One document matched: draft-wouters-edns-tcp-chain-query-01.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd" [
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<rfc category="std" ipr="trust200902" docName="draft-wouters-edns-tcp-chain-query-01">
<?xml-stylesheet type='text/xsl' href='rfc2629.xslt' ?>
<?rfc toc="yes" ?>
<?rfc symrefs="yes" ?>
<?rfc sortrefs="yes"?>
<?rfc iprnotified="no" ?>
<?rfc strict="yes" ?>
<front>
<title>TCP chain query requests in DNS</title>
<author initials='P.' surname="Wouters" fullname='Paul Wouters'>
<organization>Red Hat</organization>
<address>
<email>pwouters@redhat.com</email>
</address>
</author>
<date month="October" year="2013" />
<area>int</area>
<workgroup>dnsext</workgroup>
<abstract><t>
This document defines an EDNS0 extension that can be used
by a DNSSEC enabled Recursive Nameserver configured as
a forwarder to send a single query over TCP requesting to
receive a complete validation path along with the regular
query answer.
</t></abstract>
</front>
<middle>
<section title="Introduction">
<t>
Traditionally, clients operate in stub-mode for DNS. For
each DNS question the client needs to resolve, it sends a
single query to an upstream DNS resolver to obtain a single
DNS answer. When DNSSEC <xref target='RFC4033'/> is deployed
on such 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.
</t>
<t>
For example, the validated answer for the question of the A
record for the zone "example.com" requires over a hundred
DNS queries. That many queries adds a significant number
of round-trip delays that is considered unusable by current
user expectation. It especially affects web browsers which
usually need to lookup dozens of hostnames to render a single
web page.
</t>
<t>
This document specifies an EDNS0 extension that allows a
validating recursive name server running as a forwarder
to open a TCP connection to another recursive name server
and request a DNS chain answer using one DNS query/answer
pair. This reduces the number of round-trip times
("RTT") to two. If combined with <xref target="TCP-KEEPALIVE"/>
there is only 1 RTT. While the upstream DNS resolver
still needs to perform all these queries, it usually has
a much bigger cache and does not experience significant
slowdown from last-mile latency.
</t>
<t>
This EDNS0 extension allows the 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 has
to perform.
</t>
<t>
This EDNS0 extension is only intended for Forwarders. It can
(and should be) ignored by Authoritative Nameservers and by
Recursive Nameservers that do not support this EDNS0 option.
</t>
<section title="Requirements Notation">
<t>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 <xref target="RFC2119"/>.</t>
</section>
</section>
<section title="Terminology">
<t><list style="hanging">
<t hangText="Stub Resolver:">
A simple DNS protocol implementation on the client side
as described in <xref target="RFC1034"/> section 5.3.1.</t>
<t hangText="Authoritative Nameserver:">
A nameserver that has authority over one or more DNS zones.
These are normally not contacted by clients directly but by
Recursive Resolvers. Described in <xref target="RFC1035"/>
chapter 6.</t>
<t hangText="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 <xref target="RFC1035"/> chapter 7.</t>
<t hangText="Validating Resolver:">
A recursive nameserver that also performs DNSSEC <xref
target='RFC4033'/> validation.
</t>
<t hangText="Forwarder:">
A Recursive Resolver that is using another (upstream)
Recursive Resolver instead of querying Authoritative
Nameservers directly. It still performs validation.
</t>
</list></t>
</section>
<section title="Overview" anchor="overview">
<t>
When DNSSEC is deployed on the client, it can no longer delegate
all DNS work to the upstream Resolving Nameserer. Obtaining just
the DNS answer itself is not enough to validate that answer
using DNSSEC. For DNSSEC validation, the client requires
a locally running validating DNS server configured as Resolving
Nameserver so it can confirm DNSSEC validation of all intermediary
DNS answers. It can configure itself as a Forwarder if the DHCP
server has indicated that one or more Resolving Nameservers
are available. Regardless, generating the required queries
for validation adds a significant delay in answering the DNS
question of the locally running applications. The application
has to wait while the Forwarder on the client is querying for
all the intermediate work. Each round-trip adds to the total
time waiting on DNS resolving to complete. This makes DNSSEC
resolving impractical on networks with a high latency.
</t>
<t>
The edns-tcp-chain-query option allows the client 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.
</t>
<t>
Since this data is most likely larger than the common maximum
UDP packet size, the server must only return the additional
data when using the TCP transport. Requiring TCP furthermore
avoid DNS amplification attacks.
</t>
<t>
The format of this option is described in <xref target="format" />.
</t>
<t>
As described in <xref target="responding" />, a recursive
nameserver could use this EDNS0 option to include additional
data required by the client in the Authority Section of the
DNS answer packet when using the TCP transport. The Answer Section
remains unchanged from a traditional DNS answer and contains
the answer and related DNSSEC entries.
</t>
<t>The edns-tcp-chain-query EDNS0 option MAY be sent over UDP
as a discovery method. A DNS server receiving
edns-tcp-chain-query over UDP MAY add an empty
edns-tcp-chain-query option in its answer to indicate that it
supports edns-tcp-chain-query when the TCP transport is used.
</t>
<t>
The mechanisms provided by edns-tcp-chain-query raise various security
related concerns, related to the additional work and bandwidth as
well as privacy issues with the cache. These concerns are described in
<xref target="security" />.
</t>
</section>
<section title="Option Format" anchor="format">
<t>This draft uses an EDNS0 (<xref target="RFC2671"/>) option to
include client IP information in DNS messages. The option
is structured as follows:</t>
<figure><artwork align="left"><![CDATA[
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) ~
+---------------------------------------------------------------+
]]></artwork></figure>
<t><list style="symbols">
<t>
(Defined in <xref target="RFC2671"/>) OPTION-CODE,
2 octets, for edns-tcp-chain-query is [TBD].
</t>
<t>
(Defined in <xref target="RFC2671"/>) OPTION-LENGTH,
2 octets, contains the length of the payload (everything
after Option-length) in octets.
</t>
<t>
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-tcp-chain-query answer.
The end point of the chain is obtained from the DNS
Query Section itself. No compression is allowed for this value.
</t>
<t>
Assigned by IANA in
<eref target="http://www.iana.org/assignments/address-family-numbers/">IANA-AFI</eref>.
</t>
</list>
</t>
</section>
<section title="Protocol Description">
<section anchor="discovery" title="Discovery of Support">
<t>A Forwarder may include a zero-length edns-tcp-chain-query
option in queries over UDP or TCP to
discover the DNS server capability for
edns-tcp-chain-query. DNS Servers that support and are
willing to accept chain queries over TCP SHOULD respond to
a zero-length edns-tcp-chain-query received over UDP or TCP
queries by including a zero-length edns-tcp-chain-query
option in the answer. A Forwarder MAY then switch to the
TCP transport and sent a non-zero edns-tcp-chain-query
value to request a chain-query response from the DNS server.
</t>
</section>
<section anchor="querying" title="Generating a Query">
<t>
The edns-tcp-chain-query option should generally be deployed
by Forwarders, as described in <xref target="send_when" />.
</t>
<t>
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 <xref target="example" />.
</t>
</section>
<section anchor="responding" title="Generating a Response">
<t>
When a query containing a non-zero edns-tcp-chain-query
option is received over a TCP connection from a
Forwarder, the upstream Recursive Resolver supporting
edns-tcp-chain-query MAY respond by confirming that it is
returning a DNS Query Chain. To do so, it MUST set the
edns-tcp-chain-query option with an OPTION-LENGTH of zero to
indicate the DNS answer contains a Chain Query. It extends
the Authority Section for the DNS answer packet with the
required DNS RRSets resulting in an Authority Section that
contains a complete chain of DNS RRsets that start with the
first chain element below the received Last Known Query Name
upto 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 traditional DNS
answers. If the received query has the DNSSEC OK flag set,
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.
</t>
<t>
Recursive Resolvers that have not implemented or enabled
support for the edns-tcp-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-tcp-chain-query option when sending DNS answer
replies back, thus indicating it is not able to support
Chain Queries at this time.
</t>
<t>
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 <xref target="RFC2671"/>, Transport
Considerations.
</t>
<t>
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 <xref target="RFC2671"/>,
Transport Considerations. This refusal can be used for chains that
would be too big or chains that would reveal too much information
considered private.
</t>
<t>At any time, a DNS server that has determined that it is
running low on resources can refuse to acknowledge a Chain
Query by omitting the edns-tcp-chain-query option. It may do
so even if it conveyed support to a DNS client previously. If
<xref target="TCP-KEEPALIVE"/> is used, it may even change
its support for edns-tcp-chain-query within the same TCP
session. </t>
<t>
If the DNS request results in an CNAME or DNAME for the
Answer Section, the DNS server MUST return these records in
the Answer Section similar to regular DNS processing. It
MUST NOT follow the CNAME or DNAME. Otherwise, both the
CNAME or DNAME and the followed destination would end up
in the Answer Section. [is that actually a problem? Jelte
thought so, but I am not sure]
</t>
<t>
In any case, the response from the receiving resolver to
the client resolver MUST NOT contain the edns-tcp-chain-query
option if none was present in the client's resolver
original request.
</t>
</section>
<section anchor="send_when" title="Sending the Option">
<t>
When edns-tcp-chain-query is available, the downstream
Resolving Nameserver can adjust its query strategy based on
the desired queries and its cache contents.
</t>
<t>
A Forwarder can request the edns-tcp-chain-query option with
every outgoing DNS query. However, it 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
the edns-tcp-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.
</t>
</section>
</section>
<section title="Protocol Considerations">
<section title="DNSSEC Considerations">
<t>
The presence or absence of an OPT resource record containing
an edns-tcp-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 <xref target="RFC4033" />, <xref
target="RFC4034" /> and <xref target="RFC4035" />.
</t>
</section>
<section title="NS record Considerations">
<t>
When a DNSSEC chain is supplied via edns-tcp-chain-query, the
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, it is prefered that
the Forwarder can populate its cache with this information
regardless, to avoid requiring queries in the future just to
obtain the missing NS records. Therefor, edns-tcp-chain-query
responses MUST include the NS RRset from the child zone,
which includes DNSSEC RRSIG records required for validation.
</t>
</section>
<section title="TCP Session Management">
<t>It is recommended that TCP Chain Queries are used in combination with
<xref target="TCP-KEEPALIVE"/>.
</t>
<t>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.</t>
<t>In the event that there is greater demand for TCP Chain Queries
than can be accommodated, DNS servers may stop advertising
the edns-tcp-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.
</t>
</section>
<section title="Non-Clean Paths">
<t>Many paths between DNS clients and servers 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 <xref target="RFC6891"/> section 6.2.2 SHOULD
be employed to avoid persistent interference due to
non-clean paths.</t>
</section>
<section title="Anycast Considerations">
<t>DNS servers of various types are commonly deployed using
anycast <xref target="RFC4786"/>.</t>
<t>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-tcp-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-tcp-query-chain option.
</t>
<t>Changes in network topology between clients and anycast
servers may cause disruption to TCP sessions making use
of edns-tcp-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
<xref target="RFC6824"/> to anchor the server side of the
TCP connection to an unambiguously-unicast address in
order to avoid disruption due to topology changes.</t>
</section>
</section>
<section anchor="implementation" title="Implementation Status">
<t>
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 <xref target="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.
</t>
<t>
According to <xref target="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".
</t>
<t>
[While there is some interest, no work has started yet]
</t>
</section>
<section anchor="security" title="Security Considerations">
<section title="Amplification Attacks">
<t>
Chain Queries can potentially send very large DNS answers. A
recursive nameserver MUST NOT return Query Chain answers
to clients over UDP. It is allowed to signal support in
response to a Query Chain request over UDP by responding
using a zero-length edns-tcp-chain-query option. This is to
prevent a single spoofed UDP packet from causing extremely
large UDP response packets from being sent to a spoofed IP
address. Such Distributed Denial of Service attacks using
other DNS amplification mechanisms are fairly common.
</t>
</section>
</section>
<section anchor="example" title="Examples">
<section anchor="example1" title="Simple Query for example.com">
<t><list style="numbers">
<t>
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.
</t>
<t>
The Forwarder on the client machine checks its cache, and
notices it already has a 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.
</t>
<t>
The Forwarder on the client opens a TCP connection to
its upstream Recursive Resolver on port 53. It adds the
edns-tcp-chain-query option as follows:
<list style="symbols">
<t>Option-code, set to [TBD]</t>
<t>Option-length, set to 0x00 0x04</t>
<t>Last Known Query Name set to "com."</t>
</list>
</t>
<t>
The upstream Recursive Resolver receives a DNS query over
TCP with the edns-tcp-chain-query Last Known Query Name set to
"com.". After accepting the query it starts constructing
a DNS reply packet over TCP.
</t>
<t>
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-tcp-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.
</t>
<t>
The upstream Recursive Resolver adds the edns-tcp-chain-query option
to the DNS answer reply as follows:
<list style="symbols">
<t>Option-code, set to [TBD]</t>
<t>Option-length, set to 0x00 0x00</t>
<t>The Last Known Query Name is ommited (zero length)</t>
</list>
</t>
<t>
The upstream Recursive Resolver constructs the DNS
Authority Section and fills it with:
<list style="symbols">
<t>The DS RRset for "example.com." and its corresponding
RRSIGs (made by the "com." DNSKEY(s))</t>
<t>The DNSKEY RRset for "example.com." and its
corresponding RRSIGs (made by the "example.com"
DNSKEY(s))</t>
<t>The authoritative NS RRset for "example.com." and
its corresponding RRSIGs (from the child zone)</t>
</list>
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.
</t>
<t>
The upstream Recursive Resolver constructs the DNS Answer
Section and fills it with:
<list style="symbols">
<t>The A record of "www.example.com." and its corresponding RRSIGs</t>
</list>
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.
</t>
<t>
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.
</t>
<t>
The Forwarder receives the DNS answer over TCP. It
processes the Authority Section and the Answer Section
and places the information in its local cache. If it is a
DNSSEC validating resolver, it ensures that no unvalidated
data or out of baliwick 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.
</t>
<t>
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-tcp-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.
</t>
</list></t>
</section>
<section anchor="example2" title="Out-of-path query for example.com">
<t>A Recursive Resolver receives a query for the A record for
example.com. It includes the edns-tcp-chain-query option with
the following parameters:
<list style="symbols">
<t>Option-code, set to [TBD]</t>
<t>Option-length, set to 0x00 0x0D</t>
<t>The Last Known Query Name set to 'unrelated.ca.'</t>
</list>
As there is no chain that leads from "unrelated.ca." to
"example.com", the Resolving Nameserver answers with RCODE
"FormErr". It includes the edns-tcp-chain-query with the following
parameters:
<list style="symbols">
<t>Option-code, set to [TBD]</t>
<t>Option-length, set to 0x00 0x00</t>
<t>The Last Known Query Name is ommited (zero length)</t>
</list>
</t>
</section>
<section anchor="example3" title="non-existent data">
<t>
A Recursive Resolver receives a query for the A record for
"ipv6.toronto.redhat.ca". It includes the edns-tcp-chain-query option
with the following parameters:
<list style="symbols">
<t>Option-code, set to [TBD]</t>
<t>Option-length, set to 0x00 0x03</t>
<t>The Last Known Query Name set to 'ca.'</t>
</list>
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".
</t>
<t>
The Recursive Resolver constructs a DNS reply with the
following edns-tcp-chain-query option parameters:
<list style="symbols">
<t>Option-code, set to [TBD]</t>
<t>Option-length, set to 0x00 0x00</t>
<t>The Last Known Query Name is ommited (zero length)</t>
</list>
The RCODE is set to "NoError". The Authority Section is filled in with:
<list style="symbols">
<t>The DS RRset for "redhat.ca." plus RRSIGs</t>
<t>The DNSKEY RRset for "redhat.ca." plus RRSIGs</t>
<t>The NS RRset for "redhat.ca." plus RRSIGs (eg ns[01].redhat.ca)</t>
<t>The A RRset for "ns0.redhat.ca." and "ns1.redhat.ca." plus RRSIGs</t>
<t>The DS RRset for "toronto.redhat.ca." plus RRSIGs</t>
<t>The NS RRset for "toronto.redhat.ca." plus RRSIGs (eg ns[01].toronto.redhat.ca)</t>
<t>The DNSKEY RRset for "toronto.redhat.ca." plus RRSIGs</t>
<t>The A RRset and/or AAAA RRset for "ns0.toronto.redhat.ca." and "ns1.toronto.redhat.ca." plus RRSIGs</t>
<t>The NSEC record for "ipv6.toronto.redhat.ca." (proves what RRTYPEs do exist, does not include A)</t>
<t>The NSEC record for "toronto.redhat.ca." (proves no wildcard exists)</t>
</list>
The Answer Section is empty. The RCode is set to NOERROR.
</t>
</section>
</section>
<section title="IANA Considerations" anchor="iana">
<section title="EDNS0 option code for edns-tcp-chain-query" anchor="iana_opt">
<t>IANA has assigned option code [TBD] in the "DNS EDNS0 Option Codes
(OPT)" registry to edns-tcp-chain-query.</t>
</section>
</section>
<section title="Acknowledgements">
<t>
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.
</t>
</section>
</middle>
<back>
<references title='Normative References'>
&rfc1034;
&rfc1035;
&rfc2119;
&rfc2671;
&rfc4033;
&rfc4034;
&rfc4035;
&rfc4786;
&rfc6824;
&rfc6891;
&rfc6982;
<reference anchor='TCP-KEEPALIVE'>
<front>
<title>The edns-tcp-keepalive EDNS0 Option</title>
<author initials='P' surname='Wouters' fullname='P. Wouters'>
<organization>Red Hat</organization>
</author>
<date month='October' day='15' year='2013' />
<abstract><t>
This document defines an EDNS0 option ("edns-tcp-keepalive") that
allows DNS clients and servers to signal their respective readiness
to conduct multiple DNS transactions over individual TCP sessions.
This signalling facilitates a better balance of UDP and TCP transport
between individual clients and servers, reducing the impact of
problems associated with UDP transport and allowing the state
associated with TCP transport to be managed effectively with minimal
impact on the DNS transaction time.
</t></abstract>
</front>
<seriesInfo name='Internet-Draft' value='draft-wouters-edns-tcp-keeaplive' />
<format type='TXT'
target='http://www.ietf.org/internet-drafts/draft-wouters-edns-tcp-keeaplive-00.txt' />
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-24 07:28:39 |