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Network Working Group                                        P. Regnauld
Internet-Draft                                               catpipe ApS
Intended status: Informational                             S. Bortzmeyer
Expires: June 22, 2007                                             AFNIC
                                                       December 19, 2006

         Requirments for the Nameserver Communication protocol

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   Copyright (C) The Internet Society (2006).

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Internet-Draft          Nameserver communication           December 2006


   This document describes the requirments for a protocol to allow DNS
   nameservers to communicate among themselves, possibly outside the
   existing DNS protocol, for purposes of zone discovery and
   provisioning and remote management.

Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Use cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     3.1.  Having a homogeneous view of non-standard zones  . . . . .  5
     3.2.  Exchanging secondary name service with partners  . . . . .  5
     3.3.  Managing remote name servers . . . . . . . . . . . . . . .  5
   4.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  7
   5.  The requirments  . . . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     7.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Related work  . . . . . . . . . . . . . . . . . . . . 12
   Appendix B.  Acknowledgements  . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
   Intellectual Property and Copyright Statements . . . . . . . . . . 15

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1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [3].

   As in other RFC describing requirments (such as [5]), the MUST and
   MUST NOT have to be interpreted in terms of the protocol, not in
   terms of the implementation.  If this document says that the
   protocole MUST do something, it means that the protocol must have a
   way to describe this "something", not that every implementation has
   to implement it or that every running instance has to allow it.  For
   instance, the AXFR zone transfer of the DNS is a MUST of the protocol
   but an implementation may omit it and a specific nameserver is
   certainly free to disable it.

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2.  Introduction

   Administrators of DNS ([1], [2]) Nameservers often need to
   communicate to exchange meta-information, which cannot be distributed
   by the DNS, or to request various administrative tasks such as the
   provisioning of a new zone or querying the list of managed zones.
   Currently, this is done by ad hoc means, often manually.  When a
   formal protocol exists (see Appendix A), it is always proprietary and
   undocumented.  We believe it would be nice to have a "nameserver
   communication" protocol to address these needs.

   This document specifies the requirments for such a protocol.  The
   choice is to define one protocol for all the currently out-of-band
   tasks of nameserver management.  The rationale is that each task is
   quite simple and relatively easy to define so one protocol for each
   task would be overkill.

   The use cases below describe typical scenarios where such a protocol
   would be useful for the nameserver administrators.

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3.  Use cases

3.1.  Having a homogeneous view of non-standard zones

   If an organization uses non-standard zones (such as a purely-local
   TLD, but not only), synchronizing all the nameservers so they all see
   these zones is usually a time-consuming task.  It is even worse if
   two such organizations merge.

   This is typically done, when using BIND ([7]), with "stub" or
   "forward" zones.  But there is no way to ensure automatically that
   all the resolvers have the same set of zones at a given time, as new
   zones may be added locally, without the other nameservers being
   updated to reflect the change.  The problem can be mitigated by
   concentrating DNS queries through a core set of nameservers, but
   these still require to be updated when zones are added on the various

   Though the architecture described above is not recommended, such
   scenarios do happen in the wild, especially when several large
   organizations are connected together.

3.2.  Exchanging secondary name service with partners

   A large ISP may manage thousands of zones.  For reliability reasons,
   following [4], it should have secondary nameservers placed in widely
   different geographic areas.  A common solution is to establish cross-
   hosting agreeements (zone exchange) with a partner in the "I'll host
   your zones and you'll host mine" fashion.

   In the absence of a standard protocol to discover the available zones
   in the scope of this agreement (one server may be secondary for
   several other organizations), such exchange of service has to be done
   manually, each time a zone is created or deleted, or through
   proprietary means such as email in a structured, authenticated

   The above is equally true for the management of nameservers within a
   single organization, in order to provision secondary nameservers
   located in affiliate / branch offices from a central location in an
   automatic fashion.

3.3.  Managing remote name servers

   To implement the recommandations of [4], a one-site organization
   typically needs to request secondary hosting located on a distinct
   organization's premises.

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   Many ccTLDs do so, for instance.  But, in that case, the
   "outsourcing" organization has typically no control of the
   nameservers.  Changing the IP address of the master nameserver, or
   forcing a reload when a SOA serial number accidentally wrapped is a
   manual operation at the remote site, and may require the
   intervention, and availablity, of the staff at the remote

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4.  Terminology

   Since the two participants in a conversation are servers, we use the
   following vocabulary:

   o  Requestor: the server which requests something (an information or
      an action),

   o  Responder: the server which will reply and may be act.

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5.  The requirments

   The protocol:

   1.   MUST allow the requestor to authenticate the responder and vice-

   2.   MUST allow the communication to be hidden from snoopers (relying
        on a transport like TLS - [6] - is possible).

   3.   MUST provide anti-replay protection (making all the requests
        idempotent is a possible way),

   4.   MUST provide a standard vocabulary to express the types of zones
        ("master" or "slave" but also the non-standard terms "stub" and
        "forward" in BIND, zones for which the responder is
        authoritative but does not have the data itself).

   5.   MUST honor existing definition of views based on predefined
        shared key or IP address scope, so that information specific to
        a particular view, and only this information, will be returned
        to the requestor if the requestor's credentials match those of
        the defined view (for example, a zone may be of type master in
        one view, and forward in another).  DISCUSSION: a requestor can
        manage views where its IP address would show it another view.
        May be explicitely naming views would be better?

   6.   MUST provide a way to query a responder on the zones it serves
        with authority.  The response format MUST allow to carry other
        information besides the zone name, such as the type of the zone.

   7.   MUST provide a way to request the provisioning of a new zone.
        It MUST allow for at least the following parameters:

        1.  IP address(es) of the master(s),

        2.  type of the zone,

        3.  and may be contact information?

   8.   MUST allow a way to tell the responder, if it is acting as a
        slave, to reload a zone, regardless of the current value of the
        SOA serial number.

   9.   SHOULD be implementable as a one request / one response system
        where the request is self-sufficient and carries all the
        information that the responder needs.  Such a system would allow
        for various transports such as email or simple TCP mapping.

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   10.  MAY provide a standard vocabulary to express protections (ACL)
        for a zone.  DISCUSSION: it would be a very good thing but
        standardizing ACL language may be a daunting task.  A simpler
        solution may be simply to have a boolean telling if the zone is
        private (internal to an organization) or public.  Additionnally,
        it may be required to implement a concept of scope, so that it
        can be specified which agreement the zone is bound to (in the
        case of many-to-many secondary cross-hosting relationships).
        (Another way to implement scope could be to use the identity of
        the requestor, since it is authenticated.  See the next

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6.  Security Considerations

   Allowing remote configuration of a nameserver is a very sensitive
   issue, particularly when said server may be serving other third-party
   zones.  Therefore the security requirments listed above (allowing
   reciprocal authentication and protection against snoopers) are a

   There are no other requirments for the protocol itself but, for the
   implementations, it is reasonable to ask that, by default, all
   requests via this protocol must be denied.

   In the same way, authorisation of requestors, once they are
   authentified by the protocol, is up to the implementations.  They
   should allow fine-grained configuration of permissions.  Implementors
   should be warned that the authorized requestors of a responder may
   not trust each other.

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7.  References

7.1.  Normative References

   [1]  Mockapetris, P., "Domain names - concepts and facilities",
        STD 13, RFC 1034, November 1987.

   [2]  Mockapetris, P., "Domain names - implementation and
        specification", STD 13, RFC 1035, November 1987.

   [3]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

7.2.  Informative References

   [4]  Elz, R., Bush, R., Bradner, S., and M. Patton, "Selection and
        Operation of Secondary DNS Servers", BCP 16, RFC 2182,
        July 1997.

   [5]  Newton, A., "Cross Registry Internet Service Protocol (CRISP)
        Requirements", RFC 3707, February 2004.

   [6]  Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
        Protocol Version 1.1", RFC 4346, April 2006.

   [7]  ISC, "Berkeley Internet Name Domain is an implementation of the
        Domain Name System (DNS) protocols", October 2006,

   [8]  Hubert, "PowerDNS, an advanced high performance authoritative
        nameserver", March 2006, <http://wiki.powerdns.com/>.

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Appendix A.  Related work

   PowerDNS ([8]) has a proprietary protocol, Supermaster, which allows
   remote provisioning of zones: See

   Microsoft AD/DNS and Infoblox also have such a protocol: a zone
   created on the master can be created automatically on the slaves.

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Appendix B.  Acknowledgements

   The original idea came from Bert Hubert.  Edward Lewis, by its nice
   explanations on the bind-users mailing list, helped a lot.  Useful
   comments from Mohsen Souissi were integrated.

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Authors' Addresses

   Phil Regnauld
   catpipe ApS
   Snaregade 12, 2tv
   Copenhagen K  1205

   Email: regnauld@catpipe.net

   Stephane Bortzmeyer
   Immeuble International
   Saint-Quentin-en-Yvelines  78181

   Phone: +33 1 39 30 83 46
   Email: bortzmeyer+ietf@nic.fr
   URI:   http://www.afnic.fr/

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