ISP Location in DNS Queries
draft-pan-dnsop-edns-isp-location-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Active".
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|
|---|---|---|---|
| Authors | Pan Lanlan , Yu Fu | ||
| Last updated | 2017-05-11 (Latest revision 2017-03-13) | ||
| RFC stream | (None) | ||
| Formats | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
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| Send notices to | (None) |
draft-pan-dnsop-edns-isp-location-01
dnsop L. Pan
Internet-Draft
Intended status: Informational Y. Fu
Expires: November 12, 2017 CNNIC
May 11, 2017
ISP Location in DNS Queries
draft-pan-dnsop-edns-isp-location-01
Abstract
This document describes an Extension Mechanisms for DNS (EDNS0)
option that is in active use to carry < COUNTRY, AREA, ISP > isp
location information about the network that originated a DNS query
and the network for which the subsequent response can be cached.
It is inspired by EDNS Client Subnet (ECS) with some privacy
considerations, goals to reduce the "guess location of client's IP"
work on Authoritative Nameservers.
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 November 12, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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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 Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Path Calculation and Tailored DNS Response . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. The EIL EDNS0 option . . . . . . . . . . . . . . . . . . . . 6
6. Protocol Description . . . . . . . . . . . . . . . . . . . . 7
6.1. Originating the Option . . . . . . . . . . . . . . . . . 7
6.1.1. P-Model: Public Recursive Resolver . . . . . . . . . 7
6.1.2. I-Model: ISP Recursive Resolver . . . . . . . . . . . 8
6.1.3. L-Model: Local Forwarding Resolver . . . . . . . . . 8
6.2. Generating a Response . . . . . . . . . . . . . . . . . . 9
6.2.1. Whitelist . . . . . . . . . . . . . . . . . . . . . . 9
6.2.2. Authoritative Nameserver . . . . . . . . . . . . . . 9
6.2.3. Intermediate Nameserver . . . . . . . . . . . . . . . 9
6.3. Handling EIL Responses and Caching . . . . . . . . . . . 9
6.3.1. Caching the Response . . . . . . . . . . . . . . . . 10
6.3.2. Answering from Cache . . . . . . . . . . . . . . . . 10
6.3.3. Support ECS and EIL at the same time . . . . . . . . 10
6.4. Delegations and Negative Answers . . . . . . . . . . . . 11
6.5. Transitivity . . . . . . . . . . . . . . . . . . . . . . 12
6.6. Response Accuracy . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7.1. DNSSEC . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.2. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.3. Target Censorship . . . . . . . . . . . . . . . . . . . . 12
7.4. Cache Size . . . . . . . . . . . . . . . . . . . . . . . 13
7.5. DDoS . . . . . . . . . . . . . . . . . . . . . . . . . . 13
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
10. Appendix A. Example . . . . . . . . . . . . . . . . . . . . . 13
10.1. Example 1: P-Model . . . . . . . . . . . . . . . . . . . 14
10.2. Example 2: I-Model . . . . . . . . . . . . . . . . . . . 14
10.3. Example 3: L-Model . . . . . . . . . . . . . . . . . . . 14
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . 14
11.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
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1. Introduction
As described in EDNS Client Subnet (ECS) [RFC7871], many
Authoritative Nameservers today return different responses based on
the perceived topological location of the user. These servers use
the IP address of the incoming query to identify that location. ECS
is an EDNS0 [RFC6891] option to carry client subnet information in
DNS queries for Authoritative Nameserver. Compared to source IP
address of DNS query, ECS will help Authoritative Nameserver to guess
the client's location more precisely because of the DNS forwarding
query structure.
However, ECS raises some privacy concerns because it leaks client
subnet information on the resolution path to the Authoritative
Nameserver.
Meanwhile, many Authoritative Nameservers support GeoIP feature, for
example, BIND-GeoIP [BIND-GeoIP], PowerDNS-GeoIP [PowerDNS-GeoIP],
Amazon-Geolocation-Routing [Amazon-Geolocation-Routing], DYN-Traffic-
Director-ECS [DYN-Traffic-Director-ECS], gdnsd-GeoIP [gdnsd-GeoIP],
etc. These geographically aware Authoritative Nameservers guess the
user's geolocation by the client subnet of ECS or by the source IP
address of DNS query, return tailor DNS response based on the user's
geolocation. To sum up, these Authoritative Nameservers use ECS
client subnet information for GeoIP feature's user geolocation
detecting.
This document is an improved solution for ECS-enabled GeoIP feature
of Authoritative Nameserver, describes an EDNS ISP Location (EIL)
extension to address the privacy problem of ECS, find the right
balance between privacy improvement and user experience optimization.
EIL is defined to convey isp location < COUNTRY, AREA, ISP >
information that is relevant to the DNS message. It will directly
provide the same sufficient information for the GeoIP-based
Authoritative Nameserver that enabling ECS, to decide the response
without guessing geolocation of the IP address.
EIL is intended for those Local Forwarding Resolvers, Recursive
Resolvers and Authoritative Nameservers that would benefit from the
extension and not for general purpose deployment like ECS scenario.
It could be applied for tailor DNS response. EIL can safely be
ignored by servers that choose not to implement or enable it.
1.1. Path Calculation and Tailored DNS Response
Separate the consideration of path calculation (Data Provider) and
tailored DNS response (Authoritative Nameserver).
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Data Providers make path calculations to optimize content delivery on
the Internet based on the network topology, considering many factors
such as IP, RIPs, FIBs, AS Path hops, system load, content
availability, path latency, etc. Note that, Data Providers have the
full details of the clients, they can make any complex path
calculations without ECS and EIL.
Authoritative Nameservers configure tailored DNS response based on
the result of path calculations, allocate IP addresses to different
datacenters. Usually, users from the same < COUNTRY, AREA, ISP > isp
location are allocated to the same datacenter, the same best "network
topologically close" datacenter. For example, client IP addresses
from < China, Beijing, Telecom > are allocated to DataCenter-1,
client IP addresses from < China, Beijing, Unicom > are allocated to
DataCenter-2, etc. Above is the GeoIP-based Tailored DNS Response.
Therefore, if the GeoIP-based Authoritative Nameservers enable ECS,
they can use the client subnet information of ECS instead of
resolver's address for GeoIP detecting. Moreover, the GeoIP-based
Authoritative Nameservers can directly use the < COUNTRY, AREA, ISP >
information of EIL without GeoIP detecting.
Again, we emphasize that tailored DNS response does not affect path
calculation. Data Providers can make path calculations based on
network topology, decide network topological close datacenter for
each IP address. Authoritative Nameservers allocate tailored DNS
response to each IP address based on the "network topological close"
result of path calculations. EIL tell Authoritative Nameserver like
that, "I want to know what is best IP address for clients from <
China, Beijing, Telecom > at network topology path calculations
result", but not "I want to know what is the nearest IP address for
clients from < China, Beijing, Telecom > at physical topology path
calculations result".
EIL is satisfied if Authoritative Nameservers aggregate the IP
addresses from the same < COUNTRY, AREA, ISP > isp location to visit
the same datacenters, we call that GeoIP-based tailored DNS
responses, and these tailored responses have "network topological
close" distance to the users.
ECS is satisfied if Authoritative Nameservers make tailored DNS
response down to subnet precise level. For example, (subnet-1, ...,
subnet-100) are from the same < COUNTRY, AREA, ISP > isp location,
Data Provider applies (subnet-1, ..., subnet-50) visit DataCenter-1,
(subnet-51, ..., subnet-100) visit DataCenter-2.
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2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119] when they appear in ALL CAPS. When these words are not in
ALL CAPS (such as "should" or "Should"), they have their usual
English meanings, and are not to be interpreted as [RFC2119]
keywords.
3. Terminology
Basic terms used in this specification are defined in the documents
[RFC1034], [RFC1035], [RFC7719] and [RFC7871].
EIL: EDNS ISP Location.
ECS: EDNS Client Subnet, described in [RFC7871].
Local Forwarding Resolver: Forwarding Resolver is described in
[RFC7871]. It is the first Forwarding Resolver which receives DNS
queries from Stub Resolver, usually deployed nearby the first-hop
router such as public Wi-Fi hotspot routers and home routers.
Recursive Resolver: described in [RFC7871]. It is the last-hop
before Authoritative Nameserver in the DNS query path.
Intermediate Nameserver: described in [RFC7871]. Any nameserver in
between the Stub Resolver and the Authoritative Nameserver, such as a
Recursive Resolver or a Forwarding Resolver.
Intermediate Forwarding Resolver: Any Forwarding Resolver in between
the Local Forwarding Resolver and Recursive Resolver.
Authoritative Nameserver: described in [RFC7719] and [RFC2182]. It
is a server that knows the content of a DNS zone from local
knowledge, and thus can answer queries about that zone without
needing to query other servers.
4. Overview
This document provides an EDNS0 option to allow Local Forwarding
Resolvers and Recursive Resolvers, if they are willing, to forward
details about the isp location of client when talking to other
nameservers.
The format of EIL option is described in Section 5. EIL can be added
in queries sent by Local Forwarding Resolvers or Recursive Resolvers
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in a way that is transparent to Stub Resolvers and end users. EIL is
only defined for the Internet (IN) DNS class.
Like ECS, Authoritative Nameservers could provide a better answer by
using precise isp location in EIL. Intermediate Nameservers could
send EIL query and cache the EIL response. This document also
provides a mechanism to signal Intermediate Nameservers that they do
not want EIL treatment for specific queries.
The security concerns for EIL are like ECS, such as cache growth,
spoof EDNS0 option and privacy, etc. Mitigation techniques are
discussed in Section 6.
5. The EIL EDNS0 option
The EIL is an EDNS0 option to include the isp location of client in
DNS messages.
It is 14 octets which is structured as follows:
+0 (MSB) +1 (LSB)
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | OPTION-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | OPTION-LENGTH |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | COUNTRY-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
6: | AREA-CODE |
| |
| |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
12: | ISP |
| |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Total: 14 octets.
o OPTION-CODE, 2 octets, defined in [RFC6891]. EDNS option code
should be assigned by the IANA.
o OPTION-LENGTH, 2 octets, defined in [RFC6891], contains the length
of the payload (everything after OPTION-LENGTH) in octets.
o COUNTRY-CODE, 2 octets, uppercase, defined in [ISO3166], indicates
the country information of the client's IP. For example, China's
COUNTRY-CODE is CN.
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o AREA-CODE, 6 octets, uppercase, defined in [ISO3166] country
subdivision code, indicates the area information of the client's
IP. For example, The AREA-CODE of Fujian Province in China is 35.
o ISP, 4 octets, uppercase, indicates the ISP information of the
client's IP, using shortcut names. ISP shortcut names are unique
within the context of the COUNTRY-CODE. For example, the shortcut
name of China Telecommunications Corporation is TEL, the shortcut
name of China United Network Communications is UNI, the shortcut
name of China Mobile is MOB, etc.
All fields are in network byte order ("big-endian", per [RFC1700],
Data Notation).
The aim to use short names in the fields is to limit the data size of
EIL, decrease the DDoS risk.
The null value 0x20 signifies that the field is unknown. If all
fields in EIL are set to null value, it means that client doesn't
want to use EIL.
Authoritative Nameservers can send EIL response with the * value 0x2A
in AREA-CODE field or ISP field (not COUNTRY-CODE field), which
signifies that the field is wildcard match. For example, < CN, *,
TEL > indicates: all area in China, Telecom ISP.
Example code is in Github at: https://github.com/abbypan/dns_test_eil
.
6. Protocol Description
6.1. Originating the Option
The EIL can be initialized by Public Recursive Resolver, ISP
Recursive Resolver, or Local Forwarding Resolver.
6.1.1. P-Model: Public Recursive Resolver
Public Recursive Resolvers are not close to many users because the
service providers couldn't deploy servers in every country and every
ISP's network, which will affect the response accuracy of
Authoritative Nameservers. To encounter this problem, ECS shifts the
client subnet information to Authoritative Nameserver, but rises user
privacy concerns.
Therefore, to keep balance between precise and privacy, when a Public
Recursive Resolver receives a DNS query, it can guess isp location of
client's IP and generate the EIL OPT data, then send EIL query to the
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Authoritative Nameserver. This will move the "guess location of
client's IP" work from Authoritative Nameserver back to Public
Recursive Resolver, lighten the burden of Authoritative Nameserver,
but increase DDoS risk on Public Recursive Resolver.
In order to improve the user's privacy, if a Recursive Resolver
receives a DNS query with ECS, it can guess the isp location of
SOURCE-PREFIX from the ECS OPT data, and make a new DNS query with
EIL, then send the query to Authoritative Nameserver which supports
EIL.
P-model is the most recommended and close to the ECS.
6.1.2. I-Model: ISP Recursive Resolver
ISP Recursive Resolver only serves its customers, each of whom has a
static isp location. ISP Recursive Resolver can add EIL transparent
to end user, and then Authoritative Nameserver doesn't need to "guess
location of client's IP".
EIL will be benefit if the Authoritative Nameserver could not find
the approximate isp location of ISP Recursive Resolver, which is
crucial to DNS response accuracy in ECS.
6.1.3. L-Model: Local Forwarding Resolver
Local Forwarding Resolver is usually on the first-hop router, such as
public Wi-Fi hotspot routers and Cisco/Linksys/Netgear/TP-LINK home
routers.
When a Local Forwarding Resolver that implements EIL receives a DNS
query from an end user, it surely can know about the isp location of
client's IP, and generate the EIL OPT data, then send the EIL query
to the intermediate Recursive Resolver. Intermediate Recursive
Resolver sends the EIL query to the Authoritative Nameserver.
In this scenario, both Public Recursive Resolver and Authoritative
Nameserver don't need to "guess location of client's IP", because the
Local Forwarding Resolver supplies the isp location precisely. That
is, EIL can reduce dependence on the IP geolocation database quality,
which is crucial to DNS response accuracy in ECS.
If a Local Forwarding Resolver had sent a query with EIL, and
receives a REFUSE response, it MUST regenerate a query with no EIL.
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6.2. Generating a Response
6.2.1. Whitelist
EIL contains a whitelist for COUNTRY-CODE, AREA-CODE and ISP, which
can be discussed or maintained by the DNSOP working group.
Authoritative Nameservers that supporting EIL must only response the
EIL queries matched the whitelist. Recursive Resolver that
supporting EIL must only cache the EIL responses matched the
whitelist.
6.2.2. Authoritative Nameserver
Using the isp location specified in the EIL option of DNS query, an
Authoritative Nameserver can generate a tailored response.
Authoritative Nameservers that have not implemented or enabled
support for the EIL ought to safely ignore it within incoming
queries, response the query as a normal case without EDNS0 option.
Such a server MUST NOT include an EIL option within replies to
indicate lack of support for it.
An Authoritative Nameserver that has implemented this protocol and
receives an EIL option MUST include an EIL option in its response to
indicate that it SHOULD be cached accordingly.
An Authoritative Nameserver will return a more appropriate tailored
response for the query with an EIL option containing more precisely
AREA-CODE.
6.2.3. Intermediate Nameserver
Like ECS, Intermediate Nameserver passes a DNS response with an EIL
option to its client when the client indicates support EIL.
If an Intermediate Nameserver receives a response that has a larger
area than the AREA-CODE provided in its query, it SHOULD still
provide the result as the answer to the triggering client request
even if the client is in a smaller area.
6.3. Handling EIL Responses and Caching
If an Intermediate Nameserver had sent a query with EIL, and receives
a NOERROR response without EIL option, it SHOULD treat this answer as
suitable for all clients.
Other handling considerations are similar with ECS [RFC7871], SECTION
7.3.
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6.3.1. Caching the Response
In the cache, all resource records in the Answer section MUST be tied
to the isp location specified in the response. The Answer section is
valid for all areas which the EIL option covered. For example, an
EIL option < CN, 35, TEL > covers all 9 Cities in Fujian Province of
China Telecommunications ISP.
Same with ECS, The Additional and Authority sections are excluded.
Enabling support for EIL in an Intermediate Nameserver will increase
the size of the cache, and prevent "client subnet leak" privacy
concern of ECS.
6.3.2. Answering from Cache
Cache lookups are first done as usual for a DNS query, using the
query tuple of < name, type, class >. Then, the appropriate RRset
MUST be chosen based on the isp location matching.
If there was an EIL option, the Intermediate Nameserver will lookup
for < same COUNTRY-CODE, same ISP, same AREA-CODE > of the same query
tuple in the cache. Otherwise, try to find < same COUNTRY-CODE, same
ISP, same AREA-CODE > of the same query tuple in the cache.
If no EIL option was provided, the safest choice of the Intermediate
Nameserver is dealing the query as a normal case without EDNS0
option.
If no EIL option was provided, but the Intermediate Nameserver want
to be more aggressive, it can guess the isp location from the source
IP of the query, then respond as if there was an EIL option with the
guessed information. Users can be benefit when the Intermediate
Nameserver has a more precise IP location database than the
Authoritative Nameserver, especially in global public DNS service
like GoogleDNS(8.8.8.8).
If no matching is found, the Intermediate Nameserver MUST perform
resolution as usual.
6.3.3. Support ECS and EIL at the same time
Name servers can support ECS and EIL at the same time. ECS and EIL
can't be both initiated at the same DNS packet. It is better for
user privacy if name servers initiate the EIL query prior to the ECS
query.
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If Authoritative Nameservers support both ECS and EIL, Recursive
resolvers can cache both ECS response and EIL response, there are
some choices for Recursive Resolvers when they receive DNS queries.
Receive EIL query:
Search in EIL cache.
If cache is matched, return EIL response.
Otherwise, send EIL query to Authoritative Nameserver.
Receive ECS query:
Search in ECS cache.
If cache is matched, return ECS response.
Otherwise, send ECS query to Authoritative Nameserver.
Receive DNS query without EDNS option:
Search in ECS cache.
If cache is matched, return ECS response.
Otherwise,
Guess the isp location information of the client's IP,
build EIL option for the query packet.
Search in EIL cache.
If cache is matched, return EIL response.
Otherwise, send EIL query to Authoritative Nameserver.
Receive DNS query with not-ECS/not-EIL option:
Search in not-EDNS cache.
If cache is matched, return response.
Otherwise, send the DNS query to Authoritative Nameserver.
Receive ECS query, improve user privacy:
Guess the isp location information of the client's IP,
build EIL option for the query packet.
Search in EIL cache.
If cache is matched, return EIL response RR with origin ECS option.
Otherwise, send EIL query to Authoritative Nameserver.
6.4. Delegations and Negative Answers
EIL's delegation case is similar with ECS, Additional and Authority
Sections SHOULD ignore EIL.
For negative answers, Authoritative Nameservers return traditional
negative answers without EIL.
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6.5. Transitivity
EIL's transitivity concerns are similar with ECS.
Name servers should only enable EIL where it is expected to benefit
the end users, such as dealing with some latency-sensitive CDN domain
queries in a complex network environment.
6.6. Response Accuracy
Authoritative Nameservers that support ECS-enabled GeoIP feature can
support EIL smoothly.
Compared to ECS, EIL can reduce dependence on the IP geolocation
database quality. EIL will rise the response accuracy of
Authoritative Nameserver if its database can not find approximate isp
location of ECS client subnet, ensure user latency. EIL will help
Authoritative Nameservers to avoid cross-isp visit if its database
can not find approximate isp location of ECS client subnet, save IP
transit cost.
7. Security Considerations
7.1. DNSSEC
EIL is not signed.
7.2. Privacy
As mentioned in [RFC7871]'s abstract section, since ECS has some
known operational and privacy shortcomings, a revision will be worked
through the IETF for improvement. The biggest privacy concern on ECS
is that client subnet information is personally identifiable. The
more domains publish their zones on a third-party Authoritative
Nameserver, the more end user privacy information can be gathered by
the Authoritative Nameserver according to the ECS queries.
EIL is to improve user privacy which is inspired by ECS, prevented
leaks in the client subnet information.
Like ECS, EIL will leak the global zonefile configurations of the
Authoritative Nameservers more easily than normal case.
7.3. Target Censorship
DNS traffic is plain text by default. It is easily to be blocked or
poisoned by internet target censorship. To bypass the censorship, it
is better to encrypt the DNS traffic or use some proxy tunnel.
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EIL's isp location information covers bigger area than ECS's client
subnet information. Therefore, compared to ECS in plain text
condition, EIL is weaker at blocking record attack, but stronger at
targeted DNS poisoning attack.
7.4. Cache Size
Like ECS, cache size will raise if a Public Recursive Resolver
supports EIL. The cache size of ECS grows up with the number of
client subnets. The cache size of EIL is related to the row count in
the < COUNTRY-CODE, AREA-CODE, ISP > isp location whitelist.
Therefore, under IPv6 environment, the cache size of EIL will be
smaller than ECS.
7.5. DDoS
To migrate the DDoS problem:
o If an Authority Server receives a DNS query with unknown data in
EIL option, it SHOULD return the default response whose EIL option
with null value.
o Nameservers OPTIONAL only implement EIL when the query is from a
TCP connection.
More migration techniques described in [RFC7871], Section 11.3.
8. IANA Considerations
This document defines EIL, need request IANA to assign a new EDNS0
option code to EIL.
9. Acknowledgements
EIL is inspired by ECS, the authors especially thanks to C.
Contavalli, W. van der Gaast, D. Lawrence, and W. Kumari.
Thanks comments for Barry Raveendran Greene, Paul Vixie, Petr
Špaček, Brian Hartvigsen, Ask Bjoern Hansen.
Thanks a lot to all in the DNSOP, DNSPRIV and DNSEXT mailing list.
10. Appendix A. Example
Authoritative Nameserver of www.example.com has enabled EIL.
Stub DNS query A resource record of www.example.com .
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10.1. Example 1: P-Model
Stub DNS
-> Local Forwarding Resolver (61.48.7.2)
-> Public Forwarding Resolver(AliDNS, 223.5.5.5)
-> Public Recursive Resolver(AliDNS, 202.108.250.231)
-> Authoritative Nameserver
Public Forwarding Resolver 223.5.5.5 could enable EIL and generate
the EIL OPT data < CN, 11, UNI > based on 61.48.7.2.
P-Model will not leak client subnet to Authoritative Nameserver.
10.2. Example 2: I-Model
Stub DNS
-> Local Forwarding Resolver
-> ISP Forwarding Resolver(202.106.196.115)
-> ISP Recursive Resolver(61.135.23.92)
-> Authoritative Nameserver
ISP Recursive Resolver 61.135.23.92 could enable EIL and generate the
EIL OPT data < CN, 11, UNI > based on 61.135.23.92.
If Authoritative Nameserver doesn't know much about 61.135.23.92, EIL
will be helpful.
10.3. Example 3: L-Model
Stub DNS
-> Local Fowarding Resolver(58.60.109.234)
-> ...
-> Authoritative Nameserver
Local Fowarding Resolver 58.60.109.234 could enable EIL and generate
the option data is < CN, 44, TEL > based on 58.60.109.234.
L-Model can give the most precisely isp location information for DNS
resolution.
11. References
11.1. Normative References
[RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities",
RFC 1034, November 1987.
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[RFC1035] Mockapetris, P., "Domain Names - Implementation and
Specification", RFC 1035, November 1987.
[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700,
October 1994.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[RFC2182] ELZ, R., Bush, R., Bradner, S., and M. Patton, "Selection
and Operation of Secondary DNS Servers", RFC 2182, July
1997.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", RFC 6891, April 2013.
[RFC7719] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", RFC 7719, December 2015.
[RFC7871] Contavalli, C., van der Gasst, W., Lawrence, D., and W.
Kumari, "Client Subnet in DNS Queries", RFC 7871, May
2016.
11.2. Informative References
[Amazon-Geolocation-Routing]
Amazon, "Amazon Route 53: Geolocation Routing",
<http://docs.aws.amazon.com/Route53/latest/DeveloperGuide/
routing-policy.html#routing-policy-geo>.
[BIND-GeoIP]
ISC BIND, "Using the GeoIP Features in BIND 9.10",
<https://kb.isc.org/article/AA-01149/0>.
[DYN-Traffic-Director-ECS]
DYN, "What happens when a DNS query for a Traffic Director
instance is received with ECS information",
<https://help.dyn.com/edns-client-subnet-faq-info/#q6>.
[gdnsd-GeoIP]
gdnsd, "GdnsdPluginGeoip",
<https://github.com/gdnsd/gdnsd/wiki/GdnsdPluginGeoip>.
[ISO3166] ISO 3166, "Country Codes",
<http://www.iso.org/iso/country_codes>.
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[PowerDNS-GeoIP]
PowerDNS, "PowerDNS GeoIP backend",
<https://doc.powerdns.com/md/authoritative/backend-
geoip/>.
Authors' Addresses
Lanlan Pan
Beijing
CN
Email: abbypan@gmail.com
URI: https://github.com/abbypan
Yu Fu
CNNIC
No.4 South 4th Street, Zhongguancun
Beijing
CN
Email: fuyu@cnnic.cn
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