One document matched: draft-ops-endpoint-mib-00.txt
Internet-Draft Endpoint MIB August 1999
Expires February, 2000
Internet Endpoint MIB
<draft-ops-endpoint-mib-00.txt>
1. Status of this Memo
This document is an Internet-Draft and is in full conformance
with all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-
Drafts as reference material or to cite them other than as
"work in progress."
The list of current Internet-Drafts can be accessed at^M
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
2. Abstract
This MIB module defines constructs to represent commonly used
addressing information. The intent is that these definitions
will be imported and used in the various MIBs that would otherwise
define their own representations. This work is output from the
Operations and Management Area "IPv6MIB" design team.
3. Definitions
INET-ENDPOINT-MIB DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY FROM SNMPv2-SMI
TEXTUAL-CONVENTION FROM SNMPv2-TC;
inetEndpointMIB MODULE-IDENTITY
LAST-UPDATED "9907300000Z"
ORGANIZATION "IETF OPS Area"
CONTACT-INFO "Send comments to mibs@ops.ietf.org"
DESCRIPTION
"A MIB module for Internet address definitions."
::= { TBD }
--
--
-- New TCs for representing generic Internet endpoints.
-- These are roughly equivalent to TDomain and TAddress...
--
--
--
-- Internet endpoints types
--
InetEndpointType ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"A value that represents a type of Internet endpoint.
Note that it is possible to sub-type objects defined with
this syntax by removing one or more enumerated values.
The DESCRIPTION clause of such objects (or their corresponding
InetEndpoint object) must document specific usage."
SYNTAX INTEGER {
other(0),
ipv4(1),
ipv6(2),
dns(3)
}
InetEndpoint ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Denotes an generic Internet endpoint.
A InetEndpoint value is always interpreted within the context of a
InetEndpointType value. Thus, each definition of a InetEndpointType
value must be accompanied by a definition of a textual convention
for use with that InetEndpointType.
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]. In this case, it is recommended that the OBJECT-TYPE
declaration include a "SIZE" clause to limit the number of potential
instance sub-identifiers.
REFERENCE "See the TAddress TC in std58."
SYNTAX OCTET STRING (SIZE (0..255))
--
--
-- TCs for specific Internet endpoint values.
--
--
--
-- IPv4 Address
--
InetEndpointIPv4 ::= TEXTUAL-CONVENTION
DISPLAY-HINT "1d.1d.1d.1d"
STATUS current
DESCRIPTION
"Represents an IPv4 network address:
octets contents encoding
1-4 IP address network-byte order
The corresponding InetEndpointType is ipv4(1)."
SYNTAX OCTET STRING (SIZE (4))
--
-- IPv6 Address
--
InetEndpointIPv6 ::= 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 InetEndpointType is ipv6(2)."
REFERENCE "See the Ipv6Address TC in RFC 2465."
SYNTAX OCTET STRING (SIZE (16))
--
-- DNS Name
--
InetEndpointDNS ::= TEXTUAL-CONVENTION
DISPLAY-HINT "255a"
STATUS current
DESCRIPTION
"Represents a fully qualified DNS host name.
The corresponding InetEndpointType is dns(3).
The DESCRIPTION clause of InetEndpoint objects that
may have InetEndpointDNS values must fully describe
how (and when) such names are to be resolved to IP
addresses."
REFERENCE "RFCs 952 and 1123."
SYNTAX OCTET STRING (SIZE (1..255))
END
4. Usage
These definitions provide a mechanism to define generic
Internet-accessible endpoints within MIB specifications.
It is recommended that MIB developers use these definitions
when applicable, as opposed to defining their own constructs.
A generic Internet endpoint consists of two objects,
one whose syntax is InetEndpointType, and another whose
syntax is InetEndpoint. The value of the first object
determines how the value of the second object is encoded.
One particular usage of InetEndpointType/InetEndpoint pairs
is to avoid over-constraining an object definition by the
use of the IpAddress syntax. IpAddress limits an implementation
to using IPv4 addresses only, and as such should only be used
when the object truly is IPv4-specific.
5. Indexing
When a generic Internet endpoint is used as an index, both
the InetEndpointType and InetEndpoint objects must be used, and
the InetEndpointType object must come first in the INDEX clause.
Instance subidentifiers are then of the form T.N.O1.O2...On,
where T is the value of the InetEndpointType object, O1...On
are the octets in the InetEndpoint 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
o lookup specific endpoints of known type and value
o issue GetNext requests for endpoints of a single type
o issue GetNext requests for specific type and address prefix
It should be pointed out that another valid approach is to
define separate tables for different address types. For example,
one table might be indexed by an IpAddress object, and the other
table indexed by an Ipv6Address object. This is a decision for the
MIB designer. (For example, the tcpConnTable was left intact and a new
table added for TCP connections over IPv6, see RFC 2452.)
6. 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. 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 IPv6 address/interface is unique.
For tables indexed by InetEndpointType/InetEndpoint pairs, where
there may be non-unique instances of InetEndpointIPv6, the recommended
approach is to add a third index object to ensure uniqueness.
It is recommended that the syntax of this third index object be
InterfaceIndexOrZero, from IF-MIB. The value of this object
should be 0 when the value of the InetEndpointType object is
not ipv6(2).
<< TBD: what about Ipv6IfIndexOrZero in RFC 2465? >>
7. Multiple InetEndpoints per Host
Note that 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 represented
by multiple (unique) InetEndpointType/InetEndpoint pairs.
If this could be an implementation or usage issue the DESCRIPTION
clause of the relevant objects should fully describe required
behavior.
8. Resolving DNS Names
DNS names are translated to IP addresses when communication with
a 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?
Once, when the object was instantiated?
The DESCRIPTION clause of such objects should precisely define
how (when) any required name to address resolution is done.
9. Usage Examples
Example 1:
fooTable OBJECT-TYPE
SYNTAX SEQUENCE OF FooEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The foo table."
::= { bar 1 }
fooEntry OBJECT-TYPE
SYNTAX FooEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A foo entry."
INDEX { fooPartnerType, fooPartner }
::= { fooTable 1 }
FooEntry ::= SEQUENCE {
fooPartnerType InetEndpointType,
fooPartner InetEndpoint,
fooStatus INTEGER,
fooDescr OCTET STRING
}
fooPartnerType ::= OBJECT-TYPE
SYNTAX InetEndpointType
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The type of Internet endpoint by which the partner is reachable."
::= { fooEntry 1 }
fooPartner ::= OBJECT-TYPE
SYNTAX InetEndpoint (SIZE (0..64))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The Internet endpoint for the partner. Note that implementations
must limit themselves to a single entry in this table per reachable
partner. Also, if an Ipv6 endpoint is used, it must contain a globally
unique IPv6 address."
::= { fooEntry 2 }
Example 2:
sysAddrTable OBJECT-TYPE
SYNTAX SEQUENCE OF SysAddrEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The sysAddr table."
::= { sysAddr 1 }
sysAddrEntry OBJECT-TYPE
SYNTAX SysAddrEntry
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"A sysAddr entry."
INDEX { sysAddrType, sysAddr, sysAddrIfIndex }
::= { sysAddrTable 1 }
SysAddrEntry ::= SEQUENCE {
sysAddrPartnerType InetEndpointType,
sysAddrPartner InetEndpoint,
sysAddrIfIndex InterfaceIndexOrZero,
sysAddrStatus INTEGER,
sysAddrDescr OCTET STRING
}
sysAddrType ::= OBJECT-TYPE
SYNTAX InetEndpointType {
ipv4(1),
ipv6(2)
}
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The type of system address."
::= { sysAddrEntry 1 }
sysAddr ::= OBJECT-TYPE
SYNTAX InetEndpoint (SIZE (4 | 16))
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The system address."
::= { sysAddrEntry 2 }
sysAddrIfIndex ::= OBJECT-TYPE
SYNTAX InterfaceIndexOrZero
MAX-ACCESS not-accessible
STATUS current
DESCRIPTION
"The system address interface. This object is used to disambiguate
duplicate system IPv6 addresses, and should be 0 for non-duplicate
addresses."
::= { sysAddrEntry 3 }
10. References
TBD
11. Copyright
TBD
12. Authors
This work was done by the IETF Ops Area "IPv6MIB" Design Team.
Comments should be posted to mibs@ops.ietf.org.
Appendix
This appendix lists the issues raised over common addressing
MIB constructs, and the reasoning for the decisions made in
this module.
1. Efficient table lookups
Some existing MIBs have tables of generic addresses, indexed
by a random integer. This makes it impossible to lookup
specific addresses, or issue meaningful GetNext operations.
2. Common addressing should be defined such that no SMI changes
are required.
For example, the use of the ASN.1 CHOICE would really be an SMI
change.
3. TCs and DISPLAY-HINTS
A single object that contains both address type and value
does not provide a way to express the display characteristics
of each type.
(Also, such a single object requires code changes to handle updates,
whereas the solution chosen requires only MIB updates.)
4. Document the possible non-uniqueness of IPv6 addresses, and the
impact on indexing tables.
5. TDomain/TAddress limited to transport services
It was unclear if network layer addresses were appropriate
for use in TAddress values, since std58 refers specifically to
"transport addresses".
This point is less important than std58's definition that
TAddress values always be defined in the context of TDomain
values. Since did not want to index by OIDs, we did not
use TDomain and hence cannot use TAddress.
6. Harness the use of IpAddress
Several standard-track MIBs have used IpAddress syntax
inadvertently, needlessly limiting implementations to IPv4.
The specification under development should address this.
7. DNS names in addition to addresses
It is useful to be able to specify a system via a DNS name,
so the common addressing mechanism should support them.
Expires February, 2000
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