One document matched: draft-vandergaast-edns-client-ip-01.txt
Differences from draft-vandergaast-edns-client-ip-00.txt
dnsext C. Contavalli
Internet-Draft W. van der Gaast
Intended status: Experimental Google
Expires: November 22, 2010 S. Leach
Name.com
D. Rodden
Neustar
May 21, 2010
Client IP information in DNS requests
draft-vandergaast-edns-client-ip-01
Abstract
This draft defines an EDNS0 extension to carry relevant network range
information. In a query, it conveys the network address of the
originator. In a response, it conveys the scope of network addresses
that the answer is intended.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on November 22, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
Contavalli, et al. Expires November 22, 2010 [Page 1]
Internet-Draft Client IP information in DNS requests May 2010
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
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Option format . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Protocol description . . . . . . . . . . . . . . . . . . . . . 7
4.1. Originating the option . . . . . . . . . . . . . . . . . . 7
4.2. Generating a response . . . . . . . . . . . . . . . . . . 8
4.3. Handling edns-client-subnet replies and caching . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6. DNSSEC Considerations . . . . . . . . . . . . . . . . . . . . 12
7. NAT Considerations . . . . . . . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
8.1. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.2. Birthday attacks . . . . . . . . . . . . . . . . . . . . . 14
8.3. Cache pollution . . . . . . . . . . . . . . . . . . . . . 15
9. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 19
Appendix A. Document Editing History . . . . . . . . . . . . . . 20
Appendix A.1. Changes since -00 . . . . . . . . . . . . . . . . . 20
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
11.1. Normative References . . . . . . . . . . . . . . . . . . . 21
11.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Contavalli, et al. Expires November 22, 2010 [Page 2]
Internet-Draft Client IP information in DNS requests May 2010
1. Introduction
Many Authoritative nameservers today return different replies based
on the perceived topological location of the user. These servers use
the IP address of the incoming query to identify that location.
Since most queries come from intermediate recursive resolvers, the
source address is that of the recursive rather than of the query
originator.
Traditionally and probably still in the majority of instances,
recursive resolvers are reasonably close in the topological sense to
the stub resolvers or forwarders that are the source of queries. For
these resolvers, using their own IP address is sufficient for
authority servers that tailor responses based upon location of the
querier.
Increasingly though a class of remote recursive servers has arisen
that serves query sources without regard to topology. The motivation
for a query source to use a remote recursive server varies but is
usually because of some enhanced experience, such as greater cache
security or applying policies regarding where users may connect.
(Although political censorship usually comes to mind here, the same
actions may be used by a parent when setting controls on where a
minor may connect.) When using a remote recursive server, there can
no longer be any assumption of close proximity between the originator
and the recursive, leading to less than optimal replies from the
authority servers.
A similar situation exists within some ISPs where the recursive
servers are topologically distant from some edges of the ISP network,
resulting in less than optimal replies from the authority servers.
This draft defines an EDNS0 option to convey network information that
is relevant to the message but not otherwise included in the
datagram. This will provide the mechanism to carry sufficient
network information about the originator for the authority server to
tailor responses. It also provides for the authority server to
indicate the scope of network addresses that the tailored answer is
intended. This EDNS0 option is intended for those recursive and
authority servers that would benefit from the extension and not for
general purpose deployment. It is completely optional and can safely
be ignored by servers that choose not to implement it or enable it.
This draft also includes guidelines on how to best cache those
results and provides recommendations on when this protocol extension
should be used.
Contavalli, et al. Expires November 22, 2010 [Page 3]
Internet-Draft Client IP information in DNS requests May 2010
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].
Contavalli, et al. Expires November 22, 2010 [Page 4]
Internet-Draft Client IP information in DNS requests May 2010
2. Terminology
Stub Resolver: A simple DNS protocol implementation on the client
side as described in [RFC1034] section 5.3.1.
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 [RFC1035]
chapter 6.
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.
Intermediate Nameserver: Any nameserver (possibly a Recursive
Resolver) in between the Stub Resolver and the Authoritative
Nameserver.
Third-party Nameserver: Recursive Resolvers provided by parties that
are not Internet Service Providers (ISPs). These services are
often offered as substitutes for ISP-run nameservers.
Optimized reply: A reply from a nameserver that is optimized for the
node that sent the request, normally based on performance (i.e.
lowest latency, least number of hops, topological distance, ...).
Topologically close: Refers to two hosts being close in terms of
number of hops or time it takes for a packet to travel from one
host to the other. The concept of topological distance is only
loosely related to the concept of geographical distance: two
geographically close hosts can still be very distant from a
topological perspective.
Contavalli, et al. Expires November 22, 2010 [Page 5]
Internet-Draft Client IP information in DNS requests May 2010
3. Option format
This draft uses an EDNS0 ([RFC2671]) option to include client IP
information in DNS messages. The option is structured as follows:
+0 (MSB) +1 (LSB)
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | OPTION-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | OPTION-LENGTH |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | FAMILY |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
6: | SOURCE NETMASK | SCOPE NETMASK |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
7: | ADDRESS... /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
o (Defined in [RFC2671]) OPTION-CODE, 2 octets, for edns-client-
subnet is TBD.
o (Defined in [RFC2671]) OPTION-LENGTH, 2 octets, contains the
length of the payload (everything after OPTION-LENGTH) in bytes.
o FAMILY, 2 octets, indicates the family of the address contained in
the option, using address family codes as assigned by IANA in
IANA-AFI [1].
The format of the address part depends on the value of FAMILY. This
document only defines the format for FAMILY 1 (IP version 4) and 2
(IP version 6), which are as follows:
o SOURCE NETMASK, 1 octet, in requests, indicates how many most-
significant bits of the SOURCE ADDRESS are included (i.e. a
netmask in CIDR notation). In replies, it echoes back the value
from the query.
o SCOPE NETMASK, 1 octet, in requests, it MUST be set to 0. In
replies, it indicates for which supernets of ADDRESS the reply can
be cached, or which netmask would be necessary in requests to make
a better choice, see next few sections.
o ADDRESS, variable number of octets, contains either an IPv4 or
IPv6 address (depending on FAMILY), truncated to the number of
bits indicated by the SOURCE NETMASK field, with bits set to 0 to
pad up to the end of the last octet used.
All fields are in network byte order.
Contavalli, et al. Expires November 22, 2010 [Page 6]
Internet-Draft Client IP information in DNS requests May 2010
4. Protocol description
The edns-client-subnet extension allows DNS servers to propagate the
network address of the client that initiated the resolution through
to Authoritative Nameservers during recursion.
Servers that receive queries containing an edns-client-subnet option
can generate answers based on the original network address of the
client. Those answers will generally be optimized for that client
and other clients in the same network.
The option also allows Authoritative Nameservers to specify the
network range for which the reply can be cached and re-used.
4.1. Originating the option
The edns-client-subnet option can be added by Intermediate
Nameservers or Stub Resolvers. If an Intermediate Nameserver
receives a query from a routable (i.e. not private IP space as
described in [RFC1918]) IP address and it doesn't yet have the
option, it MAY add an edns-client-subnet option populated with the
source IP address of the query.
Alternatively, a Stub Resolver MAY generate DNS queries with an edns-
client-subnet option, for example if it has better knowledge of where
the connection following the DNS lookup is going to enter the public
network, or to request anonymization by including an edns-client-
subnet option with the address 0.0.0.0/0.
If an Intermediate Nameserver supporting edns-client-subnet receives
a query that already has a valid edns-client-subnet option, this
option MUST be passed through as-is and MUST NOT be modified.
For privacy reasons, and because the whole IP address is rarely
required to determine an optimized reply, the ADDRESS field in the
option SHOULD be truncated to a certain number of bits, chosen by the
administrators of the server, as described in Section 8.
Intermediate Nameservers that have not implemented or enabled support
for the edns-client-subnet can safely ignore the option within
incoming queries. Such a server MUST NOT include an edns-client-
subnet option within replies to indicate lack of support for the
option.
A Recursive Resolver MAY be configured to not include (or drop an
existing) edns-client-subnet option completely when querying
Authoritative Nameservers from which a delegation response is
expected, for example TLD servers or root servers.
Contavalli, et al. Expires November 22, 2010 [Page 7]
Internet-Draft Client IP information in DNS requests May 2010
4.2. Generating a response
When a query containing an edns-client-subnet option is received, an
Authoritative Nameserver supporting edns-client-subnet MAY use the
address information specified in the option in order to generate an
optimized reply.
Authoritative servers that have not implemented or enabled support
for the edns-client-subnet may safely ignore the option within
incoming queries. Such a server MUST NOT include an edns-client-
subnet option within replies to indicate lack of support for the
option.
Requests with an edns-client-subnet option considered invalid (i.e.
wrong formatting, unsupported address family, private address space)
MUST be treated as if no edns-client-subnet option was specified.
If the Authoritative Nameserver decides to use information from the
edns-client-subnet option to calculate a response, it MUST include
the option in the response to indicate that the information was used
(and has to be cached accordingly). If the option was not included
in a query, it MUST NOT be included in the response.
The FAMILY, ADDRESS and SOURCE NETMASK in the response MUST match
those in the request. Echoing back the address and netmask helps to
mitigate certain attack vectors, as described in Section 8.
The SCOPE NETMASK in the reply indicates the network range that the
answer is intended for.
A SCOPE NETMASK value larger than the SOURCE NETMASK indicates that
the address range provided in the query was not specific enough to
select a single, best response, and that an optimal reply would
require at least SCOPE NETMASK bits of address information.
Conversely, a lower SCOPE NETMASK indicates that more bits than
necessary were provided.
In both cases, the value of the SCOPE NETMASK in the reply has strong
implications with regard to how the reply will be cached by
Intermediate Nameservers, as described in Section 4.3.
If the edns-client-subnet option in the request is not used at all
(for example if an optimized reply was temporarily unavailable or not
supported for the requested domain name), a server supporting edns-
client-subnet MUST indicate that no bits of the ADDRESS in the
request have been used by specifying a SCOPE NETMASK of 0 (equivalent
to the networks 0.0.0.0/0 or ::/0).
Contavalli, et al. Expires November 22, 2010 [Page 8]
Internet-Draft Client IP information in DNS requests May 2010
If no optimized answer could be found at all for the ADDRESS and
SOURCE NETMASK indicated in the query, the Authoritative Nameserver
SHOULD still return the best result it knows of (i.e. by using the
query source IP address instead, or a sensible default), and indicate
that this result should only be cached for the FAMILY, ADDRESS and
SOURCE NETMASK indicated in the request. The server will indicate
this by copying the SOURCE NETMASK into the SCOPE NETMASK field.
4.3. Handling edns-client-subnet replies and caching
When an Intermediate Nameserver receives a reply containing an edns-
client-subnet option, it will return a reply to its client and may
cache the result.
If the FAMILY, ADDRESS and SOURCE NETMASK fields in the reply don't
match the fields in the corresponding request, the full reply MUST be
dropped, as described in Section 8.
In the cache, any resource record in the answer section will be tied
to the network specified by the FAMILY, ADDRESS and SCOPE NETMASK
fields, as detailed below.
If another query is received matching the entry in the cache, the
resolver will verify that the FAMILY and ADDRESS that represent the
client match any of the networks in the cache for that entry.
If the address of the client is within any of the networks in the
cache, then the cached response MUST be returned as usual. In case
the address of the client matches multiple networks in the cache, the
entry with the highest SCOPE NETMASK value MUST be returned, as with
most route-matching algorithms.
If the address of the client does not match any network in the cache,
then the Recursive Resolver MUST behave as if no match was found and
perform resolution as usual. This is necessary to avoid sub-optimal
replies in the cache from being returned to the wrong clients, and to
avoid a single request coming from a client on a different network
from polluting the cache with a sub-optimal reply for all the users
of that resolver.
Note that every time a Recursive Resolver queries an Authoritative
Nameserver by forwarding the edns-client-subnet option that it
received from another client, a low SOURCE NETMASK in the original
request could cause a sub-optimal reply to be returned by the
Authoritative Nameserver.
To avoid this sub-optimal reply from being served from cache for
clients for which a better reply would be available, the Recursive
Contavalli, et al. Expires November 22, 2010 [Page 9]
Internet-Draft Client IP information in DNS requests May 2010
Resolver MUST check the SCOPE NETMASK that was returned by the
Authoritative Nameserver:
o If the SCOPE NETMASK in the reply is higher than the SOURCE
NETMASK, it means that the reply might be sub-optimal. A
Recursive Resolver MUST return this entry from cache only to
queries that do not contain or allow a higher SOURCE NETMASK to be
forwarded.
o If the SCOPE NETMASK in the reply is lower or equal to the SOURCE
NETMASK, the reply is optimal, and SHOULD be returned from cache
to any client within the network range indicated by ADDRESS and
SCOPE NETMASK.
When another request is performed, the existing entries SHOULD be
kept in the cache until their TTL expires, as per standard behavior.
As another reply is received, the reply will be tied to a different
network. The server MAY keep in cache both replies, and return the
most appropriate one depending on the address of the client.
Any reply containing an edns-client-subnet option considered invalid
should be treated as if no edns-client-subnet option was specified at
all.
Replies coming from servers not supporting edns-client-subnet or
otherwise not containing an edns-client-subnet option SHOULD be
considered as containing a SCOPE NETMASK of 0 (e.g., cache the result
for 0.0.0.0/0 or ::/0) for all the supported families.
In any case, the response from the resolver to the client MUST NOT
contain the edns-client-subnet option if none was present in the
client's original request. If the original client request contained
a valid edns-client-subnet option that was used during recursion, the
Recursive Resolver MUST include the edns-client-subnet option from
the Authoritative Nameserver response in the response to the client.
Enabling support for edns-client-subnet in a recursive resolver will
significantly increase the size of the cache, reduce the number of
results that can be served from cache, and increase the load on the
server. Implementing the mitigation techniques described in
Section 8 is strongly recommended.
Contavalli, et al. Expires November 22, 2010 [Page 10]
Internet-Draft Client IP information in DNS requests May 2010
5. IANA Considerations
We request IANA to assign an option code for edns-client-subnet, as
specified in [RFC2671]. Within this document, the text 'TBD' should
be replaced with the option code assigned by IANA.
Contavalli, et al. Expires November 22, 2010 [Page 11]
Internet-Draft Client IP information in DNS requests May 2010
6. DNSSEC Considerations
The presence or absence of an OPT resource record containing an edns-
client-subnet 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].
Contavalli, et al. Expires November 22, 2010 [Page 12]
Internet-Draft Client IP information in DNS requests May 2010
7. NAT Considerations
Special awareness of edns-client-subnet in devices that perform NAT
as described in [RFC2663] is not required, queries can be passed
through as-is. The client's network address MUST NOT be added, and
existing edns-client-subnet options, if present, MUST NOT be modified
by NAT devices.
Recursive Resolvers sited behind NAT devices MUST NOT add their
external network address in an edns-client-subnet options, and MUST
behave exactly as described in the previous sections.
Note that Authoritative Nameservers or Recursive Resolvers can still
provide an optimized reply by looking at the source IP of the query.
Contavalli, et al. Expires November 22, 2010 [Page 13]
Internet-Draft Client IP information in DNS requests May 2010
8. Security Considerations
8.1. Privacy
With the edns-client-subnet option, the network address of the client
that initiated the resolution becomes visible to all servers involved
in the resolution process. Additionally, it will be visible from any
network traversed by the DNS packets.
To protect users' privacy, Recursive Resolvers are strongly
encouraged to conceal part of the IP address of the user by
truncating IPv4 addresses to 24 bits. No recommendation is provided
for IPv6 at this time, but IPv6 addresses should be similarly
truncated in order to not allow to uniquely identify the client.
Users who wish their full IP address to be hidden can include an
edns-client-subnet option specifying the wildcard address 0.0.0.0/0
(i.e. FAMILY set to 1 (IPv4), SOURCE NETMASK to 0 and no ADDRESS).
As described in previous sections, this option will be forwarded
across all the Recursive Resolvers supporting edns-client-subnet,
which MUST NOT modify it to include the network address of the
client.
Note that even without edns-client-subnet options, any server queried
directly by the user will be able to see the full client IP address.
Recursive Resolvers or Authoritative Nameservers MAY use the source
IP address of requests to return a cached entry or to generate an
optimized reply that best matches the request.
8.2. Birthday attacks
edns-client-subnet adds information to the q-tuple. This allows an
attacker to send a caching Intermediate Nameserver multiple queries
with spoofed IP addresses either in the edns-client-subnet option or
as the source IP. These queries will trigger multiple outgoing
queries with the same name, type and class, just different address
information in the edns-client-subnet option.
With multiple queries for the same name in flight, the attacker has a
higher chance of success in sending a matching response (with the
address 0.0.0.0/0 to still get it cached for many hosts).
To counter this, every edns-client-subnet option in a response packet
MUST contain the full FAMILY, ADDRESS and SOURCE NETMASK fields from
the corresponding request. Intermediate Nameservers processing a
response MUST verify that these match, and MUST discard the entire
reply if they do not.
Contavalli, et al. Expires November 22, 2010 [Page 14]
Internet-Draft Client IP information in DNS requests May 2010
8.3. Cache pollution
It is simple for an arbitrary resolver or client to provide false
information in the edns-client-subnet option, or to send UDP packets
with forged source IP addresses.
This could be used to pollute the cache of intermediate resolvers, by
filling it with results that will rarely (if ever) be used, or to
reverse engineer the algorithms (or data) used by the Authoritative
Nameserver to calculate the optimized answers.
Even without malicious intent, third-party Recursive Resolvers
providing answers to clients in multiple networks will need to cache
different replies for different networks, putting more pressure on
the cache.
To mitigate those problems:
o Recursive Resolvers implementing edns-client-subnet should only
enable it in deployments where it is expected to bring clear
advantages to the end users. For example, when expecting clients
from a variety of networks or from a wide geographical area. Due
to the high cache pressure introduced by edns-client-subnet, the
feature must be disabled in all default configurations.
o Recursive Resolvers should limit the number of networks and
answers they keep in the cache for a given query.
o Recursive Resolvers should limit the number of total different
networks that they keep in cache.
o Recursive Resolvers should never send edns-client-subnet options
with SOURCE NETMASKs providing more bits in the ADDRESS than they
are willing to cache responses for.
o Recursive Resolvers should implement algorithms to improve the
cache hit rate, given the size constraints indicated above.
Recursive Resolvers may, for example, decide to discard more
specific cache entries first.
o Authoritative Nameservers and Recursive Resolvers should discard
known to be wrong or known to be forged edns-client-subnet
options. They must at least ignore unroutable addresses,
including the ones defined in [RFC1918] and [RFC4193], and should
ignore and never forward edns-client-subnet options specifying
networks or addresses that are known not to be served by those
servers when feasible.
Contavalli, et al. Expires November 22, 2010 [Page 15]
Internet-Draft Client IP information in DNS requests May 2010
o Authoritative Nameservers consider the edns-client-subnet option
just as a hint to provide better results. They can decide to
ignore the content of the edns-client-subnet option based on black
or white lists, rate limiting mechanisms, or any other logic
implemented in the software.
Contavalli, et al. Expires November 22, 2010 [Page 16]
Internet-Draft Client IP information in DNS requests May 2010
9. Example
1. A stub resolver SR with IP address 192.0.2.37 tries to resolve
www.example.com, by forwarding the query to the Recursive
Resolver R from IP address IP, asking for recursion.
2. R, supporting edns-client-subnet, looks up www.example.com in
its cache. An entry is found neither for www.example.com, nor
for example.com.
3. R builds a query to send to the root and .com servers. The
implementation of R does not include an edns-client-subnet
option when querying TLD or root nameservers, because there is
no expectation to receive a client-network-specific response.
Thus, no edns-client-subnet option is added, and resolution is
performed as usual.
4. R now knows the Authoritative Nameserver ANS responsible for
example.com.
5. R prepares a new query for www.example.com, including an edns-
client-subnet option with:
* OPTION-CODE, set to TBD.
* OPTION-LENGTH, set to 0x00 0x07.
* FAMILY, set to 0x00 0x01 as IP is an IPv4 address.
* SOURCE NETMASK, set to 0x18, as R is configured to conceal
the last 8 bits of every IPv4 address.
* SCOPE NETMASK, set to 0x00, as specified by this document for
all requests.
* ADDRESS, set to 0xC0 0x00 0x02, providing only the first 24
bits of the IPv4 address.
6. The query is sent. Authoritative Nameserver ANS understands and
uses edns-client-subnet. It parses the edns-client-subnet
option, and generates an optimized reply.
7. Due to the internal implementation of the Authoritative
Nameserver ANS, ANS finds a reply that is optimal for the whole
/16 of the client that performed the request.
8. The Authoritative Nameserver ANS adds an edns-client-subnet
option in the reply, containing:
Contavalli, et al. Expires November 22, 2010 [Page 17]
Internet-Draft Client IP information in DNS requests May 2010
* OPTION-CODE, set to TBD.
* OPTION-LENGTH, set to 0x00 0x07.
* FAMILY, set to 0x00 0x01.
* SOURCE NETMASK, set to 0x18, copied from the request.
* SCOPE NETMASK, set to 0x10, indicating a /16 network range.
* ADDRESS, set to 0xC0 0x00 0x02, copied from the request.
9. The Recursive Resolver R receives the reply containing an edns-
client-subnet option. The resolver verifies that FAMILY, SOURCE
NETMASK, and ADDRESS match the request. If not, the option is
discarded.
10. The reply is interpreted as usual. Since the reply contains an
edns-client-subnet option, the ADDRESS, SCOPE NETMASK, and
FAMILY in the response are used to cache the entry.
11. R sends a response to stub resolver SR, without including an
edns-client-subnet option.
12. R receives another request to resolve www.example.com. This
time, a reply is cached. The reply, however, is tied to a
particular network. If the address of the client matches any
network in the cache, then the reply is returned from the cache.
Otherwise, another query is performed. If multiple results
match, the one with the longest SCOPE NETMASK is chosen, as per
common best-network match algorithms.
Contavalli, et al. Expires November 22, 2010 [Page 18]
Internet-Draft Client IP information in DNS requests May 2010
10. Acknowledgements
The authors wish to thank the following people for reviewing early
drafts of this document and for providing useful feedback: Paul S. R.
Chisholm, B. Narendran, Leonidas Kontothanassis, David Presotto,
Philip Rowlands, Chris Morrow, Kara Moscoe, Alex Nizhner, Warren
Kumari, Richard Rabbat from Google, Terry Farmer, Mark Teodoro,
Edward Lewis, Eric Burger from Neustar, David Ulevitch, Matthew
Dempsky from OpenDNS, Patrick W. Gilmore from Akamai, Colm
MacCarthaigh, Richard Sheehan and all the other people that replied
to our emails on various mailing lists.
Contavalli, et al. Expires November 22, 2010 [Page 19]
Internet-Draft Client IP information in DNS requests May 2010
Appendix A. Document Editing History
Appendix A.1. Changes since -00
o Rewritten problem statement to be more clear about the goal of
edns-client-subnet and the fact that it's entirely optional.
o Wire format changed to include the original address and netmask in
responses in defence against birthday attacks.
o Security considerations now includes a section about birthday
attacks.
o Renamed edns-client-ip in edns-client-subnet, following
suggestions on the mailing list.
o Clarified behavior of resolvers when presented with an invalid
edns-client-subnet option.
o Fully take multi-tier DNS setups in mind and be more clear about
where the option should be originated.
o Added a few definitions in the Terminology section, and a few more
aesthetic changes in the rest of the document.
Contavalli, et al. Expires November 22, 2010 [Page 20]
Internet-Draft Client IP information in DNS requests May 2010
11. References
11.1. Normative References
[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.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, February 1996.
[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.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
11.2. Informative References
[RFC2663] Srisuresh, P. and M. Holdrege, "IP Network Address
Translator (NAT) Terminology and Considerations",
RFC 2663.
Contavalli, et al. Expires November 22, 2010 [Page 21]
Internet-Draft Client IP information in DNS requests May 2010
URIs
[1] <http://www.iana.org/assignments/address-family-numbers/>
Contavalli, et al. Expires November 22, 2010 [Page 22]
Internet-Draft Client IP information in DNS requests May 2010
Authors' Addresses
Carlo Contavalli
Google
Gordon House, Barrow Street
Dublin 4
IE
Email: ccontavalli@google.com
Wilmer van der Gaast
Google
Gordon House, Barrow Street
Dublin 4
IE
Email: wilmer@google.com
Sean Leach
Name.com
125 Rampart Way, Suite 300
Denver, CO 80230
CO
Email: sleach@name.com
Darryl Rodden
Neustar
46000 Center Oak Plaza
Sterling, VA 20166
VA
Email: darryl.rodden@neustar.com
Contavalli, et al. Expires November 22, 2010 [Page 23]
| PAFTECH AB 2003-2026 | 2026-04-23 20:13:07 |