract
YANG is a data modeling language used to model configuration and
state data manipulated by the Network Configuration Protocol
(NETCONF), NETCONF remote procedure calls, and NETCONF notifications.
The Structure of Management Information (SMIv2) defines fundamental
data types, an object model, and the rules for writing and revising
MIB modules for use with the Simple Network Management Protocol
(SNMP). This document defines a translation of SMIv2 MIB modules
into YANG modules, enabling read-only (config false) access to data
objects defined in SMIv2 MIB modules via NETCONF.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6643.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
1. Introduction
This document describes a translation of SMIv2 [RFC2578], [RFC2579],
[RFC2580] MIB modules into YANG [RFC6020] modules, enabling read-only
(config false, as defined in Section 7.19.1 of RFC 6020) access to
SMIv2 objects defined in SMIv2 MIB modules via NETCONF [RFC6241].
For a discussion why SMIv2 read-write or read-create objects are
translated to read-only (config false) YANG objects, see Section 11.
YANG modules generated from SMIv2 modules should not be modified.
Any necessary changes should be made by modifying the original SMIv2
modules (with proper updates of the SMIv2 LAST-UPDATED and REVISION
clauses) and then running the translation defined in this memo again.
Note that this does not affect the usage of YANG augments and or YANG
deviations: YANG modules generated from SMIv2 modules can be
augmented like any other YANG module, and YANG deviations can be used
to document how an implementation deviates from the generated YANG
module.
SMIv1 modules can be converted to YANG by first following the rules
in [RFC3584] to convert the SMIv1 module to SMIv2 and then following
the rules in this document to convert the obtained SMIv2 module to
YANG.
The SMIv2-to-YANG mapping is illustrated by examples showing the
translation of parts of the IF-MIB [RFC2863], the DIFFSERV-MIB
[RFC3289], and the RMON2-MIB [RFC4502] SMIv2 modules.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119].
2. Mapping of Well-Known Types
The SMIv2 base types and some well-known derived textual conventions
are mapped to YANG types according to Appendix A. The mapping of the
OCTET STRING depends on the context. If an OCTET STRING type has an
associated DISPLAY-HINT, then the corresponding YANG base type is the
string type. An implementation MUST format an OCTET STRING value
according to the DISPLAY-HINT, as described in RFC 2579. If an
OCTECT STRING type does not have an associated DISPLAY-HINT, the
binary type is used. Similarly, the mapping of the INTEGER type
depends on its usage as an enumeration or a 32-bit integral type.
Implementations should provide implementation-specific options to
handle situations where DISPLAY- HINTs are added during a revision of
a module and backwards compatibility must be preserved, i.e., an
added DISPLAY-HINT needs to be ignored.
The mappings shown in Appendix A may require to import the ietf-yang-
types, ietf-inet-types, or ietf-yang-smiv2 YANG modules since some
SMIv2 types and textual conventions map to YANG types defined in the
ietf-yang-types and ietf-inet-types YANG modules defined in [RFC6021]
and the ietf-yang-smiv2 YANG module defined in this document.
Implementations MUST add any additional imports required by the type
mapping.
3. Translation of SMIv2 Modules and SMIv2 IMPORT Clauses
SMIv2 modules are mapped to corresponding YANG modules. The
generated YANG module name MUST be the same as the SMIv2 module name.
The YANG namespace MUST be constructed out of the IANA-registered
prefix urn:ietf:params:xml:ns:yang:smiv2: (see Section 12) followed
by the SMIv2 module name. Since SMIv2 module names can be assumed to
be unique (see Section 3 in [RFC2578]), the resulting YANG namespace
is unique.
The YANG prefix MAY be derived from the SMIv2 module name using the
module prefix generation algorithm described in Appendix B. The YANG
prefix is supposed to be short, and it must be unique within the set
of all prefixes used by a YANG module. The algorithm described in
Appendix B generates such prefixes.
SMIv2 IMPORT clauses are translated to YANG import statements. One
major difference between the SMIv2 import mechanism and the YANG
import mechanism is that SMIv2 IMPORT clauses import specific symbols
from an SMIv2 module, while the YANG import statement imports all
symbols of the referenced YANG module.
In order to produce correct and complete YANG import statements, the
following rules MUST be used:
o Process each item in each SMIv2 IMPORT clause as follows:
1. If an import statement for this SMIv2 module has already been
generated, then ignore this item.
2. Otherwise, if the SMIv2 module name is SNMPv2-SMI or SNMPv2-
CONF, then ignore this item. Note that these two modules can
be completely ignored since all definitions in these modules
are translated by translation rules.
3. Otherwise, if this item is a textual convention matching one
of the textual conventions in the SMIv2 types column of
Appendix A (e.g., MacAddress, PhysAddress, or TimeStamp) then
ignore this item.
4. Otherwise, if the item is used in a SYNTAX clause of an
OBJECT-TYPE whose MAX-ACCESS is not accessible-for-notify,
then generate an import statement as described below.
5. Otherwise, if the item is used in an OBJECTS clause of a
NOTIFICATION-TYPE, then generate an import statement as
described below.
6. Otherwise, if the item is used in an INDEX or AUGMENTS clause,
then generate an import statement as described below.
7. Otherwise, ignore this item. Some examples of this case are
OBJECT IDENTIFIER assignments and objects that are only
referenced in MODULE-COMPLIANCE, OBJECT-GROUP, or
NOTIFICATION-GROUP clauses.
o Generate any additional import statements as required by the type
translations according to the type mapping table Appendix A. This
requires the translator to consider all the types used in the
SMIv2 module in order to produce the imports.
o Generate an import statement for the YANG module ietf-yang-smiv2
with the prefix smiv2.
The generated import statements use the untranslated SMIv2 module
names or the names of well-known YANG modules as their argument. The
import statement must contain a prefix statement. The prefixes MAY
be generated by applying the module prefix generation algorithm
described in Appendix B.
3.1. Example: IMPORTS of IF-MIB
The translation of the IF-MIB [RFC2863] leads to the YANG module and
namespace/prefix statement and the import statements shown below.
The prefix is the translation of the SMIv2 module name IF-MIB to
lowercase (consisting of two tokens and thus no further
abbreviation).
module IF-MIB {
namespace "urn:ietf:params:xml:ns:yang:smiv2:IF-MIB";
prefix "if-mib";
import IANAifType-MIB { prefix "ianaiftype-mib"; }
import SNMPv2-TC { prefix "snmpv2-tc"; }
import ietf-yang-types { prefix "yang"; }
import ietf-yang-smiv2 { prefix "smiv2"; }
}
4. Translation of the MODULE-IDENTITY Macro
SMIv2 requires an invocation of the MODULE-IDENTITY macro to provide
contact and revision history for a MIB module. The clauses of the
SMIv2 MODULE-IDENTITY macro MUST be translated into YANG statements
as detailed below.
4.1. MODULE-IDENTITY Translation Rules
o The SMIv2 ORGANIZATION clause is mapped to the YANG organization
statement.
o The SMIv2 CONTACT-INFO clause is mapped to the YANG contact
statement.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o Each SMIv2 REVISION clause is mapped to a YANG revision statement.
The revision is identified by the date argument of the SMIv2
REVISION clause. DESCRIPTION sub-clauses of REVISION clauses are
mapped to corresponding description statement nested in revision
clauses.
o The SMIv2 LAST-UPDATED clause is ignored if the associated date
matches a REVISION clause. Otherwise, an additional revision
statement is generated.
o A top-level YANG container is generated. The container's name is
the SMIv2 module name, and the container MUST be config false.
The generation of the top-level container MAY be skipped if the
SMIv2 module does not define any objects that go into the top-
level container (e.g., an SMIv2 module only defining textual
conventions).
o The object identifier value of the invocation of the SMIv2 MODULE-
IDENTITY is translated into an smiv2:oid statement contained in an
smiv2:alias statement representing the MODULE-IDENTITY macro
invocation. Refer to the YANG extension defined in Section 10.
While all proper SMIv2 modules must have exactly one MODULE-IDENTITY
macro invocation, there are a few notable exceptions. The modules
defining the SMIv2 language (i.e., the SNMPv2-SMI, SNMPv2-TC, and
SNMPv2-CONF modules) do not invoke the MODULE-IDENTITY macro.
Furthermore, SMIv2 modules generated from SMIv1 modules may miss an
invocation of the MODULE-IDENTITY macro as well. In such cases, it
is preferable to not generate organization, contact, description, or
revision statements.
4.2. Example: MODULE-IDENTITY of IF-MIB
The translation of the MODULE-IDENTITY of the IF-MIB [RFC2863] leads
to the following YANG statements:
organization
"IETF Interfaces MIB Working Group";
contact
"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 to describe generic objects for network
interface sub-layers. This MIB is an updated version of
MIB-II's ifTable, and incorporates the extensions defined in
RFC 1229.";
revision "2000-06-14" {
description
"Clarifications agreed upon by the Interfaces MIB WG, and
published as RFC 2863.";
}
revision "1996-02-28" {
description
"Revisions made by the Interfaces MIB WG, and published in
RFC 2233.";
}
revision "1993-11-08" {
description
"Initial revision, published as part of RFC 1573.";
}
container IF-MIB {
config false;
}
5. Translation of the TEXTUAL-CONVENTION Macro
The SMIv2 uses invocations of the TEXTUAL-CONVENTION macro to define
new types derived from the SMIv2 base types. Invocations of the
TEXTUAL-CONVENTION macro MUST be translated into YANG typedef
statements as detailed below.
5.1. TEXTUAL-CONVENTION Translation Rules
The name of the TEXTUAL-CONVENTION macro invocation is used as the
name of the generated typedef statement. The clauses of the SMIv2
TEXTUAL-CONVENTION macro are mapped to YANG statements embedded in
the typedef statement as follows:
o The SMIv2 DISPLAY-HINT clause is used to determine the type
mapping of types derived form the OCTET STRING type as explained
in Section 2. Furthermore, the DISPLAY-HINT value MAY be used to
generate a regular expression for the YANG pattern statement
within the type statement.
o The SMIv2 DISPLAY-HINT is translated into an smiv2:display-hint
statement. Refer to the YANG extension defined in Section 10.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The SMIv2 SYNTAX clause is mapped to the YANG type statement.
SMIv2 range restrictions are mapped to YANG range statements,
while SMIv2 length restrictions are mapped to YANG length
statements. SMIv2 INTEGER enumerations are mapped to YANG enum/
value statements. SMIv2 BITS are mapped to YANG bit/position
statements. For OCTET STRING types that are mapped to a YANG
string base type (see Section 2), the length specified in the YANG
length statement must be consistent with the stringified
representation of values. If an implementation is unable to
derive a proper length restrictions, then the YANG length
statement MUST be omitted.
This translation assumes that labels of named numbers and named bits
do not change when an SMIv2 module is revised. This is consistent
with the clarification of the SMIv2 module revision rules in Section
4.9 of [RFC4181].
5.2. Example: OwnerString and InterfaceIndex of IF-MIB
The translations of the OwnerString and InterfaceIndex textual
conventions of the IF-MIB [RFC2863] are shown below.
typedef OwnerString {
type string {
length "0..255";
pattern '\p{IsBasicLatin}{0,255}';
}
status deprecated;
description
"This data type is used to model an administratively
assigned name of the owner of a resource. This information
is taken from the NVT ASCII character set. It is suggested
that this name contain one or more of the following: ASCII
form of the manager station's transport address, management
station name (e.g., domain name), network management
personnel's name, location, or phone number. In some cases
the agent itself will be the owner of an entry. In these
cases, this string shall be set to a string starting with
'agent'.";
smiv2:display-hint "255a";
}
typedef InterfaceIndex {
type int32 {
range "1..2147483647";
}
description
"A unique value, greater than zero, for each interface or
interface sub-layer in the managed system. 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.";
smiv2:display-hint "d";
}
5.3. Example: IfDirection of the DIFFSERV-MIB
The translation of the IfDirection textual convention of the
DIFFSERV-MIB [RFC3289] is shown below.
typedef IfDirection {
type enumeration {
enum inbound { value 1; }
enum outbound { value 2; }
}
description
"IfDirection specifies a direction of data travel on an
interface. 'inbound' traffic is operated on during reception
from the interface, while 'outbound' traffic is operated on
prior to transmission on the interface.";
}
6. Translation of OBJECT IDENTIFIER Assignments
The SMIv2 uses OBJECT IDENTIFIER assignments to introduce names for
intermediate nodes in the OBJECT IDENTIFIER tree. OBJECT IDENTIFIER
assignments are translated into smiv2:alias statements. Refer to the
YANG extension defined in Section 10.
7. Translation of the OBJECT-TYPE Macro
The SMIv2 uses the OBJECT-TYPE macro to define objects and the
structure of conceptual tables. Objects exist either as scalars
(exactly one instance within an SNMP context) or columnar objects
within conceptual tables (zero or multiple instances within an SNMP
context). A number of auxiliary objects define the index (key) of a
conceptual table. Furthermore, conceptual tables can be augmented by
other conceptual tables. All these differences must be taken into
account when translating SMIv2 OBJECT-TYPE macro invocations to YANG.
Invocations of the OBJECT-TYPE macro MUST be translated into YANG
statements as detailed below.
7.1. Scalar and Columnar Object Translation Rules
SMIv2 OBJECT-TYPE macro invocations defining scalars or columnar
objects with a MAX-ACCESS of "not-accessible", "read-only",
"read-write", and "read-create" are translated to YANG leaf
statements. Additionally, columnar objects with a MAX-ACCESS of
"accessible-for-notify" are translated to YANG leaf statements if
that columnar object is part of the INDEX clause of the table
containing that columnar object. The name of the leaf is the name
associated with the SMIv2 OBJECT-TYPE macro invocation. SMIv2
OBJECT-TYPE macro invocations with a MAX-ACCESS of
"accessible-for-notify" are not translated to YANG data tree leafs
but instead are translated into YANG notification leafs.
Leaf statements for scalar objects are created in a container
representing the scalar's parent node in the OID tree. This
container is named after the scalar's parent node in the OID tree and
placed in the top-level container representing the SMIv2 module; see
Section 4.1. In the rare case that the scalar's parent node has
multiple names, the automatic translation MUST fail with an error,
and the name clash needs to be investigated and fixed manually. In
case a previous revision of the SMIv2 module did not have an
ambiguity, then the name used by the previous revision MUST be used.
The leaf statements representing columnar objects are created in the
list representing a conceptual row; see Section 7.3.
o The SMIv2 SYNTAX clause is mapped to the YANG type statement.
SMIv2 range restrictions are mapped to YANG range statements,
while SMIv2 length restrictions are mapped to YANG length
statements. SMIv2 INTEGER enumerations are mapped to YANG enum/
value statements. SMIv2 BITS are mapped to YANG bit/position
statements. For OCTET STRING types that are mapped to a YANG
string base type (see Section 2), the length specified in the YANG
length statement must be consistent with the stringified
representation of values. If an implementation is unable to
derive proper length restrictions, then the YANG length statement
MUST be omitted.
o The SMIv2 UNITS clause is mapped to the YANG units statement.
o The SMIv2 MAX-ACCESS is translated into an smiv2:max-access
statement. Refer to the YANG extension defined in Section 10.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The SMIv2 DEFVAL clause is mapped to an smiv2:defval statement.
Refer to the YANG extension defined in Section 10.
o The value of the SMIv2 OBJECT-TYPE macro invocation is translated
into an smiv2:oid statement. Refer to the YANG extension defined
in Section 10.
This translation assumes that labels of named numbers and named bits
do not change when an SMIv2 module is revised. This is consistent
with the clarification of the SMIv2 module revision rules in Section
4.9 of [RFC4181].
7.2. Example: ifNumber and ifIndex of the IF-MIB
The translations of the ifNumber scalar object and the ifIndex
columnar object of the IF-MIB [RFC2863] are shown below. Since
ifNumber is a scalar object in the interfaces branch of the IF-MIB,
the YANG leaf ifNumber will be placed in a YANG container called
interfaces, which is registered in the top-level container IF-MIB.
leaf ifNumber {
type int32;
description
"The number of network interfaces (regardless of their
current state) present on this system.";
smiv2:max-access "read-only";
smiv2:oid "1.3.6.1.2.1.2.1";
}
leaf ifIndex {
type if-mib:InterfaceIndex;
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.";
smiv2:max-access "read-only";
smiv2:oid "1.3.6.1.2.1.2.2.1.1";
}
7.3. Non-Augmenting Conceptual Table Translation Rules
An OBJECT-TYPE macro invocation defining a non-augmenting conceptual
table is translated to a YANG container statement using the name of
the OBJECT-TYPE macro invocation. This container is created in the
top-level container representing the SMIv2 module. The clauses of
the macro are translated as follows:
o The SMIv2 SYNTAX clause is ignored
o The SMIv2 UNITS clause is ignored.
o The SMIv2 MAX-ACCESS clause is ignored.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The value of the SMIv2 OBJECT-TYPE macro invocation is translated
into an smiv2:oid statement. Refer to the YANG extension defined
in Section 10.
An OBJECT-TYPE macro invocation defining a conceptual row is
translated to a YANG list statement. It is contained in the YANG
container representing the conceptual table. The generated list uses
the name of the row OBJECT-TYPE macro invocation. The clauses of the
OBJECT-TYPE macro are translated as follows:
o The SMIv2 SYNTAX clause is ignored.
o The SMIv2 UNITS clause is ignored.
o The SMIv2 MAX-ACCESS clause is ignored.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The SMIv2 INDEX clause is mapped to the YANG key clause listing
the columnar objects forming the key of the YANG list. If the
same object appears more than once in the INDEX clause, append
'_<n>' to the duplicate object name(s) where '<n>' counts the
occurrences of the object in the INDEX clause, starting from 2.
Additional leaf statements must be created to define the leafs
introduced.
o If the SMIv2 INDEX clause contains the IMPLIED keyword, then an
smiv2:implied statement is generated to record the name of the
object preceded by the IMPLIED keyword. Refer to the YANG
extension defined in Section 10.
o The value of the SMIv2 OBJECT-TYPE macro invocation is translated
into an smiv2:oid statement. Refer to the YANG extension defined
in Section 10.
Within the list statement, YANG leaf statements are created for
columnar objects as described in Section 7.1. For objects listed in
the SMIv2 INDEX clause that are not part of the conceptual table
itself, YANG leaf statements of type leafref pointing to the
referenced definition are created.
7.4. Example: ifTable of the IF-MIB
The translation of the definition of the ifTable of the IF-MIB
[RFC2863] is shown below.
container ifTable {
description
"A list of interface entries. The number of entries is
given by the value of ifNumber.";
smiv2:oid "1.3.6.1.2.1.2.2";
list ifEntry {
key "ifIndex";
description
"An entry containing management information applicable to a
particular interface.";
smiv2:oid "1.3.6.1.2.1.2.2.1";
leaf ifIndex {
type if-mib:InterfaceIndex;
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.";
smiv2:max-access "read-only";
smiv2:oid "1.3.6.1.2.1.2.2.1.1";
}
// ...
}
}
7.5. Example: ifRcvAddressTable of the IF-MIB
The translation of the definition of the ifRcvAddressTable of the
IF-MIB [RFC2863] is shown below.
container ifRcvAddressTable {
description
"This table contains an entry for each address (broadcast,
multicast, or uni-cast) for which the system will receive
packets/frames on a particular interface, except as follows:
- for an interface operating in promiscuous mode, entries are
only required for those addresses for which the system would
receive frames were it not operating in promiscuous mode.
- for 802.5 functional addresses, only one entry is required,
for the address which has the functional address bit ANDed
with the bit mask of all functional addresses for which the
interface will accept frames.
A system is normally able to use any unicast address which
corresponds to an entry in this table as a source address.";
smiv2:oid "1.3.6.1.2.1.31.1.4";
list ifRcvAddressEntry {
key "ifIndex ifRcvAddressAddress";
description
"A list of objects identifying an address for which the
system will accept packets/frames on the particular
interface identified by the index value ifIndex.";
smiv2:oid "1.3.6.1.2.1.31.1.4.1";
leaf ifIndex {
type leafref {
path "/if-mib:IF-MIB/if-mib:ifTable" +
"/if-mib:ifEntry/if-mib:ifIndex";
}
}
leaf ifRcvAddressAddress {
type yang:phys-address;
description
"An address for which the system will accept packets/frames
on this entry's interface.";
smiv2:max-access "not-accessible";
smiv2:oid "1.3.6.1.2.1.31.1.4.1.1";
}
// ...
}
}
7.6. Example: alHostTable of the RMON2-MIB
The translation of the definition of the alHostTable of the RMON2-MIB
[RFC4502] is shown below.
container alHostTable {
description
"A collection of statistics for a particular protocol from a
particular network address that has been discovered on an
interface of this device.
The probe will populate this table for all protocols in the
protocol directory table whose value of
protocolDirHostConfig is equal to supportedOn(3), and
will delete any entries whose protocolDirEntry is deleted or
has a protocolDirHostConfig value of supportedOff(2).
The probe will add to this table all addresses
seen as the source or destination address in all packets with
no MAC errors and will increment octet and packet counts in
the table for all packets with no MAC errors. Further,
entries will only be added to this table if their address
exists in the nlHostTable and will be deleted from this table
if their address is deleted from the nlHostTable.";
smiv2:oid "1.3.6.1.2.1.16.16.1";
list alHostEntry {
key "hlHostControlIndex alHostTimeMark protocolDirLocalIndex "
+ "nlHostAddress protocolDirLocalIndex_2";
description
"A conceptual row in the alHostTable.
The hlHostControlIndex value in the index identifies the
hlHostControlEntry on whose behalf this entry was created.
The first protocolDirLocalIndex value in the index identifies
the network-layer protocol of the address.
The nlHostAddress value in the index identifies the network-
layer address of this entry.
The second protocolDirLocalIndex value in the index identifies
the protocol that is counted by this entry.
An example of the indexing in this entry is
alHostOutPkts.1.783495.18.4.128.2.6.6.34.
Note that some combinations of index values may result in an
index that exceeds 128 sub-identifiers in length, which exceeds
the maximum for the SNMP protocol. Implementations should take
care to avoid such combinations.";
smiv2:oid "1.3.6.1.2.1.16.16.1.1";
// ...
leaf protocolDirLocalIndex {
type leafref {
path "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:protocolDirTable/"
+ "rmon2-mib:protocolDirEntry/"
+ "rmon2-mib:protocolDirLocalIndex";
}
}
// ...
leaf protocolDirLocalIndex_2 {
type leafref {
path "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:protocolDirTable/"
+ "rmon2-mib:protocolDirEntry/"
+ "rmon2-mib:protocolDirLocalIndex";
}
}
// ...
}
}
7.7. Augmenting Conceptual Tables Translation Rules
An OBJECT-TYPE macro invocation defining an augmenting conceptual
table is translated to a YANG smiv2:alias statement. Refer to the
YANG extension defined in Section 10. The clauses of the macro are
translated as follows:
o The SMIv2 SYNTAX clause is ignored.
o The SMIv2 UNITS clause is ignored.
o The SMIv2 MAX-ACCESS clause is ignored.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The value of the SMIv2 OBJECT-TYPE macro invocation is translated
into an smiv2:oid statement. Refer to the YANG extension defined
in Section 10.
An OBJECT-TYPE macro invocation defining a conceptual row
augmentation is translated to a YANG smiv2:alias statement and a YANG
augment statement using the path to the augmented table as its
argument. The clauses of the OBJECT-TYPE macro are translated as
follows:
o The SMIv2 SYNTAX clause is ignored.
o The SMIv2 UNITS clause is ignored.
o The SMIv2 MAX-ACCESS clause is ignored.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The value of the SMIv2 OBJECT-TYPE macro invocation is translated
into an smiv2:oid statement. Refer to the YANG extension defined
in Section 10.
Within the augment statement, YANG leaf statements are created as
described in Section 7.1.
7.8. Example: ifXTable of the IF-MIB
The translation of the definition of the ifXTable of the IF-MIB
[RFC2863] is shown below.
smiv2:alias "ifXTable" {
description
"A list of interface entries. The number of entries is
given by the value of ifNumber. This table contains
additional objects for the interface table.";
smiv2:oid "1.3.6.1.2.1.31.1.1";
}
smiv2:alias "ifXEntry" {
description
"An entry containing additional management information
applicable to a particular interface.";
smiv2:oid "1.3.6.1.2.1.31.1.1.1";
}
augment "/if-mib:IF-MIB/if-mib:ifTable/if-mib:ifEntry" {
description
"An entry containing additional management information
applicable to a particular interface.";
smiv2:oid "1.3.6.1.2.1.31.1.1.1";
leaf ifName {
type snmpv2-tc:DisplayString;
description
"The textual name of the interface. The value of this
object should be the name of the interface as assigned by
the local device and should be suitable for use in commands
entered at the device's `console'. This might be a text
name, such as `le0' or a simple port number, such as `1',
depending on the interface naming syntax of the device. If
several entries in the ifTable together represent a single
interface as named by the device, then each will have the
same value of ifName. Note that for an agent which responds
to SNMP queries concerning an interface on some other
(proxied) device, then the value of ifName for such an
interface is the proxied device's local name for it.
If there is no local name, or this object is otherwise not
applicable, then this object contains a zero-length string.";
smiv2:max-access "read-only";
smiv2:oid "1.3.6.1.2.1.31.1.1.1.1";
}
// ...
}
8. Translation of the OBJECT-IDENTITY Macro
The SMIv2 uses invocations of the OBJECT-IDENTITY macro to define
information about an OBJECT IDENTIFIER assignment. Invocations of
the OBJECT-IDENTITY macro MUST be translated into YANG identity
statements as detailed below.
8.1. OBJECT-IDENTITY Translation Rules
The name of the OBJECT-IDENTITY macro invocation is used as the name
of the generated identity statement. The generated identity
statement uses the smiv2:object-identity defined in Section 10 as its
base. The clauses of the SMIv2 OBJECT-IDENTITY macro are mapped to
YANG statements as follows:
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The value of the SMIv2 OBJECT-IDENTITY macro invocation is
translated into an smiv2:oid statement. Refer to the YANG
extension defined in Section 10.
8.2. Example: diffServTBParamSimpleTokenBucket of the DIFFSERV-MIB
The translation of the diffServTBParamSimpleTokenBucket of the
DIFFSERV-MIB [RFC3289] is shown below. (Please note that the
description should refer to RFC 3290, Section 5.1.3.)
identity diffServTBParamSimpleTokenBucket {
base "smiv2:object-identity";
description
"Two Parameter Token Bucket Meter as described in the Informal
Differentiated Services Model section 5.2.3.";
smiv2:oid "1.3.6.1.2.1.97.3.1.1";
}
9. Translation of the NOTIFICATION-TYPE Macro
SMIv2 provides the NOTIFICATION-TYPE macro to define event
notifications. YANG provides the notification statement for the same
purpose. Invocations of the NOTIFICATION-TYPE macro MUST be
translated into YANG notification statements as detailed below.
9.1. NOTIFICATION-TYPE Translation Rules
The name of the NOTIFICATION-TYPE macro invocation is used as the
name of the generated notification statement. The clauses of the
NOTIFICATION-TYPE macro are mapped to YANG statements embedded in the
notification statement as follows.
o The SMIv2 OBJECTS clause is mapped to a sequence of YANG
containers. For each object listed in the OBJECTS clause value, a
YANG container statement is generated. The name of this container
is the string "object-<n>", where <n> is the position of the
object in the value of the OBJECTS clause (first element has
position 1). If the current object belongs to a conceptual table,
then a sequence of leaf statements is generated for each INDEX
object of the conceptual table. These leafs are named after the
INDEX objects and of type leafref. Finally, a leaf statement is
generated named after the current object. If the current object
has a MAX-ACCESS of "read-only", "read-write", or "read-create",
then the generated leaf is of type leafref. Otherwise, if the
current object has a MAX-ACCESS of "accessible-for-notify", then a
leaf is generated, following the steps in Section 7.1.
o The SMIv2 STATUS clause is mapped to the YANG status statement.
The generation of the YANG status statement is skipped if the
value of the STATUS clause is current.
o The SMIv2 DESCRIPTION clause is mapped to the YANG description
statement.
o The SMIv2 REFERENCE clause is mapped to the YANG reference
statement.
o The value of the SMIv2 NOTIFICATION-TYPE macro invocation is
translated into an smiv2:oid statement. Refer to the YANG
extension defined in Section 10.
9.2. Example: linkDown NOTIFICATION-TYPE of IF-MIB
The translation of the linkDown notification of the IF-MIB [RFC2863]
is shown below.
notification linkDown {
description
"A linkDown trap signifies that the SNMP entity, acting in
an agent role, has detected that the ifOperStatus object for
one of its communication links is about to enter the down
state from some other state (but not from the notPresent
state). This other state is indicated by the included value
of ifOperStatus.";
smiv2:oid "1.3.6.1.6.3.1.1.5.3";
container object-1 {
leaf ifIndex {
type leafref {
path "/if-mib:IF-MIB/if-mib:ifTable" +
"/if-mib:ifEntry/if-mib:ifIndex";
}
}
}
container object-2 {
leaf ifIndex {
type leafref {
path "/if-mib:IF-MIB/if-mib:ifTable" +
"/if-mib:ifEntry/if-mib:ifIndex";
}
}
leaf ifAdminStatus {
type leafref {
path "/if-mib:IF-MIB/if-mib:ifTable" +
"/if-mib:ifEntry/if-mib:ifAdminStatus";
}
}
}
container object-3 {
leaf ifIndex {
type leafref {
path "/if-mib:IF-MIB/if-mib:ifTable" +
"/if-mib:ifEntry/if-mib:ifIndex";
}
}
leaf ifOperStatus {
type leafref {
path "/if-mib:IF-MIB/if-mib:ifTable" +
"/if-mib:ifEntry/if-mib:ifOperStatus";
}
}
}
}
10. YANG Language Extension Definition
This section defines some YANG extension statements that can be used
to capture some information present in SMIv2 modules that is not
translated into core YANG statements. The YANG module references
[RFC2578] and [RFC2579].
<CODE BEGINS> file "ietf-yang-smiv2@2012-06-22.yang"
module ietf-yang-smiv2 {
namespace "urn:ietf:params:xml:ns:yang:ietf-yang-smiv2";
prefix "smiv2";
organization
"IETF NETMOD (NETCONF Data Modeling Language) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netmod/>
WG List: <mailto:netmod@ietf.org>
WG Chair: David Kessens
<mailto:david.kessens@nsn.com>
WG Chair: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>
Editor: Juergen Schoenwaelder
<mailto:j.schoenwaelder@jacobs-university.de>";
description
"This module defines YANG extensions that are used to translate
SMIv2 concepts into YANG.
Copyright (c) 2012 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC 6643; see
the RFC itself for full legal notices.";
revision 2012-06-22 {
description
"Initial revision.";
reference
"RFC 6643: Translation of Structure of Management Information
Version 2 (SMIv2) MIB Modules to YANG Modules";
}
identity object-identity {
description
"Base identity for all SMIv2 OBJECT-IDENTITYs.";
}
typedef opaque {
type binary;
description
"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 OCTET
STRING, in effect 'double-wrapping' the original ASN.1 value.
In the value set and its semantics, this type is equivalent to
the Opaque type of the SMIv2. This type exists in the SMIv2
solely for backward-compatibility reasons and this is also
true for this YANG data type.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
extension display-hint {
argument "format";
description
"The display-hint statement takes as an argument the DISPLAY-HINT
assigned to an SMIv2 textual convention.";
reference
"RFC 2579: Textual Conventions for SMIv2";
}
extension max-access {
argument "access";
description
"The max-access statement takes as an argument the MAX-ACCESS
assigned to an SMIv2 object definition.
The MAX-ACCESS value is SMIv2 specific and has no impact on
the access provided to YANG objects through protocols such
as NETCONF.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
extension defval {
argument "value";
description
"The defval statement takes as an argument a default value
defined by an SMIv2 DEFVAL clause. Note that the value is in
the SMIv2 value space defined by the SMIv2 syntax of the
corresponding object and not in the YANG value space
defined by the corresponding YANG data type.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
extension implied {
argument "index";
description
"If an SMIv2 INDEX object is preceded by the IMPLIED keyword, then
the implied statement is present in the YANG module and takes as
an argument the name of the IMPLIED index object.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
extension alias {
argument "descriptor";
description
"The alias statement introduces an SMIv2 descriptor. The body of
the alias statement is expected to contain an oid statement that
provides the numeric OID associated with the descriptor.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
extension oid {
argument "value";
description
"The oid statement takes as an argument the object identifier
assigned to an SMIv2 definition. The object identifier value
is written in decimal dotted notation.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
extension subid {
argument "value";
description
"The subid statement takes as an argument the last sub-identifier
of the object identifier assigned to an SMIv2 definition. The
sub-identifier value is a single positive decimal natural number.
The subid statement may not be used as a substatement to any
top-level node in a YANG document. The subid substatement may
be used only as a substatement to a node having a parent node
defined with either an smiv2:oid or smiv2:subid substatement.";
reference
"RFC 2578: Structure of Management Information Version 2 (SMIv2)";
}
}
<CODE ENDS>
11. Implementing Configuration Data Nodes
The result of the translation of SMIv2 MIB modules into YANG modules,
even if SMIv2 objects are read-write or read-create, consists of
read-only (config false) YANG objects. One reason is that the
persistency models of the underlying protocols, SNMP and NETCONF, are
quite different. With SNMP, the persistency of a writable object
depends either on the object definition itself (i.e., the text in the
DESCRIPTION clause) or the persistency properties of the conceptual
row it is part of, sometimes controlled via a columnar object using
the StorageType textual convention. With NETCONF, the persistency of
configuration objects is determined by the properties of the
underlying datastore. Furthermore, NETCONF as defined in [RFC6241]
does not provide a standard operation to modify operational state.
The <edit-config> and <copy-config> operations only manipulate
configuration data. As a consequence of these considerations, it is
not possible to generate YANG configuration data nodes from SMIv2
definitions in an automated way.
However, for selected SMIv2 objects where the SNMP and NETCONF
persistency semantics are consistent, implementations may choose to
implement some YANG data nodes generated from SMIv2 definitions as
configuration data nodes. Such a deviation from the generated read-
only YANG module should be formally documented in the form of a
separate YANG module that uses YANG deviation statements to change
the config property of the data nodes implemented as configuration
data nodes from false to true. Deviations that change the config
false property to true without any other changes to the semantics of
the data node do not affect the compliance with the YANG module
generated from an SMIv2 module.
11.1. Example: addressMapControlTable of RMON2-MIB
The following example demonstrates how certain columnar objects of
the addressMapControlTable of the RMON2-MIB [RFC4502] can be turned
into YANG configuration data nodes. Note that YANG deviations affect
the property of the target node only and are not inherited downwards.
module acme-RMON2-MIB-deviations {
namespace "http://acme.example.com/RMON2-MIB-deviations";
prefix "acme-rmon2-devs";
import RMON2-MIB {
prefix "rmon2-mib";
revision-date 2006-05-02;
}
revision 2012-01-11 {
description
"First version.";
}
deviation "/rmon2-mib:RMON2-MIB" {
deviate replace {
config true;
}
}
deviation "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:addressMapControlTable" {
deviate replace {
config true;
}
}
deviation "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:addressMapControlTable/"
+ "rmon2-mib:addressMapControlEntry" {
deviate replace {
config true;
}
}
deviation "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:addressMapControlTable/"
+ "rmon2-mib:addressMapControlEntry/"
+ "rmon2-mib:addressMapControlIndex" {
deviate replace {
config true;
}
}
deviation "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:addressMapControlTable/"
+ "rmon2-mib:addressMapControlEntry/"
+ "rmon2-mib:addressMapControlDataSource" {
deviate replace {
config true;
}
}
deviation "/rmon2-mib:RMON2-MIB/"
+ "rmon2-mib:addressMapControlTable/"
+ "rmon2-mib:addressMapControlEntry/"
+ "rmon2-mib:addressMapControlOwner" {
deviate replace {
config true;
}
}
}
A NETCONF server that implements the RMON2-MIB module with these
deviations would advertise the following capabilities in its <hello>
message (where whitespace has been added for readability):
<capability>
urn:ietf:params:xml:ns:yang:smiv2:RMON2-MIB?
module=RMON2-MIB&
revision=2006-05-02&
deviations=acme-RMON2-MIB-deviations
</capability>
<capability>
http://acme.example.com/RMON2-MIB-deviations?
module=acme-RMON2-MIB-deviations&
revision=2012-01-11
</capability>
12. IANA Considerations
This document registers two URIs in the IETF XML registry [RFC3688].
Following the format in RFC 3688, the following registrations have
been made.
URI: urn:ietf:params:xml:ns:yang:ietf-yang-smiv2
Registrant Contact: The NETMOD WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:smiv2
Registrant Contact: The NETMOD WG of the IETF.
XML: N/A, the requested URI is an XML namespace.
This document registers a YANG module in the YANG Module Names
registry [RFC6020].
Name: ietf-yang-smiv2
Namespace: urn:ietf:params:xml:ns:yang:ietf-yang-smiv2
Prefix: smiv2
Reference: RFC 6643
13. Security Considerations
This document defines a translation of SMIv2 MIB modules into YANG
modules, enabling read-only (config false) access to data objects
defined in SMIv2 MIB modules via NETCONF. The translation itself has
no security impact on the Internet.
Users of YANG data models generated from SMIv2 data models that have
been published in the RFC series are advised to consult the security
considerations of the respective RFCs. The security considerations
of RFCs containing SMIv2 data models explain which objects are
sensitive and important to protect. NETCONF users are encouraged to
make use of the NETCONF access control model [RFC6536], which allows
the specification of access control rules to protect potentially
sensitive information.
14. Acknowledgements
The author wishes to thank the following individuals for providing
helpful comments on various draft versions of this document: Andy
Bierman, Benoit Claise, Martin Bjorklund, Leif Johansson, David Reid,
Dan Romascanu, and David Spakes.
15. References
15.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2578] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Structure of Management Information
Version 2 (SMIv2)", STD 58, RFC 2578, April 1999.
[RFC2579] McCloghrie, K., Ed., Perkins, D., Ed., and J.
Schoenwaelder, Ed., "Textual Conventions for SMIv2",
STD 58, RFC 2579, April 1999.
[RFC2580] McCloghrie, K., Perkins, D., and J. Schoenwaelder,
"Conformance Statements for SMIv2", STD 58, RFC 2580,
April 1999.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
October 2010.
[RFC6021] Schoenwaelder, J., "Common YANG Data Types", RFC 6021,
October 2010.
15.2. Informative References
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, June 2000.
[RFC3289] Baker, F., Chan, K., and A. Smith, "Management Information
Base for the Differentiated Services Architecture",
RFC 3289, May 2002.
[RFC3584] Frye, R., Levi, D., Routhier, S., and B. Wijnen,
"Coexistence between Version 1, Version 2, and Version 3
of the Internet-standard Network Management Framework",
RFC 3584, August 2003.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004.
[RFC4181] Heard, C., "Guidelines for Authors and Reviewers of MIB
Documents", BCP 111, RFC 4181, September 2005.
[RFC4502] Waldbusser, S., "Remote Network Monitoring Management
Information Base Version 2", RFC 4502, May 2006.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, June 2011.
[RFC6536] Bierman, A., Ed. and M. Bjorklund, Ed., "Network
Configuration Protocol (NETCONF) Access Control Model",
RFC 6536, March 2012.
Appendix A. Mapping of Well-Known Types (Normative)
This normative appendix describes the mapping of SMIv2 types to YANG
types. The mapping is fully consistent with Tables 1 and 2 of
[RFC6021].
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: INTEGER (used as an enumeration)
YANG Type: enumeration
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: INTEGER (used as a numeric type)
YANG Type: int32
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: Integer32
YANG Type: int32
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: OCTET STRING (used as a binary string)
YANG Type: binary
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: OCTET STRING (used to hold UTF-8 or ASCII characters)
YANG Type: string
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: OBJECT IDENTIFIER
YANG Module: ietf-yang-types
YANG Type: object-identifier-128
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: BITS
YANG Type: bits
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: IpAddress
YANG Module: ietf-inet-types
YANG Type: ipv4-address
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: Counter32
YANG Module: ietf-yang-types
YANG Type: counter32
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: Gauge32
YANG Module: ietf-yang-types
YANG Type: gauge32
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: TimeTicks
YANG Module: ietf-yang-types
YANG Type: timeticks
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: Counter64
YANG Module: ietf-yang-types
YANG Type: counter64
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: Unsigned32
YANG Type: uint32
SMIv2 Module: SNMPv2-SMI
SMIv2 Type: Opaque
YANG Module: ietf-yang-smiv2
YANG Type: opaque
SMIv2 Module: SNMPv2-TC
SMIv2 Type: PhysAddress
YANG Module: ietf-yang-types
YANG Type: phys-address
SMIv2 Module: SNMPv2-TC
SMIv2 Type: MacAddress
YANG Module: ietf-yang-types
YANG Type: mac-address
SMIv2 Module: SNMPv2-TC
SMIv2 Type: TruthValue
YANG Type: boolean
SMIv2 Module: SNMPv2-TC
SMIv2 Type: TimeStamp
YANG Module: ietf-yang-types
YANG Type: timestamp
SMIv2 Module: RMON2-MIB
SMIv2 Type: ZeroBasedCounter32
YANG Module: ietf-yang-types
YANG Type: zero-based-counter32
SMIv2 Module: HCNUM-TC
SMIv2 Type: ZeroBasedCounter64
YANG Module: ietf-yang-types
YANG Type: zero-based-counter64
SMIv2 Module: HCNUM-TC
SMIv2 Type: CounterBasedGauge64
YANG Module: ietf-yang-types
YANG Type: gauge64
SMIv2 Module: INET-ADDRESS-MIB
SMIv2 Type: InetAutonomousSystemNumber
YANG Module: ietf-inet-types
YANG Type: as-number
SMIv2 Module: INET-ADDRESS-MIB
SMIv2 Type: InetVersion
YANG Module: ietf-inet-types
YANG Type: ip-version
SMIv2 Module: INET-ADDRESS-MIB
SMIv2 Type: InetPortNumber
YANG Module: ietf-inet-types
YANG Type: port-number
SMIv2 Module: DIFFSERV-DSCP-TC
SMIv2 Type: Dscp
YANG Module: ietf-inet-types
YANG Type: dscp
SMIv2 Module: IPV6-FLOW-LABEL-MIB
SMIv2 Type: IPv6FlowLabel
YANG Module: ietf-inet-types
YANG Type: ipv6-flow-label
SMIv2 Module: URI-TC-MIB
SMIv2 Type: Uri
YANG Module: ietf-inet-types
YANG Type: uri
Appendix B. Module Prefix Generation (Informative)
This section describes an algorithm to generate module prefixes to be
used in the import statements. The input of the prefix generation
algorithm is a set of prefixes (usually derived from imported module
names) and a specific module name to be converted into a prefix. The
algorithm described below produces a prefix for the given module name
that is unique within the set of prefixes.
+-----------------+--------+
| YANG Module | Prefix |
+-----------------+--------+
| ietf-yang-types | yang |
| ietf-inet-types | inet |
| ietf-yang-smiv2 | smiv2 |
+-----------------+--------+
Table 1: Special Prefixes For Well-Known YANG Modules
o First, some predefined translations mapping well-known YANG
modules to short prefixes are tried (see Table 1). If a fixed
translation rule exists and leads to a conflict-free prefix, then
the fixed translation is used.
o Otherwise, prefixes are generated by tokenizing a YANG module
name, using hyphens as token separators. The tokens derived from
the module name are converted to lowercase characters. The prefix
then becomes the shortest sequence of tokens concatenated using
hyphens as separators, which includes at least two tokens and
which is unique among all prefixes used in the YANG module.
In the worst case, the prefix derived from an SMIv2 module name
becomes the SMIv2 module name translated to lowercase. But on
average, much shorter prefixes are generated.
Author's Address
Juergen Schoenwaelder
Jacobs University
EMail: j.schoenwaelder@jacobs-university.de