draft-ietf-dnsop-serverid-08.txt   rfc4892.txt 
Network Working Group S. Woolf Network Working Group S. Woolf
Internet-Draft Internet Systems Consortium, Inc. Request for Comments: 4892 Internet Systems Consortium, Inc.
Intended Status: Informational D. Conrad Category: Informational D. Conrad
Expires: July 26, 2007 ICANN ICANN
January 22, 2007
Requirements for a Mechanism Identifying a Name Server Instance Requirements for a Mechanism Identifying a Name Server Instance
draft-ietf-dnsop-serverid-08
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Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
With the increased use of DNS anycast, load balancing, and other With the increased use of DNS anycast, load balancing, and other
mechanisms allowing more than one DNS name server to share a single mechanisms allowing more than one DNS name server to share a single
IP address, it is sometimes difficult to tell which of a pool of name IP address, it is sometimes difficult to tell which of a pool of name
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Identifying which name server is responding to queries is often Identifying which name server is responding to queries is often
useful, particularly in attempting to diagnose name server useful, particularly in attempting to diagnose name server
difficulties. This is most obviously useful for authoritative difficulties. This is most obviously useful for authoritative
nameservers in the attempt to diagnose the source or prevalence of nameservers in the attempt to diagnose the source or prevalence of
inaccurate data, but can also conceivably be useful for caching inaccurate data, but can also conceivably be useful for caching
resolvers in similar and other situations. Furthermore, the ability resolvers in similar and other situations. Furthermore, the ability
to identify which server is responding to a query has become more to identify which server is responding to a query has become more
useful as DNS has become more critical to more Internet users, and as useful as DNS has become more critical to more Internet users, and as
network and server deployment topologies have become more complex. network and server deployment topologies have become more complex.
The traditional means for determining which of several possible The conventional means for determining which of several possible
servers is answering a query has traditionally been based on the use servers is answering a query has traditionally been based on the use
of the server's IP address as a unique identifier. However, the of the server's IP address as a unique identifier. However, the
modern Internet has seen the deployment of various load balancing, modern Internet has seen the deployment of various load balancing,
fault-tolerance, or attack-resistance schemes such as shared use of fault-tolerance, or attack-resistance schemes such as shared use of
unicast IP addresses as documented in [RFC3258]. An unfortunate side unicast IP addresses as documented in [RFC3258]. An unfortunate side
effect of these schemes has been to make the use of IP addresses as effect of these schemes has been to make the use of IP addresses as
identifiers associated with DNS (or any other) service somewhat identifiers associated with DNS (or any other) service somewhat
problematic. Specifically, multiple dedicated DNS queries may not go problematic. Specifically, multiple dedicated DNS queries may not go
to the same server even though sent to the same IP address. Non-DNS to the same server even though sent to the same IP address. Non-DNS
methods such as ICMP ping, TCP connections, or non-DNS UDP packets methods such as ICMP ping, TCP connections, or non-DNS UDP packets
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unique "server that answered the query I sent to IP address A.B.C.D". unique "server that answered the query I sent to IP address A.B.C.D".
The widespread use of the existing convention suggests a need for a The widespread use of the existing convention suggests a need for a
documented, interoperable means of querying the identity of a documented, interoperable means of querying the identity of a
nameserver that may be part of an anycast or load-balancing cluster. nameserver that may be part of an anycast or load-balancing cluster.
At the same time, however, it also has some drawbacks that argue At the same time, however, it also has some drawbacks that argue
against standardizing it as it's been practiced so far. against standardizing it as it's been practiced so far.
2. Existing Conventions 2. Existing Conventions
For some time, the commonly deployed Berkeley Internet Name Domain For some time, the commonly deployed Berkeley Internet Name Domain
implementation of the DNS protocol suite from the Internet Systems (BIND) implementation of the DNS protocol suite from the Internet
Consortium [BIND] has supported a way of identifying a particular Systems Consortium [BIND] has supported a way of identifying a
server via the use of a standards-compliant, if somewhat unusual, DNS particular server via the use of a standards-compliant, if somewhat
query. Specifically, a query to a recent BIND server for a TXT unusual, DNS query. Specifically, a query to a recent BIND server
resource record in class 3 (CHAOS) for the domain name for a TXT resource record in class 3 (CHAOS) for the domain name
"HOSTNAME.BIND." will return a string that can be configured by the "HOSTNAME.BIND." will return a string that can be configured by the
name server administrator to provide a unique identifier for the name server administrator to provide a unique identifier for the
responding server. (The value defaults to the result of a responding server. (The value defaults to the result of a
gethostname() call). This mechanism, which is an extension of the gethostname() call). This mechanism, which is an extension of the
BIND convention of using CHAOS class TXT RR queries to sub-domains of BIND convention of using CHAOS class TXT RR queries to sub-domains of
the "BIND." domain for version information, has been copied by the "BIND." domain for version information, has been copied by
several name server vendors. several name server vendors.
A refinement to the BIND-based mechanism, which dropped the A refinement to the BIND-based mechanism, which dropped the
implementation-specific label, replaces "BIND." with "SERVER.". Thus implementation-specific label, replaces "BIND." with "SERVER.". Thus
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situations in which this simply isn't reliable. situations in which this simply isn't reliable.
2. It reserves an entire class in the DNS (CHAOS) for what amounts 2. It reserves an entire class in the DNS (CHAOS) for what amounts
to one zone. While CHAOS class is defined in [RFC1034] and to one zone. While CHAOS class is defined in [RFC1034] and
[RFC1035], it's not clear that supporting it solely for this [RFC1035], it's not clear that supporting it solely for this
purpose is a good use of the namespace or of implementation purpose is a good use of the namespace or of implementation
effort. effort.
3. The initial and still common form, using "BIND.", is 3. The initial and still common form, using "BIND.", is
implementation specific. BIND is one DNS implementation. At the implementation specific. BIND is one DNS implementation. At the
time of this writing, it is probably the most prevalent for time of this writing, it is probably most prevalent for
authoritative servers. This does not justify standardizing on authoritative servers. This does not justify standardizing on
its ad hoc solution to a problem shared across many operators and its ad hoc solution to a problem shared across many operators and
implementors. Meanwhile, the aforementioned refinement changes implementors. Meanwhile, the aforementioned refinement changes
the query label but preserves the ad hoc CHAOS/TXT mechanism. the query label but preserves the ad hoc CHAOS/TXT mechanism.
4. There is no convention or shared understanding of what 4. There is no convention or shared understanding of what
information an answer to such a query for a server identity could information an answer to such a query for a server identity could
or should contain, including a possible encoding or or should contain, including a possible encoding or
authentication mechanism. authentication mechanism.
5. Hypothetically, since DNSSEC has been defined to cover all DNS 5. Hypothetically, since DNSSEC has been defined to cover all DNS
classes, the TXT RRs returned in response to the "ID.SERVER." classes, the TXT RRs returned in response to the "ID.SERVER."
query could be signed, which has the advantages described in query could be signed, which has the advantages described in
[RFC4033]. However, since DNSSEC deployment for the CHAOS class [RFC4033]. However, since DNSSEC deployment for the CHAOS class
is neither existent nor foreseeable, and since the "ID.SERVER." is neither existent nor foreseeable, and since the "ID.SERVER."
TXT RR is expected to be unique per server, this would be TXT RR is expected to be unique per server, this would be
impossible in practice. impossible in practice.
The first of the listed disadvantages may be technically the most The first of the listed disadvantages may be technically the most
serious. It argues for an attempt to design a good answer to the serious. It argues for an attempt to design a good answer to the
problem that "I need to know what nameserver is answering my problem, "I need to know what nameserver is answering my queries",
queries", not simply a convenient one. not simply a convenient one.
3. Characteristics of an Implementation Neutral Convention 3. Characteristics of an Implementation Neutral Convention
The discussion above of advantages and disadvantages to the The discussion above of advantages and disadvantages to the
"HOSTNAME.BIND." mechanism suggest some requirements for a better "HOSTNAME.BIND." mechanism suggest some requirements for a better
solution to the server identification problem. These are summarized solution to the server identification problem. These are summarized
here as guidelines for any effort to provide appropriate protocol here as guidelines for any effort to provide appropriate protocol
extensions: extensions:
1. The mechanism adopted must be in-band for the DNS protocol. That 1. The mechanism adopted must be in-band for the DNS protocol. That
is, it needs to allow the query for the server's identifying is, it needs to allow the query for the server's identifying
information to be part of a normal, operational query. It should information to be part of a normal, operational query. It should
also permit a separate, dedicated query for the server's also permit a separate, dedicated query for the server's
identifying information. But it should preserve the ability of identifying information. But it should preserve the ability of
the CHAOS/TXT query-based mechanism to work through firewalls and the CHAOS/TXT query-based mechanism to work through firewalls and
in other situations where only DNS can be relied upon to reach in other situations where only DNS can be relied upon to reach
the server of interest. the server of interest.
2. The new mechanism should not require dedicated namespaces or 2. The new mechanism should not require dedicated namespaces or
other reserved values outside of the existing protocol mechanisms other reserved values outside of the existing protocol mechanisms
for these, i.e. the OPT pseudo-RR. In particular, it should not for these, i.e., the OPT pseudo-RR. In particular, it should not
propagate the existing drawback of requiring support for a CLASS propagate the existing drawback of requiring support for a CLASS
and top level domain in the authoritative server (or the querying and top level domain in the authoritative server (or the querying
tool) to be useful. tool) to be useful.
3. Support for the identification functionality should be easy to 3. Support for the identification functionality should be easy to
implement and easy to enable. It must be easy to disable and implement and easy to enable. It must be easy to disable and
should lend itself to access controls on who can query for it. should lend itself to access controls on who can query for it.
4. It should be possible to return a unique identifier for a server 4. It should be possible to return a unique identifier for a server
without requiring the exposure of information that may be non- without requiring the exposure of information that may be non-
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their chosen associates only. This constraint would imply both an their chosen associates only. This constraint would imply both an
ability to authenticate it to themselves and to keep it private from ability to authenticate it to themselves and to keep it private from
arbitrary other parties, which leads to characteristics 4 and 5 of an arbitrary other parties, which leads to characteristics 4 and 5 of an
improved solution. improved solution.
6. Acknowledgements 6. Acknowledgements
The technique for host identification documented here was initially The technique for host identification documented here was initially
implemented by Paul Vixie of the Internet Software Consortium in the implemented by Paul Vixie of the Internet Software Consortium in the
Berkeley Internet Name Daemon package. Comments and questions on Berkeley Internet Name Daemon package. Comments and questions on
earlier drafts were provided by Bob Halley, Brian Wellington, Andreas earlier versions were provided by Bob Halley, Brian Wellington,
Gustafsson, Ted Hardie, Chris Yarnell, Randy Bush, and members of the Andreas Gustafsson, Ted Hardie, Chris Yarnell, Randy Bush, and
ICANN Root Server System Advisory Committee. The newest version members of the ICANN Root Server System Advisory Committee. The
takes a significantly different direction from previous versions, newest version takes a significantly different direction from
owing to discussion among contributors to the DNSOP working group and previous versions, owing to discussion among contributors to the
others, particularly Olafur Gudmundsson, Ed Lewis, Bill Manning, Sam DNSOP working group and others, particularly Olafur Gudmundsson, Ed
Weiler, and Rob Austein. Lewis, Bill Manning, Sam Weiler, and Rob Austein.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities", [RFC1034] Mockapetris, P., "Domain Names - Concepts and Facilities",
RFC 1034, STD 0013, November 1987. STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain Names - Implementation and [RFC1035] Mockapetris, P., "Domain Names - Implementation and
Specification", RFC 1035, STD 0013, November 1987. Specification", STD 13, RFC 1035, November 1987.
[RFC3258] Hardie, T., "Distributing Authoritative Name Servers via [RFC3258] Hardie, T., "Distributing Authoritative Name Servers via
Shared Unicast Addresses", RFC 3258, April 2002. Shared Unicast Addresses", RFC 3258, April 2002.
7.2. Informative References 7.2. Informative References
[BIND] ISC, "BIND 9 Configuration Reference". [BIND] ISC, "BIND 9 Configuration Reference".
[NSID] Austein, S., "DNS Name Server Identifier Option (NSID)", [NSID] Austein, R., "DNS Name Server Identifier Option (NSID)",
Internet Drafts http://www.ietf.org/internet-drafts/ Work in Progress, June 2006.
draft-ietf-dnsext-nsid-02.txt, June 2006.
[RFC4033] Arends, R., Austein, S., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC 4033, Rose, "DNS Security Introduction and Requirements", RFC
March 2005. 4033, March 2005.
Authors' Addresses Authors' Addresses
Suzanne Woolf Suzanne Woolf
Internet Systems Consortium, Inc. Internet Systems Consortium, Inc.
950 Charter Street 950 Charter Street
Redwood City, CA 94063 Redwood City, CA 94063
US US
Phone: +1 650 423-1333 Phone: +1 650 423-1333
Email: woolf@isc.org EMail: woolf@isc.org
URI: http://www.isc.org/ URI: http://www.isc.org/
David Conrad David Conrad
ICANN ICANN
4676 Admiralty Way 4676 Admiralty Way
Marina del Rey, CA 90292 Marina del Rey, CA 90292
US US
Phone: +1 310 823 9358 Phone: +1 310 823 9358
Email: david.conrad@icann.org EMail: david.conrad@icann.org
URI: http://www.iana.org/ URI: http://www.iana.org/
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
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such proprietary rights by implementers or users of this such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr. http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any The IETF invites any interested party to bring to its attention any
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rights that may cover technology that may be required to implement rights that may cover technology that may be required to implement
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Acknowledgment Acknowledgement
Funding for the RFC Editor function is provided by the IETF Funding for the RFC Editor function is currently provided by the
Administrative Support Activity (IASA). Internet Society.
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