[ga] More Root-Servers?
Yesterday suggestions were made here for placing root-servers more
geographically spread around the world. The problem is that 13 is
Below an idea that RIPE (which operates K) is considering. In short:
there would be several machines with the same IP number in different
places using anycast. So there would in fact be more root-servers that
appear to be just one of the 13.
---------- Forwarded message ----------
Date: Tue, 05 Nov 2002 13:12:22 +0100
From: Daniel Karrenberg <Daniel.Karrenberg@ripe.net>
To: RIPE DNS WG <email@example.com>
Cc: RIPE Routing WG <firstname.lastname@example.org>
Subject: Distributing K-Root Service by Anycast Routing
below you find the proposal to start distributing the service
of k.root-servers.net by using anycast. I welcome comments
and suggestions either privately or on the DNS WG list.
I would like to see a good discussion so that we can proceed
with support from the RIPE community. Can we have this
discussion on the DNS WG list too please? In particular
I would like to hear technical suggestions for Appendix A.
Distributing K-Root Service by Anycast Routing of
$Id: k-any.ms,v 1.9 2002/11/05 12:03:32 dfk Exp $
This memo proposes to distribute the DNS ser-
vice provided by k.root-servers.net across multi-
ple locations in the Internet topology. It dis-
cusses the motivation for and the principles of
implementation. A first inventory of detailed
issues is provided in an appendix.
DNS root name servers need to be accessible by Internet
hosts in order for the DNS to function properly. Accessi-
bility is determined by the ability of the server to handle
a given query load and by the connectivity of the server to
the rest of the Internet.
The RIPE NCC operates k.root-servers.net (K-root) in the
RIPE region in order to help safeguard the quality of the
DNS in the Internet and in the RIPE region in particular.
The RIPE NCC obtains guidance from RIPE.
For K-root the connectivity issue has been addressed by
placing it at the LINX, a topologically very well connected
point. The server load issue has been addressed by deploy-
ing successive generations of hardware with increased pro-
cessing power and by distributing the load locally among a
number of machines at different LINX sites. A cold spare
system has been available in Amsterdam at all times to pro-
vide continuity in case of catastrophic failures at the pri-
mary server location. Over the years this set-up has pro-
vided very reliable service.
However issues about differences in connectivity to the ser-
vice across the RIPE region have been raised repeatedly. A
more distributed provision of the service is generally seen
as positive because of
- lower network delays due to shorter paths between
clients and servers,
- less dependence on connectivity to a single location,
- better load and DDoS attack resiliance because of dis-
- more overall redundancy.
For these reasons numerous organisations have offered to
host additional servers operated by the RIPE NCC. So far
this has not been considered because the number of unique IP
addresses at which the service can be provided is exhausted
by currently assigned servers.
2. Scope of this Memo
This memo proposes to deploy multiple servers providing
k.root-servers.net name service across the RIPE region, each
using the same IP address. This is commonly called 'any-
casting'. A detailed description of one implementation can
be found in RFC3258. The intention of this memo is to
establish the principles of this, inventarise the major
issues and request comments from the RIPE community and
other interested parties. An initial inventory of detailed
issues is provided as an appendix.
Simply put the RIPE NCC will provide K-root name service at
multiple locations dispersed over the Internet topology but
at the same IP address. No DNS client/resolver changes are
necessary. The service will appear exactly the same for the
users. Normal Internet routing will distribute the traffic
among the different instances of K-root.
This will be implemented by installing multiple copies of
the current server sets at different points and announcing
the current prefix 193.0.14/24 from these points.
The main challenge with this set-up is to ensure consis-
All servers will be operated in a consistent way by the
RIPE NCC. They will have appropriate out-of-band
access path to ensure that the operations centre can
The availability and responses will be monitored by
dedicated monitoring systems installed at multiple
locations. Also the BGP propagation of the prefix
193.0.14/24 will be monitored constantly by the exist-
ing remote route collectors. [http://www.ripe.net/ris]
Users will be able to identify the particular instance
they are using by published methods using DNS queries.
The correctness and authenticity of the root zone data
will eventually be guaranteed using DNSSEC. Until this
can be deployed the current method will need to be
employed: ISPs will need to closely monitor where they
route traffic to 193.0.14/24 and from where they accept
traffic from that address. The RIPE NCC will publish
and maintain a list with the locations of the k-root
instances, the BGP autonomous system numbers of their
immediate neighbors and any other information that can
help ISPs and others to ensure that they reach an
authentic instance of K-root. This list will be main-
tained until appropriate routing security technology is
The RIPE NCC and K-root itself are well suited for this mode
of operation. IANA asked the RIPE NCC to operate K-root,
the geographic and topological location of K-root was not
specified in any way other than "somewhere in the RIPE
region". The RIPE NCC was chosen because it is neutral and
professional but above all directly accountable to RIPE and
The location at the LINX was subsequently chosen based on
evaluation of the Internet topology in the region and a rec-
ommendation by the RIPE DNS working group. Distributing K-
root over a number of places is a natural continuation of
In addition to operating K-root at a remote location the
RIPE NCC has considerable experience in operating dis-
tributed services. The Test Traffic Measurements Service
operates more than 80 machines all over the world to collect
performance measurements. Some of these can be used to mon-
itor the DNS service of K-root as well. The Routing Infor-
mation Service operates 9 remote route collectors at
exchange points all over the world to collect BGP routing
information. These route collectors will be used to monitor
the routing of 193.0.14/24.
At any point in time there is a trade-off between the added
benefit of adding more servers and the difficulty of operat-
ing them consistently. The optimal number of servers
depends on a large number of constantly changing factors.
It needs to be evaluated continuously as things progress.
4. Operational & Funding Models
For the purpose of stability and for gaining experience all
instances of K-root will be operated by the RIPE NCC. This
ensures smooth transitions, consistency and correctness of
root zone data.
After the initial deployment there are a number of possible
operational and funding models.
Traditionally K-root operations have been part of general
RIPE NCC activities and thus have been collectively funded
by the RIPE NCC membership. This is an appropriate funding
model as all members benefit from stable root name service.
It is also easy to administer. Difficulties may arise when
the number of locations is such that the operational costs
increase very significantly. Another important drawback of
this model is that the number of additional sites will be
limited by available funds and the sites will have to be
determined by a selection procedure based on criteria
- position in Internet topology,
- position relative to existing K-root instances,
- local operations support,
- operational requirements [rfc2870],
- commitment to fund operations at a later stage.
4.2. Location Fees
The drawbacks of the traditional model can be largely over-
come by charging the organisations hosting K-root instances
a fee that covers the operational costs. This obviously
scales better and requires less of a beauty contest, because
the funds available will more closely match the operational
costs. It is quite possible that the initial demand will be
higher than the operational capabilities of the RIPE NCC.
Also it should be observed that in funding and some other
aspects this is exactly the opposite of the traditional
model: In the traditional model the RIPE NCC pays facilities
management fees to the hosts whereas in this model the hosts
Transition should be planned carefully.
4.3. Operated and Funded Decentrally
In this model anyone who wishes would be able to operate a
K-root instance. This model has such serious problems with
guaranteeing stability and consistency that it cannot be
implemented today or in the near future. The minimum
requirement for this operational mode is a zone signing
mechanism that ensures consistency and authenticity of root
zone data. Implementing this also requires a changed model
of service responsibility as it is obviously impossible to
hold any one entity responsible for the service. While this
may ultimately scale the best, it is extremely premature at
We propose to continue with the traditional model for now
and explore other models while gaining operational experi-
ence. The associated selection procedures will be executed
by the RIPE NCC and guided by the relevant requirements RFCs
and the RIPE DNS working group.
5. Implementation Plan
5.1. Initial BGP change
The routing announcements of the current server prefix
193.0.14/24 will change from AS5459 (LINX) to the dedicated
new K-root autonomous system number AS25152.
ISPs need to be aware of this and adapt their routing fil-
ters accordingly. It is recommended that ISPs who do not
already do so, take precautions, safeguaring that they
receive this prefix from an authentic K-root via a trusted
path and that they route traffic to it via trusted paths as
far as possible. At the same time an initial set of BGP and
DNS service monitors will be deployed.
5.2. Move the Cold Standby to Service
The current cold standby server at the RIPE NCC will be
activated as a regular server. AS25152 will be announced
also by the RIPE NCC at the AMS-IX. As the server is
already available and configured this can be done fairly
rapidly. The distribution of the load, BGP routing informa-
tion and other operational data will be gathered and evalu-
ated. ISPs will have the opportunity to test this set-up
and provide feedback. In case of problems the RIPE NCC
instance of K-root will be deactivated quickly, returning to
the previous service level.
5.3. Implement Further Instances
While monitoring continuously a number of further instances
of K-root will be deployed. Currently we expect this to be
about 5 additional instances. This number is limited by
operational and monitoring capacity. It is important not to
deploy more instances than can safely be operated and moni-
tored. Especially the capacity to detect and correct prob-
lems in this distributed set-up needs to be carefully moni-
5.4. Spreading Further
Planning further than this is currently difficult because of
lack of experience with distributed K-root operations and
possible funding models.
The author would like to thank Joao Silva Damas for comments
on an earlier draft as well as Andrei Robachevsky and Henk
Uijterwaal who provided comments on recent drafts.
Appendix A - Detailed Issues
Using a router or having a server speak BGP?
Withdrawing BGP announcements based on service availability?
Distributed service monitoring: Using current RIPE NCC oper-
ated machines all over the world is an easy option. Maybe
distributing automatic monitoring software to be run by vol-
unteers is another. What is essentially needed is to try a
small number of queries periodically including the query
identifying the instance of the server. Then transmitting
the results back to a (set of) collection point(s).
Distributed BGP Monitoring: The RIS can be used for this.
Coverage should be sufficient.
Information Campaign: What is needed to reach all ISPs that
need to know? How long a lead time do they need for the var-
ious stages of the deployment?
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