wdiff draft-ietf-dnsop-edns-chain-query-01.txt draft-ietf-dnsop-edns-chain-query-02.txt

dnsop P. Wouters
Internet-Draft Red Hat
Intended status: Standards Track October 27, 2014 March 09, 2015
Expires: April 30, September 10, 2015

Chain Query requests in DNS
draft-ietf-dnsop-edns-chain-query-01
draft-ietf-dnsop-edns-chain-query-02

Abstract

This document defines an EDNS0 extension that can be used by a DNSSEC
enabled Recursive Nameserver
security-aware validating Resolver configured as a forwarder Forwarder to send
a single DNS query query, requesting to receive a complete validation path along with the
regular DNS answer, without query answer. The reduction in queries lowers the need to rapid-fire
many latency.
This extension requries the use of source IP verified transport such
as TCP or UDP requests with DNS-COOKIES so it cannot be abused in an attempt to attain a low latency.
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
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.

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."

This Internet-Draft will expire on April 30, September 10, 2015.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.

Table of Contents

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

1. Introduction

Traditionally, clients operate a DNS client operates in stub-mode for DNS. stub-mode. For each DNS
question the DNS client needs to resolve, it sends a single query to
an upstream DNS resolver 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) intermediate information from the DNS
root down to the queried-for hostname so it can perform DNSSEC
validation on the complete chain of trust. This process increases the number of
DNS queries and answers required, and thus increases the latency
before a validated DNS answer has been obtained.

Currently, applications use a rapid-fire approach to 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 burst set of UDP questions will result in all the records
required for DNSSEC validation, and
more 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
recursive name server
Resolver running as a forwarder Forwarder to open a TCP connection to request another
recursive name server for
Resolver and request a DNS chain answer using one DNS query/
answer query/answer
pair. This reduces the number of round-trip times ("RTT") to two.
If combined with long livd TCP or [TCP-KEEPALIVE] there is only 1
RTT. While the upstream DNS resolver 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 Resolving Nameserver Recursive Resolver has to perform.

This EDNS0 extension is only intended for Forwarders. to be sent by Forwarders to
Recursive Resolvers. It can (and should be) ignored by Authoritative Nameservers and by Recursive
Nameservers that do not support this EDNS0 option.
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

Stub Resolver: A simple

The DNS protocol implementation on the client
side as described terminology used in [RFC1034] section 5.3.1.

Authoritative Nameserver: A nameserver this document is that has authority over one
or more DNS zones. These of
[DNS-TERMINOLOGY]. Additionally, the following terms are normally not contacted by clients
directly but by Recursive Resolvers. Described used:
[edit: which I hope will end up in [RFC1035]
chapter 6. 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.

Forwarder: A Recursive Resolver that is using another (upstream)
Recursive Resolver instead of querying Authoritative Nameservers
directly. It still performs validation. Also known as "security-aware
resolver".

3. Overview
When DNSSEC is deployed on the client, host, it can no longer delegate all
DNS work to the upstream Resolving Nameserer. 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 DNS server configured as Resolving Nameserver Resolver so it can confirm DNSSEC validation of all
intermediary DNS answers. It can configure itself as a DNS Forwarder
if it obtains the DHCP server has indicated that IP addresses of one or more Resolving Nameservers Recursive Resolvers
that are available. Regardless,
generating 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 has to
must wait while the Forwarder on the
client is querying for Resolver validates all the intermediate work. answers.
Each round-trip adds to the total time waiting on DNS resolving resolution with
validation to complete. This makes DNSSEC resolving impractical for
devices on networks with a high latency.

The edns-chain-query option allows the client Resolver to request all
intermediate DNS data it requires to resolve and validate a
particular DNS answer in a single round-trip DNS query and answer. round-trip. The Resolver could be
part of the application or a Recursive Resolver running on the host.

Servers answering with chain query 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 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 5.3, 5.4, a recursive nameserver Recursive Resolver could use this
EDNS0 option to include additional data required by the client 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 EDNS0 option MAY be sent over any transport
as a discovery method. A DNS server receiving such an empty edns-
chain-query option SHOULD add an empty edns-chain-query option in its
answer to indicate that it supports edns-chain-query for source IP
address verified transports.

The mechanisms provided by edns-chain-query 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 ([RFC2671]) [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 (FQDN) ~
+---------------------------------------------------------------+

o (Defined in [RFC2671]) OPTION-CODE, 2 octets, for edns-chain-query is [TBD].

o (Defined in [RFC2671]) OPTION-LENGTH, 2 octets, contains the length of the payload
(everything after Option-length) in octets.

o Last Known Query Name, 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. The end point of the chain is obtained from
the DNS Query Section itself. No compression is allowed for this
value.

o Assigned by IANA in IANA-AFI [1].

5. Protocol Description

5.1. Discovery of Support

A DNS Forwarder may include a zero-length edns-chain-query option in
queries over UDP or TCP any transport to discover the DNS server capability for
edns-chain-query. DNS Servers Recursive Resolvers that support and are willing
to accept chain queries over TCP SHOULD source IP verified transport respond to
a zero-length edns-chain-
query edns-chain-query received over UDP or TCP queries by including a zero-length
edns-chain-query option in the answer. A DNS Forwarder MAY then
switch to the TCP a source IP verified transport and sent a non-zero edns-chain-query edns-
chain-query value to request a chain-query response from the DNS server.
Recursive Resolver. Examples of source IP verification is the 3-way
TCP handshake and UDP with [DNS-COOKIES].

5.2. Generating Generate a Query

The edns-chain-query option should generally be deployed by
Forwarders, as described in Section 5.4.
In this option value, the Forwarder sets the last known entry 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. 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 option should generally be sent by system
Forwarders and Resolvers within an application that also perform
DNSSEC validation.

5.3. Generating Send the Option

When edns-chain-query 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 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 Resolver that does
support the edns-chain-query 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 option is
received over a TCP connection from a DNS Forwarder, the upstream Recursive Resolver
supporting edns-chain-query MAY respond by confirming that it is
returning a DNS Query Chain. To do so, it MUST set the edns-chain-query edns-chain-
query option with an OPTION-LENGTH of zero to indicate the DNS answer
contains a Chain Query. It extends the Authority Section for in the DNS
answer packet with the required DNS RRSets resulting in an Authority Section that contains a complete
chain of required for validating the answer.
The DNS RRsets that added start with the first chain element below the
received Last Known Query Name upto 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
answers. If the received query has the DNSSEC OK flag set, all
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 wildcard records, such as NSEC or
NSEC3 records.

Recursive Resolvers that have not implemented or enabled support for
the edns-chain-query 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 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 [RFC2671], Transport Considerations. [RFC6891].

Requests resulting in chains that the receiving resolver is unwilling
to serve can be rejected by sending a REFUSED response to the sender,
as described by [RFC2671], Transport Considerations. [RFC6891]. This refusal can be used for chains that
would be too big or chains that would reveal too much information
considered private.

At any time, a DNS server Recursive Resolver that has determined that it is
running low on resources can refuse to acknowledge a Chain Query by
omitting the edns-chain-query option. option in its reply. It may do so even
if it conveyed support to a DNS client previously. If [TCP-KEEPALIVE] is used, it It may even
change its support for edns-chain-query within the same TCP session.

If the DNS request results in an CNAME or DNAME for the Answer
Section, the DNS server 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 is are also
added to the Authority Section.

In any case, the

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

5.4. Sending the Option

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

A Forwarder can request DNS query that contains the edns-chain-query option with every
outgoing DNS query. However, it MUST also have
the DNSSEC OK bit set. If this bit is RECOMMENDED that Forwarders
remember which upstream Resolving Nameservers did not return the
option (and additional data) with their response. The Forwarder
SHOULD fallback to regular DNS for subsequent queries to those
Recursive Nameservers. It MAY switch to another Resolving Nameserver
that does support set, the edns-chain-query
option or try again later to
see if the server has become less loaded and is now willing to answer
with Query Chains. 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 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 responses MUST include the NS RRset from the child
zone, which includes DNSSEC RRSIG records required for validation.

When a DNSSEC chain is supplied via edns-chain-query, the DNS
Forwarder no longer requires 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 to
find and query Authoritative Servers directly. It is prefered preferred that
the DNS Forwarder can populate its cache with this information regardless, to avoid
requiring queries in
the future just queries to obtain the any missing NS records. This can happen on
a roaming device that needs to swich Therefor,
edns-chain-query responses MUST include the NS RRset from using a DHCP obtained DNS
server as forwarder to running in full autonomous resolver mode, for
example when the DHCP obtained DNS server is broken in some way. child
zone, which includes DNSSEC RRSIG records required for validation.

6.3. TCP Session Management

It is recommended that TCP Chain Queries sessions to the Recursive Resolver are used in combination with not
immediately 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 TCP 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 TCP Chain Queries than can
be accommodated, DNS servers may stop advertising the edns-query-
chain option in successive DNS messages. This allows, for example,
clients with other candidate servers to query to establish new TCP
sessions with different servers in expectation that those servers
might still allow TCP Chain Queries.

6.4. Non-Clean Paths

Many paths between DNS clients and servers 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 non-
clean paths.

6.5. Anycast Considerations

DNS servers

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 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 option.

Changes in network topology between clients and anycast servers may
cause disruption to TCP sessions making use of edns-chain-query 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 nameserver Recursive Resolver MUST NOT return Query Chain answers to clients
over UDP without source IP address verification, for instance using
[EASTLAKE-COOKIES]. verification. An example of UDP
based source IP address verification is [DNS-COOKIES]. A recursive nameserver Recursive
Resolver refusing a Query Chain request MUST ignore the ends-query-
chain option and answering the DNS request as if it was received
without the ends-query-chain option. It MUST NOT send an RCODE of
REFUSED.

A Recursive Resolver SHOULD signal support in response to a Query Chain zero-
length edns-chain-query request over UDP by responding using a
zero-length with an zero-
length edns-chain-query option over UDO 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 on.

3. 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 edns-chain-query
option as follows:

* Option-code, set to [TBD]

* Option-length, set to 0x00 0x04

* Last Known Query Name set to "com."

o The upstream Recursive Resolver receives a DNS query over TCP with
the edns-chain-query Last Known Query Name 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 edns-chain-query
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 option
to the DNS answer reply as follows:

* Option-code, set to [TBD]

* Option-length, set to 0x00 0x00

* The Last Known Query Name 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, 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 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.

10.

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 disgarded.

11. 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
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 Query for example.com

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

o Option-code, set to [TBD]

o Option-length, set to 0x00 0x0D

o The Last Known Query Name 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:

o Option-code, set to [TBD]

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

9.3. non-existent Non-existent data

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

o Option-code, set to [TBD]

o Option-length, set to 0x00 0x03

o The Last Known Query Name 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 option parameters:

o Option-code, set to [TBD]

o Option-length, set to 0x00 0x00

o The Last Known Query Name 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

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

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

[EASTLAKE-COOKIES]

[DNS-COOKIES]
Eastlake, Donald., "Domain Name System (DNS) Cookies",
draft-eastlake-dnsext-cookies
draft-ietf-dnsop-cookies (work in progress), October
2014. February
2015.

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

[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.

[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC
2671, August 1999.

[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC
4033, March 2005.

[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.

[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.

[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, December 2006.

[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, January 2013.

[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, April 2013.

[RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", RFC 6982, July
2013.

[TCP-KEEPALIVE]
Wouters, P., "The edns-tcp-keepalive EDNS0 Option", draft-
ietf-dnsop-edns-tcp-keeaplive
wouters-edns-tcp-keeaplive (work in progress), October February
2014.

Author's Address

Paul Wouters
Red Hat

Email: pwouters@redhat.com