draft-ietf-dnsop-serverid-07.txt   draft-ietf-dnsop-serverid-08.txt 
Network Working Group S. Woolf Network Working Group S. Woolf
Internet-Draft Internet Systems Consortium, Inc. Internet-Draft Internet Systems Consortium, Inc.
Expires: December 28, 2006 D. Conrad Intended Status: Informational D. Conrad
Internet Corporation for Assigned Expires: July 26, 2007 ICANN
Names and Numbers January 22, 2007
June 26, 2006
Requirements for a Mechanism Identifying a Name Server Instance Requirements for a Mechanism Identifying a Name Server Instance
draft-ietf-dnsop-serverid-07 draft-ietf-dnsop-serverid-08
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
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aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on December 28, 2006. This Internet-Draft will expire on July 26, 2007.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). 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
servers has answered a particular query. A standardized mechanism to servers has answered a particular query. A standardized mechanism to
determine the identity of a name server responding to a particular determine the identity of a name server responding to a particular
query would be useful, particularly as a diagnostic aid for query would be useful, particularly as a diagnostic aid for
administrators. Existing ad hoc mechanisms for addressing this need administrators. Existing ad hoc mechanisms for addressing this need
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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 traditional 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 somewhat problematic. Specifically, a dedicated DNS identifiers associated with DNS (or any other) service somewhat
query may not go to the same server as answered a previous query, problematic. Specifically, multiple dedicated DNS queries may not go
even though sent to the same IP address. Non-DNS methods such as to the same server even though sent to the same IP address. Non-DNS
ICMP ping, TCP connections, or non-DNS UDP packets (such as those methods such as ICMP ping, TCP connections, or non-DNS UDP packets
generated by tools like "traceroute"), etc., may well be even less (such as those generated by tools like "traceroute"), etc., may well
certain to reach the same server as the one which receives the DNS be even less certain to reach the same server as the one which
queries. receives the DNS queries.
There is a well-known and frequently-used technique for determining There is a well-known and frequently-used technique for determining
an identity for a nameserver more specific than the possibly-non- an identity for a nameserver more specific than the possibly-non-
unique "server that answered the query I sent to IP address XXX". 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 implementation of the DNS protocol suite from the Internet Systems
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resource record in class 3 (CHAOS) for the domain name 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 string, replaces ".BIND" with ".SERVER". implementation-specific label, replaces "BIND." with "SERVER.". Thus
Thus the query string to learn the unique name of a server may be the query label to learn the unique name of a server may appear as
queried as "ID.SERVER". "ID.SERVER.".
(For reference, the other well-known name used by recent versions of (For reference, the other well-known name used by recent versions of
BIND within the CHAOS class "BIND." domain is "VERSION.BIND." A BIND within the CHAOS class "BIND." domain is "VERSION.BIND.". A
query for a CHAOS TXT RR for this name will return an query for a CHAOS TXT RR for this name will return an
administratively defined string which defaults to the version of the administratively defined string which defaults to the software
server responding. This is, however, not generally implemented by version of the server responding. This is, however, not generally
other vendors.) implemented by other vendors.)
2.1. Advantages 2.1. Advantages
There are several valuable attributes to this mechanism, which There are several valuable attributes to this mechanism, which
account for its usefulness. account for its usefulness.
1. The "HOSTNAME.BIND" or "ID.SERVER" query response mechanism is 1. The "HOSTNAME.BIND." or "ID.SERVER." query response mechanism is
within the DNS protocol itself. An identification mechanism that within the DNS protocol itself. An identification mechanism that
relies on the DNS protocol is more likely to be successful relies on the DNS protocol is more likely to be successful
(although not guaranteed) in going to the same system as a (although not guaranteed) in going to the same system as a
"normal" DNS query. "normal" DNS query.
2. Since the identity information is requested and returned within 2. Since the identity information is requested and returned within
the DNS protocol, it doesn't require allowing any other query the DNS protocol, it doesn't require allowing any other query
mechanism to the server, such as holes in firewalls for mechanism to the server, such as holes in firewalls for
otherwise-unallowed ICMP Echo requests. Thus it is likely to otherwise-unallowed ICMP Echo requests. Thus it is likely to
reach the same server over a path subject to the same routing, reach the same server over a path subject to the same routing,
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exceptions to site security policy. exceptions to site security policy.
3. It is simple to configure. An administrator can easily turn on 3. It is simple to configure. An administrator can easily turn on
this feature and control the results of the relevant query. this feature and control the results of the relevant query.
4. It allows the administrator complete control of what information 4. It allows the administrator complete control of what information
is given out in the response, minimizing passive leakage of is given out in the response, minimizing passive leakage of
implementation or configuration details. Such details are often implementation or configuration details. Such details are often
considered sensitive by infrastructure operators. considered sensitive by infrastructure operators.
5. Hypothetically, since it's an ordinary DNS record and the
relevant DNSSEC RRs are class independent, the id.server response
RR could be signed, which has the advantages described in
[RFC4033]. However, since zone integrity of ".server." isn't
maintained from one server to another (otherwise, the RR returned
for "id.server." couldn't be unique per server), this would be
difficult or impossible in practice.
2.2. Disadvantages 2.2. Disadvantages
At the same time, there are some serious drawbacks to the CHAOS/TXT At the same time, there are some serious drawbacks to the CHAOS/TXT
query mechanism that argue against standardizing it as it currently query mechanism that argue against standardizing it as it currently
operates. operates.
1. It requires an additional query to correlate between the answer 1. It requires an additional query to correlate between the answer
to a DNS query under normal conditions and the supposed identity to a DNS query under normal conditions and the supposed identity
of the server receiving the query. There are a number of of the server receiving the query. There are a number of
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 implementation 3. The initial and still common form, using "BIND.", is
specific. BIND is one DNS implementation. At the time of this implementation specific. BIND is one DNS implementation. At the
writing, it is probably the most prevalent for authoritative time of this writing, it is probably the most prevalent for
servers. This does not justify standardizing on its ad hoc authoritative servers. This does not justify standardizing on
solution to a problem shared across many operators and its ad hoc solution to a problem shared across many operators and
implementors. Meanwhile, the proposed refinement changes the implementors. Meanwhile, the aforementioned refinement changes
string 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 include, 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
classes, the TXT RRs returned in response to the "ID.SERVER."
query could be signed, which has the advantages described in
[RFC4033]. However, since DNSSEC deployment for the CHAOS class
is neither existent nor foreseeable, and since the "ID.SERVER."
TXT RR is expected to be unique per server, this would be
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 that "I need to know what nameserver is answering my
queries", not simply a convenient one. queries", not simply a convenient one.
2.3. 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
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purposes. purposes.
5. It should be possible to authenticate the received data by some 5. It should be possible to authenticate the received data by some
mechanism analogous to those provided by DNSSEC. In this mechanism analogous to those provided by DNSSEC. In this
context, the need could be met by including encryption options in context, the need could be met by including encryption options in
the specification of a new mechanism. the specification of a new mechanism.
6. The identification mechanism should not be implementation- 6. The identification mechanism should not be implementation-
specific. specific.
3. IANA Considerations 4. IANA Considerations
This document proposes no specific IANA action. Protocol extensions, This document proposes no specific IANA action. Protocol extensions,
if any, to meet the requirements described are out of scope for this if any, to meet the requirements described are out of scope for this
document. A proposed extension, specified and adopted by normal IETF document. A proposed extension, specified and adopted by normal IETF
process, is described in [NSID], including relevant IANA action. process, is described in [NSID], including relevant IANA action.
4. Security Considerations 5. Security Considerations
Providing identifying information as to which server is responding to Providing identifying information as to which server is responding to
a particular query from a particular location in the Internet can be a particular query from a particular location in the Internet can be
seen as information leakage and thus a security risk. This motivates seen as information leakage and thus a security risk. This motivates
the suggestion above that a new mechanism for server identification the suggestion above that a new mechanism for server identification
allow the administrator to disable the functionality altogether or allow the administrator to disable the functionality altogether or
partially restrict availability of the data. It also suggests that partially restrict availability of the data. It also suggests that
the serverid data should not be readily correlated with a hostname or the server identification data should not be readily correlated with
unicast IP address that may be considered private to the nameserver a hostname or unicast IP address that may be considered private to
operator's management infrastructure. the nameserver operator's management infrastructure.
Propagation of protocol or service meta-data can sometimes expose the Propagation of protocol or service meta-data can sometimes expose the
application to denial of service or other attack. As DNS is a application to denial of service or other attack. As the DNS is a
critically important infrastructure service for the production critically important infrastructure service for the production
Internet, extra care needs to be taken against this risk for Internet, extra care needs to be taken against this risk for
designers, implementors, and operators of a new mechanism for server designers, implementors, and operators of a new mechanism for server
identification. identification.
Both authentication and confidentiality of serverid data are Both authentication and confidentiality of server identification data
potentially of interest to administrators-- that is, operators may are potentially of interest to administrators-- that is, operators
wish to make serverid data available and reliable to themselves and may wish to make such data available and reliable to themselves and
their chosen associates only. This would imply both an ability to their chosen associates only. This constraint would imply both an
authenticate it to themselves and keep it private from arbitrary ability to authenticate it to themselves and to keep it private from
other parties. This led to Characteristics 4 and 5 of an improved arbitrary other parties, which leads to characteristics 4 and 5 of an
solution. improved solution.
5. 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 drafts were provided by Bob Halley, Brian Wellington, Andreas
Gustafsson, Ted Hardie, Chris Yarnell, Randy Bush, and members of the Gustafsson, Ted Hardie, Chris Yarnell, Randy Bush, and members of the
ICANN Root Server System Advisory Committee. The newest version ICANN Root Server System Advisory Committee. The newest version
takes a significantly different direction from previous versions, takes a significantly different direction from previous versions,
owing to discussion among contributors to the DNSOP working group and owing to discussion among contributors to the DNSOP working group and
others, particularly Olafur Gudmundsson, Ed Lewis, Bill Manning, Sam others, particularly Olafur Gudmundsson, Ed Lewis, Bill Manning, Sam
Weiler, and Rob Austein. Weiler, and Rob Austein.
6. References 7. References
6.1 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. RFC 1034, STD 0013, November 1987.
[RFC1035] Mockapetris, P., "Domain Names - Implementation and [RFC1035] Mockapetris, P., "Domain Names - Implementation and
Specification", RFC 1035, STD 0013, November 1987. Specification", RFC 1035, STD 0013, November 1987.
[RFC3258] Hardie, T., "Distributing Authoritative Name Servers via Shared [RFC3258] Hardie, T., "Distributing Authoritative Name Servers via
Unicast Addresses", RFC 3258, April 2002. Shared Unicast Addresses", RFC 3258, April 2002.
6.2 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, S., "DNS Name Server Identifier Option (NSID)",
Internet Drafts http://www.ietf.org/internet-drafts/ Internet Drafts http://www.ietf.org/internet-drafts/
draft-ietf-dnsext-nsid-04.txt, December 2006. draft-ietf-dnsext-nsid-02.txt, June 2006.
[RFC4033] Arends, R., Austein, S., Larson, M., Massey, D., and S. Rose, [RFC4033] Arends, R., Austein, S., Larson, M., Massey, D., and S.
"DNS Security Introduction and Requirements", RFC 4033, Rose, "DNS Security Introduction and Requirements", RFC 4033,
March 2005. 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
Internet Corporation for Assigned Names and Numbers ICANN
4676 Admiralty Way, Suite 300 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/
Intellectual Property Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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This document and the information contained herein are provided on an
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INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement
Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is provided by the IETF
Internet Society. Administrative Support Activity (IASA).
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