wdiff draft-ietf-grow-embed-addr-03.txt draft-ietf-grow-embed-addr-04.txt

Global Routing Operations D. Plonka
Internet-Draft University of Wisconsin
Expires: December 7, 2004 June 8, April 22, 2005 October 22, 2004

Embedding Globally Routable Internet Addresses Considered Harmful
draft-ietf-grow-embed-addr-03
draft-ietf-grow-embed-addr-04

Status of this Memo

This document is an Internet-Draft and is in full conformance with subject to all provisions
of Section 10 section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of RFC2026.
which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with
RFC 3668.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as
Internet-Drafts.

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."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.

The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

This Internet-Draft will expire on December 7, 2004. April 22, 2005.

Abstract

This document means to clarify best current practices in the Internet
community. Internet hosts should not contain globally routable
Internet Protocol addresses embedded within firmware or elsewhere as
part of their default configuration such that it influences run-time
behavior.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Recommendations . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Disable Unused Features . . . . . . . . . . . . . . . . . 6
3.2 Provide User Interface for IP Features . . . . . . . . . . 6
3.3 Use Domain Names as Service Identifiers . . . . . . . . . 6
3.4 Use Special-Purpose, Reserved IP Addresses When
Available . . . . . . . . . . . . . . . . . . . . . . . . 7
3.5 Discover and Utilize Local Services . . . . . . . . . . . 7
3.6 Avoid Mentioning the IP Addresses of Services . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1 Normative References . . . . . . . . . . . . . . . . . . . . 9
8.2 Informative References . . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 10
A. Background . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . 11

Revision History

RFC-EDITOR: PLEASE REMOVE REVISION HISTORY BEFORE PUBLICATION. The
following is the recent revision history of this document

$Log: draft-ietf-grow-embed-addr.xml,v $
Revision 1.17 2004/06/08 20:27:02 1.19 2004/10/22 16:08:17 plonka
minor
edits

renamed from "-02" to "-03"

Revision 1.16 2004/06/08 20:15:03 plonka
minor edits, fixed some typos

Revision 1.15 2004/06/08 14:16:45 plonka
revised conclusion based on input from Geoff Huston

added netgear-sntp technical report to list of informative references

Revision 1.14 2004/06/07 18:16:27 plonka
split references into normative and informative sections

Revision 1.13 2004/06/07 16:32:10 plonka
Set category to BCP.

Rewrote/resized abstract and initial IESG evaluation for BCP:

* fixed a typo reported by Spencer Dawkins

* reworded the introduction as suggested by Pekka Savola.

Improved section Ted Hardie to make it clear that
the document is about using DNS names, re; hard-coding caveats, as
suggested service identifiers used by Pekka Savola.

Encouraged use of IPv4 documentation/example prefix 192.0.2.0/24 rather
than private addresses, the device, not the host
IP address it uses as noted a client of those services

* improved recommendation to use DNS names based on comments by Harald
Alvestrand, Steve Bellovin, and Pekka Savola.

Mentioned IPv6 2001:DB8::/32 documentation prefix, as noted Savola

* under Security Considerations, strengthened the opposition to ad hoc remote
control mechanisms by Tom Petch.

Added note for RFC-editor requesting mentioned that revision history they should be removed.

Reworded various portions.

Renamed from "-00" able to "-01" and updated date.

Revision 1.12 2003/12/05 15:51:23 plonka
typo fixes be disabled,
based on comment by Russ Housley

* used the term "mobility" rather than "portability" and updates from Michael Patton "networks"
rather than "internets" based on comment by Thomas Narten.

Revision 1.11 2003/12/02 22:28:04 1.18 2004/10/21 20:24:35 plonka
renamed from draft-plonka-embed-addr to draft-ietf-grow-embed-addr

integrated suggestions
changed from Paul Barford
reordered references full RFC2026 to match the text

added quote from RFC2101 re: use of IPv4 addresses as identifiers RFC3667 compliance

used compact as mentioned suggested by Brian Carpenter

Revision 1.10 2003/11/03 17:06:54 plonka Pekka Savola

added background information in appendix

Revision 1.9 2003/11/03 16:39:30 plonka
various updates table of contents and sortrefs

added headings and subsections for specific recommendations

added example of how domain names might be used, based on input from Mike O'Connor:
- indicated that DNS server(s) should be configurable
- clarified DNS round-robin behavior
- clarified "unsolicited traffic" by saying "IP traffic" suggestion by
Pekka Savola

added revision history and appendix A reference to RFC3849 now that it's available (re: IPv6 documentation
prefix)

other minor edits

Figure 1

1. Introduction

Vendors of consumer electronics and network gear have produced and
sold hundreds of thousands of Internet hosts with unfortunately
chosen to embed, or "hard-code", globally routable Internet Protocol
addresses embedded within their products' firmware. These products use these
embedded IP addresses as service identifiers and direct service
requests (unsolicited Internet traffic) to them. One recent example
was the embedding of the globally routable IP address of a Network
Time Protocol server in the firmware of hundreds of thousands of
Internet hosts that are now in operation world-wide and primarily include, world-wide. The hosts are
primarily, but are not necessarily limited to, low-cost routers and
middleboxes for personal or residential use.

This "hard-coding" of globally routable IP addresses as identifiers
within the host's firmware presents significant problems to the
operation of the Internet and to the management of its address space.

Ostensibly, this practice arose as an attempt to simplify
configuration of IP hosts by preloading them with IP addresses as
service identifiers. Products that rely on such embedded IP
addresses initially may appear convenient to both the product's
designer and its operator or user, but this dubious benefit comes at
the expense of others in the Internet community.

This document denounces the practice of embedding references to
unique, globally routable IP addresses in Internet hosts, describes
some of the resulting problems, and considers selected alternatives.
It also reminds the Internet community of the ephemeral nature of
unique, globally routable IP addresses and that the assignment and
use of IP addresses as identifiers is temporary and therefore should
not be used in fixed configurations.

2. Problems

In a number cases, the embedding of IP addresses in products has
caused an increasing number of Internet
products hosts to rely on a single
central Internet service. This can result in a service outage when
the aggregate workload overwhelms that service. When fixed addresses
are embedded in an ever-increasing number of client IP hosts, this
practice runs directly counter to the design intent of hierarchically
deployed services that would otherwise be robust solutions.

The reliability, scalability, and performance of many Internet
services require that the pool of users not directly access a service
by IP address. Instead they typically rely on a level of indirection
provided by the Domain Name System, RFC 2219 [6]. When appropriately
utilized, DNS permits the service operator to reconfigure the
resources for maintenance and to load-balance without the
participation of the users. users and without necessitating configuration
changes in the client hosts. For instance, one common load-balancing
technique employs multiple DNS records with the same name that are
then rotated in a round-robin fashion in the set of answers returned
by many DNS server implementations. Upon receiving such a response
to a query, resolvers typically will try the answers in order, until
one succeeds, thus enabling the operator to distribute the user
request load across a set of servers with discrete IP addresses that
generally remain unknown to the user.

Embedding globally unique IP addresses taints the IP address blocks
in which they reside, lessening the usefulness and portability mobility of those
IP address blocks and increasing the cost of operation. Unsolicited
traffic may continue to be delivered to the embedded address well
after the IP address or block has been reassigned and no longer hosts
the service for which that traffic was intended. Circa 1997, the
authors of RFC 2101 [5] [7] made this observation:

Due to dynamic address allocation and increasingly frequent
network renumbering, temporal uniqueness of IPv4 addresses is no
longer globally guaranteed, which puts their use as identifiers
into severe question.

When IP addresses are used as service identifiers in the
configuration of many Internet hosts, the IP address blocks become
encumbered by their historical use. This may interfere with the
ability of the Internet Assigned Numbers Authority (IANA) and the
Internet Registry (IR) hierarchy to usefully reallocate IP address
blocks. Likewise, to facilitate IP address reuse, RFC 2050 [1],
encourages Internet Service Providers (ISPs) to treat address
assignments as "loans".

Because consumers are not necessarily experienced in the operation of
Internet hosts, they are not able to be relied upon to fix problems
if and when they arise. As such, a significant responsibility lies
with the manufacturer or vendor of the Internet host to avoid
embedding IP addresses in ways which cause the aforementioned
problems.

3. Recommendations

Internet host and router designers, including network product
manufacturers, should not assume that their products will be deployed
and used in only a the single global Internet that they happen to
observe today. A myriad of private or future internets internetworks in which
these products will be used may not allow those hosts to establish
end-to-end
communications with arbitrary hosts on the global Internet. Since
the product failure modes resulting from unknown future states cannot
be fully explored, one should avoid assumptions regarding the
longevity of our current Internet.

The following recommendations are presented as best practice today:

3.1 Disable Unused Features

Vendors should, by default, disable unnecessary features in their
products. This is especially true of features that generate
unsolicited IP Internet traffic. In this way these hosts will be
conservative regarding the unsolicited Internet traffic they produce.
For instance, one of the most common uses of embedded IP addresses
has been the hard-coding of addresses of well know known public Simple
Network Time Protocol (SNTP RFC 2030 [7]) [8]) servers, even though only a
small fraction of the users benefits from these products even having
some notion of the current date and time.

3.2 Provide User Interface for IP Features

Vendors should provide an operator interface for every feature that
generates unsolicited IP Internet traffic. A prime example of this is
that the Domain Name System resolver should have an interface
enabling the operator to either explicitly set the servers of his
choosing or to enable the use of a standard automated configuration
protocol such as DHCP, defined by RFC 2132 [8]. [9]. Within the operator
interface, these features should originally be disabled so that one
consequence of subsequently enabling these features is that the
operator becomes aware that the feature exists. This will mean that
it is more likely that the product's owner or operator can
participate in problem determination and mitigation when problems
arise.

RFC 2606 [2] defines the IANA-reserved "example.com", "example.net",
and "example.org" domains for use in example configurations and
documentation. These are candidate examples to be used in user
interface documentation.

3.3 Use Domain Names as Service Identifiers

Internet hosts should use the Domain Name System to determine the IP
addresses associated with the Internet services they require.

When using domain names as service identifiers in the configurations
of deployed Internet hosts, designers and vendors are encouraged to
introduce service names either within a domain which they control or
have entered into an agreement with its operator to utilize (such as
for public services provided by the Internet community). This is
commonly done by simply introducing a service-specific prefix to the
domain name.

For instance, a vendor named "Example, Inc." with the domain
"example.com" might configure its product to find its SNTP server by
the name "sntp-server.config.example.com" or even by a product and
version-specific name such as
"sntp-server.v1.widget.config.example.com". Here, the
"config.example.com" namespace is dedicated to that vendor's product
configuration, with sub-domains introduced as deemed necessary. Such
special-purpose domain names enable ongoing maintenance and
reconfiguration of the services for their client hosts and can aid in
the ongoing measurement of service usage throughout the product's
lifetime.

An alternative to inventing vendor-specific domain naming conventions
for a product's service identifiers is to utilize SVR resource
records (RR), defined by RFC 2782 [10]. SRV records are a generic
type of RR which uses a service-specific prefix in combination with a
base domain name. For example, an SVR-cognizant SNTP client might
discover Example, Inc.'s suggested NTP server by performing an
SVR-type query to lookup for "_ntp._udp.example.com".

However, note that simply hard-coding DNS names name service identifiers
rather than IP addresses is not a panacea. Entries in the domain
name space are also ephemeral and can change owners for various
reasons including acquisitions and litigation. A given vendor ought not assume that anyone will retain As such, developers
and vendors should explore a product's potential failure modes
resulting from the loss of administrative control of a given zone indefinitely. RFC 2606 [2] defines the
IANA-reserved "example.com", "example.net", and "example.org" domains
for use in example configurations and documentation. domain
for whatever reason.

3.4 Use Special-Purpose, Reserved IP Addresses When Available

Default configurations, documentation, and example configurations for
Internet hosts should use Internet addresses that reside within
special blocks that have been reserved for these purposes, rather
than unique, globally routable IP addresses. For IPv4, RFC 3330 [3]
states that the 192.0.2.0/24 block has been assigned for use in
documentation and example code. The IPv6 global unicast address
prefix 2001:DB8::/32 has been similarly reserved for documentation
purposes.
purposes RFC 3849 [4]. Private Internet Addresses, as defined by RFC
1918 [4], [5], should not be used for such purposes.

3.5 Discover and Utilize Local Services

Service providers and enterprise network operators should advertise
the identities of suitable local services, such as NTP. Very often
these services exist, but the advertisement and automated
configuration of their use is missing. For instance, the DHCP
protocol, as defined by RFC 2132 [8], [9], enables one to configure a
server to answer queries for service identitifiers to clients that
ask for them. When local services including NTP are available but
not pervasively advertised using such common protocols, designers are
more likely deploy ad hoc initialization mechanisms that
unnecessarily rely on central services.

3.6 Avoid Mentioning the IP Addresses of Services

Operators that provide public services on the global Internet, such
as those in the NTP community, should deprecate the explicit
advertisement of the IP addresses of public services. These
addresses are ephemeral. As such, their widespread citation in
public service indexes interferes with the ability to reconfigure the
service as necessary to address unexpected, increased traffic. traffic and the
aforementioned problems.

4. Security Considerations

Embedding or "hard-coding" IP addresses within a host's configuration
often means that a host-based trust model is being employed, and that
the Internet host with the given address is trusted in some way. Due
to the ephemeral roles of globally routable IP addresses, the
practice of embedding them within products' firmware or default
configurations presents a security risk in that unknown parties may
inadvertently be trusted.

Internet host designers may be tempted to implement some sort of
remote control mechanism within a product, by which its Internet host
configuration can be changed without reliance on, interaction with,
or even the knowledge of its operator or user. This raises security
issues of its own. If such a scheme is implemented, this its presence
should be fully disclosed to the customer, operator, and user so that
an informed decision can be made, perhaps in accordance with local
security or privacy policy. Furthermore, the significant possibility
of malicious parties exploiting such a remote control mechanism may
completely negate any potential benefit of the remote control scheme.
As such, remote control mechanisms should be disabled by default to
be subsequently enabled and disabled by the user.

5. IANA Considerations

This document creates no new requirements on IANA namespaces.

6. Conclusion

When large numbers of homogenous Internet hosts are deployed, it is
particularly important that both their designers and other members of
the Internet community diligently assess host implementation quality
and reconfigurability.

Implementors of host services should avoid any kind of use of unique
globally routable IP addresses within a fixed configuration part of
the service implementation. If there is a requirement for
pre-configured state then care should be taken to use an appropriate
service identifier and use standard resolution mechanisms to
dynamically resolve the identifier into an IP address. Also, any
such identifiers should be alterable in the field through a
conventional command and control interface for the service.

7. Acknowledgements

The author thanks the following reviewers for their contributions to
this document: Paul Barford, Geoff Huston, David Meyer, Mike
O'Connor, Michael Patton, Tom Petch, and Pekka Savola.

8. References

8.1 Normative References

[1] Hubbard, K., "INTERNET REGISTRY IP ALLOCATION GUIDELINES", RFC
2050, BCP 12, November 1996.

[2] Eastlake, D., "Reserved Top Level DNS Names", RFC 2606, BCP 32,
June 1999.

[3] Internet Assigned Numbers Authority, "Special-Use IPv4
Addresses", RFC 3330, September 2002.

[4] Huston, G., "IPv6 Address Prefix Reserved for Documentation",
RFC 3849, July 2004.

[5] Rekhter, Y., "Address Allocation for Private Internets", RFC
1918, BCP 5, February 1996.

8.2 Informative References

[5] Carpenter, B., "IPv4 Address Behaviour Today", RFC 2101,
February 1997.

[6] Hamilton, M., "Use of DNS Aliases for Network Services", RFC
2219, BCP 17, October 1997.

[7] Carpenter, B., "IPv4 Address Behaviour Today", RFC 2101,
February 1997.

[8] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for
IPv4, IPv6 and OSI", RFC 2030, October 1996.

[8]

[9] Alexander, S., "DHCP Options and BOOTP Vendor Extensions", RFC
2132, March 1997.

[9]

[10] Gulbrandsen, A., "A DNS RR for specifying the location of
services (DNS SRV)", RFC 2782, February 2000.

[11] Plonka, D., "Flawed Routers Flood University of Wisconsin
Internet Time Server", August 2003,
<http://www.cs.wisc.edu/~plonka/netgear-sntp/>.

Author's Address

David Plonka
University of Wisconsin - Madison

EMail: plonka AT doit DOT wisc DOT edu
URI: http://net.doit.wisc.edu/~plonka/

Appendix A. Background

In June 2003, the University of Wisconsin discovered that a network
product vendor named NetGear had manufactured and shipped over
700,000 routers with firmware containing a hard-coded reference to
the IP address of one of the University's NTP servers:
128.105.39.11, which was also known as "ntp1.cs.wisc.edu", a public
stratum-2 NTP server.

Due to that embedded fixed configuration and an unrelated bug in the
SNTP client, the affected products occasionally exhibit a failure
mode in which each flawed router produces one query per second
destined for the IP address 128.105.39.11, and hence produces a
large-scale flood of Internet traffic from hundreds-of-thousands of
source addresses, destined for the University's network, resulting in
significant operational problems.

These flawed routers are widely deployed throughout the global
Internet and are likely to remain in use for years to come. As such,
the University of Wisconsin with the cooperation of NetGear will
build a new anycast time service which aims to mitigate the damage
caused by the misbehavior of these flawed routers.

A technical report regarding the details of this situation is
available on the world wide web: Flawed Routers Flood University of
Wisconsin Internet Time Server [9]. [11].

Intellectual Property Statement

The IETF takes no position regarding the validity or scope of any
intellectual property
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; neither nor does it represent that it has
made any independent effort to identify any such rights. Information
on the
IETF's procedures with respect to rights in standards-track and
standards-related documentation RFC documents can be
found in BCP-11. BCP 78 and BCP 79.

Copies of
claims of rights IPR disclosures made available for publication to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementors implementers or users of this
specification can be obtained from the IETF Secretariat. on-line IPR repository at
http://www.ietf.org/ipr.

The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which that may cover technology that may be required to practice implement
this standard. Please address the information to the IETF Executive
Director.

Full Copyright Statement

This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose at
ietf-ipr@ietf.org.

Disclaimer of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.

The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assignees. Validity

This document and the information contained herein is are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
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 (C) The Internet Society (2004). 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

Funding for the RFC Editor function is currently provided by the
Internet Society.