Transport Area Working Group M. Cotton
Internet-Draft ICANN
Updates: 2780, 4340 L. Eggert
(if approved) Nokia
Intended status: BCP A. Mankin
Expires: February 12, 2010 Johns Hopkins Univ.
J. Touch
USC/ISI
M. Westerlund
Ericsson
August 11, 2009
Internet Assigned Numbers Authority (IANA) Procedures for the Management
of the Transport Protocol Port Number and Service Name Registry
draft-ietf-tsvwg-iana-ports-02
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
copyright in some of this material may not have granted the IETF
Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
document may not be modified outside the IETF Standards Process, and
derivative works of it may not be created outside the IETF Standards
Process, except to format it for publication as an RFC or to
translate it into languages other than English.
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.
Cotton, et al. Expires February 12, 2010 [Page 1]
Internet-Draft Port Number and Service Name Procedures August 2009
This Internet-Draft will expire on February 12, 2010.
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Abstract
This document defines the procedures that the Internet Assigned
Numbers Authority (IANA) uses when handling registration and other
requests related to the transport protocol port number and service
name registry. It also discusses the rationale and principles behind
these procedures and how they facilitate the long-term sustainability
of the registry.
This document updates RFC2780 by obsoleting Sections 8 and 9.1 of
that RFC, and it updates the IANA allocation procedures for DCCP as
defined in RFC4340.
Cotton, et al. Expires February 12, 2010 [Page 2]
Internet-Draft Port Number and Service Name Procedures August 2009
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Conventions Used in this Document . . . . . . . . . . . . . . 5
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Port Number Ranges . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Port Numbers and Service Names for Experimentation . . . . 7
5. Principles for Port Number and Service Name Registry
Management . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.1. Basic Principles of Port Number Conservation . . . . . . . 9
5.2. Variances for Specific Port Number Ranges . . . . . . . . 10
5.3. New Principles . . . . . . . . . . . . . . . . . . . . . . 11
6. IANA Procedures for Managing the Port Number and Service
Name Registry . . . . . . . . . . . . . . . . . . . . . . . . 12
6.1. Port Number or Service Name Registration . . . . . . . . . 12
6.2. Port Number and Service Name De-Registration . . . . . . . 14
6.3. Port Number and Service Name Re-Use . . . . . . . . . . . 14
6.4. Port Number and Service Name Revocation . . . . . . . . . 15
6.5. Port Number and Service Name Transfers . . . . . . . . . . 15
6.6. Maintenance Issues . . . . . . . . . . . . . . . . . . . . 16
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8.1. Service Name Consistency . . . . . . . . . . . . . . . . . 17
8.2. Port Numbers for SCTP and DCCP Experimentation . . . . . . 18
8.3. Updates to DCCP Registries . . . . . . . . . . . . . . . . 19
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
10.1. Normative References . . . . . . . . . . . . . . . . . . . 21
10.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Cotton, et al. Expires February 12, 2010 [Page 3]
Internet-Draft Port Number and Service Name Procedures August 2009
1. Introduction
The Transmission Control Protocol (TCP) [RFC0793] and the User
Datagram Protocol (UDP) [RFC0768] have enjoyed a remarkable success
over the decades as the two most widely used transport protocols on
the Internet. They have introduced the concept of "ports" as logical
entities for Internet communication. Ports serve two purposes:
first, they provide a demultiplexing identifier to differentiate
transport sessions between the same pair of endpoints, and second,
they also identify the application protocol and associated service to
which processes bind. Newer transport protocols, such as the Stream
Control Transmission Protocol (SCTP) [RFC4960] and the Datagram
Congestion Control Protocol (DCCP) [RFC4342] have adopted the concept
of ports for their communication sessions and use port numbers in the
same way as TCP and UDP. UDP-Lite [RFC3828], a variant of UDP, is
also making use of UDP port numbers. For the purposes of this
document, all rules stated for UDP also apply to UDP-Lite, because it
uses the same assignments as UDP.
Port numbers are the original and most widely used means for
application and service identification on the Internet. Ports are
16-bit numbers, and the combination of source and destination port
numbers together with the IP addresses of the communicating end
systems uniquely identifies a session of a given transport protocol.
Port numbers are also known by their corresponding service names such
as "telnet" for port number 23 and both "http" and "www" for port
number 80.
Hosts running services, hosts accessing services on other hosts, and
intermediate devices (such as firewalls and NATs) that restrict
services need to agree on which service corresponds to a particular
destination port. Although this can be a local decision between the
endpoints of a connection, most Internet components use a single,
shared view of this association, provided by the Internet Assigned
Numbers Authority (IANA) through the port number registry [REGISTRY].
Applications either use numeric port numbers directly, look up port
numbers based on service names via system calls such as
getservbyname() on UNIX, or - more recently - use service names to
look up a service resource records (SRV RRs) [RFC2782] via the Domain
Name System (DNS) [RFC1034] in a variety of ways [RFC1078]
[I-D.cheshire-dnsext-dns-sd][I-D.cheshire-dnsext-multicastdns] to
obtain the port number of a given service.
Designers of applications and application-level protocols may apply
to IANA for an assigned port number and service name for a specific
application, and may - after successful registration - assume that no
other application will use that port number and service name for its
Cotton, et al. Expires February 12, 2010 [Page 4]
Internet-Draft Port Number and Service Name Procedures August 2009
communication sessions. Alternatively, application designers may
also only ask for an assigned service name, if their application does
not require a port number. The latter alternative is encouraged when
possible, in order to conserve the more limited port number space.
It is important to note that ownership of registered port numbers and
service names remains with IANA.
For protocols developed by IETF working groups, IANA offers a method
for the "early" assignment of port numbers and service names, in line
with [RFC4020], as described in Section 6.1.
This document updates [RFC2780] by obsoleting Sections 8 and 9.1 of
that RFC. Note that [RFC5237] updates a different subset of the IANA
allocation guidelines originally given in [RFC2780] (specifically,
the policies on the namespace of the IP protocol number and IPv6 next
header).
2. Conventions Used in this Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119
[RFC2119].
3. Motivation
For many years, the allocation and registration of new port number
values and service names for use with TCP and UDP have had less than
clear guidelines. Information about the registration procedures for
the port registry existed in three locations: the forms for
requesting port number registrations on the IANA web site [SYSFORM]
[USRFORM], an introductory text section in the file listing the port
number registrations themselves [REGISTRY], and two brief sections of
[RFC2780].
Similarly, the procedures surrounding service names have been
historically unclear. Service names were originally created as
mnemonic identifiers for port numbers without a well-defined syntax,
beyond the 14-character limit mentioned on the IANA website [SYSFORM]
[USRFORM]. (Even that length limit has not been consistently
applied, and some assigned service names are 15 characters long.)
When service identification via DNS SRV RRs became popular, the
ambiguities in the syntactic definition of the service namespace,
together with a requirement by IANA to only assign service names and
port numbers in combination, led to the creation of an ad-hoc service
name registry outside of the control of IANA [SRVTYPE].
Cotton, et al. Expires February 12, 2010 [Page 5]
Internet-Draft Port Number and Service Name Procedures August 2009
This document aggregates this scattered information into a single
reference that aligns and clearly defines the management procedures
for both port numbers and service names. It gives more detailed
guidance to prospective requesters of ports and service names than
the existing documentation, and it streamlines the IANA procedures
for the management of the registry, so that management requests can
complete in a timely manner. It also merges the service name
registrations that have occurred in the ad-hoc [SRVTYPE] registry
into the IANA registry [REGISTRY], because under the new IANA
guidelines, registering service names without port numbers has become
possible.
A key factor of this procedural streamlining is to establish
identical registration procedures for all IETF transport protocols.
This document brings the IANA procedures for TCP and UDP in line with
those already in effect for SCTP and DCCP, resulting in a single
process that requesters and IANA follow for all requests for all
transport protocols, including those not yet defined.
A second purpose of this document is to describe the principles that
guide the IETF and IANA in their role as the long-term joint stewards
of the port number registry. TCP and UDP have been a remarkable
success over the last decades. Thousands of applications and
application-level protocols have registered ports and service names
for their use, and there is every reason to believe that this trend
will continue into the future. It is hence extremely important that
management of the registry follow principles that ensure its long-
term usefulness as a shared resource. Section 5 discusses these
principles in detail.
In addition to detailing the IANA procedures for the initial
assignment of port numbers and service names, this document also
specifies post-assignment procedures that until now have been handled
in an ad-hoc manner. These include procedures to de-register a port
number that is no longer in use, to re-use a port number allocated
for one application that is no longer in use for another application,
and procedure by which IANA can unilaterally revoke a prior port
number registration. Section 6 discusses the specifics of these
procedures.
4. Port Number Ranges
TCP, UDP (and UDP-Lite), SCTP and DCCP use 16-bit namespaces for
their port number registries. The port registries for all these
transport protocols are subdivided into three ranges of numbers, and
Section 5.2 describes the IANA procedures for each range in detail:
Cotton, et al. Expires February 12, 2010 [Page 6]
Internet-Draft Port Number and Service Name Procedures August 2009
o the Well Known Ports, also known as the System Ports, from 0-1023
(assigned by IANA)
o the Registered Ports, also known as the User Ports, from 1024-
49151 (assigned by IANA)
o the Dynamic Ports, also known as the Private Ports, from 49152-
65535 (never assigned)
Of the assignable port ranges (Well Known and Registered, i.e., port
numbers 0-49151), individual port numbers are in one of three states
at any given time:
o Assigned: Assigned port numbers are currently allocated to the
service indicated in the registry.
o Unassigned: Unassigned port numbers are currently available for
assignment upon request, as per the procedures outlined in this
document.
o Reserved: Reserved port numbers are not available for regular
assignment; they are "assigned to IANA" for special purposes.
Reserved port numbers include values at the edges of each range,
e.g., 0, 1023, 1024, etc., which may be used to extend these
ranges or the overall port number space in the future.
In order to keep the size of the registry manageable, IANA typically
only records the Assigned and Reserved port numbers and service names
in the registry. Unassigned values are typically not explicitly
listed.
As a data point, when this document was written, approximately 76% of
the TCP and UDP Well Known Ports were assigned, as were a significant
fraction of the Registered Ports. (As noted, Dynamic Ports are never
assigned.)
4.1. Port Numbers and Service Names for Experimentation
Of the Well Known ports, two TCP and UDP port numbers (1021 and
1022), together with their respective service names ("exp1" and
"exp2"), have been assigned for experimentation with new applications
and application-layer protocols that require a port number in the
assigned ports ranges [RFC4727]. This document registers the same
two port numbers and service names for experimentation with new
application-layer protocols over SCTP and DCCP in Section 8.2.
Please refer to Sections 1 and 1.1 of [RFC3692] for how these
experimental port numbers are to be used. Specifically, they SHOULD
Cotton, et al. Expires February 12, 2010 [Page 7]
Internet-Draft Port Number and Service Name Procedures August 2009
only be used for local experiments in controlled environments, and
they SHOULD NOT be used on the global Internet. Many new
applications and application-layer protocols can be experimented with
without requiring a port in the Well Known or Registered ports range,
and port numbers in the Dynamic Ports range can be also used.
Unfortunately, it can be difficult to limit access to these ports.
Users SHOULD take measures to ensure that experimental ports are
connecting to the intended process. For example, users of these
experimental ports might include a 64-bit nonce, once on each segment
of a message-oriented channel (e.g., UDP), or once at the beginning
of a byte-stream (e.g., TCP), which is used to confirm that the port
is being used as intended. Such confirmation of intended use is
especially important when these ports are associated with privileged
(e.g., system or administrator) processes.
5. Principles for Port Number and Service Name Registry Management
Management procedures for the port number and service name registry
include allocation of port numbers and service names upon request, as
well as coordination of information about existing allocations. The
latter includes maintaining contact and description information about
assignments, revoking abandoned assignments, and redefining
assignments when needed. Of these procedures, port number allocation
is most critical, because of the limited number of remaining port
numbers. The namespace available for service names is much larger,
which allows for simpler management procedures.
Before the publication of this document, the principles of port
number and service name management followed some simple, mostly
undocumented guidelines:
o TCP and UDP ports were simultaneously allocated when either was
requested
o Port numbers were the primary allocation; service names were
informative only, and did not have a well-defined syntax
o Port numbers were conserved informally, and sometimes
inconsistently (e.g., some services were allocated ranges of many
port numbers even where not strictly necessary)
o SCTP and DCCP port number and service name registries were managed
separately from the TCP/UDP registries
o Until recently, service names could not be assigned without
assigning a corresponding port number
Cotton, et al. Expires February 12, 2010 [Page 8]
Internet-Draft Port Number and Service Name Procedures August 2009
This document attempts to document, clarify and align these
guidelines in order to more conservatively manage the limited
remaining port number space and to enable and promote the use of
service names for service identification without associated port
numbers, where possible.
5.1. Basic Principles of Port Number Conservation
This section summarizes the basic principles by which IANA attempts
to conserve the port number space. This description is intended to
inform applicants requesting port numbers. IANA decisions are not
required to be bound to these principles, however; other factors may
come into play, and exceptions may occur where deemed in the best
interest of the Internet.
The basic principle of port number registry management is to conserve
use of the port space where possible. Extensions to support larger
port number spaces would require changing many core protocols of the
current Internet in a way that would not be backward compatible and
interfere with both current and legacy applications.
Conservation of the port number space recognizes that because this
space is a limited resource, applications are expected to participate
in the traffic demultiplexing process where feasible. The port
numbers are expected to encode as little information as possible that
will still enable an application to perform further demultiplexing by
itself. In particular, there should be:
o only one assigned port number per service or application
o only one assigned port number for all versions of a service (e.g.,
running the service with or without a security mechanism)
o only one assigned port number for all different types of devices
using or participating in the same service
A given service is expected to further demultiplex messages where
possible. For example, applications and protocols are expected to
include in-band version information, so that future versions of the
application or protocol can share the same allocated port.
Applications and protocols are also expected to be able to
efficiently use a single allocated port for multiple sessions, either
by demultiplexing multiple streams within one port, or using the
allocated port to coordinate using dynamic ports for subsequent
exchanges (e.g., in the spirit of FTP [RFC0959]).
Ports are used in various ways, notably:
Cotton, et al. Expires February 12, 2010 [Page 9]
Internet-Draft Port Number and Service Name Procedures August 2009
o as endpoint process identifiers
o as application protocol identifiers
o for firewall filtering purposes
The process and protocol identifier use suggests that anything a
single process can demultiplex, or that can be encoded into a single
protocol, should be. The firewall filtering use suggests that some
uses that could be de-multiplexed or encoded must be separated to
allow for firewall management. Note that this latter use is much
less sound, because port numbers have meaning only for the two
endpoints involved in a connection, and drawing conclusions about the
service that generated a given flow based on observed port numbers is
inherently problematic.
5.2. Variances for Specific Port Number Ranges
Section 4 describes the different port number ranges. It is
important to note that IANA applies slightly different procedures
when managing the different ranges of the port number registry:
o Ports in the Dynamic Ports range (49152-65535) have been
specifically set aside for local and dynamic use and cannot be
registered through IANA. Applications may simply use them for
communication without any sort of registration. On the other
hand, applications MUST NOT assume that a specific port number in
the Dynamic Ports range will always be available for communication
at all times, and a port number in that range hence MUST NOT be
used as a service identifier.
o Ports in the Registered Ports range (1024-49151) are available for
registration through IANA, and MAY be used as service identifiers
upon successful registration. Because registering a port number
for a specific application consumes a fraction of the shared
resource that is the port number registry, IANA will require the
requester to document the intended use of the port number. This
documentation will be input to the "Expert Review" allocation
procedure [RFC5226], by which IANA will have a technical expert
review the request to determine whether to grant the registration.
The submitted documentation MUST explain why using a port number
in the Dynamic Ports range is unsuitable for the given
application.
o Ports in the Well Known Ports range (0-1023) are also available
for registration through IANA. Because the Well Known Ports range
is both the smallest and the most densely allocated one, the bar
for new allocations is higher than that for the Registered Ports
Cotton, et al. Expires February 12, 2010 [Page 10]
Internet-Draft Port Number and Service Name Procedures August 2009
range, and will only be granted under the "IETF Review" allocation
procedure [RFC5226]. A request for a Well Known port number MUST
document why using a port number from both the Registered Ports
and Dynamic Ports ranges is unsuitable for the given application.
5.3. New Principles
Several new practices stem from the conservation principle that
guides management of the port number and service name registry, and
will take effect with the approval of this document:
o IANA will allocate port numbers only to the transport protocols
explicitly named in an allocation request
o IANA will recover unused port numbers, via the new procedures of
de-registration, revocation, and transfer
o IANA will begin assigning service names without requiring a
corresponding port number allocation
IANA will begin assigning protocol numbers only for those transport
protocols explicitly included in a registration request. This ends
the long-standing practice of automatically assigning a port number
to an application for both TCP and a UDP, even if the request is only
for one of these transport protocols. The new allocation procedure
conserves resources by only allocating a port number to an
application for those transport protocols (TCP, UDP, SCTP and/or
DCCP) it actually uses. The port number will be marked as Reserved -
instead of Assigned - in the port number registries of the other
transport protocols. When applications start supporting the use of
some of those additional transport protocols, their implementors MUST
request IANA to convert the reservation into an assignment. An
application MUST NOT assume that it can use a port number assigned to
it for use with one transport protocol with another transport
protocol without asking IANA to convert the reservation into an
assignment.
Conservation of port numbers is improved by procedures that allow
previously allocated port numbers to become Unassigned, either
through de-registration or through revocation, and by a procedure
that lets application designers transfer an allocated but unused port
number to a new application. Section 6 describes these procedures,
which so far were undocumented. Port number conservation is also
improved by recommending that applications that do not require an
allocated port, e.g., because they can use service-name-based
lookups, chose this option and only register a service name.
Cotton, et al. Expires February 12, 2010 [Page 11]
Internet-Draft Port Number and Service Name Procedures August 2009
6. IANA Procedures for Managing the Port Number and Service Name
Registry
This section describes the process for requests associated with
IANA's management of the port number and service name registry. Such
requests include initial registration, de-registration, re-use,
changes to the service name, as well as updates to the contact
information or description associated with an assignment. Revocation
is initiated by IANA.
6.1. Port Number or Service Name Registration
Registration refers to the allocation of port numbers or service
names to applicants. All such, registrations are made from port
numbers or service names that are Unassigned or Reserved at the time
of the allocation. Unassigned numbers and names are allocated as
needed, and without further explanation. Reserved numbers and names
are assigned only after review by IANA and the IETF, and are
accompanied by a statement explaining the reason a Reserved number or
name is appropriate for this action.
When a registration for one or more (but not all) transport protocols
is approved, the port number for the non-requested transport
protocol(s) will be marked as Reserved. IANA SHOULD NOT assign that
port number to any other application or service until no other port
numbers remain Unassigned in the requested range. The current
registration owner of a port number MAY register these Reserved port
numbers for other transport protocols when needed.
Service names, on the other hand, are not tied to a specific
transport protocol, and registration requests for only a service name
(but not a port number) allocate that service name for use with all
transport protocols.
A port number or service name registration consists of the following
information:
o Registration Technical Contact: Name and email address of the
technical contact person for the registration. This is REQUIRED.
Additional address information MAY be provided. For registrations
done through IETF-published RFCs, one or more technical contact
persons SHALL be provided.
o Registration Owner: Name and email address of the owner of the
registration. This is REQUIRED. For individuals, this is the
same as the registration technical contact; for organizations,
this is a point of contact at that organization. For
registrations done through IETF-published RFCs, the registration
Cotton, et al. Expires February 12, 2010 [Page 12]
Internet-Draft Port Number and Service Name Procedures August 2009
ownership will belong to the IETF and not the technical contact
persons.
o Transport Protocol: The transport protocol(s) for which the port
number or service name allocation is requested MUST be provided.
This field is currently limited to one or more of TCP, UDP, SCTP,
and DCCP.
o Port Number: If assignment of port number(s) is desired, either
the currently Unassigned port number(s) the requester suggests for
allocation or the tag "ANY" MUST be provided. If only a service
name is to be assigned, this field MUST be empty. If specific
port numbers are requested, IANA is encouraged to allocate the
suggested numbers. If the tag "ANY" is specified, IANA will
choose a suitable number from the Registered Ports range. Note
that the applicant MUST NOT use the suggested ports prior to the
completion of the registration.
o Service Name: A desired unique service name for the service
associated with the registration request, for use in various
service selection and discovery mechanisms, MUST be provided.
Valid service names MUST only contain these US-ASCII
[ANSI.X3-4.1986] characters: letters from A to Z, digits from 0 to
9, and hyphens ("-", ASCII 0x2D or decimal 45). They MUST be at
MOST fifteen characters long, MUST NOT begin or end with a hyphen,
and MUST NOT consist of only digits, in order to be
distinguishable from port numbers. In order to be unique, they
MUST NOT be identical to any currently registered service names in
the IANA registry [REGISTRY]. Service names are case-insensitive;
they may be provided and entered into the registry with mixed case
(e.g., for clarity), but for the purposes of comparison, the case
is ignored.
o Service Code: A desired unique service code for the service
associated with the registration request. Service codes are
specific to the DCCP protocol [I-D.ietf-dccp-serv-codes]; the
request MUST include a desired service code when the registration
requests includes DCCP as a transport protocol, and MUST NOT
include one otherwise.
o Description: A short description of the service associated with
the registration request is REQUIRED. It should avoid all but the
most well known acronyms.
o Reference: A reference document describing the protocol or
application using this port, including whether the protocol
supports either broadcast, multicast, or anycast communication.
For registration requests for Registered Ports, this documentation
Cotton, et al. Expires February 12, 2010 [Page 13]
Internet-Draft Port Number and Service Name Procedures August 2009
MUST explain why a port number in the Dynamic Ports range is
unsuitable for the given application. For registration requests
for Well Known Ports, this documentation MUST explain why a port
number in the Registered Ports or Dynamic Ports ranges is
unsuitable.
"Early" registration requests can be made by IETF working groups
without including such a reference document, although it is
RECOMMENDED that at least a reference to an Internet Draft
describing the work in progress is provided.
6.2. Port Number and Service Name De-Registration
The original requesters of a granted port number assignment can
return the port number to IANA at any time if they no longer have a
need for it. The port number will be de-registered and will be
marked as Reserved. IANA should not re-assign port numbers that have
been de-registered until all other available port numbers in the
specific range have been assigned.
Before proceeding with a port number de-registration, IANA needs to
reasonably establish that the value is actually no longer in use.
Because there is much less danger of exhausting the service name
space compared to the port number space, it is RECOMMENDED that a
given service name remain assigned even after all associated port
number assignments have become de-registered. It will afterwards
appear in the registry as if it had been created through a service
name registration request that did not include any port numbers.
On rare occasions, it may still be useful to de-register a service
name. In such cases, IANA will mark the service name as Reserved.
6.3. Port Number and Service Name Re-Use
If the original requesters of a granted port number assignment no
longer have a need for the registered number, but would like to re-
use it for a different application, they can submit a request to IANA
to do so.
Logically, port number re-use is to be thought of as a de-
registration (Section 6.2) followed by an immediate re-registration
(Section 6.1) of the same port number for a new application.
Consequently, the information that needs to be provided about the
proposed new use of the port number is identical to what would need
to be provided for a new port number allocation for the specific
ports range.
Cotton, et al. Expires February 12, 2010 [Page 14]
Internet-Draft Port Number and Service Name Procedures August 2009
Because there is much less danger of exhausting the service name
space compared to the port number space, it is RECOMMENDED that the
original service name associated with the prior use of the port
number remains assigned, and a new service be created and associated
with the port number. This is again consistent with viewing a re-use
request as a de-registration followed by an immediate re-
registration. Re-using an assigned service name for a different
application is NOT RECOMMENDED.
IANA needs to carefully review such requests before approving them.
In some instances, the Expert Reviewer will determine that the
application that the port number was assigned to has found usage
beyond the original requester, or that there is a concern that it may
have such users. This determination MUST be made quickly. A
community call concerning revocation of a port number (see below) MAY
be considered, if a broader use of the port number is suspected.
6.4. Port Number and Service Name Revocation
A port number revocation can be thought of as an IANA-initiated de-
registration (Section 6.2), and has exactly the same effect on the
registry.
Sometimes, it will be clear that a specific port number is no longer
in use and that IANA can revoke it and mark it as Reserved. At other
times, it may be unclear whether a given assigned port number is
still in use somewhere in the Internet. In those cases, IANA must
carefully consider the consequences of revoking the port number, and
SHOULD only do so if there is an overwhelming need.
With the help of their IESG-appointed Expert Reviewer, IANA SHALL
formulate a request to the IESG to issue a four-week community call
concerning the pending port number revocation. The IESG and IANA,
with the Expert Reviewer's support, SHALL determine promptly after
the end of the community call whether revocation should proceed and
then communicate their decision to the community. This procedure
typically involves similar steps to de-registration except that it is
initiated by IANA.
Because there is much less danger of exhausting the service name
space compared to the port number space, revoking service names is
NOT RECOMMENDED.
6.5. Port Number and Service Name Transfers
The value of port numbers and service names is defined by their
careful management as a shared Internet resource, whereas enabling
transfer allows the potential for associated monetary exchanges. As
Cotton, et al. Expires February 12, 2010 [Page 15]
Internet-Draft Port Number and Service Name Procedures August 2009
a result, current IANA procedures do not permit port number or
service name assignments to be transferred between parties, even when
they are mutually consenting.
The appropriate alternate procedure is a coordinated de-registration
and registration: The new party requests the port number or service
name via a registration and the previous party releases its
assignment via the de-registration procedure outlined above.
With the help of their IESG-appointed Expert Reviewer, IANA SHALL
carefully determine if there is a valid technical, operational or
managerial reason before performing the transfer.
6.6. Maintenance Issues
The previous procedures help IANA manage the defining properties of
the port name and service name registry. There are additional
procedures which are administrative and help IANA maintain non-
defining information in a registration. This includes changes to the
Port Description and changes to contact information. These changes
are coordinated by IANA in an informal manner, and may be initiated
by either the registrant or by IANA, e.g., the latter when requesting
an update to current contact information.
7. Security Considerations
The IANA guidelines described in this document do not change the
security properties of either TCP, SCTP, DCCP or UDP.
Assignment of a port number or service name does not in any way imply
an endorsement of an application or product, and the fact that
network traffic is flowing to or from a registered port number does
not mean that it is "good" traffic, or even that it is used by the
assigned service. Firewall and system administrators should choose
how to configure their systems based on their knowledge of the
traffic in question, not whether there is a port number or service
name registered or not.
8. IANA Considerations
This document obsoletes Sections 8 and 9.1 of [RFC2780]. Upon
approval of this document, IANA is requested to adopt the procedures
described herein.
Cotton, et al. Expires February 12, 2010 [Page 16]
Internet-Draft Port Number and Service Name Procedures August 2009
8.1. Service Name Consistency
Section 6.1 defines which character strings are well-formed service
names, which until now had not been clearly defined. The definition
on Section 6.1 was chosen to allow maximum compatibility of service
names with various service discovery mechanisms.
Unfortunately, the current port number registry [REGISTRY] contains a
few assigned service names that do not conform to the new naming
rules. In all cases, this is because they contain illegal characters
such as asterisks, dots, plusses, slashes, or underscores. (All
current service names conform to the length requirement of 15
characters or less.)
Upon approval of this document, IANA SHALL take immediate actions to
resolve these inconsistencies. For any registry assignment with an
illegal service name, IANA SHALL add an alias to the registry that
assigns a well-formed service name for the existing service but
otherwise duplicates the original assignment information. It is
desirable if the alias closely resembles the original service name,
e.g., by remapping underscores to dashes, etc. In the description
field of the new alias, IANA SHALL record that it assigns a well-
formed service name for the previous service and point to the
original assignment. In the description field of the original
assignment, IANA SHALL add a note that the service name is historic,
is not usable with many common service discovery mechanisms, and
provide a reference to the new alias, which can be used in this way.
As of 2009-8-5 [REGISTRY], these service names were illegal under the
rules stated in Section 6.1:
Cotton, et al. Expires February 12, 2010 [Page 17]
Internet-Draft Port Number and Service Name Procedures August 2009
+-----------------+-----------------+----------------+
| 914c/g | EtherNet/IP-1 | EtherNet/IP-2 |
| LiebDevMgmt_A | LiebDevMgmt_C | LiebDevMgmt_DM |
| acmaint_dbd | acmaint_transd | atex_elmd |
| avanti_cdp | badm_priv | badm_pub |
| bdir_priv | bdir_pub | bmc_ctd_ldap |
| bmc_patroldb | boks_clntd | boks_servc |
| boks_servm | broker_service | bues_service |
| canit_store | cedros_fds | cl/1 |
| contamac_icm | corel_vncadmin | csc_proxy |
| cvc_hostd | dbcontrol_agent | dec_dlm |
| dl_agent | documentum_s | dsmeter_iatc |
| dsx_monitor | elpro_tunnel | elvin_client |
| elvin_server | encrypted_admin | erunbook_agent |
| erunbook_server | esri_sde | event_listener |
| flr_agent | gds_db | ibm_wrless_lan |
| iceedcp_rx | iceedcp_tx | iclcnet_svinfo |
| idig_mux | ife_icorp | instl_bootc |
| instl_boots | intel_rci | interhdl_elmd |
| lan900_remote | mapper-ws_ethd | matrix_vnet |
| mdbs_daemon | menandmice_noh | msl_lmd |
| nburn_id | ncr_ccl | nds_sso |
| netmap_lm | nms_topo_serv | notify_srvr |
| novell-lu6.2 | nuts_bootp | nuts_dem |
| ocs_amu | ocs_cmu | pipe_server |
| pra_elmd | printer_agent | redstorm_diag |
| redstorm_find | redstorm_info | redstorm_join |
| resource_mgr | rmonitor_secure | rsvp_tunnel |
| sai_sentlm | sge_execd | sge_qmaster |
| shiva_confsrvr | srvc_registry | stm_pproc |
| subntbcst_tftp | udt_os | universe_suite |
| veritas_pbx | vision_elmd | vision_server |
| whois++ | wrs_registry | z39.50 |
+-----------------+-----------------+----------------+
8.2. Port Numbers for SCTP and DCCP Experimentation
Two Well Known ports, 1021 and 1022, have been reserved for
experimentation UDP and TCP [RFC4727]. This document registers the
same port numbers for SCTP and DCCP, and also instructs IANA to
automatically register these two port numbers for any new transport
protocol that will in the future share the port number namespace.
Note that these port numbers are meant for temporary experimentation
and development in controlled environments. Before using these port
numbers, carefully consider the advice in Section 4.1 in this
document, as well as in Sections 1 and 1.1 of [RFC3692]. Most
importantly, application developers must request a permanent port
Cotton, et al. Expires February 12, 2010 [Page 18]
Internet-Draft Port Number and Service Name Procedures August 2009
number assignment from IANA as described in Section 6.1 before any
kind of non-experimental deployment.
+--------------------------------+----------------------------+
| Registration Technical Contact | IESG <iesg@ietf.org> |
| Registration Owner | IETF <iesg@ietf.org> |
| Transport Protocol | SCTP, DCCP |
| Port Number | 1021 |
| Port Name | RFC3692-style Experiment 1 |
| Service Name | exp1 |
| Reference | [RFCyyyy] |
+--------------------------------+----------------------------+
+--------------------------------+----------------------------+
| Registration Technical Contact | IESG <iesg@ietf.org> |
| Registration Owner | IETF <iesg@ietf.org> |
| Transport Protocol | SCTP, DCCP |
| Port Number | 1022 |
| Port Name | RFC3692-style Experiment 2 |
| Service Name | exp2 |
| Reference | [RFCyyyy] |
+--------------------------------+----------------------------+
[RFC Editor Note: Please change "yyyy" to the RFC number allocated to
this document before publication.]
8.3. Updates to DCCP Registries
This document updates the IANA allocation procedures for the DCCP
Port Number and DCCP Service Codes Registries as defined in
[RFC4340].
8.3.1. DCCP Service Code Registry
Service Codes are allocated first-come-first-served according to
Section 19.8 of [RFC4340]. This document updates Section 19.8 of
[RFC4340] by extending the guidelines given there in the following
ways:
o IANA MAY assign new Service Codes without seeking Expert Review
using their discretion, but SHOULD seek expert review when a
request seeks an appreciable number of Service Codes (e.g., more
than five).
o IANA should feel free to contact the DCCP Expert Reviewer with
questions on any registry, regardless of the registry policy, for
clarification or if there is a problem with a request [RFC4340].
Cotton, et al. Expires February 12, 2010 [Page 19]
Internet-Draft Port Number and Service Name Procedures August 2009
8.3.2. DCCP Port Numbers Registry
The DCCP ports registry is defined by [RFC4340] in Section 19.9.
Allocations in this registry require prior allocation of a Service
Code. Not all Service Codes require IANA-registered ports. This
document updates Section 19.9 of [RFC4340] by extending the
guidelines given there in the following way:
o IANA should normally assign a value in the range 1024-49151 to a
DCCP server port. IANA allocation requests to allocate port
numbers in the Well Known Ports range (0 through 1023), require an
"IETF Review" [RFC5226] prior to allocation by IANA [RFC4340].
Section 19.9 of [RFC4340] requires each DCCP server port assignment
to be associated with at least one Service Code value. This document
updates [RFC4340] in the following way:
o IANA MUST NOT allocate a single Service Code value to more than
one DCCP server port.
o The set of Service Code values associated with a DCCP server port
should be recorded in the ports registry.
o A request for additional Service Codes to be associated with an
already allocated Port Number requires Expert Review. These
requests will normally be accepted when they originate from the
contact associated with the port registration. In other cases,
these applications will be expected to use an unallocated port,
when this is available.
[RFC4340] notes that a short port name MUST be associated with each
DCCP server port that has been registered. This document requires
that this name MUST be unique.
9. Acknowledgments
The text in Section 8.3 is based on a suggestion by Tom Phelan.
Lars Eggert is partly funded by [TRILOGY], a research project
supported by the European Commission under its Seventh Framework
Program.
10. References
Cotton, et al. Expires February 12, 2010 [Page 20]
Internet-Draft Port Number and Service Name Procedures August 2009
10.1. Normative References
[ANSI.X3-4.1986]
American National Standards Institute, "Coded Character
Set - 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986.
[RFC0768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
August 1980.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, September 1981.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2780] Bradner, S. and V. Paxson, "IANA Allocation Guidelines For
Values In the Internet Protocol and Related Headers",
BCP 37, RFC 2780, March 2000.
[RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., and
G. Fairhurst, "The Lightweight User Datagram Protocol
(UDP-Lite)", RFC 3828, July 2004.
[RFC4020] Kompella, K. and A. Zinin, "Early IANA Allocation of
Standards Track Code Points", BCP 100, RFC 4020,
February 2005.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340, March 2006.
[RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4,
ICMPv6, UDP, and TCP Headers", RFC 4727, November 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
10.2. Informative References
[I-D.cheshire-dnsext-dns-sd]
Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", draft-cheshire-dnsext-dns-sd-05 (work in
progress), September 2008.
[I-D.cheshire-dnsext-multicastdns]
Cheshire, S. and M. Krochmal, "Multicast DNS",
draft-cheshire-dnsext-multicastdns-07 (work in progress),
Cotton, et al. Expires February 12, 2010 [Page 21]
Internet-Draft Port Number and Service Name Procedures August 2009
September 2008.
[I-D.ietf-dccp-serv-codes]
Fairhurst, G., "The DCCP Service Code",
draft-ietf-dccp-serv-codes-11 (work in progress),
May 2009.
[REGISTRY]
Internet Assigned Numbers Authority (IANA), "Port
Numbers", http://www.iana.org/assignments/port-numbers.
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC1078] Lottor, M., "TCP port service Multiplexer (TCPMUX)",
RFC 1078, November 1988.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692, January 2004.
[RFC4342] Floyd, S., Kohler, E., and J. Padhye, "Profile for
Datagram Congestion Control Protocol (DCCP) Congestion
Control ID 3: TCP-Friendly Rate Control (TFRC)", RFC 4342,
March 2006.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol",
RFC 4960, September 2007.
[RFC5237] Arkko, J. and S. Bradner, "IANA Allocation Guidelines for
the Protocol Field", BCP 37, RFC 5237, February 2008.
[SRVTYPE] "DNS SRV (RFC 2782) Service Types",
http://www.dns-sd.org/ServiceTypes.html.
[SYSFORM] Internet Assigned Numbers Authority (IANA), "Application
for System (Well Known) Port Number",
http://www.iana.org/cgi-bin/sys-port-number.pl.
[TRILOGY] "Trilogy Project", http://www.trilogy-project.org/.
[USRFORM] Internet Assigned Numbers Authority (IANA), "Application
Cotton, et al. Expires February 12, 2010 [Page 22]
Internet-Draft Port Number and Service Name Procedures August 2009
for User (Registered) Port Number",
http://www.iana.org/cgi-bin/usr-port-number.pl.
Authors' Addresses
Michelle Cotton
Internet Corporation for Assigned Names and Numbers
4676 Admiralty Way, Suite 330
Marina del Rey, CA 90292
USA
Phone: +1 310 823 9358
Email: michelle.cotton@icann.org
URI: http://www.iana.org/
Lars Eggert
Nokia Research Center
P.O. Box 407
Nokia Group 00045
Finland
Phone: +358 50 48 24461
Email: lars.eggert@nokia.com
URI: http://research.nokia.com/people/lars_eggert/
Allison Mankin
Johns Hopkins University
Phone: +1 301 728 7199
Email: mankin@psg.com
URI: http://www.psg.com/~mankin/
Joe Touch
USC/ISI
4676 Admiralty Way
Marina del Rey, CA 90292
USA
Phone: +1 310 448 9151
Email: touch@isi.edu
URI: http://www.isi.edu/touch
Cotton, et al. Expires February 12, 2010 [Page 23]
Internet-Draft Port Number and Service Name Procedures August 2009
Magnus Westerlund
Ericsson
Torshamsgatan 23
Stockholm 164 80
Sweden
Phone: +46 8 719 0000
Email: magnus.westerlund@ericsson.com
Cotton, et al. Expires February 12, 2010 [Page 24]
