wdiff draft-ietf-dnsop-edns-chain-query-03.txt draft-ietf-dnsop-edns-chain-query-04.txt

dnsop P. Wouters
Internet-Draft Red Hat
Intended status: Standards Track October 03, 19, 2015
Expires: April 05, 21, 2016

Chain Query requests in DNS
draft-ietf-dnsop-edns-chain-query-03
draft-ietf-dnsop-edns-chain-query-04

Abstract

This document defines an EDNS0 extension that can be used by a
security-aware validating Resolver configured as a Forwarder to send
a single query, requesting a complete validation path along with the
regular query answer. The reduction in queries lowers the latency.
This extension requries the use of source IP verified transport such
as TCP or UDP with DNS-COOKIES EDNS-COOKIE so it cannot be abused in
amplification attacks.

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on April 05, 21, 2016.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Option Format . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Protocol Description . . . . . . . . . . . . . . . . . . . . 5
5.1. Discovery of Support . . . . . . . . . . . . . . . . . . 5
5.2. Generate a Query . . . . . . . . . . . . . . . . . . . . 5
5.3. Send the Option . . . . . . . . . . . . . . . . . . . . . 6
5.4. Generate a Response . . . . . . . . . . . . . . . . . . . 6
6. Protocol Considerations . . . . . . . . . . . . . . . . . . . 7 8
6.1. DNSSEC Considerations . . . . . . . . . . . . . . . . . . 7 8
6.2. NS record Considerations . . . . . . . . . . . . . . . . 8
6.3. TCP Session Management . . . . . . . . . . . . . . . . . 8
6.4. Negative Trust Anchors . . . . . . . . . . . . . . . . . 9
6.5. Non-Clean Paths . . . . . . . . . . . . . . . . . . . . . 9
6.5.
6.6. Anycast Considerations . . . . . . . . . . . . . . . . . 9
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8.1. Amplification Attacks . . . . . . . . . . . . . . . . . . 10
9. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Simple Query for example.com . . . . . . . . . . . . . . 10
9.2. Out-of-path Query for example.com . . . . . . . . . . . . 12
9.3. Non-existent data . . . . . . . . . . . . . . . . . . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
10.1. EDNS0 option code for edns-chain-query CHAIN . . . . . . . . . . . . . . 14
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
12. Normative References . . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15 16

1. Introduction

Traditionally, a DNS client operates in stub-mode. For each DNS
question the DNS client needs to resolve, it sends a single query to
an upstream Recursive Resolver to obtain a single DNS answer. When
DNSSEC [RFC4033] is deployed on such DNS clients, validation requires
that the client obtains all the intermediate information from the DNS
root down to the queried-for hostname so it can perform DNSSEC
validation on the complete chain of trust.

Currently, applications send out many UDP requests concurrently.
This requires more resources on the DNS client with respect to state
(cpu, memory, battery) and bandwidth. There is also no guarantee
that the initial set of UDP questions will result in all the records
required for DNSSEC validation. More round trips could be required
depending on the resulting DNS answers. This especially affects
high-latency links.

This document specifies an EDNS0 extension that allows a validating
Resolver running as a Forwarder to open a TCP connection to another
Resolver and request a DNS chain answer using one DNS query/answer
pair. This reduces the number of round-trip times ("RTT") round trips to two. If combined
with long livd lived TCP or [TCP-KEEPALIVE] there is only 1
RTT. one round trip.
While the upstream Resolver still needs to perform all the individual
queries required for the complete answer, it usually has a much
bigger cache and does not experience significant slowdown from
last-mile last-
mile latency.

This EDNS0 extension allows the DNS Forwarder to indicate which part of
the DNS hierarchy it already contains in its cache. This reduces the
amount of data required to be transferred and reduces the work the
upstream Recursive Resolver has to perform.

This EDNS0 extension is only intended to be sent by Forwarders to
Recursive Resolvers. It can (and should be) should) be ignored by Authoritative
Servers.

1.1. Requirements Notation

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 [RFC2119].

2. Terminology

The DNS terminology used in this document is that of
[DNS-TERMINOLOGY]. Additionally, the following terms are used:
[edit: which I hope will end up in the terminology document]

Recursive Resolver: A nameserver that is responsible for resolving
domain names for clients by following the domain's delegation
chain, starting at the root. Recursive Resolvers frequently use
caches to be able to respond to client queries quickly. Described
in [RFC1035] chapter 7.

Validating Resolver: A recursive nameserver that also performs
DNSSEC [RFC4033] validation. Also known as "security-aware
resolver".

3. Overview
When DNSSEC is deployed on the a host, it can no longer delegate all DNS
work to the upstream Recursive Resolver. Obtaining just the DNS
answer itself is not enough to validate that answer using DNSSEC.
For DNSSEC validation, the DNS client requires a locally running
validating Resolver so it can confirm DNSSEC validation of all
intermediary DNS answers. It can configure itself as a DNS Forwarder if
it obtains the IP addresses of one or more Recursive Resolvers that
are available, or as a stand-alone Recursive Resolver if no
functional Recursive Resolvers were obtained. Generating the
required queries for validation adds a significant delay in answering
the DNS question of the locally running application. The application
must wait while the Resolver validates all intermediate answers.
Each round-trip adds to the total time waiting on DNS resolution with
validation to complete. This makes DNSSEC resolving impractical for
devices on networks with a high latency.

The edns-chain-query

This document defines the CHAIN option that allows the Resolver to
request all intermediate DNS data it requires to resolve and validate
a particular DNS answer in a single round-trip. The Resolver could
be part of the application or a Recursive Resolver running on the
host.

Servers answering with chain query CHAIN data exceeding 512 bytes should ensure that the transport is
TCP or source IP address verified UDP. See Section 8. This avoids
abuse in DNS amplification attacks.

Applications that support edns-chain-query CHAIN internally can perform validation
without requiring the host the run a Recursive Resolver. This is
particularly useful for virtual servers in a cloud or container based
deployment where it is undesirable to run a Recursive Resolver per
virtual machine.

The format of this option is described in Section 4.

As described in Section 5.4, a Recursive Resolver could use this
EDNS0 option to include additional data required by the Resolver in
the Authority Section of the DNS answer packet when using a source IP
verified transport. The Answer Section remains unchanged from a
traditional DNS answer and contains the answer and related DNSSEC
entries.

An empty edns-chain-query CHAIN EDNS0 option MAY be sent over any transport as a
discovery method. A DNS server receiving such an empty edns-
chain-query CHAIN option
SHOULD add an empty edns-chain-query CHAIN option in its answer to indicate that it
supports edns-chain-query CHAIN for source IP address verified transports.

The mechanisms provided by edns-chain-query CHAIN raise various security related
concerns, related to the additional work, bandwidth, amplification
attacks as well as privacy issues with the cache. These concerns are
described in Section 8.

4. Option Format

This draft uses an EDNS0 [RFC6891] option to include client IP
information in DNS messages. The option is structured as follows:

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-------------------------------+-------------------------------+
! OPTION-CODE ! OPTION-LENGTH !
+-------------------------------+-------------------------------+
~ Last Known Query Name Closest Trust Point (FQDN) ~
+---------------------------------------------------------------+

o OPTION-CODE, 2 octets, for edns-chain-query CHAIN is [TBD]. [TBD1].

o OPTION-LENGTH, 2 octets, contains the length of the payload
(everything after Option-length) in octets.

o Last Known Query Name, Closest Trust Point, a variable length FDQN of the requested start
point of the chain. This entry is the 'lowest' known entry in the
DNS chain known by the recursive server seeking a edns-
chain-query answer. CHAIN answer for
which it has a validated DS and DNSKEY record. The end point of
the chain is obtained from the DNS Query Section itself. No DNS
name compression is allowed for this value.

5. Protocol Description

5.1. Discovery of Support

A DNS Forwarder may include a zero-length edns-chain-query CHAIN option in
queries a regular query
over any transport to discover the DNS server capability for
edns-chain-query. CHAIN.
Recursive Resolvers that support and are willing to accept chain CHAIN
queries over source IP verified transport respond to a zero-length edns-chain-query
CHAIN received by including a zero-length
edns-chain-query CHAIN option in the answer. A DNS
If not already using a source IP verified transport, the Forwarder
MAY then switch to a source IP verified transport and sent a non-zero edns-
chain-query value start sending
queries with the CHAIN option to request a chain-query CHAIN response from the
Recursive Resolver. Examples of source IP verification is are the 3-way
TCP handshake and UDP with [DNS-COOKIES]. [EDNS-COOKIE].

5.2. Generate a Query
In this option value, the Forwarder sets the last known entry point Closest Trust Point in
the chain - furthest from the root - that it already has a DNSSEC
validated (secure or not) answer for in its cache. The upstream
Recursive Resolver does not need to include any part of the chain
from the root down to this option's FQDN. A complete example is
described in Section 9.1.

Depending on the size of the labels of the last known entry point
value, a DNS Query packet could be arbitrarily large. If using the
last known entry point would result in a query size of more then 512
bytes, the last known entry point should be replaced with its parent
entry until the query size would be 512 bytes or less. A separate
query should be send for the remainder of the validation chain.

The edns-chain-query CHAIN option should generally be sent by system Forwarders and
Resolvers within an application that also perform DNSSEC validation.

5.3. Send the Option

When edns-chain-query CHAIN is available, the downstream Recursive Resolver can adjust
its query strategy based on the desired queries and its cache
contents.

A DNS Forwarder can request the edns-chain-query CHAIN option with every outgoing DNS
query. However, it is RECOMMENDED that DNS Forwarders remember which
upstream Recursive Resolvers did not return the option (and
additional data) with their response. The DNS Forwarder SHOULD fallback
to regular DNS for subsequent queries to those Recursive Resolvers.
It MAY switch to another Resolving Recursive Resolver that does support the edns-chain-query
CHAIN option or try again later to see if the server has become less
loaded and is now willing to answer with Query Chains.

5.4. Generate a Response

When a query containing a non-zero edns-chain-query CHAIN option is received from a DNS
Forwarder, the upstream Recursive Resolver supporting edns-chain-query CHAIN MAY
respond by confirming that it is returning a DNS Query Chain. CHAIN. To do so, it
MUST set the edns-chain-
query CHAIN option with an OPTION-LENGTH of zero to indicate the DNS answer
contains a Chain Query. lowest Trust Point sent as part of
the chain, with its corresponding OPTION-LENGTH. It extends the
Authority Section in the DNS answer packet with the DNS RRSets RRsets
required for validating the answer. The DNS RRsets added start with
the first chain element below the received Last Known Query Name Closest Trust Point up to
and including the NS and DS RRsets that represent the zone cut
(authoritative servers) of the QNAME. The actual DNS answer to the
question in the Query Section is placed in the DNS Answer
Section identical to the traditional DNS answer. All required DNSSEC
related records must be added to their appropriate sections. This
includes records required for proof of non-existence of regular and/or and/
or wildcard records, such as NSEC or NSEC3 records.

Recursive Resolvers that have not implemented or enabled support for
the edns-chain-query CHAIN option, or are otherwise unwilling to perform the
additional work for a Chain Query due to work load, may safely ignore
the option in the incoming queries. Such a server MUST NOT include
an edns-chain-query CHAIN option when sending DNS answer replies back, thus indicating
it is not able or willing to support Chain Queries at this time.

Requests with wrongly formatted options (i.e. bogus FQDN) MUST be
rejected and a FORMERR response must be returned to the sender, as
described by [RFC6891].

Requests resulting in chains that the receiving resolver is unwilling
to serve can be rejected by sending a REFUSED response to answering the sender, query as described by [RFC6891]. This refusal a regular DNS
reply but with an empty CHAIN payload. Replying with an empty CHAIN
can be used for chains that would be too big or chains that would
reveal too much information considered private.

At any time, a Recursive Resolver that has determined that it is
running low on resources can refuse to acknowledge a Chain Query CHAIN queries by
omitting replying with a
regular DNS reply with an empty CHAIN payload.

If a CHAIN answer would be bigger than the edns-chain-query option in its reply. It may do so even
if it conveyed support Recursive Resolver is
willing to serve, it SHOULD send a DNS partial chain starting with the
data closest to the top of the chain. The client previously. It may even
change its support for edns-chain-query within MAY re-send the same TCP session.
query with an updated Closest Trust Point until it has received the
full chain. The CHAIN response will contain the lowest Closest Trust
Point that was included in the CHAIN answer.

If the DNS request results in an CNAME or DNAME for the Answer
Section, the Recursive Resolver MUST return these records in the
Answer Section similar to regular DNS processing. The CNAME or DNAME
target MAY be placed in the Additional Section only if all supporting
records for DNSSEC validation of the CNAME or DNAME target are also
added to the Authority Section.

The response from a Recursive Resolver to a Resolver MUST NOT contain
the edns-chain-query CHAIN option if none was present in the Resolver's original
request.

A DNS query that contains the edns-chain-query CHAIN option MUST also have the DNSSEC
OK bit set. If this bit is not set, the edns-chain-query CHAIN option received MUST
be ignored.

6. Protocol Considerations

6.1. DNSSEC Considerations

The presence or absence of an OPT resource record containing an edns-
chain-query CHAIN
option in a DNS query does not change the usage of those resource
records and mechanisms used to provide data origin authentication and
data integrity to the DNS, as described in [RFC4033], [RFC4034] and
[RFC4035].

6.2. NS record Considerations

edns-chain-query

CHAIN responses MUST include the NS RRset from the child
zone, which includes DNSSEC zone
including the RRSIG records required for validation.

When a DNSSEC chain is supplied via edns-chain-query, CHAIN, the DNS Forwarder is no longer requires
required to use the NS RRset, as it can construct the validation path
via the DNSKEY and DS RRsets without using the NS RRset. However,
the DNS Forwarder might be forced to switch from Forwarder mode to
Recursive Resolver mode due to a network topology change. In
Recursive Resolver mode, it requires the NS RRsets are needed to find and query
Authoritative Servers directly. It is preferred RECOMMENDED that the DNS
Forwarder populate its cache with this information to avoid requiring
future queries to obtain any missing NS records. Therefor,
edns-chain-query Therefore, CHAIN
responses MUST include the NS RRset from the child zone, which includes DNSSEC including
the RRSIG records required for validation.

6.3. TCP Session Management

It is recommended RECOMMENDED that TCP sessions to the Recursive Resolver are not immediately be closed after
the DNS answer to the first query is received. It is recommended to
use [TCP-KEEPALIVE].

Both DNS clients and servers are subject to resource constraints
which will limit the extent to which Chain Queries can be executed.
Effective limits for the number of active sessions that can be
maintained on individual clients and servers should be established,
either as configuration options or by interrogation of process limits
imposed by the operating system.

In the event that there is greater demand for Chain Queries than can
be accommodated, DNS servers may stop advertising the edns-query-
chain CHAIN option in
successive DNS messages. This allows, for example, clients with
other candidate servers to query to establish new sessions with
different servers in expectation that those servers might still allow
Chain Queries.

6.4. Negative Trust Anchors

If a CHAIN answer would intersect with a Negative Trust Anchor
[RFC7646], a partian CHAIN up to the node above the Negative Trust
Anchor should be returned.

6.5. Non-Clean Paths

Many paths between DNS clients and Recursive Resolvers suffer from
poor hygiene, limiting the free flow of DNS messages that include
particular EDNS0 options, or messages that exceed a particular size.
A fallback strategy similar to that described in [RFC6891] section
6.2.2 SHOULD be employed to avoid persistent interference due to non-
clean paths.

6.5.

6.6. Anycast Considerations

Recursive Resolvers of various types are commonly deployed using
anycast [RFC4786].

Successive DNS transactions between a client and server using UDP
transport may involve responses generated by different anycast nodes,
and the use of anycast in the implementation of a DNS server is
effectively undetectable by the client. The edns-chain-query CHAIN option SHOULD NOT
be included in responses using UDP transport from servers provisioned
using anycast unless all anycast server nodes are capable of
processing the edns-query-chain CHAIN option.

Changes in network topology between clients and anycast servers may
cause disruption to TCP sessions making use of edns-chain-query CHAIN more often than
with TCP sessions that omit it, since the TCP sessions are expected
to be longer-lived. Anycast servers MAY make use of TCP multipath
[RFC6824] to anchor the server side of the TCP connection to an
unambiguously-unicast address in order to avoid disruption due to
topology changes.

7. Implementation Status

This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC6982].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.

According to [RFC6982], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".

[While there is some interest, no work has started yet]

8. Security Considerations

8.1. Amplification Attacks

Chain Queries can potentially send very large DNS answers. Attackers
could abuse this using spoofed source IP addresses to inflict large
Distributed Denial of Service attacks using query-chains as an
amplification vector in their attack. While TCP is not vulnerable
for this type of abuse, the UDP protocol is vulnerable to this.

A Recursive Resolver MUST NOT return Query Chain CHAIN answers to clients over
UDP without source IP address verification. An example of UDP based
source IP address verification is [DNS-COOKIES]. [EDNS-COOKIE]. A Recursive
Resolver refusing a Query Chain request CHAIN option MUST ignore the ends-query-
chain respond with a zero-length
CHAIN option and answering the DNS request as if it was received
without the ends-query-chain option. to indicate support for CHAIN queries when a proper
transport is used. It MUST NOT send an RCODE of REFUSED.

A Recursive Resolver SHOULD signal support in response to a zero-
length edns-chain-query request over UDP by responding with an zero-
length edns-chain-query option even without source IP address
verification. This allows a client to detect edns-chain-query
support without the need for [DNS-COOKIES] or TCP.

9. Examples

9.1. Simple Query for example.com

o A web browser on a client machine asks the Forwarder running on
localhost to resolve the A record of "www.example.com." by sending
a regular DNS UDP query on port 53 to 127.0.0.1.

o The Forwarder on the client machine checks its cache, and notices
it already has a DNSSEC validated entry of "com." in its cache.
This includes the DNSKEY RRset with its RRSIG records. In other
words, according to its cache, ".com" is DNSSEC validated as
"secure" and can be used to continue a DNSSEC validated chain.

o The Forwarder on the client opens a TCP connection to its upstream
Recursive Resolver on port 53. It adds the edns-chain-query CHAIN option as
follows:

* Option-code, set to [TBD] [TBD1]
* Option-length, set to 0x00 0x04

* Last Known Query Name Closest Trust Point set to "com."

o The upstream Recursive Resolver receives a DNS query over TCP with
the edns-chain-query Last Known Query Name CHAIN Closest Trust Point set to "com.". After accepting the
query it starts constructing a DNS reply packet.

o The upstream Recursive Resolver performs all the regular work to
ensure it has all the answers to the query for the A record of
"www.example.com.". It does so without using the edns-chain-query CHAIN option -
unless it is also configured as a Forwarder. The answer to the
original DNS question could be the actual A record, the DNSSEC
proof of non-existence, or an insecure NXDOMAIN response.

o The upstream Recursive Resolver adds the edns-chain-query CHAIN option to the DNS answer reply
response as follows:

* Option-code, set to [TBD] [TBD1]

* Option-length, set to 0x00 0x00

* The Last Known Query Name Closest Trust Point is ommited (zero length)

o The upstream Recursive Resolver constructs the DNS Authority
Section and fills it with:

* The DS RRset for "example.com." and its corresponding RRSIGs
(made by the "com." DNSKEY(s))

* The DNSKEY RRset for "example.com." and its corresponding
RRSIGs (made by the "example.com" DNSKEY(s))

* The authoritative NS RRset for "example.com." and its
corresponding RRSIGs (from the child zone)

If the answer does not exist, and the zone uses DNSSEC, it also
adds the proof of non-existance, non-existence, such as NSEC or NSEC3 records, to
the Authority Section.

o The upstream Recursive Resolver constructs the DNS Answer
Section and fills it with:

* The A record of "www.example.com." and its corresponding RRSIGs
If the answer does not exist (no-data (NODATA or NXDOMAIN), the Answer
Section remains empty. For the NXDOMAIN case, the RCode of the
DNS answer packet is set to NXDOMAIN. Otherwise it remains
NOERROR.

o The upstream Recursive Resolver returns the DNS answer over the
existing TCP connection. When all data is sent, it SHOULD keep
the TCP connection open to allow for additional incoming DNS
queries - provided it has enough resources to do so.

o The Forwarder receives the DNS answer. It processes the Authority
Section and the Answer Section and places the information in its
local cache. It ensures that no data is accepted into the cache
without having proper DNSSEC validation. It MAY do so by looping
over the entries in the Authority and Answer Sections. When an
entry is validated for its cache, it is removed from the
processing list. If an entry cannot be validated it is left in
the process list. When the end of the list is reached, the list
is processed again until either all entries are placed in the
cache, or the remaining items cannot be placed in the cache due to
lack of validation. Those entries are then discarded.

o If the cache contains a valid answer to the application's query,
this answer is returned to the application via a regular DNS
answer packet. This packet MUST NOT contain an edns-chain-query CHAIN option. If
no valid answer can be returned, normal error processing is done.
For example, an NXDOMAIN or an empty Answer Section could be
returned depending on the error condition.

9.2. Out-of-path Query for example.com

A Recursive Resolver receives a query for the A record for
example.com. It includes the edns-chain-query CHAIN option with the following
parameters:

o Option-code, set to [TBD] [TBD1]

o Option-length, set to 0x00 0x0D

o The Last Known Query Name Closest Trust Point set to 'unrelated.ca.'

As there is no chain that leads from "unrelated.ca." to
"example.com", the Resolving Nameserver answers with RCODE "FormErr".
It includes the edns-chain-query with the following parameters: an empty CHAIN
specified using:

o Option-code, set to [TBD] [TBD1]

o Option-length, set to 0x00 0x00
o The Last Known Query Name Closest Trust Point is ommited omitted (zero length)

Note that the regular answer is still present just as it would be for
a query that did not specify the CHAIN option.

9.3. Non-existent data

A Recursive Resolver receives a query for the A record for
"ipv6.toronto.redhat.ca". It includes the edns-chain-query CHAIN option with the
following parameters:

o Option-code, set to [TBD] [TBD1]

o Option-length, set to 0x00 0x03

o The Last Known Query Name Closest Trust Point set to 'ca.'

Using regular UDP queries towards Authoritative Nameservers, it
locates the NS RRset for "toronto.redhat.ca.". When querying for the
A record it receives a reply with RCODE "NoError" and an empty Answer
Section. The Authority Section contains NSEC3 and RRSIG records
proving there is no A RRtype for the QNAME "ipv6.toronto.redhat.ca".

The Recursive Resolver constructs a DNS reply with the following
edns-chain-query
CHAIN option parameters:

o Option-code, set to [TBD] [TBD1]

o Option-length, set to 0x00 0x00

o The Last Known Query Name Closest Trust Point is ommited (zero length)

The RCODE is set to "NoError". The Authority Section is filled in
with:

o The DS RRset for "redhat.ca." plus RRSIGs

o The DNSKEY RRset for "redhat.ca." plus RRSIGs

o The NS RRset for "redhat.ca." plus RRSIGs (eg ns[01].redhat.ca)

o The A RRset for "ns0.redhat.ca." and "ns1.redhat.ca." plus RRSIGs

o The DS RRset for "toronto.redhat.ca." plus RRSIGs

o The NS RRset for "toronto.redhat.ca." plus RRSIGs (eg
ns[01].toronto.redhat.ca)

o The DNSKEY RRset for "toronto.redhat.ca." plus RRSIGs

o The A RRset and/or AAAA RRset for "ns0.toronto.redhat.ca." and
"ns1.toronto.redhat.ca." plus RRSIGs

o The NSEC record for "ipv6.toronto.redhat.ca." (proves what RRTYPEs
do exist, does not include A)

o The NSEC record for "toronto.redhat.ca." (proves no wildcard
exists)

The Answer Section is empty. The RCode is set to NOERROR.

10. IANA Considerations

10.1. EDNS0 option code for edns-chain-query CHAIN

IANA has assigned option code [TBD] [TBD1] in the "DNS EDNS0 Option Codes
(OPT)" registry to edns-chain-query. CHAIN.

11. Acknowledgements

Andrew Sullivan pointed out that we do not need any new data formats
to support DNS chains. Olafur Gudmundsson ensured the RRsets are
returned in the proper Sections. Thanks to Tim Wicinski for his
thorough review.

12. Normative References

[DNS-COOKIES]
Eastlake, Donald., "Domain Name System (DNS) Cookies",
draft-ietf-dnsop-cookies (work in progress), August 2015.

[DNS-TERMINOLOGY]
Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", draft-hoffman-dns-terminology draft-ietf-dnsop-dns-terminology-05 (work in
progress), March September 2015.

[EDNS-COOKIE]
Eastlake, Donald., "Domain Name System (DNS) Cookies",
draft-ietf-dnsop-cookies (work in progress), August 2015.

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987. 1987,
<http://www.rfc-editor.org/info/rfc1034>.

[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987. 1987, <http://www.rfc-editor.org/info/rfc1035>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997. 1997,
<http://www.rfc-editor.org/info/rfc2119>.

[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC
4033, DOI 10.17487/RFC4033, March 2005. 2005,
<http://www.rfc-editor.org/info/rfc4033>.

[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005. 2005,
<http://www.rfc-editor.org/info/rfc4034>.

[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005. 2005,
<http://www.rfc-editor.org/info/rfc4035>.

[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
December 2006, <http://www.rfc-editor.org/info/rfc4786>.

[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
<http://www.rfc-editor.org/info/rfc6824>.

[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/
RFC6891, April 2013,
<http://www.rfc-editor.org/info/rfc6891>.

[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982, DOI
10.17487/RFC6982, July 2013,
<http://www.rfc-editor.org/info/rfc6982>.

[RFC7646] Ebersman, P., Kumari, W., Griffiths, C., Livingood, J.,
and R. Weber, "Definition and Use of DNSSEC Negative Trust
Anchors", RFC 7646, DOI 10.17487/RFC7646, September 2015,
<http://www.rfc-editor.org/info/rfc7646>.

[TCP-KEEPALIVE]
Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The
edns-tcp-keepalive EDNS0 Option", draft-
wouters-edns-tcp-keeaplive draft-ietf-dnsop-edns-
tcp-keepalive-03 (work in progress), February
2014. September 2015.

Author's Address

Paul Wouters
Red Hat

Email: pwouters@redhat.com