view Side-By-Side changes
Cisco Systems, Inc.
Keith McCloghrie
Cisco Systems, Inc.
Randy Presuhn
BMC Software, Inc.
22 October
27 December 1999
SMI Extensions
Textual Conventions for Additional High Capacity Data Types
<draft-kzm-hcdata-types-01.txt>
<draft-kzm-hcdata-types-02.txt>
Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026 [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
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.
Distribution of this document is unlimited. Please send comments to the
authors.
1. Copyright Notice
Copyright (C) The Internet Society (1999). All Rights Reserved.
Internet-Draft High Capacity Data Types October December 1999
2. Abstract
This memo specifies clarifications to the Structure of Management
Information [SMIv2] new textual conventions for the purpose of providing
a broader range of data types for high capacity numbers.
3. Table of Contents
1 Copyright Notice ................................................ 1
2 Abstract ........................................................ 2
3 Table of Contents ............................................... 2
4 The SNMP Management Framework ................................... 2
5 Overview ........................................................ 3
5.1 New Data Types Needed ......................................... 3
5.2 Short Term and Long Term Objectives ........................... 3
5.3 Backward Compatibility with Counter64 ......................... 5
5.4 ASN.1 Vs.
5.2 Limitations of the Textual Convention Approach ......................... 5
5.5 SMI Interpretation Supporting the TC Approach ................. 5 ................ 4
6 New Textual Conventions ......................................... 6
6.1 CounterBasedGauge64 ........................................... 6
6.2 ZeroBasedCounter64 ............................................ 6
7 Definitions ..................................................... 7
7 6
8 Intellectual Property ........................................... 8
8 10
9 References ...................................................... 8
9 10
10 Security Considerations ......................................... ........................................ 13
11
10 Authors' Addresses ............................................. 14
12
11 Full Copyright Statement ....................................... 13 15
4. The SNMP Management Framework
The SNMP Management Framework presently consists of five major
components:
o An overall architecture, described in RFC 2571 [RFC2571].
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
RFC 1155 [RFC1155], RFC 1212 [RFC1212] and RFC 1215 [RFC1215].
The second version, called SMIv2, is described in RFC 2578
[RFC2578], RFC 2579 [RFC2579] and RFC 2580 [RFC2580].
o Message protocols for transferring management information. The
first version of the SNMP message protocol is called SNMPv1 and
described in RFC 1157 [RFC1157]. A second version of the SNMP
message protocol, which is not an Internet standards track
protocol, is called SNMPv2c and described in RFC 1901 [RFC1901]
and RFC 1906 [RFC1906]. The third version of the message
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protocol is called SNMPv3 and described in RFC 1906 [RFC1906],
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RFC 2572 [RFC2572] and RFC 2574 [RFC2574].
o Protocol operations for accessing management information. The
first set of protocol operations and associated PDU formats is
described in RFC 1157 [RFC1157]. A second set of protocol
operations and associated PDU formats is described in RFC 1905
[RFC1905].
o A set of fundamental applications described in RFC 2573
[RFC2573] and the view-based access control mechanism described
in RFC 2575 [RFC2575].
A more detailed introduction to the current SNMP Management Framework
can be found in RFC 2570 [RFC2570].
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 document does not define memo specifies a MIB module.
5. Overview
There module that is a need for a standardized way of representing different types 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 high capacity numbers Counter64). Some machine readable
information in MIB modules, SMIv2 will be converted into textual descriptions in a manner suitable for use
with existing SNMP engines.
SMIv1 during the translation process. However, this loss of machine
readable information is not considered to change the semantics of the
MIB.
5. Overview
The SMIv2 [RFC2578] currently contains
support for high-speed counters (i.e., Counter64), but Structure of Management Information [SMIv2] does not contain
support for explicitly
address the question of how to represent integer objects other than
counters that would require up to 64 bit gauges or (signed bits to provide the necessary range
and unsigned) integers.
5.1. New Data Types Needed precision. There are standards track MIBs in progress, which require 64 bit gauges
and integers. There are some MIB features such as polling history or
alarm thresholding, that are supported for 32-bit counters, but not
strictly supported for 64-bit counters. The SMI does not provide the
right base types or textual conventions RMON
MIB for 64-bit High Capacity Networks [HC-RMON], which need such data types. The SMI
is also ambiguous regarding the semantics of a MIB object defined with a
This memo specifies textual convention (TC), instead of a base type.
5.2. conventions to meet these needs.
5.1. Short Term and Long Term Objectives
In order to support Gigabit Ethernet and other high speed interfaces
properly, the following new 'Gauge64' and 'Integer64' data types are needed:
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- Gauge64
- Unsigned64
- Integer64 needed.
There is an immediate need to provide a Gauge64 and Unsigned64 data types, type, similar in
semantics to the Gauge32 and Unsigned32 data types. type, in order to support common data
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representations such as:
- a snapshot of a Counter64 at a given moment, e.g., history ring
buffer
- the difference between 2 Counter64 values
Signed integers can be stored in two MIB objects (sign and absolute
value) as is done with the usrHistoryTable in the RMON-2 MIB [RFC2021],
so there is not an immediate need for an Integer64 data type. A new
ASN.1 tag for 64-bit integers should be added to the SMI as soon as
possible. This
document does not suggest a short-term solution for signed 64-bit
integers.
In order to be backward compatible with existing implementations of
Counter64, the short term, textual conventions defining new ASN.1 encoding of unsigned 64-bit data types need to must be defined in a document which augments, but does not
invalidate anything contained in the existing SMI documents. Resolutions
identical to the ambiguities regarding the use encoding of Counter64 objects, i.e., identified by the
[APPLICATION 6] ASN.1 tag.
The textual conventions also needs
to be resolved defined in the short-term.
During IETF WG discussions about progressing the SNMPv2 specifications
(RFCs 1902-1908) to a higher level of the standardization status, the
issue of supporting new SMI data types was deferred to the future. One
school of thought suggests that such future SMI capability should be this document represent a
generalized limited and
short-term solution for being able to transition to support any new
data type. However, the definition of a generalized solution will take
time, both to specify and to get implementations of it deployed. problem. The
updates to the SMIv2 specified in this memo are will not intended be changed to
prejudice the argument about whether such
accomodate this approach, and these textual conventions will be
deprecated as a generalized long term solution is
needed.
Meanwhile, there is an immediate need defined and deployed to add replace
them.
5.2. Limitations of the Textual Convention Approach
New unsigned data types for 64 bit
unsigned numbers, and that these additions be done in a way that will be
supportable by any underlying SNMP engine which already implements with textual conventions based on the Counter64 MIB objects.
tag, instead of a new (or other existing) ASN.1 tag has some
limitations:
- The approach in this memo is motivated by MAX-ACCESS of the observation that TC must be read-only, because the SMIv2
specification already specifies two base-level data types (Gauge32 and
Unsigned32) which map onto the same underlying ASN.1 tag, and thus are
indistinguishable when contained in an SNMP packet in transmission. So,
why not have the additional high capacity data types map onto the same
underlying ASN.1 tag as Counter64, so that they are similarly
indistinguishable when contained in an SNMP packet?
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5.3. Backward Compatibility with Counter64
In order to be backward compatible with existing implementations of
Counter64, the encoding of Gauge64 and Unsigned64 objects needs to be
identical to the encoding of Counter64 objects, i.e., identified by the
[APPLICATION 6] ASN.1 tag.
5.4. ASN.1 Vs. Textual Convention Approach
Defining new unsigned data types with textual conventions based on the
Counter64 tag, instead of a new (or other existing) ASN.1 tag has some
advantages and some limitations:
- The MAX-ACCESS of the TC must be read-only, because the MAX-ACCESS
of MAX-ACCESS
of the underlying Counter64 type is read-only, (as established in
RFC 2578 clause 7.1.10 [RFC2578]).
- No sub-range can be specified on the TC-derived types, because sub-
ranges are not allowed on Counter64 objects.
- No DEFVAL clause can be specified for the TC-derived types, because
DEFVALs are not allowed on read-only objects.
- The TC-derived types cannot be used in an INDEX clause. This is
not an important feature, and supporting it would have a
significant impact on MIB compliers.
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- Enumerated integers cannot be defined with a value larger than
2147483647. This is not an important feature, and supporting it
would have a significant impact on MIB compliers.
- The ASN.1 tag should carry only encoding information, not encoding
and semantic information. Semantic content should be determined
entirely by the SYNTAX clause in the MIB object definition.
5.5. SMI Interpretation Supporting the TC Approach
Clause 3.3 of RFC 2579, 'Mapping of the DESCRIPTION clause' states:
The DESCRIPTION clause, which must be present, contains a
textual definition of the textual convention, which provides
all semantic definitions necessary for implementation, and
should embody any information which would otherwise be
communicated in any ASN.1 commentary annotations associated
with the object.
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Note the use of the word "all".
Clause 3.5 of RFC 2579, 'Mapping of the SYNTAX clause' states:
6. New Textual Conventions
The SYNTAX clause, which must be present, defines abstract
data structure corresponding to the following textual convention. The
data structure must be one of the alternatives conventions are defined in the
ObjectSyntax CHOICE or the BITS construct (see section 7.1 in
[2]). Note that this means that the SYNTAX clause of a
Textual Convention can not refer to support unsigned 64-bit
data types for HC-RMON.
6.1. CounterBasedGauge64
This textual convention defines a previously 64-bit gauge, but defined
Textual Convention.
An extended subset of the full capabilities of ASN.1 (1988)
sub- typing is allowed, as appropriate to the underlying ASN.1
type. Any such restriction on size, range or enumerations
specified in this clause represents the maximal level of
support which makes "protocol sense". Restrictions on sub-
typing are specified in detail in Section 9 and Appendix A of
[2].
Note that with
Counter64 syntax, since no mention is made of any underlying data Gauge64 base type semantics.
Taken together, these two passages indicate that the unsigned 64-bit TCs
are perfectly legal.
There is a passage in RFC 2579 that hints otherwise is a slightly
ambiguous passage in the introduction:
When designing a MIB module, it available.
This TC is often useful to define new
types similar to those defined in used for storing the SMI. In comparison to difference between 2 Counter64 values,
or simply storing a
type defined in the SMI, each snapshot of these new types has a
different name, a similar syntax, but Counter64 value at a more precise
semantics. ...
The ambiguity depends on how one reads "more precise semantics". One
could read it given moment in the strict sense of
time.
6.2. ZeroBasedCounter64
This textual convention defines a type hierarchy 64-bit counter with inheritance an initial value
of semantics, or one could read it in the spirit zero, instead of clause 3.3, an arbitrary initial value.
This TC is used for counter objects in tables which
states that ALL semantics are in the TC's DESCRIPTION clause.
Therefore, the ambiguity is whether the semantics of the base type
have to be inherited instantiated by a new TC based on that underlying type.
I.e., whether a TC based on the
management application action.
7. Definitions
SMIv2-HCNUM-TC DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, experimental, Counter64 base type must inherit the
'delta-only' characteristics of Counter64, or whether the description of
the TC can override that. The definitions in section 6 assume that a TC
can override it.
FROM SNMPv2-SMI
TEXTUAL-CONVENTION
FROM SNMPv2-TC;
hcnumTC MODULE-IDENTITY
LAST-UPDATED "9912260000Z"
ORGANIZATION "IETF OPS Area"
CONTACT-INFO
" E-mail: ops-area@ops.ietf.org
Subscribe: majordomo@psg.com
w/ msg body: subscribe ops-area
Andy Bierman
Cisco Systems Inc.
170 West Tasman Drive
San Jose, CA 95134
+1 408-527-3711
abierman@cisco.com
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6. Definitions
The following
Keith McCloghrie
Cisco Systems Inc.
170 West Tasman Drive
San Jose, CA 95134
+1 408-526-5260
kzm@cisco.com
Randy Presuhn
BMC Software, Inc.
Office 1-3141
2141 North First Street
San Jose, California 95131 USA
+1 408 546-1006
rpresuhn@bmc.com"
DESCRIPTION
"A MIB module containing textual conventions are defined to support unsigned 64-bit
for high capacity data types.
SMIv2-HCNUM-EXT DEFINITIONS types."
REVISION "9912260000Z"
DESCRIPTION
"Initial Version of the High Capacity Numbers
MIB module. This version published as RFC xxxx
(to be assigned by the RFC Editor)."
::= BEGIN
IMPORTS
TEXTUAL-CONVENTION
FROM SNMPv2-TC;
Gauge64 { experimental xxx }
CounterBasedGauge64 ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"The Gauge64 CounterBasedGauge64 type represents a non-negative
integer, which may increase or decrease, but shall never
exceed a maximum value, nor fall below a minimum value. The
maximum value can not be greater than 2^64-1
(18446744073709551615 decimal), and the minimum value can
not be smaller than 0. The value of a Gauge64 CounterBasedGauge64
has its maximum value whenever whenever the information being modeled
is greater than or equal to its maximum value, and has its
minimum value whenever the information being modeled is
smaller than or equal to its minimum value. If the
information being modeled subsequently decreases below
(increases above) the maximum (minimum) value, the
CounterBasedGauge64 also decreases (increases). (Note that
despite of the use of the term 'latched' in the original
definition of this type, it does not become 'stuck' at its
maximum or minimum value.)
Note that this TC is not strictly legal in SMIv2, because
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the 'always increasing' and 'counter wrap' semantics
associated with the Counter64 base type are not preserved.
It is possible that management applications which rely
solely upon the (Counter64) ASN.1 tag to determine object
semantics will mistakenly operate upon objects of this type
as they would for Counter64 objects.
This textual convention represents a limited and short-term
solution, and will be deprecated as a long term solution is
defined and deployed to replace it."
SYNTAX Counter64
ZeroBasedCounter64 ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"This TC describes an object which counts events with the
following semantics: objects of this type will be set to
zero(0) on creation and will thereafter count appropriate
events, wrapping back to zero(0) when the value 2^64 is
reached.
Provided that an application discovers the new object within
the minimum time to wrap it can use the initial value as a
delta since it last polled the
information being modeled table of which this object is greater than or equal
part. It is important for a management station to its
maximum value, and has its be aware
of this minimum value whenever time and the
information being modeled actual time between polls, and
to discard data if the actual time is smaller than too long or equal to its there is
no defined minimum value. If the information being modeled
subsequently decreases below (increases above) time.
Typically this TC is used in tables where the maximum
(minimum) value, INDEX space is
constantly changing and/or the Gauge64 also decreases (increases).
(Note TimeFilter mechanism is in
use.
Note that despite of this textual convention does not retain all the use
semantics of the term "latched" in the
original definition of Counter64 base type. Specifically, a
Counter64 has an arbitrary initial value, but objects
defined with this type, it does not become "stuck" TC are required to start at its maximum or minimum value.)"
SYNTAX the value
zero. This behavior is not likely to have any adverse
effects on management applications which are expecting
Counter64
Unsigned64 ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
The Unsigned64 type semantics.
This textual convention represents integer-valued information
between 0 a limited and 2^64-1 inclusive (0 short-term
solution, and will be deprecated as a long term solution is
defined and deployed to 18446744073709551615
decimal)." replace it."
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SYNTAX Counter64
END
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7.
8. Intellectual Property
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.
8.
9. References
[HC-RMON]
Waldbusser, S., "Remote Network Monitoring Management Information
Base for High Capacity Networks", draft-ietf-rmonmib-hcrmon-06.txt,
International Network Services, June 1999.
[RFC1155]
Rose, M., and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based Internets", RFC 1155, STD
16, Performance Systems International, Hughes LAN Systems, May
1990.
[RFC1157]
Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network
Management Protocol", RFC 1157, STD 15, SNMP Research, Performance
Systems International, Performance Systems International, MIT
Laboratory for Computer Science, May 1990.
[RFC1212]
Rose, M., and K. McCloghrie, "Concise MIB Definitions", RFC 1212,
STD 16, Performance Systems International, Hughes LAN Systems,
March 1991.
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[RFC1215]
M. Rose, "A Convention for Defining Traps for use with the SNMP",
RFC 1215, Performance Systems International, March 1991.
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[RFC1901]
Case, J., McCloghrie, K., Rose, M., and S. Waldbusser,
"Introduction to Community-based SNMPv2", RFC 1901, SNMP Research,
Inc., Cisco Systems, Inc., Dover Beach Consulting, Inc.,
International Network Services, January 1996.
[RFC1905]
Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Protocol
Operations for Version 2 of the Simple Network Management Protocol
(SNMPv2)", RFC 1905, SNMP Research, Inc., Cisco Systems, Inc.,
Dover Beach Consulting, Inc., International Network Services,
January 1996.
[RFC1906]
Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport
Mappings for Version 2 of the Simple Network Management Protocol
(SNMPv2)", RFC 1906, SNMP Research, Inc., Cisco Systems, Inc.,
Dover Beach Consulting, Inc., International Network Services,
January 1996.
[RFC2021]
S. Waldbusser, "Remote Network Monitoring MIB (RMON-2)", RFC 2021,
International Network Services, January 1997.
[RFC2026]
Bradner, S., "The Internet Standards Process -- Revision 3", RFC
2026, Harvard University, October, 1996.
[RFC2570]
Case, J., Mundy, R., Partain, D., and B. Stewart, "Introduction to
Version 3 of the Internet-standard Network Management Framework",
RFC 2570, SNMP Research, Inc., TIS Labs at Network Associates,
Inc., Ericsson, Cisco Systems, April 1999.
[RFC2571]
Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for
Describing SNMP Management Frameworks", RFC 2571, Cabletron
Systems, Inc., BMC Software, Inc., IBM T. J. Watson Research, April
1999.
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[RFC2572]
Case, J., Harrington D., Presuhn R., and B. Wijnen, "Message
Processing and Dispatching for the Simple Network Management
Protocol (SNMP)", RFC 2572, SNMP Research, Inc., Cabletron Systems,
Inc., BMC Software, Inc., IBM T. J. Watson Research, April 1999.
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[RFC2573]
Levi, D., Meyer, P., and B. Stewart, "SNMPv3 Applications", RFC
2573, SNMP Research, Inc., Secure Computing Corporation, Cisco
Systems, April 1999.
[RFC2574]
Blumenthal, U., and B. Wijnen, "User-based Security Model (USM) for
version 3 of the Simple Network Management Protocol (SNMPv3)", RFC
2574, IBM T. J. Watson Research, April 1999.
[RFC2575]
Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access
Control Model (VACM) for the Simple Network Management Protocol
(SNMP)", RFC 2575, IBM T. J. Watson Research, BMC Software, Inc.,
Cisco Systems, Inc., April 1999.
[RFC2578]
McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.,
and S. Waldbusser, "Structure of Management Information Version 2
(SMIv2)", RFC 2578, STD 58, Cisco Systems, SNMPinfo, TU
Braunschweig, SNMP Research, First Virtual Holdings, International
Network Services, April 1999.
[RFC2579]
McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.,
and S. Waldbusser, "Textual Conventions for SMIv2", RFC 2579, STD
58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research, First
Virtual Holdings, International Network Services, April 1999.
[RFC2580]
McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., Rose, M.,
and S. Waldbusser, "Conformance Statements for SMIv2", RFC 2580,
STD 58, Cisco Systems, SNMPinfo, TU Braunschweig, SNMP Research,
First Virtual Holdings, International Network Services, April 1999.
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9.
10. Security Considerations
There are no security issues raised by this document.
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10.
11. Authors' Addresses
Andy Bierman
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134 USA
Phone: +1 408-527-3711
Email: abierman@cisco.com
Keith McCloghrie
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134 USA
Phone: +1 408-526-5260
Email: kzm@cisco.com
Randy Presuhn
BMC Software, Inc.
1190 Saratoga Avenue
Suite 130
Office 1-3141
2141 North First Street
San Jose, CA 95129 California 95131 USA
Phone: +1 408-556-0720 408 546-1006
EMail: rpresuhn@bmc.com
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11.
12. Full Copyright Statement
Copyright (C) The Internet Society (1999). 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."
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----