INTERNET-DRAFT Thomas Narten
IBM
<draft-iesg-iana-considerations-02.txt> Harald Tveit Alvestrand
UNINETT
January 30, 1997
Guidelines for Writing an IANA Considerations Section in RFCs
<draft-iesg-iana-considerations-02.txt>
Status of this Memo
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This Internet Draft expires July 30, 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 authentication algorithm). To
insure that such quantities have unique values, their assignment must
be administered by a central authority. In the Internet, 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
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. Registration maintenance................................. 6
4. What To Put In Documents................................. 7
5. Security Considerations.................................. 8
6. Acknowledgements......................................... 8
7. References............................................... 8
8. Authors' Addresses....................................... 9
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
authentication algorithm for IPSec [IPSEC]). To insure that such
fields have unique values, their assignment must be administered by a
central authority. In the Internet, 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
IANA only deals with assignments at the higher-levels, while
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
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can be delegated, the IANA only deals with assignments at the top
level.
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 is straightforward and requires no
subject subjective decision making. On those cases, it is reasonable
for the IANA to review prospective assignments, provided that the
IANA is given specific guidelines on what types of requests it should
grant, and what information must be provided before a request of 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, some of which are in use today:
Local Use - For local use only, with the type and 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.
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
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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.
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]
IETF Consensus - New values are assigned through the IETF
consensus process. Specifically, new assignments must be
approved by the IESG. Typically, 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]
In some cases, it may 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 is 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 on a more general
mailing list on which (e.g., that of a current or former IETF Working
Group). Such a mailing list may serve to give new registrations a
public review before getting registered, or 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
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cannot determine if or when such discussion reaches a consensus, the
IANA in all cases relies on a designated subject matter expert to
advise it in these matters. That is, the IANA must be directed to
forward the requests it receives to a specific point-of-contact (one
or a small number of individuals) and act upon the returned
recommendation from the designated subject matter expert. In all
cases, it is the designated subject matter 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 subject matter 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 subject matter
expert.
In some cases, it makes sense to partition the number 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
earlier, while options number 128-254 are "site specific", i.e.,
Local Use.
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.
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4. What To Put In Documents
The previous section 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. Such a section should state clearly:
- who reviews an application for an assigned number. If a request
should be reviewed by a designated subject matter expert,
contact information must be provided.
- who has authority to replace the designated subject matter
expert, should a replacement be needed (e.g., if multiple
attempts to reach the designated subject matter fail). The
specific procedure to appoint the person should also be
indicated; it may often be appropriate to let the relevant IESG
Area Director designate the subject matter expert when a
replacement is necessary.
- If the request should also be reviewed by a specific public
mailing list (such as the ietf-types@iana.org for media types),
that mailing address should be specified. Note, however, that a
designated subject matter expert must also be specified.
- if the IANA is expected to review requests itself, sufficient
guidance must be provided so that the requests can be evaluated
with minimal subjectivity.
It should also be noted that the following are unacceptable:
- listing a Working Group mailing list as the designated subject
matter expert
- specifying that "the current Working Group Chairs of the FooBar
Working Group" are the designated subject matter experts, since
Working Groups eventually close down. However, it is acceptable
to list the current WG Chairs individually.
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:
numbers are allocated as First Come First Served as defined in
[IANA-CONSIDERATIONS]
For examples of documents that provide good and detailed guidance to
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the IANA on the issue of assigning identifiers, consult [MIME-REG,
MIME-LANG].
5. Security Considerations
Information that creates or updates a registration needs to be
authenticated.
Information concerning possible security vulnerabilities of a
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 for all types
registered in the IETF Tree [MIME-REG]. A similar analysis for media
types registered in the vendor or personal trees is encouraged but
not required. However, regardless of what security analysis has or
has not been done, all descriptions of security issues must be as
accurate as possible regardless of registration tree. 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.
6. Acknowledgements
Jon Postel and Joyce Reynolds provided a detailed explanation on what
the IANA needs in order to manage assignments efficiently. Brian
Carpenter provided helpful comments on earlier versions of the
document. One paragraph in the Security Considerations section was
borrowed from [MIME-REG].
7. 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
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[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-02.txt.
[IP] J. Postel, Internet Protocol, RFC 791, September 1, 1981.
[IPSEC] Atkinson, R., Security Architecture for the Internet
Protocol, RFC 1825, August 1995.
[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.
8. 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
UNINETT
P.O.Box 6883 Elgeseter
N-7002 TRONDHEIM
NORWAY
Phone: +47 73 59 70 94
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EMail: Harald.T.Alvestrand@uninett.no
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