RFC3417
Network Working Group Editor of this version: Request for Comments: 3417 R. Presuhn STD: 62 BMC Software, Inc. Obsoletes: 1906 Authors of previous version: Category: Standards Track J. Case
SNMP Research, Inc.
K. McCloghrie
Cisco Systems, Inc.
M. Rose
Dover Beach Consulting, Inc.
S. Waldbusser
International Network Services
December 2002
Transport Mappings for
the Simple Network Management Protocol (SNMP)
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 document defines the transport of Simple Network Management Protocol (SNMP) messages over various protocols. This document obsoletes RFC 1906.
Contents
Introduction
For a detailed overview of the documents that describe the current Internet-Standard Management Framework, please refer to section 7 of RFC 3410 RFC3410.
Managed objects are accessed via a virtual information store, termed the Management Information Base or MIB. MIB objects are generally accessed through the Simple Network Management Protocol (SNMP). Objects in the MIB are defined using the mechanisms defined in the Structure of Management Information (SMI). This memo specifies a MIB
module that is compliant to the SMIv2, which is described in STD 58, RFC 2578 RFC2578, STD 58, RFC 2579 RFC2579 and STD 58, RFC 2580 RFC2580.
This document, Transport Mappings for the Simple Network Management Protocol, defines how the management protocol RFC3416 may be carried over a variety of protocol suites. It is the purpose of this document to define how the SNMP maps onto an initial set of transport domains. At the time of this writing, work was in progress to define an IPv6 mapping, described in RFC3419. Other mappings may be defined in the future.
Although several mappings are defined, the mapping onto UDP over IPv4 is the preferred mapping for systems supporting IPv4. Systems implementing IPv4 MUST implement the mapping onto UDP over IPv4. To maximize interoperability, systems supporting other mappings SHOULD also provide for access via the UDP over IPv4 mapping.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 RFC2119.
Definitions
SNMPv2-TM DEFINITIONS ::= BEGIN
IMPORTS
MODULE-IDENTITY, OBJECT-IDENTITY,
snmpModules, snmpDomains, snmpProxys
FROM SNMPv2-SMI
TEXTUAL-CONVENTION
FROM SNMPv2-TC;
snmpv2tm MODULE-IDENTITY
LAST-UPDATED "200210160000Z"
ORGANIZATION "IETF SNMPv3 Working Group"
CONTACT-INFO
"WG-EMail: [email protected]
Subscribe: [email protected]
Co-Chair: Russ Mundy
Network Associates Laboratories
postal: 15204 Omega Drive, Suite 300
Rockville, MD 20850-4601
USA
EMail: [email protected]
phone: +1 301 947-7107
Co-Chair: David Harrington
Enterasys Networks
postal: 35 Industrial Way
P. O. Box 5005
Rochester, NH 03866-5005
USA
EMail: [email protected]
phone: +1 603 337-2614
Editor: Randy Presuhn
BMC Software, Inc.
postal: 2141 North First Street
San Jose, CA 95131
USA
EMail: [email protected]
phone: +1 408 546-1006"
DESCRIPTION
"The MIB module for SNMP transport mappings.
Copyright (C) The Internet Society (2002). This
version of this MIB module is part of RFC 3417;
see the RFC itself for full legal notices.
"
REVISION "200210160000Z"
DESCRIPTION
"Clarifications, published as RFC 3417."
REVISION "199601010000Z"
DESCRIPTION
"Clarifications, published as RFC 1906."
REVISION "199304010000Z"
DESCRIPTION
"The initial version, published as RFC 1449."
::= { snmpModules 19 }
-- SNMP over UDP over IPv4
snmpUDPDomain OBJECT-IDENTITY
STATUS current
DESCRIPTION
"The SNMP over UDP over IPv4 transport domain.
The corresponding transport address is of type
SnmpUDPAddress."
::= { snmpDomains 1 }
SnmpUDPAddress ::= TEXTUAL-CONVENTION
DISPLAY-HINT "1d.1d.1d.1d/2d"
STATUS current
DESCRIPTION
"Represents a UDP over IPv4 address:
octets contents encoding
1-4 IP-address network-byte order
5-6 UDP-port network-byte order
"
SYNTAX OCTET STRING (SIZE (6))
-- SNMP over OSI
snmpCLNSDomain OBJECT-IDENTITY
STATUS current
DESCRIPTION
"The SNMP over CLNS transport domain.
The corresponding transport address is of type
SnmpOSIAddress."
::= { snmpDomains 2 }
snmpCONSDomain OBJECT-IDENTITY
STATUS current
DESCRIPTION
"The SNMP over CONS transport domain.
The corresponding transport address is of type
SnmpOSIAddress."
::= { snmpDomains 3 }
SnmpOSIAddress ::= TEXTUAL-CONVENTION
DISPLAY-HINT "*1x:/1x:"
STATUS current
DESCRIPTION
"Represents an OSI transport-address:
octets contents encoding
1 length of NSAP 'n' as an unsigned-integer
(either 0 or from 3 to 20)
2..(n+1) NSAP concrete binary representation
(n+2)..m TSEL string of (up to 64) octets
"
SYNTAX OCTET STRING (SIZE (1 | 4..85))
-- SNMP over DDP
snmpDDPDomain OBJECT-IDENTITY
STATUS current
DESCRIPTION
"The SNMP over DDP transport domain. The corresponding
transport address is of type SnmpNBPAddress."
::= { snmpDomains 4 }
SnmpNBPAddress ::= TEXTUAL-CONVENTION
STATUS current
DESCRIPTION
"Represents an NBP name:
octets contents encoding
1 length of object 'n' as an unsigned integer
2..(n+1) object string of (up to 32) octets
n+2 length of type 'p' as an unsigned integer
(n+3)..(n+2+p) type string of (up to 32) octets
n+3+p length of zone 'q' as an unsigned integer
(n+4+p)..(n+3+p+q) zone string of (up to 32) octets
For comparison purposes, strings are
case-insensitive. All strings may contain any octet
other than 255 (hex ff)."
SYNTAX OCTET STRING (SIZE (3..99))
-- SNMP over IPX
snmpIPXDomain OBJECT-IDENTITY
STATUS current
DESCRIPTION
"The SNMP over IPX transport domain. The corresponding
transport address is of type SnmpIPXAddress."
::= { snmpDomains 5 }
SnmpIPXAddress ::= TEXTUAL-CONVENTION
DISPLAY-HINT "4x.1x:1x:1x:1x:1x:1x.2d"
STATUS current
DESCRIPTION
"Represents an IPX address:
octets contents encoding
1-4 network-number network-byte order
5-10 physical-address network-byte order
11-12 socket-number network-byte order
"
SYNTAX OCTET STRING (SIZE (12))
-- for proxy to SNMPv1 (RFC 1157)
rfc1157Proxy OBJECT IDENTIFIER ::= { snmpProxys 1 }
rfc1157Domain OBJECT-IDENTITY
STATUS deprecated
DESCRIPTION
"The transport domain for SNMPv1 over UDP over IPv4.
The corresponding transport address is of type
SnmpUDPAddress."
::= { rfc1157Proxy 1 }
-- ::= { rfc1157Proxy 2 } this OID is obsolete
END
SNMP over UDP over IPv4
This is the preferred transport mapping.
Serialization
Each instance of a message is serialized (i.e., encoded according to the convention of [BER]) onto a single UDP RFC768 over IPv4 RFC791 datagram, using the algorithm specified in Section 8.
Well-known Values
It is suggested that administrators configure their SNMP entities supporting command responder applications to listen on UDP port 161. Further, it is suggested that SNMP entities supporting notification receiver applications be configured to listen on UDP port 162.
When an SNMP entity uses this transport mapping, it must be capable of accepting messages up to and including 484 octets in size. It is recommended that implementations be capable of accepting messages of up to 1472 octets in size. Implementation of larger values is encouraged whenever possible.
SNMP over OSI
This is an optional transport mapping.
Serialization
Each instance of a message is serialized onto a single TSDU [IS8072] [IS8072A] for the OSI Connectionless-mode Transport Service (CLTS), using the algorithm specified in Section 8.
Well-known Values
It is suggested that administrators configure their SNMP entities supporting command responder applications to listen on transport selector "snmp-l" (which consists of six ASCII characters), when using a CL-mode network service to realize the CLTS. Further, it is suggested that SNMP entities supporting notification receiver applications be configured to listen on transport selector "snmpt-l" (which consists of seven ASCII characters, six letters and a hyphen) when using a CL-mode network service to realize the CLTS. Similarly, when using a CO-mode network service to realize the CLTS, the suggested transport selectors are "snmp-o" and "snmpt-o", for command responders and notification receivers, respectively.
When an SNMP entity uses this transport mapping, it must be capable of accepting messages that are at least 484 octets in size. Implementation of larger values is encouraged whenever possible.
SNMP over DDP
This is an optional transport mapping.
Serialization
Each instance of a message is serialized onto a single DDP datagram [APPLETALK], using the algorithm specified in Section 8.
Well-known Values
SNMP messages are sent using DDP protocol type 8. SNMP entities supporting command responder applications listen on DDP socket number 8, while SNMP entities supporting notification receiver applications listen on DDP socket number 9.
Administrators must configure their SNMP entities supporting command responder applications to use NBP type "SNMP Agent" (which consists of ten ASCII characters) while those supporting notification receiver applications must be configured to use NBP type "SNMP Trap Handler" (which consists of seventeen ASCII characters).
The NBP name for SNMP entities supporting command responders and notification receivers should be stable - NBP names should not change any more often than the IP address of a typical TCP/IP node. It is suggested that the NBP name be stored in some form of stable storage.
When an SNMP entity uses this transport mapping, it must be capable of accepting messages that are at least 484 octets in size. Implementation of larger values is encouraged whenever possible.
Discussion of AppleTalk Addressing
The AppleTalk protocol suite has certain features not manifest in the TCP/IP suite. AppleTalk's naming strategy and the dynamic nature of address assignment can cause problems for SNMP entities that wish to manage AppleTalk networks. TCP/IP nodes have an associated IP address which distinguishes each from the other. In contrast, AppleTalk nodes generally have no such characteristic. The network- level address, while often relatively stable, can change at every reboot (or more frequently).
Thus, when SNMP is mapped over DDP, nodes are identified by a "name", rather than by an "address". Hence, all AppleTalk nodes that implement this mapping are required to respond to NBP lookups and confirms (e.g., implement the NBP protocol stub), which guarantees that a mapping from NBP name to DDP address will be possible.
In determining the SNMP identity to register for an SNMP entity, it is suggested that the SNMP identity be a name which is associated with other network services offered by the machine.
NBP lookups, which are used to map NBP names into DDP addresses, can cause large amounts of network traffic as well as consume CPU resources. It is also the case that the ability to perform an NBP lookup is sensitive to certain network disruptions (such as zone table inconsistencies) which would not prevent direct AppleTalk communications between two SNMP entities.
Thus, it is recommended that NBP lookups be used infrequently, primarily to create a cache of name-to-address mappings. These cached mappings should then be used for any further SNMP traffic. It is recommended that SNMP entities supporting command generator applications should maintain this cache between reboots. This caching can help minimize network traffic, reduce CPU load on the network, and allow for (some amount of) network trouble shooting when the basic name-to-address translation mechanism is broken.
How to Acquire NBP names
An SNMP entity supporting command generator applications may have a pre-configured list of names of "known" SNMP entities supporting command responder applications. Similarly, an SNMP entity supporting command generator or notification receiver applications might interact with an operator. Finally, an SNMP entity supporting command generator or notification receiver applications might communicate with all SNMP entities supporting command responder or notification originator applications in a set of zones or networks.
When to Turn NBP names into DDP addresses
When an SNMP entity uses a cache entry to address an SNMP packet, it should attempt to confirm the validity mapping, if the mapping hasn't been confirmed within the last T1 seconds. This cache entry lifetime, T1, has a minimum, default value of 60 seconds, and should be configurable.
An SNMP entity supporting a command generator application may decide to prime its cache of names prior to actually communicating with another SNMP entity. In general, it is expected that such an entity may want to keep certain mappings "more current" than other mappings, e.g., those nodes which represent the network infrastructure (e.g., routers) may be deemed "more important".
Note that an SNMP entity supporting command generator applications should not prime its entire cache upon initialization - rather, it should attempt resolutions over an extended period of time (perhaps in some pre-determined or configured priority order). Each of these resolutions might, in fact, be a wildcard lookup in a given zone.
An SNMP entity supporting command responder applications must never prime its cache. When generating a response, such an entity does not need to confirm a cache entry. An SNMP entity supporting notification originator applications should do NBP lookups (or confirms) only when it needs to send an SNMP trap or inform.
How to Turn NBP names into DDP addresses
If the only piece of information available is the NBP name, then an NBP lookup should be performed to turn that name into a DDP address. However, if there is a piece of stale information, it can be used as a hint to perform an NBP confirm (which sends a unicast to the network address which is presumed to be the target of the name lookup) to see if the stale information is, in fact, still valid.
An NBP name to DDP address mapping can also be confirmed implicitly using only SNMP transactions. For example, an SNMP entity supporting command generator applications issuing a retrieval operation could also retrieve the relevant objects from the NBP group RFC1742 for the SNMP entity supporting the command responder application. This information can then be correlated with the source DDP address of the response.
What if NBP is broken
Under some circumstances, there may be connectivity between two SNMP entities, but the NBP mapping machinery may be broken, e.g.,
o the NBP FwdReq (forward NBP lookup onto local attached network)
mechanism might be broken at a router on the other entity's network; or,
o the NBP BrRq (NBP broadcast request) mechanism might be broken at
a router on the entity's own network; or,
o NBP might be broken on the other entity's node.
An SNMP entity supporting command generator applications which is dedicated to AppleTalk management might choose to alleviate some of these failures by directly implementing the router portion of NBP. For example, such an entity might already know all the zones on the AppleTalk internet and the networks on which each zone appears. Given an NBP lookup which fails, the entity could send an NBP FwdReq to the network in which the SNMP entity supporting the command responder or notification originator application was last located. If that failed, the station could then send an NBP LkUp (NBP lookup packet) as a directed (DDP) multicast to each network number on that network. Of the above (single) failures, this combined approach will solve the case where either the local router's BrRq-to-FwdReq mechanism is broken or the remote router's FwdReq-to-LkUp mechanism is broken.
SNMP over IPX
This is an optional transport mapping.
Serialization
Each instance of a message is serialized onto a single IPX datagram [NOVELL], using the algorithm specified in Section 8.
Well-known Values
SNMP messages are sent using IPX packet type 4 (i.e., Packet Exchange Protocol).
It is suggested that administrators configure their SNMP entities supporting command responder applications to listen on IPX socket 36879 (900f hexadecimal). Further, it is suggested that those supporting notification receiver applications be configured to listen on IPX socket 36880 (9010 hexadecimal).
When an SNMP entity uses this transport mapping, it must be capable of accepting messages that are at least 546 octets in size. Implementation of larger values is encouraged whenever possible.
Proxy to SNMPv1
Historically, in order to support proxy to SNMPv1, as defined in RFC2576, it was deemed useful to define a transport domain, rfc1157Domain, which indicates the transport mapping for SNMP messages as defined in RFC1157.
Serialization using the Basic Encoding Rules
When the Basic Encoding Rules [BER] are used for serialization:
(1) When encoding the length field, only the definite form is used;
use of the indefinite form encoding is prohibited. Note that
when using the definite-long form, it is permissible to use
more than the minimum number of length octets necessary to
encode the length field.
(2) When encoding the value field, the primitive form shall be used
for all simple types, i.e., INTEGER, OCTET STRING, and OBJECT
IDENTIFIER (either IMPLICIT or explicit). The constructed form
of encoding shall be used only for structured types, i.e., a
SEQUENCE or an IMPLICIT SEQUENCE.
(3) When encoding an object whose syntax is described using the
BITS construct, the value is encoded as an OCTET STRING, in
which all the named bits in (the definition of) the bitstring,
commencing with the first bit and proceeding to the last bit,
are placed in bits 8 (high order bit) to 1 (low order bit) of
the first octet, followed by bits 8 to 1 of each subsequent
octet in turn, followed by as many bits as are needed of the
final subsequent octet, commencing with bit 8. Remaining bits,
if any, of the final octet are set to zero on generation and
ignored on receipt.
These restrictions apply to all aspects of ASN.1 encoding, including the message wrappers, protocol data units, and the data objects they contain.
Usage Example
As an example of applying the Basic Encoding Rules, suppose one wanted to encode an instance of the GetBulkRequest-PDU RFC3416:
[5] IMPLICIT SEQUENCE {
request-id 1414684022,
non-repeaters 1,
max-repetitions 2,
variable-bindings {
{ name sysUpTime,
value { unSpecified NULL } },
{ name ipNetToMediaPhysAddress,
value { unSpecified NULL } },
{ name ipNetToMediaType,
value { unSpecified NULL } }
}
}
Applying the BER, this may be encoded (in hexadecimal) as:
[5] IMPLICIT SEQUENCE a5 82 00 39
INTEGER 02 04 54 52 5d 76
INTEGER 02 01 01
INTEGER 02 01 02
SEQUENCE (OF) 30 2b
SEQUENCE 30 0b
OBJECT IDENTIFIER 06 07 2b 06 01 02 01 01 03
NULL 05 00
SEQUENCE 30 0d
OBJECT IDENTIFIER 06 09 2b 06 01 02 01 04 16 01 02
NULL 05 00
SEQUENCE 30 0d
OBJECT IDENTIFIER 06 09 2b 06 01 02 01 04 16 01 04
NULL 05 00
Note that the initial SEQUENCE in this example was not encoded using the minimum number of length octets. (The first octet of the length, 82, indicates that the length of the content is encoded in the next two octets.)
Notice on 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.
10. Acknowledgments
This document is the product of the SNMPv3 Working Group. Some special thanks are in order to the following Working Group members:
Randy Bush Jeffrey D. Case Mike Daniele Rob Frye Lauren Heintz Keith McCloghrie Russ Mundy David T. Perkins Randy Presuhn Aleksey Romanov Juergen Schoenwaelder Bert Wijnen
This version of the document, edited by Randy Presuhn, was initially based on the work of a design team whose members were:
Jeffrey D. Case Keith McCloghrie David T. Perkins Randy Presuhn Juergen Schoenwaelder
The previous versions of this document, edited by Keith McCloghrie, was the result of significant work by four major contributors:
Jeffrey D. Case Keith McCloghrie Marshall T. Rose Steven Waldbusser
Additionally, the contributions of the SNMPv2 Working Group to the previous versions are also acknowledged. In particular, a special thanks is extended for the contributions of:
Alexander I. Alten Dave Arneson Uri Blumenthal Doug Book Kim Curran Jim Galvin Maria Greene Iain Hanson Dave Harrington Nguyen Hien Jeff Johnson Michael Kornegay Deirdre Kostick David Levi Daniel Mahoney Bob Natale Brian O'Keefe Andrew Pearson Dave Perkins Randy Presuhn Aleksey Romanov Shawn Routhier Jon Saperia Juergen Schoenwaelder Bob Stewart Kaj Tesink Glenn Waters Bert Wijnen
11. IANA Considerations
The SNMPv2-TM MIB module requires the allocation of a single object identifier for its MODULE-IDENTITY. IANA has allocated this object identifier in the snmpModules subtree, defined in the SNMPv2-SMI MIB module.
12. Security Considerations
SNMPv1 by itself is not a secure environment. Even if the network itself is secure (for example by using IPSec), even then, there is no control as to who on the secure network is allowed to access and GET/SET (read/change) the objects accessible through a command responder application.
It is recommended that the implementors consider the security features as provided by the SNMPv3 framework. Specifically, the use of the User-based Security Model STD 62, RFC 3414 RFC3414 and the View-based Access Control Model STD 62, RFC 3415 RFC3415 is recommended.
It is then a customer/user responsibility to ensure that the SNMP entity giving access to a MIB is properly configured to give access to the objects only to those principals (users) that have legitimate rights to indeed GET or SET (change) them.
13. References
13.1. Normative References
[BER] Information processing systems - Open Systems
Interconnection - Specification of Basic Encoding Rules
for Abstract Syntax Notation One (ASN.1), International
Organization for Standardization. International Standard
8825, December 1987.
[IS8072] Information processing systems - Open Systems
Interconnection - Transport Service Definition,
International Organization for Standardization.
International Standard 8072, June 1986.
[IS8072A] Information processing systems - Open Systems
Interconnection - Transport Service Definition - Addendum
1: Connectionless-mode Transmission, International
Organization for Standardization. International Standard
8072/AD 1, December 1986.
RFC768 Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
RFC791 Postel, J., "Internet Protocol", STD 5, RFC 791,
September 1981.
RFC2119 Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
RFC2578 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.
RFC2579 McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Textual Conventions for
SMIv2", STD 58, RFC 2579, April 1999.
RFC2580 McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J.,
Rose, M. and S. Waldbusser, "Conformance Statements for
SMIv2", STD 58, RFC 2580, April 1999.
RFC3414 Blumenthal, U. and B. Wijnen, "The User-Based Security
Model (USM) for Version 3 of the Simple Network
Management Protocol (SNMPv3)", STD 62, RFC 3414, December
2002.
RFC3415 Wijnen, B., Presuhn, R. and K. McCloghrie, "View-based
Access Control Model (VACM) for the Simple Network
Management Protocol (SNMP)", STD 62, RFC 3415, December
2002.
RFC3416 Presuhn, R., Case, J., McCloghrie, K., Rose, M. and S.
Waldbusser, "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62, RFC
3416, December 2002.
13.2. Informative References
[APPLETALK] Sidhu, G., Andrews, R. and A. Oppenheimer, Inside
AppleTalk (second edition). Addison-Wesley, 1990.
[NOVELL] Network System Technical Interface Overview. Novell,
Inc., June 1989.
RFC1157 Case, J., Fedor, M., Schoffstall, M. and J. Davin,
"Simple Network Management Protocol", STD 15, RFC 1157, May 1990.
RFC1742 Waldbusser, S. and K. Frisa, "AppleTalk Management
Information Base II", RFC 1742, January 1995.
RFC2576 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 2576, March 2000.
RFC3410 Case, J., Mundy, R., Partain, D. and B. Stewart,
"Introduction and Applicability Statements for Internet-
Standard Management Framework", RFC 3410, December 2002.
RFC3419 Daniele, M. and J. Schoenwaelder, "Textual Conventions
for Transport Addresses", RFC 3419, November 2002.
14. Changes from RFC 1906
This document differs from RFC 1906 only in editorial improvements. The protocol is unchanged.
15. Editor's Address
Randy Presuhn BMC Software, Inc. 2141 North First Street San Jose, CA 95131 USA
Phone: +1 408 546-1006 EMail: [email protected]
16. 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.
