path: root/doc/rfc/rfc3291.txt

Network Working Group                                         M. Daniele
Request for Comments: 3291                                    Consultant
Obsoletes: 2851                                              B. Haberman
Category: Standards Track                                     Consultant
                                                             S. Routhier
                                                Wind River Systems, Inc.
                                                        J. Schoenwaelder
                                                         TU Braunschweig
                                                                May 2002


           Textual Conventions for Internet Network Addresses

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   This MIB module defines textual conventions to represent commonly
   used Internet network layer addressing information.  The intent is
   that these textual conventions (TCs) will be imported and used in MIB
   modules that would otherwise define their own representations.

   This document obsoletes RFC 2851.


















Daniele, et. al.            Standards Track                     [Page 1]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  2
   2.  The SNMP Management Framework  . . . . . . . . . . . . . . . .  4
   3.  Definitions  . . . . . . . . . . . . . . . . . . . . . . . . .  5
   4.  Usage Hints  . . . . . . . . . . . . . . . . . . . . . . . . . 11
   4.1 Table Indexing . . . . . . . . . . . . . . . . . . . . . . . . 12
   4.2 Uniqueness of Addresses  . . . . . . . . . . . . . . . . . . . 12
   4.3 Multiple Addresses per Host  . . . . . . . . . . . . . . . . . 13
   4.4 Resolving DNS Names  . . . . . . . . . . . . . . . . . . . . . 13
   5.  Table Indexing Example . . . . . . . . . . . . . . . . . . . . 13
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   7.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 16
   8.  Intellectual Property Notice . . . . . . . . . . . . . . . . . 16
   9.  Changes from RFC 2851  . . . . . . . . . . . . . . . . . . . . 16
   References . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . . 20

1. Introduction

   Several standards-track MIB modules use the IpAddress SMIv2 base
   type.  This limits the applicability of these MIB modules to IP
   Version 4 (IPv4) since the IpAddress SMIv2 base type can only contain
   4 byte IPv4 addresses.  The IpAddress SMIv2 base type has become
   problematic with the introduction of IP Version 6 (IPv6) addresses
   [19].

   This document defines multiple textual conventions as a mechanism to
   express generic Internet network layer addresses within MIB module
   specifications.  The solution is compatible with SMIv2 (STD 58) and
   SMIv1 (STD 16).  New MIB definitions which need to express network
   layer Internet addresses SHOULD use the textual conventions defined
   in this memo.  New MIB modules SHOULD NOT use the SMIv2 IpAddress
   base type anymore.

   A generic Internet address consists of two objects, one whose syntax
   is InetAddressType, and another whose syntax is InetAddress.  The
   value of the first object determines how the value of the second
   object is encoded.  The InetAddress textual convention represents an
   opaque Internet address value.  The InetAddressType enumeration is
   used to "cast" the InetAddress value into a concrete textual
   convention for the address type.  This usage of multiple textual
   conventions allows expression of the display characteristics of each
   address type and makes the set of defined Internet address types
   extensible.





Daniele, et. al.            Standards Track                     [Page 2]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   The textual conventions defined in this document can also be used to
   represent generic Internet subnets and Internet address ranges.  A
   generic Internet subnet is represented by three objects, one whose
   syntax is InetAddressType, a second one whose syntax is InetAddress
   and a third one whose syntax is InetAddressPrefixLength.  The
   InetAddressType value again determines the concrete format of the
   InetAddress value while the InetAddressPrefixLength identifies the
   Internet network address prefix.

   A generic range of consecutive Internet addresses is represented by
   three objects.  The first one has the syntax InetAddressType while
   the remaining objects have the syntax InetAddress and specify the
   start and end of the address range.  The InetAddressType value again
   determines the format of the InetAddress values.

   The textual conventions defined in this document can be used to
   define Internet addresses by using DNS domain names in addition to
   IPv4 and IPv6 addresses.  A MIB designer can write compliance
   statements to express that only a subset of the possible address
   types must be supported by a compliant implementation.

   MIB developers who need to represent Internet addresses SHOULD use
   these definitions whenever applicable, as opposed to defining their
   own constructs.  Even MIB modules that only need to represent IPv4 or
   IPv6 addresses SHOULD use the InetAddressType/InetAddress textual
   conventions defined in this memo.

   There are many widely deployed MIB modules that use IPv4 addresses
   and which need to be revised to support IPv6.  These MIBs can be
   categorized as follows:

   1. MIB modules which define management information that is in
      principle IP version neutral, but the MIB currently uses
      addressing constructs specific to a certain IP version.

   2. MIB modules which define management information that is specific
      to particular IP version (either IPv4 or IPv6) and which is very
      unlikely to ever be applicable to another IP version.

   MIB modules of the first type SHOULD provide object definitions
   (e.g., tables) that work with all versions of IP.  In particular,
   when revising a MIB module which contains IPv4 specific tables, it is
   suggested to define new tables using the textual conventions defined
   in this memo which support all versions of IP.  The status of the new
   tables SHOULD be "current" while the status of the old IP version
   specific tables SHOULD be changed to "deprecated".  The other
   approach of having multiple similar tables for different IP versions
   is strongly discouraged.



Daniele, et. al.            Standards Track                     [Page 3]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   MIB modules of the second type, which are inherently IP version
   specific, do not need to be redefined.  Note that even in this case,
   any additions to these MIB modules or new IP version specific MIB
   modules SHOULD use the textual conventions defined in this memo.

   MIB developers SHOULD NOT use the textual conventions defined in this
   document to represent generic transport layer addresses.  Instead the
   SMIv2 TAddress textual convention and associated definitions should
   be used for transport layer addresses.

   The key words "MUST", "MUST NOT", "SHOULD", "SHOULD NOT" and "MAY" in
   this document are to be interpreted as described in RFC 2119 [1].

2. The SNMP Management Framework

   The SNMP Management Framework presently consists of five major
   components:

   o  An overall architecture, described in RFC 2571 [2].

   o  Mechanisms for describing and naming objects and events for the
      purpose of management.  The first version of this Structure of
      Management Information (SMI) is called SMIv1 and described in STD
      16, RFC 1155 [3], STD 16, RFC 1212 [4] and RFC 1215 [5].  The
      second version, called SMIv2, is described in STD 58, RFC 2578
      [6], STD 58, RFC 2579 [7] and STD 58, RFC 2580 [8].

   o  Message protocols for transferring management information.  The
      first version of the SNMP message protocol is called SNMPv1 and
      described in STD 15, RFC 1157 [9].  A second version of the SNMP
      message protocol, which is not an Internet standards track
      protocol, is called SNMPv2c and described in RFC 1901 [10] and RFC
      1906 [11].  The third version of the message protocol is called
      SNMPv3 and described in RFC 1906 [11], RFC 2572 [12] and RFC 2574
      [13].

   o  Protocol operations for accessing management information.  The
      first set of protocol operations and associated PDU formats is
      described in STD 15, RFC 1157 [9].  A second set of protocol
      operations and associated PDU formats is described in RFC 1905
      [14].

   o  A set of fundamental applications described in RFC 2573 [15] and
      the view-based access control mechanism described in RFC 2575
      [16].

   A more detailed introduction to the current SNMP Management Framework
   can be found in RFC 2570 [17].



Daniele, et. al.            Standards Track                     [Page 4]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   Managed objects are accessed via a virtual information store, termed
   the Management Information Base or MIB.  Objects in the MIB are
   defined using the mechanisms defined in the SMI.

   This 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 (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. Definitions

INET-ADDRESS-MIB DEFINITIONS ::= BEGIN

IMPORTS
    MODULE-IDENTITY, mib-2, Unsigned32 FROM SNMPv2-SMI
    TEXTUAL-CONVENTION                 FROM SNMPv2-TC;

inetAddressMIB MODULE-IDENTITY
    LAST-UPDATED "200205090000Z"
    ORGANIZATION
        "IETF Operations and Management Area"
    CONTACT-INFO
        "Juergen Schoenwaelder (Editor)
         TU Braunschweig
         Bueltenweg 74/75
         38106 Braunschweig, Germany

         Phone: +49 531 391-3289
         EMail: schoenw@ibr.cs.tu-bs.de

         Send comments to <mibs@ops.ietf.org>."
    DESCRIPTION
        "This MIB module defines textual conventions for
         representing Internet addresses. An Internet
         address can be an IPv4 address, an IPv6 address
         or a DNS domain name. This module also defines
         textual conventions for Internet port numbers,
         autonomous system numbers and the length of an
         Internet address prefix."
    REVISION     "200205090000Z"
    DESCRIPTION
        "Second version, published as RFC 3291. This
         revisions contains several clarifications and it



Daniele, et. al.            Standards Track                     [Page 5]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


         introduces several new textual conventions:
         InetAddressPrefixLength, InetPortNumber,
         InetAutonomousSystemNumber, InetAddressIPv4z,
         and InetAddressIPv6z."
    REVISION     "200006080000Z"
    DESCRIPTION
        "Initial version, published as RFC 2851."
    ::= { mib-2 76 }

InetAddressType ::= TEXTUAL-CONVENTION
    STATUS      current
    DESCRIPTION
        "A value that represents a type of Internet address.
         unknown(0)  An unknown address type. This value MUST
                     be used if the value of the corresponding
                     InetAddress object is a zero-length string.
                     It may also be used to indicate an IP address
                     which is not in one of the formats defined
                     below.

         ipv4(1)     An IPv4 address as defined by the
                     InetAddressIPv4 textual convention.

         ipv6(2)     A global IPv6 address as defined by the
                     InetAddressIPv6 textual convention.

         ipv4z(3)    A non-global IPv4 address including a zone
                     index as defined by the InetAddressIPv4z
                     textual convention.

         ipv6z(4)    A non-global IPv6 address including a zone
                     index as defined by the InetAddressIPv6z
                     textual convention.

         dns(16)     A DNS domain name as defined by the
                     InetAddressDNS textual convention.

         Each definition of a concrete InetAddressType value must be
         accompanied by a definition of a textual convention for use
         with that InetAddressType.

         To support future extensions, the InetAddressType textual
         convention SHOULD NOT be sub-typed in object type definitions.
         It MAY be sub-typed in compliance statements in order to
         require only a subset of these address types for a compliant
         implementation.

         Implementations must ensure that InetAddressType objects



Daniele, et. al.            Standards Track                     [Page 6]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


         and any dependent objects (e.g. InetAddress objects) are
         consistent.  An inconsistentValue error must be generated
         if an attempt to change an InetAddressType object would,
         for example, lead to an undefined InetAddress value.  In
         particular, InetAddressType/InetAddress pairs must be
         changed together if the address type changes (e.g. from
         ipv6(2) to ipv4(1))."
    SYNTAX      INTEGER {
                    unknown(0),
                    ipv4(1),
                    ipv6(2),
                    ipv4z(3),
                    ipv6z(4),
                    dns(16)
                }

InetAddress ::= TEXTUAL-CONVENTION
    STATUS      current
    DESCRIPTION
        "Denotes a generic Internet address.

         An InetAddress value is always interpreted within the context
         of an InetAddressType value. Every usage of the InetAddress
         textual convention is required to specify the InetAddressType
         object which provides the context.  It is suggested that the
         InetAddressType object is logically registered before the
         object(s) which use the InetAddress textual convention if
         they appear in the same logical row.

         The value of an InetAddress object must always be
         consistent with the value of the associated InetAddressType
         object. Attempts to set an InetAddress object to a value
         which is inconsistent with the associated InetAddressType
         must fail with an inconsistentValue error.

         When this textual convention is used as the syntax of an
         index object, there may be issues with the limit of 128
         sub-identifiers specified in SMIv2, STD 58. In this case,
         the object definition MUST include a 'SIZE' clause to
         limit the number of potential instance sub-identifiers."
    SYNTAX      OCTET STRING (SIZE (0..255))

InetAddressIPv4 ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "1d.1d.1d.1d"
    STATUS       current
    DESCRIPTION
        "Represents an IPv4 network address:




Daniele, et. al.            Standards Track                     [Page 7]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


           octets   contents         encoding
            1-4     IPv4 address     network-byte order

         The corresponding InetAddressType value is ipv4(1).

         This textual convention SHOULD NOT be used directly in object
         definitions since it restricts addresses to a specific format.
         However, if it is used, it MAY be used either on its own or in
         conjunction with InetAddressType as a pair."
    SYNTAX       OCTET STRING (SIZE (4))

InetAddressIPv6 ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "2x:2x:2x:2x:2x:2x:2x:2x"
    STATUS       current
    DESCRIPTION
        "Represents an IPv6 network address:

           octets   contents         encoding
            1-16    IPv6 address     network-byte order

         The corresponding InetAddressType value is ipv6(2).

         This textual convention SHOULD NOT be used directly in object
         definitions since it restricts addresses to a specific format.
         However, if it is used, it MAY be used either on its own or in
         conjunction with InetAddressType as a pair."
    SYNTAX       OCTET STRING (SIZE (16))

InetAddressIPv4z ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "1d.1d.1d.1d%4d"
    STATUS       current
    DESCRIPTION
        "Represents a non-global IPv4 network address together
         with its zone index:

           octets   contents         encoding
            1-4     IPv4 address     network-byte order
            5-8     zone index       network-byte order

         The corresponding InetAddressType value is ipv4z(3).

         The zone index (bytes 5-8) is used to disambiguate identical
         address values on nodes which have interfaces attached to
         different zones of the same scope. The zone index may contain
         the special value 0 which refers to the default zone for each
         scope.

         This textual convention SHOULD NOT be used directly in object



Daniele, et. al.            Standards Track                     [Page 8]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


         definitions since it restricts addresses to a specific format.
         However, if it is used, it MAY be used either on its own or in
         conjunction with InetAddressType as a pair."
    SYNTAX OCTET STRING (SIZE (8))

InetAddressIPv6z ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "2x:2x:2x:2x:2x:2x:2x:2x%4d"
    STATUS       current
    DESCRIPTION
        "Represents a non-global IPv6 network address together
         with its zone index:

           octets   contents         encoding
            1-16    IPv6 address     network-byte order
           17-20    zone index       network-byte order

         The corresponding InetAddressType value is ipv6z(4).

         The zone index (bytes 17-20) is used to disambiguate
         identical address values on nodes which have interfaces
         attached to different zones of the same scope. The zone index
         may contain the special value 0 which refers to the default
         zone for each scope.

         This textual convention SHOULD NOT be used directly in object
         definitions since it restricts addresses to a specific format.
         However, if it is used, it MAY be used either on its own or in
         conjunction with InetAddressType as a pair."
    SYNTAX OCTET STRING (SIZE (20))

InetAddressDNS ::= TEXTUAL-CONVENTION
    DISPLAY-HINT "255a"
    STATUS       current
    DESCRIPTION
        "Represents a DNS domain name. The name SHOULD be fully
         qualified whenever possible.

         The corresponding InetAddressType is dns(16).

         The DESCRIPTION clause of InetAddress objects that may have
         InetAddressDNS values must fully describe how (and when) such
         names are to be resolved to IP addresses.

         This textual convention SHOULD NOT be used directly in object
         definitions since it restricts addresses to a specific format.
         However, if it is used, it MAY be used either on its own or in
         conjunction with InetAddressType as a pair."
    SYNTAX       OCTET STRING (SIZE (1..255))



Daniele, et. al.            Standards Track                     [Page 9]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


InetAddressPrefixLength ::= TEXTUAL-CONVENTION
    STATUS      current
    DESCRIPTION
        "Denotes the length of a generic Internet network address
         prefix. A value of n corresponds to an IP address mask
         which has n contiguous 1-bits from the most significant
         bit (MSB) and all other bits set to 0.

         An InetAddressPrefixLength value is always interpreted within
         the context of an InetAddressType value. Every usage of the
         InetAddressPrefixLength textual convention is required to
         specify the InetAddressType object which provides the
         context.  It is suggested that the InetAddressType object is
         logically registered before the object(s) which use the
         InetAddressPrefixLength textual convention if they appear in
         the same logical row.

         InetAddressPrefixLength values that are larger than
         the maximum length of an IP address for a specific
         InetAddressType are treated as the maximum significant
         value applicable for the InetAddressType. The maximum
         significant value is 32 for the InetAddressType
         'ipv4(1)' and 'ipv4z(3)' and 128 for the InetAddressType
         'ipv6(2)' and 'ipv6z(4)'. The maximum significant value
         for the InetAddressType 'dns(16)' is 0.

         The value zero is object-specific and must be defined as
         part of the description of any object which uses this
         syntax. Examples of the usage of zero might include
         situations where the Internet network address prefix
         is unknown or does not apply."
    SYNTAX      Unsigned32

InetPortNumber ::= TEXTUAL-CONVENTION
    STATUS      current
    DESCRIPTION
        "Represents a 16 bit port number of an Internet transport
         layer protocol. Port numbers are assigned by IANA. A
         current list of all assignments is available from
         <http://www.iana.org/>.

         The value zero is object-specific and must be defined as
         part of the description of any object which uses this
         syntax. Examples of the usage of zero might include
         situations where a port number is unknown, or when the
         value zero is used as a wildcard in a filter."
    REFERENCE  "STD 6 (RFC 768), STD 7 (RFC 793) and RFC 2960"
    SYNTAX      Unsigned32 (0..65535)



Daniele, et. al.            Standards Track                    [Page 10]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


InetAutonomousSystemNumber ::= TEXTUAL-CONVENTION
    STATUS      current
    DESCRIPTION
        "Represents an autonomous system number which identifies an
         Autonomous System (AS). An AS is a set of routers under a
         single technical administration, using an interior gateway
         protocol and common metrics to route packets within the AS,
         and using an exterior gateway protocol to route packets to
         other ASs'. IANA maintains the AS number space and has
         delegated large parts to the regional registries.

         Autonomous system numbers are currently limited to 16 bits
         (0..65535). There is however work in progress to enlarge the
         autonomous system number space to 32 bits. This textual
         convention therefore uses an Unsigned32 value without a
         range restriction in order to support a larger autonomous
         system number space."
    REFERENCE  "RFC 1771, RFC 1930"
    SYNTAX      Unsigned32

END

4. Usage Hints

   The InetAddressType and InetAddress textual conventions have been
   introduced to avoid over-constraining an object definition by the use
   of the IpAddress SMI base type which is IPv4 specific.  An
   InetAddressType/InetAddress pair can represent IP addresses in
   various formats.

   The InetAddressType and InetAddress objects SHOULD NOT be sub-typed
   in object definitions.  Sub-typing binds the MIB module to specific
   address formats, which may cause serious problems if new address
   formats need to be introduced.  Note that it is possible to write
   compliance statements in order to express that only a subset of the
   defined address types must be implemented to be compliant.

   Every usage of the InetAddress or InetAddressPrefixLength textual
   conventions must specify which InetAddressType object provides the
   context for the interpretation of the InetAddress or
   InetAddressPrefixLength textual convention.

   It is suggested that the InetAddressType object is logically
   registered before the object(s) which uses the InetAddress or
   InetAddressPrefixLength textual convention.  An InetAddressType
   object is logically registered before an InetAddress or
   InetAddressPrefixLength object if it appears before the InetAddress
   or InetAddressPrefixLength object in the conceptual row (which



Daniele, et. al.            Standards Track                    [Page 11]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   includes any index objects).  This rule allows programs such as MIB
   compilers to identify the InetAddressType of a given InetAddress or
   InetAddressPrefixLength object by searching for the InetAddressType
   object which precedes an InetAddress or InetAddressPrefixLength
   object.

4.1 Table Indexing

   When a generic Internet address is used as an index, both the
   InetAddressType and InetAddress objects MUST be used.  The
   InetAddressType object MUST be listed before the InetAddress object
   in the INDEX clause.

   The IMPLIED keyword MUST NOT be used for an object of type
   InetAddress in an INDEX clause.  Instance sub-identifiers are then of
   the form T.N.O1.O2...On, where T is the value of the InetAddressType
   object, O1...On are the octets in the InetAddress object, and N is
   the number of those octets.

   There is a meaningful lexicographical ordering to tables indexed in
   this fashion.  Command generator applications may lookup specific
   addresses of known type and value, issue GetNext requests for
   addresses of a single type, or issue GetNext requests for a specific
   type and address prefix.

4.2 Uniqueness of Addresses

   IPv4 addresses were intended to be globally unique, current usage
   notwithstanding.  IPv6 addresses were architected to have different
   scopes and hence uniqueness [19].  In particular, IPv6 "link-local"
   and "site-local" addresses are not guaranteed to be unique on any
   particular node.  In such cases, the duplicate addresses must be
   configured on different interfaces.  So the combination of an IPv6
   address and a zone index is unique [21].

   The InetAddressIPv6 textual convention has been defined to represent
   global IPv6 addresses and non-global IPv6 addresses in cases where no
   zone index is needed (e.g., on end hosts with a single interface).
   The InetAddressIPv6z textual convention has been defined to represent
   non-global IPv6 addresses in cases where a zone index is needed
   (e.g., a router connecting multiple zones).  MIB designers who use
   InetAddressType/InetAddress pairs therefore do not need to define
   additional objects in order to support non-global addresses on nodes
   that connect multiple zones.

   The InetAddressIPv4z is intended for use in MIBs (like the TCP-MIB)
   which report addresses in the address family used on the wire, but
   where the entity instrumented obtains such addresses from



Daniele, et. al.            Standards Track                    [Page 12]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   applications or administrators in a form which includes a zone index,
   such as v4-mapped IPv6 addresses.

   The size of the zone index has been chosen so that it is consistent
   with (i) the numerical zone index defined in [21] and (ii) the
   sin6_scope_id field of the sockaddr_in6 structure defined in RFC 2553
   [20].

4.3 Multiple Addresses per Host

   A single host system may be configured with multiple addresses (IPv4
   or IPv6), and possibly with multiple DNS names.  Thus it is possible
   for a single host system to be accessible by multiple
   InetAddressType/InetAddress pairs.

   If this could be an implementation or usage issue, the DESCRIPTION
   clause of the relevant objects must fully describe which address is
   reported in a given InetAddressType/InetAddress pair.

4.4 Resolving DNS Names

   DNS names MUST be resolved to IP addresses when communication with
   the named host is required.  This raises a temporal aspect to
   defining MIB objects whose value is a DNS name: When is the name
   translated to an address?

   For example, consider an object defined to indicate a forwarding
   destination, and whose value is a DNS name.  When does the forwarding
   entity resolve the DNS name?  Each time forwarding occurs or just
   once when the object was instantiated?

   The DESCRIPTION clause of such objects SHOULD precisely define how
   and when any required name to address resolution is done.

   Similarly, the DESCRIPTION clause of such objects SHOULD precisely
   define how and when a reverse lookup is being done if an agent has
   accessed instrumentation that knows about an IP address and the MIB
   module or implementation requires it to map the IP address to a DNS
   name.

5. Table Indexing Example

   This example shows a table listing communication peers that are
   identified by either an IPv4 address, an IPv6 address or a DNS name.
   The table definition also prohibits entries with an empty address
   (whose type would be "unknown").  The size of a DNS name is limited
   to 64 characters in order to satisfy OID length constraints.




Daniele, et. al.            Standards Track                    [Page 13]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   peerTable OBJECT-TYPE
       SYNTAX      SEQUENCE OF PeerEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
           "A list of communication peers."
       ::= { somewhere 1 }

   peerEntry OBJECT-TYPE
       SYNTAX      PeerEntry
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
           "An entry containing information about a particular peer."
       INDEX       { peerAddressType, peerAddress }
       ::= { peerTable 1 }

   PeerEntry ::= SEQUENCE {
       peerAddressType     InetAddressType,
       peerAddress         InetAddress,
       peerStatus          INTEGER
   }

   peerAddressType OBJECT-TYPE
       SYNTAX      InetAddressType
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
           "The type of Internet address by which the peer
            is reachable."
       ::= { peerEntry 1 }

   peerAddress OBJECT-TYPE
       SYNTAX      InetAddress (SIZE (1..64))
       MAX-ACCESS  not-accessible
       STATUS      current
       DESCRIPTION
           "The Internet address for the peer. The type of this
            address is determined by the value of the peerAddressType
            object. Note that implementations must limit themselves
            to a single entry in this table per reachable peer.
            The peerAddress may not be empty due to the SIZE
            restriction.








Daniele, et. al.            Standards Track                    [Page 14]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


            If a row is created administratively by an SNMP
            operation and the address type value is dns(16), then
            the agent stores the DNS name internally. A DNS name
            lookup must be performed on the internally stored DNS
            name whenever it is being used to contact the peer.

            If a row is created by the managed entity itself and
            the address type value is dns(16), then the agent
            stores the IP address internally. A DNS reverse lookup
            must be performed on the internally stored IP address
            whenever the value is retrieved via SNMP."
       ::= { peerEntry 2 }

   The following compliance statement specifies that compliant
   implementations need only support IPv4/IPv6 addresses without a zone
   indices.  Support for DNS names or IPv4/IPv6 addresses with zone
   indices is not required.

   peerCompliance MODULE-COMPLIANCE
       STATUS      current
       DESCRIPTION
           "The compliance statement of the peer MIB."

       MODULE      -- this module
       MANDATORY-GROUPS    { peerGroup }

       OBJECT  peerAddressType
       SYNTAX  InetAddressType { ipv4(1), ipv6(2) }
       DESCRIPTION
           "An implementation is only required to support IPv4
            and IPv6 addresses without zone indices."

       ::= { somewhere 2 }

   Note that the SMIv2 does not permit inclusion of not-accessible
   objects in an object group (see section 3.1 in STD 58, RFC 2580 [8]).
   It is therefore not possible to formally refine the syntax of
   auxiliary objects which are not-accessible.  In such a case, it is
   suggested to express the refinement informally in the DESCRIPTION
   clause of the MODULE-COMPLIANCE macro invocation.











Daniele, et. al.            Standards Track                    [Page 15]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


6. Security Considerations

   This module does not define any management objects.  Instead, it
   defines a set of textual conventions which may be used by other MIB
   modules to define management objects.

   Meaningful security considerations can only be written in the MIB
   modules that define management objects.  This document has therefore
   no impact on the security of the Internet.

7. Acknowledgments

   This document was produced by the Operations and Management Area
   "IPv6MIB" design team.  The authors would like to thank Fred Baker,
   Randy Bush, Richard Draves, Mark Ellison, Bill Fenner, Jun-ichiro
   Hagino, Mike Heard, Tim Jenkins, Glenn Mansfield, Keith McCloghrie,
   Thomas Narten, Erik Nordmark, Peder Chr. Norgaard, Randy Presuhn,
   Andrew Smith, Dave Thaler, Kenneth White, Bert Wijnen, and Brian Zill
   for their comments and suggestions.

8. Intellectual Property Notice

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be claimed to
   pertain to the implementation or use of the technology described in
   this document or the extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the
   IETF's procedures with respect to rights in standards-track and
   standards-related documentation can be found in BCP 11.  Copies of
   claims of rights made available for publication and any assurances of
   licenses to be made available, or the result of an attempt made to
   obtain a general license or permission for the use of such
   proprietary rights by implementors or users of this specification can
   be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to practice
   this standard.  Please address the information to the IETF Executive
   Director.

9. Changes from RFC 2851

   The following changes have been made relative to RFC 2851:

   o  Added new textual conventions InetAddressPrefixLength,
      InetPortNumber, and InetAutonomousSystemNumber.



Daniele, et. al.            Standards Track                    [Page 16]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   o  Rewrote the introduction to say clearly that in general, one
      should define MIB tables that work with all versions of IP.  The
      other approach of multiple tables for different IP versions is
      strongly discouraged.

   o  Added text to the InetAddressType and InetAddress descriptions
      which requires that implementations must reject set operations
      with an inconsistentValue error if they lead to inconsistencies.

   o  Removed the strict ordering constraints.  Description clauses now
      must explain which InetAddressType object provides the context for
      an InetAddress or InetAddressPrefixLength object.

   o  Aligned wordings with the IPv6 scoping architecture document.

   o  Split the InetAddressIPv6 textual convention into the two textual
      conventions (InetAddressIPv6 and InetAddressIPv6z) and introduced
      a new textual convention InetAddressIPv4z.  Added ipv4z(3) and
      ipv6z(4) named numbers to the InetAddressType enumeration.
      Motivations for this change: (i) enable the introduction of a
      textual conventions for non-global IPv4 addresses, (ii) alignment
      with the textual conventions for transport addresses, (iii)
      simpler compliance statements in cases where support for IPv6
      addresses with zone indices is not required, (iv) simplify
      implementations for host systems which will never have to report
      zone indices.

References

   [1]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [2]  Harrington, D., Presuhn, R. and B. Wijnen, "An Architecture for
        Describing SNMP Management Frameworks", RFC 2571, April 1999.

   [3]  Rose, M. and K. McCloghrie, "Structure and Identification of
        Management Information for TCP/IP-based Internets", STD 16, RFC
        1155, May 1990.

   [4]  Rose, M. and K. McCloghrie, "Concise MIB Definitions", STD 16,
        RFC 1212, March 1991.

   [5]  Rose, M., "A Convention for Defining Traps for use with the
        SNMP", RFC 1215, March 1991.

   [6]  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.



Daniele, et. al.            Standards Track                    [Page 17]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   [7]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
        M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58,
        RFC 2579, April 1999.

   [8]  McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose,
        M. and S. Waldbusser, "Conformance Statements for SMIv2", STD
        58, RFC 2580, April 1999.

   [9]  Case, J., Fedor, M., Schoffstall, M. and J. Davin, "A Simple
        Network Management Protocol (SNMP)", STD 15, RFC 1157, May 1990.

   [10] Case, J., McCloghrie, K., Rose, M. and S. Waldbusser,
        "Introduction to Community-based SNMPv2", RFC 1901, January
        1996.

   [11] 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.

   [12] Case, J., Harrington, D., Presuhn, R. and B. Wijnen, "Message
        Processing and Dispatching for the Simple Network Management
        Protocol (SNMP)", RFC 2572, April 1999.

   [13] Blumenthal, U. and B. Wijnen, "User-based Security Model (USM)
        for version 3 of the Simple Network Management Protocol
        (SNMPv3)", RFC 2574, April 1999.

   [14] 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.

   [15] Levi, D., Meyer, P. and B. Stewart, "SNMP Applications", RFC
        2573, April 1999.

   [16] Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based Access
        Control Model (VACM) for the Simple Network Management Protocol
        (SNMP)", RFC 2575, April 1999.

   [17] Case, J., Mundy, R., Partain, D. and B. Stewart, "Introduction
        to Version 3 of the Internet-standard Network Management
        Framework", RFC 2570, April 1999.

   [18] McCloghrie, K. and F. Kastenholz, "The Interfaces Group MIB",
        RFC 2863, June 2000.

   [19] Hinden, R. and S. Deering, "IP Version 6 Addressing
        Architecture", RFC 2373, July 1998.




Daniele, et. al.            Standards Track                    [Page 18]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


   [20] Gilligan, R., Thomson, S., Bound, J. and W. Stevens, "Basic
        Socket Interface Extensions for IPv6", RFC 2553, March 1999.

   [21] Deering, S., Haberman, B., Jinmei, T., Nordmark, E., Onoe, A.
        and B. Zill, "IPv6 Scoped Address Architecture", Work in
        Progress.

Authors' Addresses

   Mike Daniele
   Consultant
   19 Pinewood Rd
   Hudson, NH  03051
   USA

   Phone: +1 603 883-6365
   EMail: md@world.std.com


   Brian Haberman

   Phone: +1 919 949-4828
   EMail: bkhabs@nc.rr.com


   Shawn A. Routhier
   Wind River Systems, Inc.
   500 Wind River Way
   Alameda, CA 94501
   USA

   Phone: +1 510 749 2095
   EMail: sar@epilogue.com


   Juergen Schoenwaelder
   TU Braunschweig
   Bueltenweg 74/75
   38106 Braunschweig
   Germany

   Phone: +49 531 391-3289
   EMail: schoenw@ibr.cs.tu-bs.de








Daniele, et. al.            Standards Track                    [Page 19]
^L
RFC 3291           TCs for Internet Network Addresses           May 2002


Full Copyright Statement

   Copyright (C) The Internet Society (2002).  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.



















Daniele, et. al.            Standards Track                    [Page 20]
^L