view Side-By-Side changes
INTERNET-DRAFT Thomas Narten
IBM
<draft-iesg-iana-considerations-03.txt>
<draft-iesg-iana-considerations-04.txt> Harald Tveit Alvestrand
UNINETT
March 13,
May 21, 1998
Guidelines for Writing an IANA Considerations Section in RFCs
<draft-iesg-iana-considerations-03.txt> |
<draft-iesg-iana-considerations-04.txt> |
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
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Distribution of this memo is unlimited.
This Internet Draft expires September 13, November, 1998. |
Abstract
Many protocols make use of identifiers consisting of constants and
other well-known values. Even after a protocol has been defined and
deployment has begun, new values may need to be assigned (e.g., for a |
new option type in DHCP, or a new encryption or authentication algorithm). |
algorithm for IPSec). To insure that such quantities have unique values, consistent |
values and interpretations in different implementations, their |
assignment must be administered by a central authority. In the Internet, For IETF |
protocols, that role is provided by the Internet Assigned Numbers |
Authority (IANA).
In order for the IANA to manage a given numbering space prudently, it
needs guidelines describing the conditions under which new values can
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be assigned. If the IANA is expected to play a role in the management
of a numbering space, the IANA must be given clear and concise
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instructions describing that role. This document discusses issues
that should be considered in formulating an identifier assignment
policy and provides guidelines to document authors on the specific
text that must be included in documents that place demands on the
IANA.
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Contents
Status of this Memo.......................................... 1 |
1. Introduction............................................. 3 |
2. Issues To Consider....................................... 4 |
3. Designated Experts....................................... 6
4. Registration maintenance................................. 7
5. |
4. What To Put In Documents................................. 7
6. 8 |
5. Applicability to Past and Future RFCs.................... 8
7. 9 |
6. Security Considerations.................................. 8
8. 9 |
7. Acknowledgements......................................... 9
9. |
8. References............................................... 9
10. Authors' Addresses...................................... 10 |
9. Authors' Addresses....................................... 11 |
1. Introduction
Many protocols make use of fields that contain constants and other
well-known values (e.g., the Protocol field in the IP header [IP] or |
MIME types in mail messages [MIME-REG]). Even after a protocol has |
been defined and deployment has begun, new values may need to be |
assigned (e.g., a new option type in DHCP [DHCP] or a new encryption |
or authentication algorithm for IPSec [IPSEC]). To insure that such |
fields have unique values, consistent values and interpretations in different |
implementations, their assignment must be administered by a central |
authority. In the Internet, For IETF protocols, that role is provided by the Internet |
Assigned Numbers Authority (IANA).
In order for the IANA to manage a given numbering space prudently, it
needs guidelines describing the conditions under which new values
should be assigned. This document provides guidelines to authors on
what sort of text should be added to their documents, and reviews
issues that should be considered in formulating an appropriate policy
for assigning identifiers.
Not all name spaces require centralized administration. In some
cases, it is possible to delegate a name space in such a way that
further assignments can be made independently and with no further
(central) coordination. In the Domain Name System, for example, the
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IANA only deals with assignments at the higher-levels, while
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subdomains are administered by the organization to which the space
has been delegated. As another example, Object Identifiers (OIDs) as
defined by the ITU are also delegated [ASSIGNED]. When a name space
can be delegated, the IANA only deals with assignments at the top
level.
This document uses the terms 'MUST', 'SHOULD' and 'MAY', and their
negatives, in the way described in RFC 2119 [KEYWORDS]. In this case,
"the specification" as used by RFC 2119 refers to the processing of
protocols being submitted to the IETF standards process.
2. Issues To Consider
The primary issue to consider in managing a numbering space is its
size. If the space is small and limited in size, assignments must be
made carefully to insure that the space doesn't become exhausted. If
the space is essentially unlimited, on the other hand, it may be
perfectly reasonable to hand out new values to anyone that wants one.
Even when the space is essentially unlimited, however, it is usually
desirable to have a minimal review to prevent hoarding of the space.
For example, if the space consists of text strings, it may be
desirable to prevent organizations from obtaining large sets of
strings that correspond to the "best" names (e.g., existing company
names).
A second consideration is whether it makes sense to delegate the name
space in some manner. This route should be pursued when appropriate,
as it lessens the burden on the IANA for dealing with assignments.
In most cases, some review of prospective allocations is appropriate,
and the first question to consider is who should perform the review.
In some cases, reviewing requests the name space is straightforward essentially unlimited, and requires |
identifiers can safely be given out to anyone. When no subjective decision making. On those cases, it |
review is reasonable for needed, the IANA to review prospective assignments, can make assignments directly, provided |
that the IANA is given specific guidelines instructions on what types of |
requests it should grant, and what information must be provided |
before a request of for an assigned number will be considered. Note that |
the IANA will not define an assignment policy; it should be given a |
set of guidelines that allow it to make allocation decisions with |
little subjectivity. The
following are example policies, |
In most cases, some review of which are in use today:
Local Use - For local use only, with prospective allocations is appropriate, |
and the type question becomes who should perform the review and purpose defined
by how |
rigorous the local site. No attempt is made review needs to prevent multiple
sites from using be. In many cases, one might think that |
an IETF Working Group (WG) familiar with the same value in different (and
incompatible) ways. There identifier space at hand |
should be consulted. In practice, however, WGs eventually disband, so |
they cannot be considered a permanent evaluator. It is no need also possible |
for IANA identifier spaces to review
draft-iesg-iana-considerations-03.txt be created through individual submission |
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such assignments and assignments are not generally useful
documents, for interoperability.
Examples: Site-specific options in DHCP [DHCP] which no WG is ever formed. |
The standard way to insure community review of prospective |
assignments is to have
significance only within the requestor submit a single site. XXX X-foo header
lines in email message (and mime types?)
Hierarchical allocation - Delegated managers can assign
identifiers provided they have been given control over document for |
publication as an RFC. Such an action insures that
part of the identifier space. IANA controls IESG and |
relevant WGs review the higher
levels of assignment. This is the namespace according to one prefered way of the other
policies.
Examples: DNS names, Object Identifiers
First Come First Served - Anyone |
insuring review, and is particularly important if any potential |
interoperability issues can obtain arise. For example, many assignments are |
not just assignments, but also involve an identifier, so long
as they provide a point of contact and a brief description element of what the identifier would protocol |
specification. A new option may define fields that need to be used for. For numbers, parsed |
and acted on, which (if specified poorly) may not fit cleanly with |
the
exact value is generally assigned by architecture of other options or the IANA, with names,
specific names base protocols on which they |
are usually requested.
Examples: vnd. MIME types [MIME-REG], TCP and UDP port
numbers.
Specification Required - Values and their meaning must be
documented in built. |
In some cases, however, the burden of publishing an RFC or other permanent and readily
available reference, in sufficient detail so that
interoperability between independent implementations order to |
get an assignment is
possible.
Examples: SCSP [SCSP]
IETF Consensus - New values are assigned through the IETF
consensus process. Specifically, new assignments are made
via RFCs approved by excessive. However, it is generally still useful |
(and sometimes necessary) to discuss proposed additions on a mailing |
list dedicated to the IESG. Typically, purpose (e.g., the IESG will
seek input on prospective assignments from appropriate
persons (e.g., a relevant Working Group if one exists).
Examples: SMTP extensions [SMTP-EXT], BGP Subsequent
Address Family Identifiers [BGP4-EXT].
Standards Action - Identifiers are assigned only for Standards
Track RFCs approved by the IESG.
Examples: MIME top level types [MIME-REG]
It should be noted that it often makes sense to partition a number
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space into several categories, with assignments out of each category
handled differently. For example, the DHCP option space [DHCP] is
split into two parts. Option numbers in the range of 1-127 are
globally unique and assigned according to the Specification Required
policy described above, while options number 128-254 are "site
specific", i.e., Local Use. Dividing the number space up makes it
possible to allow some assignments to be made with minimal review,
while simultaneously reserving some part of the space for future use
via a more stringent review process.
3. Designated Experts
In many cases, it is be appropriate for the IANA to serve as a
point-of-contact for publishing information about numbers that have
been assigned, without actually having it evaluate and grant
requests. For example, it may be useful (and sometimes necessary) to
discuss proposed additions on a mailing list dedicated to the purpose
(e.g., the ietf-types@iana.org for media types) or ietf-types@iana.org for |
media types) or on a more general mailing list (e.g., that of a |
current or former IETF Working Group). WG). Such a mailing list provides a way for |
new registrations to be publically reviewed prior to getting |
assigned, or to give advice for persons who want help in |
understanding what a proper registration should contain. |
Since the IANA cannot participate in all of these mailing lists and |
cannot determine if or when discussions on such discussion reaches lists reach a |
consensus, the IANA in all cases relies on a "designated expert" can make use of "Designated Expert" to advise it |
in assignment matters. That is, the IANA forwards the requests it |
receives to a specific point-of-contact (one or a small number of |
individuals) and acts upon the returned recommendation from the
designated expert. |
Designated Expert. In all cases, it is the designated expert Designated Expert that the |
IANA relies on for an authoritative response. In those cases where |
wide review of a request is needed, it is the responsibility of the |
Designated Expert to initiate such a review (e.g., by engaging the |
relevant mailing lists). In no cases will the IANA allow general |
mailing lists (e.g., that of a former or existing IETF Working Group) |
to fill the role of the Designated Expert. |
Designated Experts serve at the pleasure of the IESG (i.e., they are |
appointed by the relevant Area Director) and are typically named at |
the time a document that creates a new numbering space is published |
as an RFC. Any decisions made by the Designated Expert can be |
appealed using the normal IETF appeals process as outlined in Section |
6.5 of [IETF-PROCESS]. |
The following are example policies, some of which are in use today:
Private Use - For private or local use only, with the type and |
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purpose defined by the local site. No attempt is made to |
prevent multiple sites from using the same value in |
different (and incompatible) ways. There is no need for |
IANA to review such assignments and assignments are not |
generally useful for interoperability.
Examples: Site-specific options in DHCP [DHCP] have
significance only within a single site. XXX X-foo header |
lines in email messages.
Hierarchical allocation - Delegated managers can assign
identifiers provided they have been given control over that
part of the identifier space. IANA controls the higher
levels of the namespace according to one of the other
policies.
Examples: DNS names, Object Identifiers
First Come First Served - Anyone can obtain an identifier, so long
as they provide a point of contact and a brief description
of what the identifier would be used for. For numbers, the
exact value is generally assigned by the IANA, with names,
specific names are usually requested.
Examples: vnd. MIME types [MIME-REG], TCP and UDP port
numbers.
Expert Review - approval by a Designated Expert is required. |
Specification Required - Values and their meaning must be
documented in an RFC or other permanent and readily
available reference, in sufficient detail so that
interoperability between independent implementations is
possible.
Examples: SCSP [SCSP]
IESG Approval - New assignments must be approved by the IESG, but |
there is no requirement that the
IANA relies on for an authoritative response. In those cases where
wide review of a request is needed, it is the responsibility of be documented in |
an RFC (though the
designated expert IESG has discretion to initiate such request documents |
or other supporting materials on a review (e.g., case-by-case basis). |
IETF Consensus - New values are assigned through the IETF
consensus process. Specifically, new assignments are made
via RFCs approved by engaging the
relevant mailing lists). In no cases will IESG. Typically, the IANA allow general
mailing lists IESG will
seek input on prospective assignments from appropriate
persons (e.g., that of a former or existing IETF relevant Working Group)
to fill Group if one exists).
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Examples: SMTP extensions [SMTP-EXT], BGP Subsequent
Address Family Identifiers [BGP4-EXT].
Standards Action - Identifiers are assigned only for Standards
Track RFCs approved by the role IESG.
Examples: MIME top level types [MIME-REG]
It should be noted that it often makes sense to partition a number
space into several categories, with assignments out of each category
handled differently. For example, the designated subject matter expert.
Designated experts serve at DHCP option space [DHCP] is
split into two parts. Option numbers in the pleasure range of the IESG (e.g,, they 1-127 are
appointed by the relevant Area Director)
globally unique and are typically named at assigned according to the time a document that creates a new numbering space is published
as an RFC. Any decisions made by Specification Required
policy described above, while options number 128-254 are "site
specific", i.e., Local Use. Dividing the designated expert can number space up makes it
possible to allow some assignments to be
appealed using the normal IETF appeals process as outlined in Section
6.5 made with minimal review,
while simultaneously reserving some part of [IETF-PROCESS].
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4. the space for future use
via a more stringent review process.
3. Registration maintenance *
Registrations sometimes contain information that needs to be
maintained; in particular, point of contact information may need to
be changed, claims of freedom from security problems may need to be
modified, or new versions of a registration may need to be published.
A document must clearly state who is responsible for such
maintenance. It is appropriate to:
- Let the author update the registration, subject to the same
constraints and review as with new registrations
- Allow some mechanism to attach comments to the registration, for
cases where others have significant objections to claims in a
registration, but the author does not agree to change the
registration.
- Designate the IESG or another authority as having the right to
reassign ownership of a registration. This is mainly to get
around the problem when some registration owner cannot be
reached in order to make necessary updates.
In the absense of specific instructions, the designated expert will
assume such responsibilities.
5.
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4. What To Put In Documents *
The previous sections presented some issues that should be considered
in formulating a policy for assigning well-known numbers and other
protocol constants. It is the Working Group and/or document author's
job to formulate an appropriate policy and specify it in the
appropriate document. In some cases, having an "IANA Considerations"
section may be appropriate. Specifically, documents that create an
identifier space (or modify the definition of an existing space) and
that expect the IANA to play a role in maintaining that space (e.g.,
serving as a repository for registered values) MUST document the
process through which future assignments are made. Such a section
should |
MUST state clearly:
- whether or not an application for an assigned number should
first needs to be reviewed by a designated expert. |
reviewed. If review is necessary, the review mechanism MUST be |
specified. When a designated
expert Designated Expert is used, documents MUST NOT |
name the designated expert Designated Expert in the document itself; instead, the |
name should be relayed to the appropriate IESG Area Director at |
the time the document is sent to the IESG for approval.
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- If the request should also be reviewed by on a specific public |
mailing list (such as the ietf-types@iana.org for media types),
that mailing address should be specified. Note, however, that |
use of a
designated subject matter expert Designated Expert must also be specified.
- if the IANA is expected to review requests itself, make assignments without requiring an |
outside review, sufficient guidance must MUST be provided so that the |
requests can be evaluated with minimal subjectivity.
Authors SHOULD attempt to provide guidelines that allow the IANA to |
assign new values directly without requiring review by a designated
expert. Designated |
Expert. This can be done easily in many cases by designating a range
of values for direct assignment by the IANA while simultaneously |
reserving some of the sufficient identifier space for future use by requiring
that assignments from that space be made only after a more stringent
review.
Finally, it is quite acceptable to pick one of the example policies
cited above and refer to it by name. For example, a document could
say something like:
Following the policies outlined in [IANA-CONSIDERATIONS], |
numbers in the range 0-127 0-63 are allocated as First Come First
Served as defined in [IANA-CONSIDERATIONS], |
Served, numbers between
128-255 must be approved by 64-240 are allocated through an IETF |
Consensus action and values in the designated expert. range 241-255 are reserved |
for Private Use.
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For examples of documents that provide good and detailed guidance to
the IANA on the issue of assigning identifiers, consult [MIME-REG,
MIME-LANG].
6.
5. Applicability to Past and Future RFCs
All
For all existing RFCs that either explicitely or implicitly rely on |
the IANA to evaluate assignments without specifying a precise |
evaluation policy, the IANA will have assignments evaluated by a designated expert, as
outlined in Section 3. continue to decide what policy is |
appropriate. The default policy has typically been first come, first |
served. Changes to existing policies can always be initiated through |
the normal IETF consensus process.
All future RFCs that either explicitely or implicitly rely on the
IANA to register or otherwise manage assignments MUST provide
guidelines for managing the identifier space.
7.
6. Security Considerations
Information that creates or updates a registration needs to be
authenticated.
Information concerning possible security vulnerabilities of a
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protocol may change over time. Consequently, claims as to the
security properties of a registered protocol may change as well. As
new vulnerabilities are discovered, information about such
vulnerabilities may need to be attached to existing registrations, so
that users are not mislead as to the true security properties of a
registered protocol.
An analysis of security issues is required for all types registered parameters (data |
types, operation codes, keywords, etc.) used in the IETF Tree [MIME-REG]. A similar analysis for media types protocols or |
registered in by the vendor or personal trees is encouraged but not
required. However, regardless of what security analysis has or has
not been done, all IANA. All descriptions of security issues must be |
as accurate as possible regardless of registration tree. level of registration. In |
particular, a statement that there are "no security issues associated |
with this type" must not be confused with "the security issues |
associated with this type have not been assessed".
Delegations of a name space should only be assigned to someone with
adequate security.
8.
7. Acknowledgements
Jon Postel and Joyce Reynolds provided a detailed explanation on what |
the IANA needs in order to manage assignments efficiently. efficiently, and |
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patiently provided comments on multiple versions of this document. |
Brian Carpenter provided helpful comments on earlier versions of the |
document. One paragraph in the Security Considerations section was |
borrowed from [MIME-REG].
9.
8. References
[ASSIGNED] Reynolds, J., Postel, J., "Assigned Numbers", October
1994k, RFC 1700.
[BGP4-EXT] Bates. T., Chandra, R., Katz, D., Rekhter, Y.,
Multiprotocol Extensions for BGP-4, draft-ietf-idr-bgp4-
multiprotocol-02.txt, January, 1998
[DHCP-OPTIONS] S. Alexander, R. Droms, DHCP Options and BOOTP
Vendor Extensions, RFC 2132, March 1997.
[IANA-CONSIDERATIONS] Alvestrand, H., Narten, T., "Guidelines for
Writing an IANA Considerations Section in RFCs", draft-
iesg-iana-considerations-03.txt. |
iesg-iana-considerations-04.txt.
[IETF-PROCESS] Bradner, S., "The Internet Standards Process --
Revision 3", RFC 2026, October 1996.
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[IP] J. Postel, Internet Protocol, RFC 791, September 1, 1981.
[IPSEC] Atkinson, R., Security Architecture for the Internet
Protocol, RFC 1825, August 1995.
[KEYWORDS] S. Bradner, "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, March 1997.
[MIME-LANG] Freed, N., Moore, K., "MIME Parameter Value and Encoded
Word Extensions: Character Sets, Languages, and
Continuations", RFC 2184, August, 1997.
[MIME-REG] N. Freed, J. Klensin & J. Postel, Multipurpose Internet
Mail Extension (MIME) Part Four: Registration Procedures.
RFC 2048, November, 1996.
[SCSP] Luciani, J., Armitage, G, Halpern, J., "Server Cache
Synchronization Protocol (SCSP)" draft-ietf-ion-scsp-
02.txt.
[SMTP-EXT] Klensin, J., Freed, N., Rose, M., Stefferud, E.,
Crocker, D.. "SMTP Service Extensions", RFC 1869, November
1995.
10.
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9. Authors' Addresses
Thomas Narten
IBM Corporation
3039 Cornwallis Ave.
PO Box 12195 - BRQA/502
Research Triangle Park, NC 27709-2195
Phone: 919-254-7798
EMail: narten@raleigh.ibm.com
Harald Tveit Alvestrand
Maxware
Pirsenteret
N-7005 Trondheim
Norway
Phone: +47 73 54 57 97
Email: Harald@Alvestrand.no
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