draft-ietf-dnsext-rfc2671bis-edns0-01.txt   draft-ietf-dnsext-rfc2671bis-edns0-02.txt 
DNSEXT Working Group Paul Vixie, ISC DNSEXT Working Group M. Graff
INTERNET-DRAFT Internet-Draft P. Vixie
<draft-ietf-dnsext-rfc2671bis-edns0-01.txt> March 17, 2008 Obsoletes: 2671 (if approved) Internet Systems Consortium
Intended status: Standards Track July 28, 2009
Intended Status: Standards Track Expires: January 29, 2010
Obsoletes: 2671 (if approved)
Revised extension mechanisms for DNS (EDNS0) Extension Mechanisms for DNS (EDNS0)
draft-ietf-dnsext-rfc2671bis-edns0-02
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Abstract Abstract
The Domain Name System's wire protocol includes a number of fixed The Domain Name System's wire protocol includes a number of fixed
fields whose range has been or soon will be exhausted and does not fields whose range has been or soon will be exhausted and does not
allow clients to advertise their capabilities to servers. This allow requestors to advertise their capabilities to responders. This
document describes backward compatible mechanisms for allowing the document describes backward compatible mechanisms for allowing the
protocol to grow. protocol to grow.
1 - Introduction This document updates the EDNS0 specification based on 10 years of
operational experience.
1.1. DNS (see [RFC1035]) specifies a Message Format and within such Table of Contents
messages there are standard formats for encoding options, errors, and
name compression. The maximum allowable size of a DNS Message is fixed.
Many of DNS's protocol limits are too small for uses which are or which
are desired to become common. There is no way for implementations to
advertise their capabilities.
1.2. Unextended agents will not know how to interpret the protocol 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
extensions detailed here. In practice, these clients will be upgraded 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
when they have need of a new feature, and only new features will make 3. EDNS Support Requirement . . . . . . . . . . . . . . . . . . . 3
use of the extensions. Extended agents must be prepared for behaviour 4. Affected Protocol Elements . . . . . . . . . . . . . . . . . . 3
of unextended clients in the face of new protocol elements, and fall 4.1. Message Header . . . . . . . . . . . . . . . . . . . . . . 3
back gracefully to unextended DNS. RFC 2671 originally has proposed 4.2. Label Types . . . . . . . . . . . . . . . . . . . . . . . 4
extensions to the basic DNS protocol to overcome these deficiencies. 4.3. UDP Message Size . . . . . . . . . . . . . . . . . . . . . 4
This memo refines that specification and obsoletes RFC 2671. 5. Extended Label Types . . . . . . . . . . . . . . . . . . . . . 4
6. OPT pseudo-RR . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. OPT Record Behavior . . . . . . . . . . . . . . . . . . . 4
6.2. OPT Record Format . . . . . . . . . . . . . . . . . . . . 5
6.3. Requestor's Payload Size . . . . . . . . . . . . . . . . . 6
6.4. Responder's Payload Size . . . . . . . . . . . . . . . . . 6
6.5. Payload Size Selection . . . . . . . . . . . . . . . . . . 7
6.6. Middleware Boxes . . . . . . . . . . . . . . . . . . . . . 7
6.7. Extended RCODE . . . . . . . . . . . . . . . . . . . . . . 7
6.8. OPT Options Type Allocation Procedure . . . . . . . . . . 8
7. Transport Considerations . . . . . . . . . . . . . . . . . . . 8
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
11.1. Normative References . . . . . . . . . . . . . . . . . . . 10
11.2. Informative References . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
1.3. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 1. Introduction
DNS [RFC1035] specifies a Message Format and within such messages
there are standard formats for encoding options, errors, and name
compression. The maximum allowable size of a DNS Message is fixed.
Many of DNS's protocol limits are too small for uses which are or
which are desired to become common. There is no way for
implementations to advertise their capabilities.
Unextended agents will not know how to interpret the protocol
extensions detailed here. In practice, these clients will be
upgraded when they have need of a new feature, and only new features
will make use of the extensions. Extended agents must be prepared
for behaviour of unextended clients in the face of new protocol
elements, and fall back gracefully to unextended DNS. [RFC2671]
originally proposed extensions to the basic DNS protocol to overcome
these deficiencies. This memo refines that specification and
obsoletes [RFC2671].
2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2 - Affected Protocol Elements 3. EDNS Support Requirement
2.1. The DNS Message Header's (see [RFC1035 4.1.1]) second full 16-bit EDNS support is manditory in a modern world. DNSSEC requires EDNS
word is divided into a 4-bit OPCODE, a 4-bit RCODE, and a number of support, and many other featres are made possible only by EDNS
1-bit flags. The original reserved Z bits have been allocated to support to request or advertise them.
various purposes, and most of the RCODE values are now in use. More
flags and more possible RCODEs are needed. The OPT pseudo-RR specified
in Section 4 contains subfields that carry a bit field extension of the
RCODE field and additional flag bits, respectively; for details see
Section 4.6 below.
2.2. The first two bits of a wire format domain label are used to denote 4. Affected Protocol Elements
the type of the label. [RFC1035 4.1.4] allocates two of the four
possible types and reserves the other two. Proposals for use of the
remaining types far outnumber those available. More label types were
needed, and an extension mechanism was proposed in RFC 2671 [RFC2671
Section 3]. Section 3 of this document reserves DNS labels with a first
octet in the range of 64-127 decimal (label type 01) for future
standardization of Extended DNS Labels.
2.3. DNS Messages are limited to 512 octets in size when sent over UDP. 4.1. Message Header
While the minimum maximum reassembly buffer size still allows a limit of
512 octets of UDP payload, most of the hosts now connected to the
Internet are able to reassemble larger datagrams. Some mechanism must
be created to allow requestors to advertise larger buffer sizes to
responders. To this end, the OPT pseudo-RR specified in Section 4
contains a maximum payload size field; for details see Section 4.5
below.
3 - Extended Label Types The DNS Message Header's (see , section 4.1.1 [RFC1035]) second full
16-bit word is divided into a 4-bit OPCODE, a 4-bit RCODE, and a
number of 1-bit flags. The original reserved Z bits have been
allocated to various purposes, and most of the RCODE values are now
in use. More flags and more possible RCODEs are needed. The OPT
pseudo-RR specified below contains subfields that carry a bit field
extension of the RCODE field and additional flag bits, respectively.
4.2. Label Types
The first two bits of a wire format domain label are used to denote
the type of the label. ,section 4.1.4 [RFC1035] allocates two of the
four possible types and reserves the other two. More label types
were proposed in [RFC2671] section 3.
4.3. UDP Message Size
DNS Messages are limited to 512 octets in size when sent over UDP.
While the minimum maximum reassembly buffer size still allows a limit
of 512 octets of UDP payload, most of the hosts now connected to the
Internet are able to reassemble larger datagrams. Some mechanism
must be created to allow requestors to advertise larger buffer sizes
to responders. To this end, the OPT pseudo-RR specified below
contains a maximum payload size field.
5. Extended Label Types
The first octet in the on-the-wire representation of a DNS label The first octet in the on-the-wire representation of a DNS label
specifies the label type; the basic DNS specification [RFC1035] specifies the label type; the basic DNS specification [RFC1035]
dedicates the two most significant bits of that octet for this purpose. dedicates the two most significant bits of that octet for this
purpose.
This document reserves DNS label type 0b01 for use as an indication for
Extended Label Types. A specific extended label type is selected by the
6 least significant bits of the first octet. Thus, Extended Label Types
are indicated by the values 64-127 (0b01xxxxxx) in the first octet of
the label.
Allocations from this range are to be made for IETF documents fully This document reserves DNS label type 0b01 for use as an indication
describing the syntax and semantics as well as the applicability of the for Extended Label Types. A specific extended label type is selected
particular Extended Label Type. by the 6 least significant bits of the first octet. Thus, Extended
Label Types are indicated by the values 64-127 (0b01xxxxxx) in the
first octet of the label.
This document does not describe any specific Extended Label Type. This document does not describe any specific Extended Label Type.
4 - OPT pseudo-RR In practice, Extended Label Types are difficult to use due to support
in clients and intermediate gateways. Therefore, the registry of
Extended Label Types is requested to be closed. They cause
interoperability problems and at present no defined label types are
in use.
4.1. One OPT pseudo-RR (RR type 41) MAY be added to the additional data 6. OPT pseudo-RR
section of a request, and to responses to such requests. An OPT is
called a pseudo-RR because it pertains to a particular transport level
message and not to any actual DNS data. OPT RRs MUST NOT be cached,
forwarded, or stored in or loaded from master files. The quantity of
OPT pseudo-RRs per message MUST be either zero or one, but not greater.
4.2. An OPT RR has a fixed part and a variable set of options expressed 6.1. OPT Record Behavior
as {attribute, value} pairs. The fixed part holds some DNS meta data
and also a small collection of new protocol elements which we expect to
be so popular that it would be a waste of wire space to encode them as
{attribute, value} pairs.
4.3. The fixed part of an OPT RR is structured as follows: One OPT pseudo-RR (RR type 41) MAY be added to the additional data
section of a request. If present in requests, compliant responders
which implement EDNS MUST include an OPT record in non-truncated
responses, and SHOULD attempt to include them in all responses. An
OPT is called a pseudo-RR because it pertains to a particular
transport level message and not to any actual DNS data. OPT RRs MUST
NOT be cached, forwarded, or stored in or loaded from master files.
The quantity of OPT pseudo-RRs per message MUST be either zero or
one, but not greater.
Field Name Field Type Description 6.2. OPT Record Format
NAME domain name empty (root domain)
TYPE u_int16_t OPT (41)
CLASS u_int16_t sender's UDP payload size
TTL u_int32_t extended RCODE and flags
RDLEN u_int16_t describes RDATA
RDATA octet stream {attribute,value} pairs
4.4. The variable part of an OPT RR is encoded in its RDATA and is An OPT RR has a fixed part and a variable set of options expressed as
{attribute, value} pairs. The fixed part holds some DNS meta data
and also a small collection of basic extension elements which we
expect to be so popular that it would be a waste of wire space to
encode them as {attribute, value} pairs.
The fixed part of an OPT RR is structured as follows:
+------------+--------------+------------------------------+
| Field Name | Field Type | Description |
+------------+--------------+------------------------------+
| NAME | domain name | empty (root domain) |
| TYPE | u_int16_t | OPT |
| CLASS | u_int16_t | requestor's UDP payload size |
| TTL | u_int32_t | extended RCODE and flags |
| RDLEN | u_int16_t | describes RDATA |
| RDATA | octet stream | {attribute,value} pairs |
+------------+--------------+------------------------------+
OPT RR Format
The variable part of an OPT RR is encoded in its RDATA and is
structured as zero or more of the following: structured as zero or more of the following:
: +0 (MSB) : +1 (LSB) : +0 (MSB) +1 (LSB)
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | OPTION-CODE | 0: | OPTION-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | OPTION-LENGTH | 2: | OPTION-LENGTH |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | | 4: | |
/ OPTION-DATA / / OPTION-DATA /
/ / / /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
OPTION-CODE
Assigned by Expert Review.
OPTION-CODE (Assigned by IANA.) OPTION-LENGTH
Size (in octets) of OPTION-DATA.
OPTION-LENGTH Size (in octets) of OPTION-DATA. OPTION-DATA
Varies per OPTION-CODE.
OPTION-DATA Varies per OPTION-CODE. Order of appearance of option tuples is never relevant. Any option
whose meaning is affected by other options is so affected no matter
which one comes first in the OPT RDATA.
4.4.1. Order of appearance of option tuples is never relevant. Any Any OPTION-CODE values not understood by a responder or requestor
option whose meaning is affected by other options is so affected no MUST be ignored. Specifications of such options might wish to
matter which one comes first in the OPT RDATA. include some kind of signalled acknowledgement. For example, an
option specification might say that if a responder sees option XYZ,
it SHOULD include option XYZ in its response.
4.4.2. Any OPTION-CODE values not understood by a responder or requestor 6.3. Requestor's Payload Size
MUST be ignored. So, specifications of such options might wish to
include some kind of signalled acknowledgement. For example, an option
specification might say that if a responder sees option XYZ, it SHOULD
include option XYZ in its response.
4.5. The sender's UDP payload size (which OPT stores in the RR CLASS The requestor's UDP payload size (which OPT stores in the RR CLASS
field) is the number of octets of the largest UDP payload that can be field) is the number of octets of the largest UDP payload that can be
reassembled and delivered in the sender's network stack. Note that path reassembled and delivered in the requestor's network stack. Note
MTU, with or without fragmentation, may be smaller than this. Values that path MTU, with or without fragmentation, may be smaller than
lower than 512 are undefined, and may be treated as format errors, or this. Values lower than 512 MUST be treated as equal to 512.
may be treated as equal to 512, at the implementor's discretion.
4.5.1. Note that a 512-octet UDP payload requires a 576-octet IP Note that a 512-octet UDP payload requires a 576-octet IP reassembly
reassembly buffer. Choosing 1280 on an Ethernet connected requestor buffer. Choosing 1280 for IPv4 over Ethernet would be reasonable.
would be reasonable. The consequence of choosing too large a value may The consequence of choosing too large a value may be an ICMP message
be an ICMP message from an intermediate gateway, or even a silent drop from an intermediate gateway, or even a silent drop of the response
of the response message. message.
4.5.2. Both requestors and responders are advised to take account of the The requestor's maximum payload size can change over time, and MUST
path's discovered MTU (if already known) when considering message sizes. therefore not be cached for use beyond the transaction in which it is
advertised.
4.5.3. The requestor's maximum payload size can change over time, and 6.4. Responder's Payload Size
therefore MUST NOT be cached for use beyond the transaction in which it
is advertised.
4.5.4. The responder's maximum payload size can change over time, but The responder's maximum payload size can change over time, but can be
can be reasonably expected to remain constant between two sequential reasonably expected to remain constant between two sequential
transactions; for example, a meaningless QUERY to discover a responder's transactions; for example, a meaningless QUERY to discover a
maximum UDP payload size, followed immediately by an UPDATE which takes responder's maximum UDP payload size, followed immediately by an
advantage of this size. (This is considered preferrable to the outright UPDATE which takes advantage of this size. (This is considered
use of TCP for oversized requests, if there is any reason to suspect preferrable to the outright use of TCP for oversized requests, if
that the responder implements EDNS, and if a request will not fit in the there is any reason to suspect that the responder implements EDNS,
default 512 payload size limit.) and if a request will not fit in the default 512 payload size limit.)
4.5.5. Due to transaction overhead, it is unwise to advertise an 6.5. Payload Size Selection
Due to transaction overhead, it is unwise to advertise an
architectural limit as a maximum UDP payload size. Just because your architectural limit as a maximum UDP payload size. Just because your
stack can reassemble 64KB datagrams, don't assume that you want to spend stack can reassemble 64KB datagrams, don't assume that you want to
more than about 4KB of state memory per ongoing transaction. spend more than about 4KB of state memory per ongoing transaction.
4.6. The extended RCODE and flags (which OPT stores in the RR TTL field) A requestor MAY choose to implement a fallback to smaller advertised
sizes to work around firewall or other network limitations. A
requestor SHOULD choose to use a fallback mechanism which begins with
a large size, such as 4096. If that fails, a fallback around the
1220 byte range SHOULD be tried, as it has a reasonable chance to fit
within a single Ethernet frame. Failing that, a requestor MAY choose
a 512 byte packet, which with large answers may cause a TCP retry.
6.6. Middleware Boxes
Middleware boxes MUST NOT limit DNS messages over UDP to 512 bytes.
Middleware boxes which simply forward requests to a recursive
resolver MUST NOT modify the OPT record contents in either direction.
6.7. Extended RCODE
The extended RCODE and flags (which OPT stores in the RR TTL field)
are structured as follows: are structured as follows:
: +0 (MSB) : +1 (LSB) : +0 (MSB) +1 (LSB)
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | EXTENDED-RCODE | VERSION | 0: | EXTENDED-RCODE | VERSION |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | DO| Z | 2: | DO| Z |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
EXTENDED-RCODE Forms upper 8 bits of extended 12-bit RCODE. Note that EXTENDED-RCODE
EXTENDED-RCODE value zero (0) indicates that an Forms upper 8 bits of extended 12-bit RCODE. Note that
unextended RCODE is in use (values zero (0) through EXTENDED-RCODE value "0" indicates that an unextended RCODE is
fifteen (15)). in use (values "0" through "15").
VERSION Indicates the implementation level of whoever sets it. VERSION
Full conformance with this specification is indicated by Indicates the implementation level of whoever sets it. Full
version zero (0). Requestors are encouraged to set this conformance with this specification is indicated by version
to the lowest implemented level capable of expressing a ``0.'' Requestors are encouraged to set this to the lowest
transaction, to minimize the responder and network load implemented level capable of expressing a transaction, to
of discovering the greatest common implementation level minimize the responder and network load of discovering the
between requestor and responder. A requestor's version greatest common implementation level between requestor and
numbering strategy should ideally be a run time responder. A requestor's version numbering strategy MAY
configuration option. ideally be a run time configuration option.
If a responder does not implement the VERSION level of If a responder does not implement the VERSION level of the
the request, then it answers with RCODE=BADVERS. All request, then it answers with RCODE=BADVERS. All responses
responses MUST be limited in format to the VERSION level MUST be limited in format to the VERSION level of the request,
of the request, but the VERSION of each response MUST be but the VERSION of each response SHOULD be the highest
the highest implementation level of the responder. In implementation level of the responder. In this way a requestor
this way a requestor will learn the implementation level will learn the implementation level of a responder as a side
of a responder as a side effect of every response, effect of every response, including error responses and
including error responses, including RCODE=BADVERS. including RCODE=BADVERS.
DO DNSSEC OK bit [RFC3225]. DO
DNSSEC OK bit as defined by [RFC3225].
Z Set to zero by senders and ignored by receivers, unless Z
modified in a subsequent specification [IANAFLAGS]. Set to zero by senders and ignored by receivers, unless
modified in a subsequent specification.
5 - Transport Considerations 6.8. OPT Options Type Allocation Procedure
5.1. The presence of an OPT pseudo-RR in a request is an indication that Allocations assigned by expert review. TBD
the requestor fully implements the given version of EDNS, and can
correctly understand any response that conforms to that feature's
specification.
5.2. Lack of use of these features in a request is an indication that 7. Transport Considerations
the requestor does not implement any part of this specification and that
the responder SHOULD NOT use any protocol extension described here in
its response.
5.3. Responders who do not understand these protocol extensions are The presence of an OPT pseudo-RR in a request should be taken as an
expected to send a response with RCODE NOTIMPL, FORMERR, or SERVFAIL, or indication that the requestor fully implements the given version of
to appear to "time out" due to inappropriate action by a "middle box" EDNS, and can correctly understand any response that conforms to that
such as a NAT, or to ignore extensions and respond only to unextended feature's specification.
protocol elements. Therefore use of extensions SHOULD be "probed" such Lack of presence of an OPT record in a request MUST be taken as an
that a responder who isn't known to support them be allowed a retry with indication that the requestor does not implement any part of this
no extensions if it responds with such an RCODE, or does not respond. specification and that the responder MUST NOT use any protocol
If a responder's capability level is cached by a requestor, a new probe extension described here in its response.
SHOULD be sent periodically to test for changes to responder capability.
5.4. If EDNS is used in a request, and the response arrives with TC set Responders who do not implement these protocol extensions MUST
and with no EDNS OPT RR, a requestor should assume that truncation respond with FORMERR messages without any OPT record.
prevented the OPT RR from being appended by the responder, and further,
that EDNS is not used in the response. Correspondingly, an EDNS
responder who cannot fit all necessary elements (including an OPT RR)
into a response, should respond with a normal (unextended) DNS response,
possibly setting TC if the response will not fit in the unextended
response message's 512-octet size.
6 - Security Considerations If there is a problem with processing the OPT record itself, such as
an option value that is badly formatted or includes out of range
values, a FORMERR MAY be retured. If this occurs the response MUST
include an OPT record. This MAY be used to distinguish between
servers whcih do not implement EDNS and format errors within EDNS.
Requestor-side specification of the maximum buffer size may open a new If EDNS is used in a request, and the response arrives with TC set
DNS denial of service attack if responders can be made to send messages and with no EDNS OPT RR, a requestor SHOULD assume that truncation
which are too large for intermediate gateways to forward, thus leading prevented the OPT RR from being appended by the responder, and
to potential ICMP storms between gateways and responders. further, that EDNS is not used in the response. Correspondingly, an
EDNS responder who cannot fit all necessary elements (including an
OPT RR) into a response, SHOULD respond with a normal (unextended)
DNS response, possibly setting TC if the response will not fit in the
unextended response message's 512-octet size.
7 - IANA Considerations 8. Security Considerations
IANA has allocated RR type code 41 for OPT. Requestor-side specification of the maximum buffer size may open a
new DNS denial of service attack if responders can be made to send
messages which are too large for intermediate gateways to forward,
thus leading to potential ICMP storms between gateways and
responders.
This document controls the following IANA sub-registries in registry Announcing very large UDP buffer sizes may result in dropping by
"DOMAIN NAME SYSTEM PARAMETERS": firewalls. This could cause retransmissions with no hope of success.
Some devices reject fragmented UDP packets.
"EDNS Extended Label Type" Announcing too small UDP buffer sizes may result in fallback to TCP.
"EDNS Option Codes" This is especially important with DNSSEC, where answers are much
"EDNS Version Numbers" larger.
"Domain System Response Code"
9. IANA Considerations
The IANA has assigned RR type code 41 for OPT.
[RFC2671] specified a number of IANA sub-registries within "DOMAIN
NAME SYSTEM PARAMETERS:" "EDNS Extended Label Type", "EDNS Option
Codes", "EDNS Version Numbers", and "Domain System Response Code."
IANA is advised to re-parent these subregistries to this document. IANA is advised to re-parent these subregistries to this document.
This document assigns label type 0b01xxxxxx as "EDNS Extended Label RFC 2671 created an extended label type registry. We request that
Type." We request that IANA record this assignment. this registry be closed.
This document assigns extended label type 0bxx111111 as "Reserved for
future extended label types." We request that IANA record this
assignment.
This document assigns option code 65535 to "Reserved for future This document assigns option code 65535 to "Reserved for future
expansion." expansion."
This document expands the RCODE space from 4 bits to 12 bits. This
will allow IANA to assign more than the 16 distinct RCODE values
allowed in RFC 1035 [RFC1035].
This document assigns EDNS Extended RCODE "16" to "BADVERS". This document assigns EDNS Extended RCODE "16" to "BADVERS".
IESG approval is required to create new entries in the EDNS Extended IESG approval should be required to create new entries in the EDNS
Label Type or EDNS Version Number registries, while any published RFC Extended Label Type or EDNS Version Number registries, while any
(including Informational, Experimental, or BCP) is grounds for published RFC (including Informational, Experimental, or BCP) should
allocation of an EDNS Option Code. be grounds for allocation of an EDNS Option Code.
8 - Acknowledgements 10. Acknowledgements
Paul Mockapetris, Mark Andrews, Robert Elz, Don Lewis, Bob Halley, Paul Mockapetris, Mark Andrews, Robert Elz, Don Lewis, Bob Halley,
Donald Eastlake, Rob Austein, Matt Crawford, Randy Bush, Thomas Narten, Donald Eastlake, Rob Austein, Matt Crawford, Randy Bush, and Thomas
Alfred Hoenes and Markku Savela were each instrumental in creating and Narten were each instrumental in creating and refining this
refining this specification. specification.
9 - References 11. References
[RFC1035] P. Mockapetris, "Domain Names - Implementation and 11.1. Normative References
Specification," RFC 1035, USC/Information Sciences
Institute, November 1987.
[RFC2119] S. Bradner, "Key words for use in RFCs to Indicate [RFC1035] Mockapetris, P., "Domain names - implementation and
Requirement Levels," RFC 2119, Harvard University, March specification", STD 13, RFC 1035, November 1987.
1997.
[RFC2671] P. Vixie, "Extension mechanisms for DNS (EDNS0)," RFC 2671, [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
Internet Software Consortium, August 1999. RFC 2671, August 1999.
[RFC3225] D. Conrad, "Indicating Resolver Support of DNSSEC," RFC [RFC3225] Conrad, D., "Indicating Resolver Support of DNSSEC",
3225, Nominum Inc., December 2001. RFC 3225, December 2001.
[IANAFLAGS] IANA, "DNS Header Flags and EDNS Header Flags," web site 11.2. Informative References
http://www.iana.org/assignments/dns-header-flags, as of
June 2005 or later.
10 - Author's Address [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Paul Vixie Authors' Addresses
Michael Graff
Internet Systems Consortium Internet Systems Consortium
950 Charter Street 950 Charter Street
Redwood City, CA 94063 Redwood City, California 94063
+1 650 423 1301 US
EMail: vixie@isc.org
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Acknowledgement Phone: +1 650.423.1304
Email: mgraff@isc.org
Paul Vixie
Internet Systems Consortium
950 Charter Street
Redwood City, California 94063
US
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Administrative Support Activity (IASA). Email: vixie@isc.org
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