Considerations for Large Authoritative DNS Servers Operators
draft-moura-dnsop-authoritative-recommendations-04
The information below is for an old version of the document.
draft-moura-dnsop-authoritative-recommendations-04
DNSOP Working Group G. Moura
Internet-Draft SIDN Labs/TU Delft
Intended status: Informational W. Hardaker
Expires: December 13, 2019 J. Heidemann
USC/Information Sciences Institute
M. Davids
SIDN Labs
June 11, 2019
Considerations for Large Authoritative DNS Servers Operators
draft-moura-dnsop-authoritative-recommendations-04
Abstract
This document summarizes recent research work exploring DNS
configurations and offers specific, tangible considerations to
operators for configuring authoritative servers.
This document is not an Internet Standards Track specification; it is
published for informational purposes.
Ed note
This draft will be renamed to draft-moura-dnsop-large-authoritative-
considerations in case adpoted by the WG, to reflect the new title.
Text inside square brackets ([RF:ABC]) refers to:
o individual comments we have received about the draft, and
enumerated under <https://github.com/gmmoura/draft-moura-dnsop-
authoritative-recommendations/blob/master/reviews/reviews-
dnsop.md>.
o Issues listed on our Github repository
Both types will be removed before publication.
This draft is being hosted on GitHub - <https://github.com/gmmoura/
draft-moura-dnsop-authoritative-recommendations>, where the most
recent version of the document and open issues can be found. The
authors gratefully accept pull requests.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Moura, et al. Expires December 13, 2019 [Page 1]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
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 https://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 December 13, 2019.
Copyright Notice
Copyright (c) 2019 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
(https://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 Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. C1: Use equally strong IP anycast in every authoritative
server (NS) for better load distribution . . . . . . . . . . 5
4. C2: Routing Can Matter More Than Locations . . . . . . . . . 6
5. C3: Collecting Detailed Anycast Catchment Maps Ahead of
Actual Deployment Can Improve Engineering Designs . . . . . . 7
6. C4: When under stress, employ two strategies . . . . . . . . 9
7. C5: Consider longer time-to-live values whenever possible . . 10
8. Security considerations . . . . . . . . . . . . . . . . . . . 12
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12
10. IANA considerations . . . . . . . . . . . . . . . . . . . . . 13
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.1. Normative References . . . . . . . . . . . . . . . . . . 13
12.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
Moura, et al. Expires December 13, 2019 [Page 2]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
1. Introduction
This document summarizes recent research work exploring DNS
configurations and offers specific tangible considerations to DNS
authoritative servers operators (DNS operators hereafter).
[RF:JAb2]], [RF:MSJ1], [RF:DW2]. The considerations (C1-C5)
presented in this document are backed by previous research work,
which used wide-scale Internet measurements upon which to draw their
conclusions. This document describes the key engineering options,
and points readers to the pertinent papers for details and
[RF:Issue15] other research works related to each consideration here
presented.
[RF:JAb1, Issue#2, SJa-02]. These considerations are designed for
operators of "large" authoritative servers. In this context, "large"
authoritative servers refers to those with a significant global user
population, like TLDs, run by a single or multiple operators. These
considerations may not be appropriate for smaller domains, such as
those used by an organization with users in one city or region, where
goals such as uniform low latency are less strict.
It is likely that these considerations might be useful in a wider
context, such as for any stateless/short-duration, anycasted service.
Because the conclusions of the studies don't verify this fact, the
wording in this document discusses DNS authoritative services only
([RF:Issue13]).
2. Background
The domain name system (DNS) has main two types of DNS servers:
authoritative servers and recursive resolvers. Figure 1 shows their
relationship. An authoritative server (ATn in Figure 1) knows the
content of a DNS zone from local knowledge, and thus can answer
queries about that zone without needing to query other servers
[RFC2181]. A recursive resolver (Re_n) is a program that extracts
information from name servers in response to client requests
[RFC1034]. A client (stub in Figure 1) refers to stub resolver
[RFC1034] that is typically located within the client software.
Moura, et al. Expires December 13, 2019 [Page 3]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
+-----+ +-----+ +-----+ +-----+
| AT1 | | AT2 | | AT3 | | AT4 |
+-----+ +-----+ +-----+ +-----+
^ ^ ^ ^
| | | |
| +-----+ | |
+------|Re_1 |------+ |
| +-----+ |
| ^ |
| | |
| +-----+ +-----+ |
+------|Re_2 | |Re_3 |-----+
+-----+ +-----+
^ ^
| |
| +------+ |
+-| stub |--+
+------+
Figure 1: Relationship between recursive resolvers (Re_n) and
authoritative name servers (ATn)
DNS queries/responses contribute to user's perceived latency and
affect user experience [Sigla2014], and the DNS system has been
subject to repeated Denial of Service (DoS) attacks (for example, in
November 2015 [Moura16b]) in order to degrade user experience.
To reduce latency and improve resiliency against DoS attacks, DNS
uses several types of server replication. Replication at the
authoritative server level can be achieved with (i) the deployment of
multiple servers for the same zone [RFC1035] (AT1--AT4 in Figure 1),
(ii) the use of IP anycast [RFC1546][RFC4786][RFC7094] that allows
the same IP address to be announced from multiple locations (each of
them referred to as anycast instance [RFC8499]) and (iii) by using
load balancers to support multiple servers inside a single
(potentially anycasted) instance. As a consequence, there are many
possible ways an authoritative DNS provider can engineer its
production authoritative server network, with multiple viable choices
and no single optimal design.
In the next sections we cover specific considerations (C1-C5) for
large authoritative DNS servers operators.
Moura, et al. Expires December 13, 2019 [Page 4]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
3. C1: Use equally strong IP anycast in every authoritative server (NS)
for better load distribution
Authoritative DNS servers operators announce their authoritative
servers as NS records[RFC1034]. Different authoritatives for a given
zone should return the same content, typically by staying
synchronized using DNS zone transfers (AXFR[RFC5936] and
IXFR[RFC1995]) to coordinate the authoritative zone data to return to
their clients.
DNS heavily relies upon replication to support high reliability,
capacity and to reduce latency [Moura16b]. DNS has two complementary
mechanisms to replicate the service. First, the protocol itself
supports nameserver replication of DNS service for a DNS zone through
the use of multiple nameservers that each operate on different IP
addresses, listed by a zone's NS records. Second, each of these
network addresses can run from multiple physical locations through
the use of IP anycast[RFC1546][RFC4786][RFC7094], by announcing the
same IP address from each instance and allowing Internet routing
(BGP[RFC4271]) to associate clients with their topologically nearest
anycast instance. Outside the DNS protocol, replication can be
achieved by deploying load balancers at each physical location.
Nameserver replication is recommended for all zones (multiple NS
records), and IP anycast is used by most large zones such as the DNS
Root, most top-level domains[Moura16b] and large commercial
enterprises, governments and other organizations.
Most DNS operators strive to reduce latency for users of their
service. However, because they control only their authoritative
servers, and not the recursive resolvers communicating with those
servers, it is difficult to ensure that recursives will be served by
the closest authoritative server. Server selection is up to the
recursive resolver's software implementation, and different software
vendors and releases employ different criteria to chose which
authoritative servers with which to communicate.
Knowing how recursives choose authoritative servers is a key step to
better engineer the deployment of authoritative servers.
[Mueller17b] evaluates this with a measurement study in which they
deployed seven unicast authoritative name servers in different global
locations and queried these authoritative servers from more than 9k
RIPE Atlas probes and and their respective recursive resolvers.
In the wild, [Mueller17b] found that recursives query all available
authoritative servers, regardless of the observed latency. But the
distribution of queries tend to be skewed towards authoritatives with
lower latency: the lower the latency between a recursive resolver and
an authoritative server, the more often the recursive will send
Moura, et al. Expires December 13, 2019 [Page 5]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
queries to that authoritative. These results were obtained by
aggregating results from all vantage points and not specific to any
vendor/version.
The hypothesis is that this behavior is a consequence of two main
criteria employed by resolvers when choosing authoritatives:
performance (lower latency) and diversity of authoritatives, where a
resolver checks all authoritative servers to determine which is
closer and to provide alternatives if one is unavailable.
For a DNS operator, this policy means that latency of all
authoritatives (NS records [RF:SJa-01]) matter, so all must be
similarly capable, since all available authoritatives will be queried
by most recursive resolvers. Since unicast cannot deliver good
latency worldwide (a unicast authoritative server in Europe will
always have high latency to resolvers in California, for example,
given its geographical distance), [Mueller17b] recommends to DNS
operators that they deploy equally strong IP anycast in every
authoritative server (ie.e, on each NS record [RF:SJa-01]), in terms
of number of instances and peering, and, consequently, to phase out
unicast, so they can deliver good latency values to global clients.
However, [Mueller17b] also notes that DNS operators should also take
architectural considerations into account when planning for deploying
anycast [RFC1546].
This consideration was deployed at the ".nl" TLD zone, which
originally had seven authoritative severs (mixed unicast/anycast
setup). .nl has moved in early 2018 to a setup with 4 anycast
authoritative name servers. This is not to say that .nl was the
first - other zones, have been running anycast only authoritatives
(e.g., .be since 2013). [Mueller17b] contribution is to show that
unicast cannot deliver good latency worldwide, and that anycast has
to be deployed to deliver good latency worldwide.
4. C2: Routing Can Matter More Than Locations
A common metric when choosing an anycast DNS provider or setting up
an anycast service is the number of anycast instances[RFC4786], i.e.,
the number of global locations from which the same address is
announced with BGP. Intuitively, one could think that more instances
will lead to shorter response times.
However, this is not necessarily true. In fact, [Schmidt17a] found
that routing can matter more than the total number of locations.
They analyzed the relationship between the number of anycast
instances and the performance of a service (latency-wise, RTT) and
measured the overall performance of four DNS Root servers, namely C,
F, K and L, from more than 7.9k RIPE Atlas probes.
Moura, et al. Expires December 13, 2019 [Page 6]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
[Schmidt17a] found that C-Root, a smaller anycast deployment
consisting of only 8 instances (they refer to anycast instance as
anycast site), provided a very similar overall performance than that
of the much larger deployments of K and L, with 33 and 144 instances
respectively. The median RTT for C, K and L Root was between
30-32ms.
Given that Atlas has better coverage in Europe than other regions,
the authors specifically analyzed results per region and per country
(Figure 5 in [Schmidt17a]), and show that Atlas bias to Europe does
not change the conclusion that location of anycast instances
dominates latency. [RF:Issue12]
[Schmidt17a] consideration for DNS operators when engineering anycast
services is consider factors other than just the number of instances
(such as local routing connectivity) when designing for performance.
They showed that 12 instances can provide reasonable latency, given
they are globally distributed and have good local interconnectivity.
However, more instances can be useful for other reasons, such as when
handling DDoS attacks [Moura16b].
5. C3: Collecting Detailed Anycast Catchment Maps Ahead of Actual
Deployment Can Improve Engineering Designs
An anycast DNS service may have several dozens or even more than one
hundred instances (such as L-Root does). Anycast leverages Internet
routing to distribute the incoming queries to a service's distributed
anycast instances; in theory, BGP (the Internet's defacto routing
protocol) forwards incoming queries to a nearby anycast instance (in
terms of BGP distance). However, usually queries are not evenly
distributed across all anycast instances, as found in the case of
L-Root [IcannHedge18].
Adding new instances to an anycast service may change the load
distribution across all instances, leading to suboptimal usage of the
service or even stressing some instances while others remain
underutilized. This is a scenario that operators constantly face
when expanding an anycast service. Besides, when setting up a new
anycast service instance, operators cannot directly estimate the
query distribution among the instances in advance of enabling the new
instance.
To estimate the query loads across instances of an expanding service
or a when setting up an entirely new service, operators need detailed
anycast maps and catchment estimates (i.e., operators need to know
which prefixes will be matched to which anycast instance). To do
that, [Vries17b] developed a new technique enabling operators to
carry out active measurements, using an open-source tool called
Moura, et al. Expires December 13, 2019 [Page 7]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
Verfploeter (available at [VerfSrc]). Verfploeter maps a large
portion of the IPv4 address space, allowing DNS operators to predict
both query distribution and clients catchment before deploying new
anycast instances.
[Vries17b] shows how this technique was used to predict both the
catchment and query load distribution for the new anycast service of
B-Root. Using two anycast instances in Miami (MIA) and Los Angeles
(LAX) from the operational B-Root server, they sent ICMP echo packets
to IP addresses to each IPv4 /24 on the Internet using a source
address within the anycast prefix. Then, they recorded which
instance the ICMP echo replies arrived at based on the Internet's BGP
routing. This analysis resulted in an Internet wide catchment map.
Weighting was then applied to the incoming traffic prefixes based on
of 1 day of B-Root traffic (2017-04-12, DITL datasets [Ditl17]). The
combination of the created catchment mapping and the load per prefix
created an estimate predicting that 81.6% of the traffic would go to
the LAX instance. The actual value was 81.4% of traffic going to
LAX, showing that the estimation was pretty close and the Verfploeter
technique was a excellent method of predicting traffic loads in
advance of a new anycast instance deployment ([Vries17b] also uses
the term anycast site to refer to anycast instance).
Besides that, Verfploeter can also be used to estimate how traffic
shifts among instances when BGP manipulations are executed, such as
AS Path prepending that is frequently used by production networks
during DDoS attacks. A new catchment mapping for each prepending
configuration configuration: no prepending, and prepending with 1, 2
or 3 hops at each instance. Then, [Vries17b] shows that this mapping
can accurately estimate the load distribution for each configuration.
An important operational takeaway from [Vries17b] is that DNS
operators can make informed choices when engineering new anycast
instances or when expending new ones by carrying out active
measurements using Verfploeter in advance of operationally enabling
the fully anycast service. Operators can spot sub-optimal routing
situations early, with a fine granularity, and with significantly
better coverage than using traditional measurement platforms such as
RIPE Atlas.
To date, Verfploeter has been deployed on B-Root[Vries17b], on a
operational testbed (Anycast testbed) [AnyTest], and on a large
unnamed operator.
The consideration is therefore to deploy a small test Verfploeter-
enabled platform in advance at a potential anycast instance may
reveal the realizable benefits of using that instance as an anycast
interest, potentially saving significant financial and labor costs of
Moura, et al. Expires December 13, 2019 [Page 8]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
deploying hardware to a new instance that was less effective than as
had been hoped.
6. C4: When under stress, employ two strategies
DDoS attacks are becoming bigger, cheaper, and more frequent
[Moura16b]. The most powerful recorded DDoS attack to DNS servers to
date reached 1.2 Tbps, by using IoT devices [Perlroth16]. Such
attacks call for an answer for the following question: how should a
DNS operator engineer its anycast authoritative DNS server react to
the stress of a DDoS attack? This question is investigated in study
[Moura16b] in which empirical observations are grounded with the
following theoretical evaluation of options.
An authoritative DNS server deployed using anycast will have many
server instances distributed over many networks. Ultimately, the
relationship between the DNS provider's network and a client's ISP
will determine which anycast instance will answer queries for a given
client, given that BGP is the protocol that maps clients to specific
anycast instances by using routing information [RF:KDar02]. As a
consequence, when an anycast authoritative server is under attack,
the load that each anycast instance receives is likely to be unevenly
distributed (a function of the source of the attacks), thus some
instances may be more overloaded than others which is what was
observed analyzing the Root DNS events of Nov. 2015 [Moura16b].
Given the fact that different instances may have different capacity
(bandwidth, CPU, etc.), making a decision about how to react to
stress becomes even more difficult.
In practice, an anycast instance under stress, overloaded with
incoming traffic, has two options:
o It can withdraw or pre-prepend its route to some or to all of its
neighbors, ([RF:Issue3]) perform other traffic shifting tricks
(such as reducing the propagation of its announcements using BGP
communities[RFC1997]) which shrinks portions of its catchment),
use FlowSpec [RFC5575] or other upstream communication mechanisms
to deploy upstream filtering. The goals of these techniques is to
perform some combination of shifting of both legitimate and attack
traffic to other anycast instances (with hopefully greater
capacity) or to block the traffic entirely.
o Alternatively, it can be become a degraded absorber, continuing to
operate, but with overloaded ingress routers, dropping some
incoming legitimate requests due to queue overflow. However,
continued operation will also absorb traffic from attackers in its
catchment, protecting the other anycast instances.
Moura, et al. Expires December 13, 2019 [Page 9]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
[Moura16b] saw both of these behaviors in practice in the Root DNS
events, observed through instance reachability and route-trip time
(RTTs). These options represent different uses of an anycast
deployment. The withdrawal strategy causes anycast to respond as a
waterbed, with stress displacing queries from one instance to others.
The absorption strategy behaves as a conventional mattress,
compressing under load, with some queries getting delayed or dropped.
Although described as strategies and policies, these outcomes are the
result of several factors: the combination of operator and host ISP
routing policies, routing implementations withdrawing under load, the
nature of the attack, and the locations of the instances and the
attackers. Some policies are explicit, such as the choice of local-
only anycast instances, or operators removing an instance for
maintenance or modifying routing to manage load. However, under
stress, the choices of withdrawal and absorption can also be results
that emerge from a mix of explicit choices and implementation
details, such as BGP timeout values.
[Moura16b] speculates that more careful, explicit, and automated
management of policies may provide stronger defenses to overload, an
area currently under study. For DNS operators, that means that
besides traditional filtering, two other options are available
(withdraw/prepend/communities or isolate instances), and the best
choice depends on the specifics of the attack.
Note that this consideration refers to the operation of one anycast
service, i.e., one anycast NS record. However, DNS zones with
multiple NS anycast services may expect load to spill from one
anycast server to another,as resolvers switch from authoritative to
authoritative when attempting to resolve a name [Mueller17b].
7. C5: Consider longer time-to-live values whenever possible
[RF:Issue7]: this section has been completely rewritten.
Caching is the cornerstone of good DNS performance and reliability.
A 15 ms response to a new DNS query is fast, but a 1 ms cache hit to
a repeat query is far faster. Caching also protects users from short
outages and can mute even significant DDoS attacks [Moura18b].
DNS record TTLs (time-to-live values) directly control cache
durations [RFC1034][RFC1035] and, therefore, affect latency,
resilience, and the role of DNS in CDN server selection. Some early
work modeled caches as a function of their TTLs [Jung03a], and recent
work examined their interaction with DNS[Moura18b], but no research
provides considerations about what TTL values are good. With this
Moura, et al. Expires December 13, 2019 [Page 10]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
goal Moura et. al. [Moura19a] carried out a measurement study
investigating TTL choices and its impact on user experience.
First, they identified several reasons why operators/zone owners may
want to choose longer or shorter TTLs:
o Longer caching results in faster responses, given that cache hits
are faster than cache misses in resolvers. [Moura19a] shows that
the change in TTL for .uy TLD from 1 day to 5 minutes reduced the
RTT from 15k Atlas vantage points significantly: the median was
reduced from 28.7ms to 8ms, while the 75%ile decreased from 183ms
to 21ms.
o Longer caching results in lower DNS traffic: authoritative servers
will experience less traffic if TTLs are extended, given that
repeated queries will be answered by resolver caches.
o Longer caching results in lower cost if DNS is metered: some DNS-
As-A-Service providers charges are metered, with a per query cost
(often added to a fixed monthly cost).
o Longer caching is more robust to DDoS attacks on DNS: DDoS attacks
on a DNS service provider harmed several prominent websites
[Perlroth16]. Recent work has shown that DNS caching can greatly
reduce the effects of DDoS on DNS, provided caches last longer
than the attack [Moura18b].
o Shorter caching supports operational changes: An easy way to
transition from an old server to a new one is to change the DNS
records. Since there is no method to remove cached DNS records,
the TTL duration represents a necessary transition delay to fully
shift to a new server, so low TTLs allow more rapid transition.
However, when deployments are planned in advance (that is, longer
than the TTL), then TTLs can be lowered ''just-before'' a major
operational change, and raised again once accomplished.
o Shorter caching can with DNS-based load balancing: Some DDoS-
scrubbing services use DNS to redirect traffic during an attack.
Since DDoS attacks arrive unannounced, DNS-based traffic
redirection requires the TTL be kept quite low at all times to be
ready to respond to a potential attack.
As such, choice of TTL depends in part on external factors so no
single recommendation is appropriate for all. Organizations must
weigh these trade-offs to find a good balance. Still, some
guidelines can be used when choosing TTLs:
Moura, et al. Expires December 13, 2019 [Page 11]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
o For general users, [Moura19a] recommends longer TTLs, of at least
one hour, and ideally 4, 8, 12, or 24 hours. Assuming planned
maintenance can be scheduled at least a day in advance, long TTLs
have little cost.
o For TLD operators: TLD operators that allow public registration of
domains (such as most ccTLDs and .com, .net, .org) host, in their
zone files, NS records (and glues if in-bailiwick) of their
respective domains. [Moura19a] shows that most resolvers will use
TTL values provided by the child delegations, but some will choose
the TTL provided by the parents. As such, similarly to general
users, [Moura19a] recommends longer TTLs for NS records of their
delegations (at least one hour, preferably more).
o Users of DNS-based load balancing or DDoS-prevention may require
short TTLs: TTLs may be as short as 5 minutes, although 15 minutes
may provide sufficient agility for many operators. Shorter TTLs
here help agility; they are are an exception to the consideration
for longer TTLs.
o Use A/AAAA and NS records: TTLs of A/AAAA records should be
shorter or equal to the TTL for NS records for in-bailiwick
authoritative DNS servers, given that the authors [Moura19a] found
that, for such scenarios, once NS record expires, their associated
A/AAAA will also be updated (glue is sent by the parents). For
out-of-bailiwick servers, A and NS records are usually cached
independently, so different TTLs, if desired, will be effective.
In either case, short A and AAAA records may be desired if DDoS-
mitigation services are an option.
8. Security considerations
This document suggests the use of [I-D.ietf-dnsop-serve-stale]. It
be noted that usage of such methods may affect data integrity of DNS
information. This document describes methods of mitigating changes
of a denial of service threat within a DNS service.
As this document discusses research, there are no further security
considerations, other than the ones mentioned in the normative
references.
9. Privacy Considerations
This document does not add any practical new privacy issues.
Moura, et al. Expires December 13, 2019 [Page 12]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
10. IANA considerations
This document has no IANA actions.
11. Acknowledgements
This document is a summary of the main considerations of six research
works referred in this document. As such, they were only possible
thanks to the hard work of the authors of these research works.
The authors of this document are also co-authors of these research
works. However, not all thirteen authors of these research papers
are also authors of this document. We would like to thank those not
included in this document's author list for their work: Ricardo de O.
Schmidt, Wouter B de Vries, Moritz Mueller, Lan Wei, Cristian
Hesselman, Jan Harm Kuipers, Pieter-Tjerk de Boer and Aiko Pras.
We would like also to thank the various reviewers of different
versions of this draft: Duane Wessels, Joe Abley, Toema Gavrichenkov,
John Levine, Michael StJohns, Kristof Tuyteleers, Stefan Ubbink,
Klaus Darilion and Samir Jafferali, and comments provided at the IETF
DNSOP session (IETF104).
Besides those, we would like thank those who have been individually
thanked in each research work, RIPE NCC and DNS OARC for their tools
and datasets used in this research, as well as the funding agencies
sponsoring the individual research works.
12. References
12.1. Normative References
[I-D.ietf-dnsop-serve-stale]
Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data
to Improve DNS Resiliency", draft-ietf-dnsop-serve-
stale-05 (work in progress), April 2019.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC1546] Partridge, C., Mendez, T., and W. Milliken, "Host
Anycasting Service", RFC 1546, DOI 10.17487/RFC1546,
November 1993, <https://www.rfc-editor.org/info/rfc1546>.
Moura, et al. Expires December 13, 2019 [Page 13]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
[RFC1995] Ohta, M., "Incremental Zone Transfer in DNS", RFC 1995,
DOI 10.17487/RFC1995, August 1996,
<https://www.rfc-editor.org/info/rfc1995>.
[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
<https://www.rfc-editor.org/info/rfc1997>.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, DOI 10.17487/RFC2181, July 1997,
<https://www.rfc-editor.org/info/rfc2181>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4786] Abley, J. and K. Lindqvist, "Operation of Anycast
Services", BCP 126, RFC 4786, DOI 10.17487/RFC4786,
December 2006, <https://www.rfc-editor.org/info/rfc4786>.
[RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
and D. McPherson, "Dissemination of Flow Specification
Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
<https://www.rfc-editor.org/info/rfc5575>.
[RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
(AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
<https://www.rfc-editor.org/info/rfc5936>.
[RFC7094] McPherson, D., Oran, D., Thaler, D., and E. Osterweil,
"Architectural Considerations of IP Anycast", RFC 7094,
DOI 10.17487/RFC7094, January 2014,
<https://www.rfc-editor.org/info/rfc7094>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
12.2. Informative References
[AnyTest] Schmidt, R., "Anycast Testbed", December 2018,
<http://www.anycast-testbed.com/>.
[Ditl17] OARC, D., "2017 DITL data", October 2018,
<https://www.dns-oarc.net/oarc/data/ditl/2017>.
Moura, et al. Expires December 13, 2019 [Page 14]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
[IcannHedge18]
ICANN, ., "DNS-STATS - Hedgehog 2.4.1", October 2018,
<http://stats.dns.icann.org/hedgehog/>.
[Jung03a] Jung, J., Berger, A., and H. Balakrishnan, "Modeling TTL-
based Internet caches", ACM 2003 IEEE INFOCOM,
DOI 10.1109/INFCOM.2003.1208693, July 2003,
<http://www.ieee-infocom.org/2003/papers/11_01.PDF>.
[Moura16b]
Moura, G., Schmidt, R., Heidemann, J., Mueller, M., Wei,
L., and C. Hesselman, "Anycast vs DDoS Evaluating the
November 2015 Root DNS Events.", ACM 2016 Internet
Measurement Conference, DOI /10.1145/2987443.2987446,
October 2016,
<https://www.isi.edu/~johnh/PAPERS/Moura16b.pdf>.
[Moura18b]
Moura, G., Heidemann, J., Mueller, M., Schmidt, R., and M.
Davids, "When the Dike Breaks: Dissecting DNS Defenses
During DDos", ACM 2018 Internet Measurement Conference,
DOI 10.1145/3278532.3278534, October 2018,
<https://www.isi.edu/~johnh/PAPERS/Moura18b.pdf>.
[Moura19a]
Moura, G., Heidemann, J., Schmidt, R., and W. Hardaker,
"TBA", June 2019,
<https://www.isi.edu/~johnh/PAPERS/Moura19a.pdf>.
[Mueller17b]
Mueller, M., Moura, G., Schmidt, R., and J. Heidemann,
"Recursives in the Wild- Engineering Authoritative DNS
Servers.", ACM 2017 Internet Measurement Conference,
DOI 10.1145/3131365.3131366, October 2017,
<https://www.isi.edu/%7ejohnh/PAPERS/Mueller17b.pdf>.
[Perlroth16]
Perlroth, N., "Hackers Used New Weapons to Disrupt Major
Websites Across U.S.", October 2016,
<https://www.nytimes.com/2016/10/22/business/
internet-problems-attack.html>.
[Schmidt17a]
Schmidt, R., Heidemann, J., and J. Kuipers, "Anycast
Latency - How Many Sites Are Enough. In Proceedings of the
Passive and Active Measurement Workshop", PAM Passive and
Active Measurement Conference, March 2017,
<https://www.isi.edu/%7ejohnh/PAPERS/Schmidt17a.pdf>.
Moura, et al. Expires December 13, 2019 [Page 15]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
[Sigla2014]
Singla, A., Chandrasekaran, B., Godfrey, P., and B. Maggs,
"The Internet at the speed of light. In Proceedings of the
13th ACM Workshop on Hot Topics in Networks (Oct 2014)",
ACM Workshop on Hot Topics in Networks, October 2014,
<http://speedierweb.web.engr.illinois.edu/cspeed/papers/
hotnets14.pdf>.
[VerfSrc] Vries, W., "Verfploeter source code", November 2018,
<https://github.com/Woutifier/verfploeter>.
[Vries17b]
Vries, W., Schmidt, R., Hardaker, W., Heidemann, J., Boer,
P., and A. Pras, "Verfploeter - Broad and Load-Aware
Anycast Mapping", ACM 2017 Internet Measurement
Conference, DOI 10.1145/3131365.3131371, October 2017,
<https://www.isi.edu/%7ejohnh/PAPERS/Vries17b.pdf>.
Authors' Addresses
Giovane C. M. Moura
SIDN Labs/TU Delft
Meander 501
Arnhem 6825 MD
The Netherlands
Phone: +31 26 352 5500
Email: giovane.moura@sidn.nl
Wes Hardaker
USC/Information Sciences Institute
PO Box 382
Davis 95617-0382
U.S.A.
Phone: +1 (530) 404-0099
Email: ietf@hardakers.net
John Heidemann
USC/Information Sciences Institute
4676 Admiralty Way
Marina Del Rey 90292-6695
U.S.A.
Phone: +1 (310) 448-8708
Email: johnh@isi.edu
Moura, et al. Expires December 13, 2019 [Page 16]
Internet-Draft Considerations-Large-Auth-DNS-Ops June 2019
Marco Davids
SIDN Labs
Meander 501
Arnhem 6825 MD
The Netherlands
Phone: +31 26 352 5500
Email: marco.davids@sidn.nl
Moura, et al. Expires December 13, 2019 [Page 17]