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rfc:rfc6335

Internet Engineering Task Force (IETF) M. Cotton Request for Comments: 6335 ICANN BCP: 165 L. Eggert Updates: 2780, 2782, 3828, 4340, 4960, 5595 Nokia Category: Best Current Practice J. Touch ISSN: 2070-1721 USC/ISI

                                                         M. Westerlund
                                                              Ericsson
                                                           S. Cheshire
                                                                 Apple
                                                           August 2011

Internet Assigned Numbers Authority (IANA) Procedures for the Management

  of the Service Name and Transport Protocol Port Number Registry

Abstract

 This document defines the procedures that the Internet Assigned
 Numbers Authority (IANA) uses when handling assignment and other
 requests related to the Service Name and Transport Protocol Port
 Number 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 IANA's procedures by obsoleting the previous
 UDP and TCP port assignment procedures defined in Sections 8 and 9.1
 of the IANA Allocation Guidelines, and it updates the IANA service
 name and port assignment procedures for UDP-Lite, the Datagram
 Congestion Control Protocol (DCCP), and the Stream Control
 Transmission Protocol (SCTP).  It also updates the DNS SRV
 specification to clarify what a service name is and how it is
 registered.

Status of This Memo

 This memo documents an Internet Best Current Practice.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 BCPs is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc6335.

Cotton, et al. Best Current Practice [Page 1] RFC 6335 Service Name and Port Number Procedures August 2011

Copyright Notice

 Copyright (c) 2011 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
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.
 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.

Cotton, et al. Best Current Practice [Page 2] RFC 6335 Service Name and Port Number Procedures August 2011

Table of Contents

 1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
 2.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  5
 3.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  6
 4.  Conventions Used in This Document  . . . . . . . . . . . . . .  8
 5.  Service Names  . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.1.  Service Name Syntax  . . . . . . . . . . . . . . . . . . .  9
   5.2.  Service Name Usage in DNS SRV Records  . . . . . . . . . . 10
 6.  Port Number Ranges . . . . . . . . . . . . . . . . . . . . . . 11
   6.1.  Service Names and Port Numbers for Experimentation . . . . 12
 7.  Principles for Service Name and Transport Protocol Port
     Number Registry Management . . . . . . . . . . . . . . . . . . 12
   7.1.  Past Principles  . . . . . . . . . . . . . . . . . . . . . 13
   7.2.  Updated Principles . . . . . . . . . . . . . . . . . . . . 13
 8.  IANA Procedures for Managing the Service Name and
     Transport Protocol Port Number Registry  . . . . . . . . . . . 16
   8.1.  Service Name and Port Number Assignment  . . . . . . . . . 16
   8.2.  Service Name and Port Number De-Assignment . . . . . . . . 21
   8.3.  Service Name and Port Number Reuse . . . . . . . . . . . . 21
   8.4.  Service Name and Port Number Revocation  . . . . . . . . . 22
   8.5.  Service Name and Port Number Transfers . . . . . . . . . . 22
   8.6.  Maintenance Issues . . . . . . . . . . . . . . . . . . . . 23
   8.7.  Disagreements  . . . . . . . . . . . . . . . . . . . . . . 23
 9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 23
 10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 24
   10.1. Service Name Consistency . . . . . . . . . . . . . . . . . 24
   10.2. Port Numbers for SCTP and DCCP Experimentation . . . . . . 26
   10.3. Updates to DCCP Registries . . . . . . . . . . . . . . . . 27
 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28
 12. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 28
 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 29
   13.1. Normative References . . . . . . . . . . . . . . . . . . . 29
   13.2. Informative References . . . . . . . . . . . . . . . . . . 30

Cotton, et al. Best Current Practice [Page 3] RFC 6335 Service Name and Port Number Procedures August 2011

1. Introduction

 For many years, the assignment of new service names and port number
 values for use with the Transmission Control Protocol (TCP) [RFC0793]
 and the User Datagram Protocol (UDP) [RFC0768] has had less than
 clear guidelines.  New transport protocols have been added -- the
 Stream Control Transmission Protocol (SCTP) [RFC4960] and the
 Datagram Congestion Control Protocol (DCCP) [RFC4342] -- and new
 mechanisms like DNS SRV records [RFC2782] have been developed, each
 with separate registries and separate guidelines.  The community also
 recognized the need for additional procedures beyond just assignment;
 notably modification, revocation, and release.
 A key element of the procedural streamlining specified in this
 document is to establish identical assignment procedures for all IETF
 transport protocols.  This document brings the IANA procedures for
 TCP and UDP in line with those for SCTP and DCCP, resulting in a
 single process that requesters and IANA follow for all requests for
 all transport protocols, including future protocols not yet defined.
 In addition to detailing the IANA procedures for the initial
 assignment of service names and port numbers, this document also
 specifies post-assignment procedures that until now have been handled
 in an ad hoc manner.  These include procedures to de-assign a port
 number that is no longer in use, to take a port number assigned for
 one service that is no longer in use and reuse it for another
 service, and the procedure by which IANA can unilaterally revoke a
 prior port number assignment.  Section 8 discusses the specifics of
 these procedures and processes that requesters and IANA follow for
 all requests for all current and future transport protocols.
 IANA is the authority for assigning service names and port numbers.
 The registries that are created to store these assignments are
 maintained by IANA.  For protocols developed by IETF working groups,
 IANA now also offers a method for the "early assignment" [RFC4020] of
 service names and port numbers, as described in Section 8.1.
 This document updates IANA's procedures for UDP and TCP port numbers
 by obsoleting Sections 8 and 9.1 of the IANA Allocation Guidelines
 [RFC2780].  (Note that other sections of the IANA Allocation
 Guidelines, relating to the protocol field values in IPv4 headers,
 were also updated in February 2008 [RFC5237].)  This document also
 updates the IANA assignment procedures for DCCP [RFC4340] [RFC5595]
 and SCTP [RFC4960].

Cotton, et al. Best Current Practice [Page 4] RFC 6335 Service Name and Port Number Procedures August 2011

 The Lightweight User Datagram Protocol (UDP-Lite) shares the port
 space with UDP.  The UDP-Lite specification [RFC3828] says: "UDP-Lite
 uses the same set of port number values assigned by the IANA for use
 by UDP".  An update of the UDP procedures therefore also results in a
 corresponding update of the UDP-Lite procedures.
 This document also clarifies what a service name is and how it is
 assigned.  This will impact the DNS SRV specification [RFC2782],
 because that specification merely makes a brief mention that the
 symbolic names of services are defined in "Assigned Numbers"
 [RFC1700], without stating to which section it refers within that
 230-page document.  The DNS SRV specification may have been referring
 to the list of Port Assignments (known as /etc/services on Unix), or
 to the "Protocol And Service Names" section, or to both, or to some
 other section.  Furthermore, "Assigned Numbers" [RFC1700] has been
 obsoleted [RFC3232] and has been replaced by on-line registries
 [PORTREG] [PROTSERVREG].
 The development of new transport protocols is a major effort that the
 IETF does not undertake very often.  If a new transport protocol is
 standardized in the future, it is expected to follow these guidelines
 and practices around using service names and port numbers as much as
 possible, for consistency.
 At the time of writing of this document, the internal procedures of
 "Expert Review" teams, including that of IANA's port review team, are
 not documented in any RFC and this document doesn't change that.

2. Motivation

 Information about the assignment procedures for the port registry has
 existed in three locations: the forms for requesting port number
 assignments on the IANA web site [SYSFORM] [USRFORM], an introductory
 text section in the file listing the port number assignments
 themselves (known as the port numbers registry) [PORTREG], and two
 brief sections of the IANA Allocation Guidelines [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,
 apart from 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 Resource
 Records (RRs) was introduced [RFC2782], it became useful to start
 assigning service names alone, and because IANA had no procedure for
 assigning a service name without an associated port number, this led

Cotton, et al. Best Current Practice [Page 5] RFC 6335 Service Name and Port Number Procedures August 2011

 to the creation of an informal temporary service name registry
 outside of the control of IANA, which now contains roughly 500
 service names [SRVREG].
 This document aggregates all this scattered information into a single
 reference that aligns and clearly defines the management procedures
 for both service names and port numbers.  It gives more detailed
 guidance to prospective requesters of service names and ports than
 the existing documentation, and it streamlines the IANA procedures
 for the management of the registry, so that requests can be completed
 in a timely manner.
 This document defines rules for assignment of service names without
 associated port numbers, for such usages as DNS SRV records
 [RFC2782], which was not possible under the previous IANA procedures.
 The document also merges service name assignments from the non-IANA
 ad hoc registry [SRVREG] and from the IANA Protocol and Service Names
 registry [PROTSERVREG] into the IANA Service Name and Transport
 Protocol Port Number registry [PORTREG], which from here on is the
 single authoritative registry for service names and port numbers.
 An additional 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 service name and port number registry.  TCP and UDP
 have had remarkable success over the last decades.  Thousands of
 applications and application-level protocols have service names and
 port numbers assigned 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 7
 discusses these principles in detail.

3. Background

 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 relied on 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 may also identify the application protocol and associated
 service to which processes connect.  Newer transport protocols, such
 as the Stream Control Transmission Protocol (SCTP) [RFC4960] and the
 Datagram Congestion Control Protocol (DCCP) [RFC4342], have also
 adopted the concept of ports for their communication sessions and use
 16-bit port numbers in the same way as TCP and UDP (and UDP-Lite
 [RFC3828], a variant of UDP).

Cotton, et al. Best Current Practice [Page 6] RFC 6335 Service Name and Port Number Procedures August 2011

 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 associated service names such as
 "telnet" for port number 23 and "http" (as well as "www" and
 "www-http") for port number 80.
 All involved parties -- 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 is
 ultimately a local decision with meaning only between the endpoints
 of a connection, it is common for many services to have a default
 port upon which those servers usually listen, when possible, and
 these ports are recorded by the Internet Assigned Numbers Authority
 (IANA) through the service name and port number registry [PORTREG].
 Over time, the assumption that a particular port number necessarily
 implies a particular service may become less true.  For example,
 multiple instances of the same service on the same host cannot
 generally listen on the same port, and multiple hosts behind the same
 NAT gateway cannot all have a mapping for the same port on the
 external side of the NAT gateway, whether using static port mappings
 configured by hand by the user, or dynamic port mappings configured
 automatically using a port mapping protocol like the NAT Port Mapping
 Protocol [NAT-PMP] or Internet Gateway Device [IGD].
 Applications may use port numbers directly, look up port numbers
 based on service names via system calls such as getservbyname() on
 UNIX, look up port numbers by performing queries for DNS SRV records
 [RFC2782] [DNS-SD], or determine port numbers in a variety of other
 ways like the TCP Port Service Multiplexer (TCPMUX) [RFC1078].
 Designers of applications and application-level protocols may apply
 to IANA for an assigned service name and port number for a specific
 application, and may -- after assignment -- assume that no other
 application will use that service name or port number for its
 communication sessions.  Application designers also have the option
 of requesting only an assigned service name without a corresponding
 fixed port number if their application does not require one, such as
 applications that use DNS SRV records to look up port numbers
 dynamically at run-time.  Because the port number space is finite
 (and therefore conservation is an important goal), the alternative of
 using service names instead of port numbers is RECOMMENDED whenever
 possible.

Cotton, et al. Best Current Practice [Page 7] RFC 6335 Service Name and Port Number Procedures August 2011

4. Conventions Used in This Document

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
 "OPTIONAL" in this document are to be interpreted as described in
 "Key words for use in RFCs to Indicate Requirement Levels" [RFC2119].
 This document uses the term "assignment" to refer to the procedure by
 which IANA provides service names and/or port numbers to requesting
 parties; other RFCs refer to this as "allocation" or "registration".
 This document assumes that all these terms have the same meaning, and
 will use terms other than "assignment" only when quoting from or
 referring to text in these other documents.

5. Service Names

 Service names are the unique key in the Service Name and Transport
 Protocol Port Number registry.  This unique symbolic name for a
 service may also be used for other purposes, such as in DNS SRV
 records [RFC2782].  Within the registry, this unique key ensures that
 different services can be unambiguously distinguished, thus
 preventing name collisions and avoiding confusion about who is the
 Assignee for a particular entry.
 There may be more than one service name associated with a particular
 transport protocol and port.  There are three ways that such port
 number overloading can occur:
 o  Overloading occurs when one service is an extension of another
    service, and an in-band mechanism exists for determining if the
    extension is present or not.  One example is port 3478, which has
    the service name aliases "stun" and "turn".  Traversal Using
    Relays around NAT (TURN) [RFC5766] is an extension to the Session
    Traversal Utilities for NAT (STUN) [RFC5389] service.  TURN-
    enabled clients wishing to locate TURN servers could attempt to
    discover "stun" services and then check in-band if the server also
    supports TURN, but this would be inefficient.  Enabling them to
    directly query for "turn" servers by name is a better approach.
    (Note that TURN servers in this case should also be locatable via
    a "stun" discovery, because every TURN server is also a STUN
    server.)
 o  By historical accident, the service name "http" has two synonyms
    "www" and "www-http".  When used in SRV records [RFC2782] and
    similar service discovery mechanisms, only the service name "http"
    should be used, not these additional names.  If a server were to
    advertise "www", it would not be discovered by clients browsing
    for "http".  Advertising or browsing for the aliases as well as

Cotton, et al. Best Current Practice [Page 8] RFC 6335 Service Name and Port Number Procedures August 2011

    the primary service name is inefficient, and achieves nothing that
    is not already achieved by using the service name "http"
    exclusively.
 o  As indicated in this document in Section 10.1, overloading has
    been used to create replacement names that are consistent with the
    syntax this document prescribes for legacy names that do not
    conform to this syntax already.  For such cases, only the new name
    should be used in SRV records, to avoid the same issues as with
    historical cases of multiple names, and also because the legacy
    names are incompatible with SRV record use.
 Assignment requests for new names for existing registered services
 will be rejected, as a result.  Implementers are requested to inform
 IANA if they discover other cases where a single service has multiple
 names, so that one name may be recorded as the primary name for
 service discovery purposes.
 Service names are assigned on a "first come, first served" basis, as
 described in Section 8.1.  Names should be brief and informative,
 avoiding words or abbreviations that are redundant in the context of
 the registry (e.g., "port", "service", "protocol", etc.)  Names
 referring to discovery services, e.g., using multicast or broadcast
 to identify endpoints capable of a given service, SHOULD use an
 easily identifiable suffix (e.g., "-disc").

5.1. Service Name Syntax

 Valid service names are hereby normatively defined as follows:
 o  MUST be at least 1 character and no more than 15 characters long
 o  MUST contain only US-ASCII [ANSI.X3.4-1986] letters 'A' - 'Z' and
    'a' - 'z', digits '0' - '9', and hyphens ('-', ASCII 0x2D or
    decimal 45)
 o  MUST contain at least one letter ('A' - 'Z' or 'a' - 'z')
 o  MUST NOT begin or end with a hyphen
 o  hyphens MUST NOT be adjacent to other hyphens
 The reason for requiring at least one letter is to avoid service
 names like "23" (could be confused with a numeric port) or "6000-
 6063" (could be confused with a numeric port range).  Although
 service names may contain both upper-case and lower-case letters,
 case is ignored for comparison purposes, so both "http" and "HTTP"
 denote the same service.

Cotton, et al. Best Current Practice [Page 9] RFC 6335 Service Name and Port Number Procedures August 2011

 Service names are purely opaque identifiers, and no semantics are
 implied by any superficial structure that a given service name may
 appear to have.  For example, a company called "Example" may choose
 to register service names "Example-Foo" and "Example-Bar" for its
 "Foo" and "Bar" products, but the "Example" company cannot claim to
 "own" all service names beginning with "Example-"; they cannot
 prevent someone else from registering "Example-Baz" for a different
 service, and they cannot prevent other developers from using the
 "Example-Foo" and "Example-Bar" service types in order to
 interoperate with the "Foo" and "Bar" products.  Technically
 speaking, in service discovery protocols, service names are merely a
 series of byte values on the wire; for the mnemonic convenience of
 human developers, it can be convenient to interpret those byte values
 as human-readable ASCII characters, but software should treat them as
 purely opaque identifiers and not attempt to parse them for any
 additional embedded meaning.
 As of August 5, 2009, approximately 98% of the so-called "Short
 Names" [SYSFORM] [USRFORM] for existing port number assignments
 [PORTREG] already met the rules for legal service names stated in
 Section 8.1, and hence for these services their service name is
 exactly the same as their historical "Short Name".  In approximately
 2% of cases, the new "service name" is derived based on the old
 "Short Name" as described below in Section 10.1.
 The rules for valid service names, excepting the limit of 15
 characters maximum, are also expressed below (as a non-normative
 convenience) using ABNF [RFC5234].
    SRVNAME = *(1*DIGIT [HYPHEN]) ALPHA *([HYPHEN] ALNUM)
    ALNUM   = ALPHA / DIGIT     ; A-Z, a-z, 0-9
    HYPHEN  = %x2D              ; "-"
    ALPHA   = %x41-5A / %x61-7A ; A-Z / a-z [RFC5234]
    DIGIT   = %x30-39           ; 0-9       [RFC5234]

5.2. Service Name Usage in DNS SRV Records

 The DNS SRV specification [RFC2782] states that the Service Label
 part of the owner name of a DNS SRV record includes a "Service"
 element, described as "the symbolic name of the desired service", but
 as discussed above, it is not clear precisely what this means.
 This document clarifies that the Service Label MUST be a service name
 as defined herein with an underscore prepended.  The service name
 SHOULD be registered with IANA and recorded in the Service Name and
 Transport Protocol Port Number registry [PORTREG].

Cotton, et al. Best Current Practice [Page 10] RFC 6335 Service Name and Port Number Procedures August 2011

 The details of using Service Names in SRV Service Labels are
 specified in the DNS SRV specification [RFC2782].

6. Port Number Ranges

 TCP, UDP, UDP-Lite, SCTP, and DCCP use 16-bit namespaces for their
 port number registries.  The port registries for all of these
 transport protocols are subdivided into three ranges of numbers
 [RFC1340], and Section 8.1.2 describes the IANA procedures for each
 range in detail:
 o  the System Ports, also known as the Well Known Ports, from 0-1023
    (assigned by IANA)
 o  the User Ports, also known as the Registered Ports, from 1024-
    49151 (assigned by IANA)
 o  the Dynamic Ports, also known as the Private or Ephemeral Ports,
    from 49152-65535 (never assigned)
 Of the assignable port ranges (System Ports and User Ports, 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 assigned 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 service names and port numbers
 in the registry.  Unassigned values are typically not explicitly
 listed.  (There are very many Unassigned service names and
 enumerating them all would not be practical.)
 As a data point, when this document was written, approximately 76% of
 the TCP and UDP System Ports were assigned, and approximately 9% of
 the User Ports were assigned.  (As noted, Dynamic Ports are never
 assigned.)

Cotton, et al. Best Current Practice [Page 11] RFC 6335 Service Name and Port Number Procedures August 2011

6.1. Service Names and Port Numbers for Experimentation

 Of the System 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 range [RFC4727].
 Please refer to Sections 1 and 1.1 of "Assigning Experimental and
 Testing Numbers Considered Useful" [RFC3692] for how these
 experimental port numbers are to be used.
 This document assigns the same two service names and port numbers for
 experimentation with new application-layer protocols over SCTP and
 DCCP in Section 10.2.
 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.

7. Principles for Service Name and Transport Protocol Port Number

  Registry Management
 Management procedures for the Service Name and Transport Protocol
 Port Number registry include assignment of service names and port
 numbers upon request, as well as management of information about
 existing assignments.  The latter includes maintaining contact and
 description information about assignments, revoking abandoned
 assignments, and redefining assignments when needed.  Of these
 procedures, careful port number assignment is most critical, in order
 to continue to conserve the remaining port numbers.
 As noted earlier, only about 9% of the User Port space is currently
 assigned.  The current rate of assignment is approximately 400 ports
 per year, and has remained steady for the past 8 years.  At that
 rate, if similar conservation continues, this resource will sustain
 another 85 years of assignment - without the need to resort to
 reassignment of released values or revocation.  The namespace
 available for service names is much larger, which allows for simpler
 management procedures.

Cotton, et al. Best Current Practice [Page 12] RFC 6335 Service Name and Port Number Procedures August 2011

7.1. Past Principles

 The principles for service name and port number management are based
 on the recommendations of the IANA "Expert Review" team.  Until
 recently, that team followed a set of informal guidelines developed
 based on the review experience from previous assignment requests.
 These original guidelines, although informal, had never been publicly
 documented.  They are recorded here for historical purposes only; the
 current guidelines are described in Section 7.2.  These guidelines
 previously were:
 o  TCP and UDP ports were simultaneously assigned when either was
    requested
 o  Port numbers were the primary assignment; 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 assigned ranges of many
    port numbers even where not strictly necessary)
 o  SCTP and DCCP service name and port number registries were managed
    separately from the TCP/UDP registries
 o  Service names could not be assigned in the old ports registry
    without assigning an associated port number at the same time

7.2. Updated Principles

 This section summarizes the current principles by which IANA both
 handles the Service Name and Transport Protocol Port Number registry
 and attempts to conserve the port number space.  This description is
 intended to inform applicants requesting service names and port
 numbers.  IANA has flexibility beyond these principles when handling
 assignment requests; other factors may come into play, and exceptions
 may be made to best serve the needs of the Internet.  Applicants
 should be aware that IANA decisions are not required to be bound to
 these principles.  These principles and general advice to users on
 port use are expected to change over time.
 IANA strives to assign service names that do not request an
 associated port number assignment under a simple "First Come First
 Served" policy [RFC5226].  IANA MAY, at its discretion, refer service
 name requests to "Expert Review" in cases of mass assignment requests
 or other situations where IANA believes "Expert Review" is advisable
 [RFC5226]; use of the "Expert Review" helps advise IANA informally in
 cases where "IETF Review" or "IESG Approval" is used, as with most
 IETF protocols.

Cotton, et al. Best Current Practice [Page 13] RFC 6335 Service Name and Port Number Procedures August 2011

 The basic principle of service name and 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 is required because this space
 is a limited resource, so 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, the principles form a goal that IANA strives
 to achieve for new applications (with exceptions as deemed
 appropriate, especially as for extensions to legacy services) as
 follows:
 o  IANA strives to assign only one assigned port number per service
    or application.
    Note: At the time of writing of this document, there is no IETF
    consensus on when it is appropriate to use a second port for an
    insecure version of a protocol.
 o  IANA strives to assign only one assigned port number for all
    variants of a service (e.g., for updated versions of a service).
 o  IANA strives to encourage the deployment of secure protocols.
 o  IANA strives to assign only one assigned port number for all
    different types of devices using or participating in the same
    service.
 o  IANA strives to assign port numbers only for the transport
    protocol(s) explicitly named in an assignment request.
 o  IANA may recover unused port numbers, via the new procedures of
    de-assignment, revocation, and transfer.
 Where possible, a given service is expected to demultiplex messages
 if necessary.  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 assigned port.
 Applications and protocols are also expected to be able to
 efficiently use a single assigned port for multiple sessions, either
 by demultiplexing multiple streams within one port or by using the
 assigned port to coordinate using dynamic ports for subsequent
 exchanges (e.g., in the spirit of FTP [RFC0959]).

Cotton, et al. Best Current Practice [Page 14] RFC 6335 Service Name and Port Number Procedures August 2011

 Ports are used in various ways, notably:
 o  as endpoint process identifiers
 o  as application protocol identifiers
 o  for firewall-filtering purposes
 Both the process-identifier and the protocol-identifier uses suggest
 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 multiplexed or encoded
 could instead be separated to allow for easier 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 not always reliable.
 Effective with the publication of this document, IANA will begin
 assigning port numbers for only those transport protocols explicitly
 included in an assignment request.  This ends the long-standing
 practice of automatically assigning a port number to an application
 for both TCP and UDP, even if the request is for only one of these
 transport protocols.  The new assignment procedure conserves
 resources by assigning a port number to an application for only 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, the Assignee for the assignment MUST request
 that IANA convert these reserved ports into assignments.  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 IANA converting the reservation into an assignment.
 When the available pool of unassigned numbers has run out in a port
 range, it will be necessary for IANA to consider the Reserved ports
 for assignment.  This is part of the motivation for not automatically
 assigning ports for transport protocols other than the requested
 one(s).  This will allow more ports to be available for assignment at
 that point.  To help conserve ports, application developers SHOULD
 request assignment of only those transport protocols that their
 application currently uses.
 Conservation of port numbers is improved by procedures that allow
 previously assigned port numbers to become Unassigned, either through
 de-assignment or through revocation, and by a procedure that lets
 application designers transfer an assigned but unused port number to

Cotton, et al. Best Current Practice [Page 15] RFC 6335 Service Name and Port Number Procedures August 2011

 a new application.  Section 8 describes these procedures, which until
 now were undocumented.  Port number conservation is also improved by
 recommending that applications that do not require an assigned port
 should register only a service name without an associated port
 number.

8. IANA Procedures for Managing the Service Name and Transport Protocol

  Port Number Registry
 This section describes the process for handling requests associated
 with IANA's management of the Service Name and Transport Protocol
 Port Number registry.  Such requests include initial assignment, de-
 assignment, reuse, and updates to the contact information or
 description associated with an assignment.  Revocation is an
 additional process, initiated by IANA.

8.1. Service Name and Port Number Assignment

 Assignment refers to the process of providing service names or port
 numbers to applicants.  All such assignments are made from service
 names or port numbers that are Unassigned or Reserved at the time of
 the assignment.
 o  Unassigned names and numbers are assigned according to the rules
    described in Section 8.1.2 below.
 o  Reserved numbers and names are generally only assigned by a
    "Standards Action" or "IESG Approval", and MUST be accompanied by
    a statement explaining the reason a Reserved number or name is
    appropriate for this action.  The only exception to this rule is
    that the current Assignee of a port number MAY request the
    assignment of the corresponding Reserved port number for other
    transport protocols when needed.  IANA will initiate an "Expert
    Review" [RFC5226] for such requests.
 When an assignment for one or more transport protocols is approved,
 the port number for any 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.  It is anticipated that at such
 time a new document will be published specifying IANA procedures for
 assignment of such ports.

Cotton, et al. Best Current Practice [Page 16] RFC 6335 Service Name and Port Number Procedures August 2011

8.1.1. General Assignment Procedure

 A service name or port number assignment request contains the
 following information.  The service name is the unique identifier of
 a given service:
    Service Name (REQUIRED)
    Transport Protocol(s) (REQUIRED)
    Assignee (REQUIRED)
    Contact (REQUIRED)
    Description (REQUIRED)
    Reference (REQUIRED)
    Port Number (OPTIONAL)
    Service Code (REQUIRED for DCCP only)
    Known Unauthorized Uses (OPTIONAL)
    Assignment Notes (OPTIONAL)
 o  Service Name: A desired unique service name for the service
    associated with the assignment request MUST be provided.  This
    name may be used with various service selection and discovery
    mechanisms (including, but not limited to, DNS SRV records
    [RFC2782]).  The name MUST be compliant with the syntax defined in
    Section 5.1.  In order to be unique, they MUST NOT be identical to
    any currently assigned service name in the IANA registry
    [PORTREG].  Service names are case-insensitive; they may be
    provided and entered into the registry with mixed case for
    clarity, but case is ignored otherwise.
 o  Transport Protocol(s): The transport protocol(s) for which an
    assignment is requested MUST be provided.  This field is currently
    limited to one or more of TCP, UDP, SCTP, and DCCP.  Requests
    without any port assignment and only a service name are still
    required to indicate which protocol the service uses.
 o  Assignee: Name and email address of the party to whom the
    assignment is made.  This is REQUIRED.  The Assignee is the
    organization, company or individual person responsible for the
    initial assignment.  For assignments done through RFCs published
    via the "IETF Document Stream" [RFC4844], the Assignee will be the
    IESG <iesg@ietf.org>.
 o  Contact: Name and email address of the Contact person for the
    assignment.  This is REQUIRED.  The Contact person is the
    responsible person for the Internet community to send questions
    to.  This person is also authorized to submit changes on behalf of
    the Assignee; in cases of conflict between the Assignee and the
    Contact, the Assignee decisions take precedence.  Additional

Cotton, et al. Best Current Practice [Page 17] RFC 6335 Service Name and Port Number Procedures August 2011

    address information MAY be provided.  For assignments done through
    RFCs published via the "IETF Document Stream" [RFC4844], the
    Contact will be the IETF Chair <chair@ietf.org>.
 o  Description: A short description of the service associated with
    the assignment request is REQUIRED.  It should avoid all but the
    most well-known acronyms.
 o  Reference: A description of (or a reference to a document
    describing) the protocol or application using this port.  This is
    REQUIRED.  The description must state whether the protocol uses
    IP-layer broadcast, multicast, or anycast communication.
    For assignments requesting only a Service Name, or a Service Name
    and User Port, a statement that the protocol is proprietary and
    not publicly documented is also acceptable, provided that the
    required information regarding the use of IP broadcast, multicast,
    or anycast is given.
    For any assignment request that includes a User Port, the
    assignment request MUST explain why a port number in the Dynamic
    Ports range (discovered by clients dynamically at run-time) is
    unsuitable for the given application.
    For any assignment request that includes a System Port, the
    assignment request MUST explain why a port number in the User
    Ports or Dynamic Ports ranges is unsuitable, and a reference to a
    stable protocol specification document MUST be provided.
    IANA MAY accept early assignment [RFC4020] requests (known as
    "early allocation" therein) from IETF working groups that
    reference a sufficiently stable Internet-Draft instead of a
    published Standards-Track RFC.
 o  Port Number: If assignment of a port number is desired, either the
    port number the requester suggests for assignment or indication of
    port range (user or system) MUST be provided.  If only a service
    name is to be assigned, this field is left empty.  If a specific
    port number is requested, IANA is encouraged to assign the
    requested number.  If a range is specified, IANA will choose a
    suitable number from the User or System Ports ranges.  Note that
    the applicant MUST NOT use the requested port in implementations
    deployed for use on the public Internet prior to the completion of
    the assignment, because there is no guarantee that IANA will
    assign the requested port.

Cotton, et al. Best Current Practice [Page 18] RFC 6335 Service Name and Port Number Procedures August 2011

 o  Service Code: If the assignment request includes DCCP as a
    transport protocol, then the request MUST include a desired unique
    DCCP service code [RFC5595], and MUST NOT include a requested DCCP
    service code otherwise.  Section 19.8 of the DCCP specification
    [RFC4340] defines requirements and rules for assignment, updated
    by this document.  Note that, as per the DCCP Service Codes
    document [RFC5595], some service codes are not assigned; zero
    (absence of a meaningful service code) and 4294967295 (0xFFFFFFFF;
    invalid service code) are permanently reserved, and the Private
    service codes 1056964608-1073741823 (0x3F000000-0x3FFFFFFF; i.e.,
    32-bit values with the high-order byte equal to a value of 63
    (0x3F), corresponding to the ASCII character '?') are not
    centrally assigned.
 o  Known Unauthorized Uses: A list of uses by applications or
    organizations who are not the Assignee.  This is OPTIONAL.  This
    list may be augmented by IANA after assignment when unauthorized
    uses are reported.
 o  Assignment Notes: Indications of owner/name change, or any other
    assignment process issue.  This is OPTIONAL.  This list may be
    updated by IANA after assignment to help track changes to an
    assignment, e.g., de-assignment, owner/name changes, etc.
 If the assignment request is for the addition of a new transport
 protocol to a previously assigned service name and the requester is
 not the Assignee or Contact for the previously assigned service name,
 IANA needs to confirm with the Assignee for the existing assignment
 whether this addition is appropriate.
 If the assignment request is for a new service name sharing the same
 port as a previously assigned service name (see port number
 overloading in Section 5), IANA needs to confirm with the Assignee
 for the existing service name and other appropriate experts whether
 the overloading is appropriate.
 When IANA receives an assignment request -- containing the above
 information -- that is requesting a port number, IANA SHALL initiate
 an "Expert Review" [RFC5226] in order to determine whether an
 assignment should be made.  For requests that are not seeking a port
 number, IANA SHOULD assign the service name under a simple "First
 Come First Served" policy [RFC5226].

Cotton, et al. Best Current Practice [Page 19] RFC 6335 Service Name and Port Number Procedures August 2011

8.1.2. Variances for Specific Port Number Ranges

 Section 6 describes the different port number ranges.  It is
 important to note that IANA applies slightly different procedures
 when managing the different port ranges of the service name and 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
    assigned through IANA.  Application software may simply use any
    dynamic port that is available on the local host, without any sort
    of assignment.  On the other hand, application software 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 User Ports range (1024-49151) are available for
    assignment through IANA, and MAY be used as service identifiers
    upon successful assignment.  Because assigning 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.  For most IETF
    protocols, ports in the User Ports range will be assigned under
    the "IETF Review" or "IESG Approval" procedures [RFC5226] and no
    further documentation is required.  Where these procedures do not
    apply, then the requester must input the documentation to the
    "Expert Review" procedure [RFC5226], by which IANA will have a
    technical expert review the request to determine whether to grant
    the assignment.  Regardless of the path ("IETF Review", "IESG
    Approval", or "Expert Review"), the submitted documentation is
    expected to be the same, as described in this section, and MUST
    explain why using a port number in the Dynamic Ports range is
    unsuitable for the given application.  Further, IANA MAY utilize
    the "Expert Review" process informally to inform their position in
    participating in "IETF Review" and "IESG Approval".
 o  Ports in the System Ports range (0-1023) are also available for
    assignment through IANA.  Because the System Ports range is both
    the smallest and the most densely assigned, the requirements for
    new assignments are more strict than those for the User Ports
    range, and will only be granted under the "IETF Review" or "IESG
    Approval" procedures [RFC5226].  A request for a System Port
    number MUST document *both* why using a port number from the
    Dynamic Ports range is unsuitable *and* why using a port number
    from the User Ports range is unsuitable for that application.

Cotton, et al. Best Current Practice [Page 20] RFC 6335 Service Name and Port Number Procedures August 2011

8.2. Service Name and Port Number De-Assignment

 The Assignee 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-assigned and will be marked as Reserved.  IANA
 should not reassign port numbers that have been de-assigned until all
 unassigned port numbers in the specific range have been assigned.
 Before proceeding with a port number de-assignment, 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-assigned.  Under this policy, it
 will appear in the registry as if it had been created through a
 service name assignment request that did not include any port
 numbers.
 On rare occasions, it may still be useful to de-assign a service
 name.  In such cases, IANA will mark the service name as Reserved.
 IANA will involve their IESG-appointed expert in such cases.
 IANA will include a comment in the registry when de-assignment
 happens to indicate its historic usage.

8.3. Service Name and Port Number Reuse

 If the Assignee of a granted port number assignment no longer has a
 need for the assigned number, but would like to reuse it for a
 different application, they can submit a request to IANA to do so.
 Logically, port number reuse is to be thought of as a de-assignment
 (Section 8.2) followed by an immediate (re-)assignment (Section 8.1)
 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 assignment for the specific ports range.
 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 name be created and
 associated with the port number.  This is again consistent with
 viewing a reuse request as a de-assignment followed by an immediate
 (re-)assignment.  Reusing an assigned service name for a different
 application is NOT RECOMMENDED.

Cotton, et al. Best Current Practice [Page 21] RFC 6335 Service Name and Port Number Procedures August 2011

 IANA needs to carefully review such requests before approving them.
 In some instances, the Expert Reviewer will determine that the
 application the port number was assigned to has found usage beyond
 the original Assignee, 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.

8.4. Service Name and Port Number Revocation

 A port number revocation can be thought of as an IANA-initiated de-
 assignment (Section 8.2), 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-assignment 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.

8.5. Service Name and Port Number Transfers

 The value of service names and port numbers is defined by their
 careful management as a shared Internet resource, whereas enabling
 transfer allows the potential for associated monetary exchanges.  As
 a result, the IETF does not permit service name or port number
 assignments to be transferred between parties, even when they are
 mutually consenting.
 The appropriate alternate procedure is a coordinated de-assignment
 and assignment: The new party requests the service name or port
 number via an assignment and the previous party releases its
 assignment via the de-assignment procedure outlined above.

Cotton, et al. Best Current Practice [Page 22] RFC 6335 Service Name and Port Number Procedures August 2011

 With the help of their IESG-appointed Expert Reviewer, IANA SHALL
 carefully determine if there is a valid technical, operational, or
 managerial reason to grant the requested new assignment.

8.6. Maintenance Issues

 In addition to the formal procedures described above, updates to the
 Description and Contact information are coordinated by IANA in an
 informal manner, and may be initiated by either the Assignee or by
 IANA, e.g., by the latter requesting an update to current Contact
 information.  (Note that the Assignee cannot be changed as a separate
 procedure; see instead Section 8.5 above.)

8.7. Disagreements

 In the case of disagreements around any request, there is the
 possibility of appeal following the normal appeals process for IANA
 assignments as defined by Section 7 of "Guidelines for Writing an
 IANA Considerations Section in RFCs" [RFC5226].

9. Security Considerations

 The IANA guidelines described in this document do not change the
 security properties of UDP, TCP, SCTP, or DCCP.
 Assignment of a service name or port number does not in any way imply
 an endorsement of an application or product, and the fact that
 network traffic is flowing to or from an assigned 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 based on whether or not there is an assigned
 service name or port number.
 Services are expected to include support for security, either as
 default or dynamically negotiated in-band.  The use of separate
 service name or port number assignments for secure and insecure
 variants of the same service is to be avoided in order to discourage
 the deployment of insecure services.

Cotton, et al. Best Current Practice [Page 23] RFC 6335 Service Name and Port Number Procedures August 2011

10. IANA Considerations

 This document obsoletes Sections 8 and 9.1 of the March 2000 IANA
 Allocation Guidelines [RFC2780].
 Upon approval of this document for publication as an RFC, IANA worked
 with Stuart Cheshire, maintainer of the independent service name
 registry [SRVREG], to merge the contents of that private registry
 into the official IANA registry.  The independent registry web page
 has been updated with pointers to the IANA registry and to this RFC.
 IANA created a new service name entry in the service name and port
 number registry [PORTREG] for all entries in the Protocol and Service
 Names registry [PROTSERVREG] that did not already have one assigned.
 IANA also indicates in the Assignment Notes for "www" and "www-http"
 that they are duplicate terms that refer to the "http" service, and
 should not be used for discovery purposes.  For this conceptual
 service (human-readable web pages served over HTTP), the correct
 service name to use for service discovery purposes is "http" (see
 Section 5).

10.1. Service Name Consistency

 Section 8.1 defines which character strings are well-formed service
 names, which until now had not been clearly defined.  The definition
 in Section 8.1 was chosen to allow maximum compatibility of service
 names with current and future service discovery mechanisms.
 As of August 5, 2009, approximately 98% of the so-called "Short
 Names" from existing port number assignments [PORTREG] met the rules
 for legal service names stated in Section 8.1, and hence for these
 services their service name is exactly the same as their "Short
 Name".
 The remaining approximately 2% of the existing "Short Names" are not
 suitable to be used directly as well-formed service names because
 they contain illegal characters such as asterisks, dots, pluses,
 slashes, or underscores.  All existing "Short Names" conform to the
 length requirement of 15 characters or fewer.  For these 96
 unsuitable "Short Names", listed in the table below, the service name
 is the Short Name with any illegal characters replaced by hyphens.
 IANA added an entry to the registry that uses the new well-formed
 primary service name for the existing service and that otherwise
 duplicates the original assignment information.  In the description
 field of this new entry giving the primary service name, IANA
 recorded that it has assigned a well-formed service name for the
 previous service and references the original assignment.  In the

Cotton, et al. Best Current Practice [Page 24] RFC 6335 Service Name and Port Number Procedures August 2011

 Assignment Notes field of the original assignment, IANA added a note
 that this entry is an alias to the new well-formed service name, and
 that the old service name is historic, not usable for use with many
 common service discovery mechanisms.
 96 names containing illegal characters to be replaced by hyphens:
        +----------------+-----------------+-----------------+
        | 914c/g         | 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        |
        | EtherNet/IP-1  | EtherNet/IP-2   | 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  | LiebDevMgmt_A   | LiebDevMgmt_C   |
        | LiebDevMgmt_DM | 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 | sql*net         | srvc_registry   |
        | stm_pproc      | subntbcst_tftp  | udt_os          |
        | universe_suite | veritas_pbx     | vision_elmd     |
        | vision_server  | wrs_registry    | z39.50          |
        +----------------+-----------------+-----------------+
 In addition to the 96 names listed above, the service name for
 "whois++" is "whoispp", following the example set by the
 "application/whoispp-query" MIME Content-Type [RFC2957].

Cotton, et al. Best Current Practice [Page 25] RFC 6335 Service Name and Port Number Procedures August 2011

 There were four names recorded in IANA's Port Number Registry
 [PORTREG] that conflicted with names previously recorded in the ad
 hoc SRV name registry [SRVREG]: esp, hydra, recipe, and xmp.
 The name conflicts were resolved amicably:
 The IANA Port Number Registry Short Name "esp" had been registered by
 Andrew Chernow, and he informed the authors that the port was no
 longer in use and the registration was no longer required.  The SRV
 registry entry for "esp" remains in effect.
 The SRV name "hydra" for SubEthaEdit had already been retired in
 favor of the new SRV name "see".  The IANA Port Number Registry entry
 for "hydra" remains in effect.
 The SRV name "recipe" was in use in an open source project that had
 not yet been packaged for distribution, and the registrant Daniel
 Taylor was willing to change to a different service name.  Thanks to
 Daniel Taylor for accommodating this change.  The IANA Port Number
 Registry entry for "recipe" remains in effect.
 The IANA Port Number Registry Short Name "xmp" had been registered by
 Bobby Krupczak, but since his registration included an assigned port
 number (which is still in use and remains unaffected by this change),
 he was willing to switch to a different service name.  Thanks to
 Bobby Krupczak for accommodating this change.  The SRV registry entry
 for "xmp" remains in effect.

10.2. Port Numbers for SCTP and DCCP Experimentation

 Two System UDP and TCP ports, 1021 and 1022, have been reserved for
 experimental use [RFC4727].  This document assigns the same port
 numbers for SCTP and DCCP, updates the TCP and UDP assignments, and
 also instructs IANA to automatically assign these two port numbers
 for any future transport protocol with a similar 16-bit 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 6.1 in this
 document, as well as in Sections 1 and 1.1 of "Assigning Experimental
 and Testing Numbers Considered Useful" [RFC3692].  Most importantly,
 application developers must request a permanent port number
 assignment from IANA as described in Section 8.1 before any kind of
 non-experimental deployment.

Cotton, et al. Best Current Practice [Page 26] RFC 6335 Service Name and Port Number Procedures August 2011

         +--------------------+-----------------------------+
         | Service Name       | exp1                        |
         | Transport Protocol | DCCP, SCTP, TCP, UDP        |
         | Assignee           | IESG <iesg@ietf.org>        |
         | Contact            | IETF Chair <chair@ietf.org> |
         | Description        | RFC3692-style Experiment 1  |
         | Reference          | [RFC4727] [RFC6335]         |
         | Port Number        | 1021                        |
         +--------------------+-----------------------------+
         +--------------------+-----------------------------+
         | Service Name       | exp2                        |
         | Transport Protocol | DCCP, SCTP, TCP, UDP        |
         | Assignee           | IESG <iesg@ietf.org>        |
         | Contact            | IETF Chair <chair@ietf.org> |
         | Description        | RFC3692-style Experiment 2  |
         | Reference          | [RFC4727] [RFC6335]         |
         | Port Number        | 1022                        |
         +--------------------+-----------------------------+

10.3. Updates to DCCP Registries

 This document updates the IANA assignment procedures for the DCCP
 Port Number and DCCP Service Codes Registries [RFC4340].

10.3.1. DCCP Service Code Registry

 Service codes are assigned on a "first come, first served" basis
 according to Section 19.8 of the DCCP specification [RFC4340].  This
 document updates that section 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" if a
    request asks for more than five service codes.
 o  IANA should feel free to contact the DCCP Expert Reviewer with any
    questions related to requests for DCCP-related codepoints.

Cotton, et al. Best Current Practice [Page 27] RFC 6335 Service Name and Port Number Procedures August 2011

10.3.2. DCCP Port Numbers Registry

 The DCCP ports registry is defined by Section 19.9 of the DCCP
 specification [RFC4340].  Assignments in this registry require prior
 assignment of a service code.  Not all service codes require IANA-
 assigned ports.  This document updates that section 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 requests to assign port numbers in the
    System Ports range (0 through 1023) require an "IETF Review"
    [RFC5226] prior to assignment by IANA [RFC4340].
 o  IANA MUST NOT assign more than one DCCP server port to a single
    service code value.
 o  The assignment of multiple service codes to the same DCCP port is
    allowed, but subject to "Expert Review".
 o  The set of service code values associated with a DCCP server port
    should be recorded in the service name and port number registry.
 o  A request for additional service codes to be associated with an
    already assigned port number requires "Expert Review".  These
    requests will normally be accepted when they originate from the
    contact associated with the port assignment.  In other cases,
    these applications will be expected to use an unassigned port,
    when this is available.
 The DCCP specification [RFC4340] notes that a short port name MUST be
 associated with each DCCP server port that has been assigned.  This
 document clarifies that this short port name is the service name as
 defined here, and this name MUST be unique.

11. Contributors

 Alfred Hoenes (ah@tr-sys.de) and Allison Mankin (mankin@psg.com) have
 contributed text and ideas to this document.

12. Acknowledgments

 The text in Section 10.3 is based on a suggestion originally proposed
 as a part of the DCCP Service Codes document [RFC5595] by Gorry
 Fairhurst.
 Lars Eggert is partly funded by the Trilogy Project [TRILOGY], a
 research project supported by the European Commission under its
 Seventh Framework Program.

Cotton, et al. Best Current Practice [Page 28] RFC 6335 Service Name and Port Number Procedures August 2011

13. References

13.1. 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.
 [RFC2782]         Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS
                   RR for specifying the location of services (DNS
                   SRV)", RFC 2782, February 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.
 [RFC4960]         Stewart, R., "Stream Control Transmission
                   Protocol", RFC 4960, September 2007.
 [RFC5226]         Narten, T. and H. Alvestrand, "Guidelines for
                   Writing an IANA Considerations Section in RFCs",
                   BCP 26, RFC 5226, May 2008.

Cotton, et al. Best Current Practice [Page 29] RFC 6335 Service Name and Port Number Procedures August 2011

 [RFC5234]         Crocker, D. and P. Overell, "Augmented BNF for
                   Syntax Specifications: ABNF", STD 68, RFC 5234,
                   January 2008.
 [RFC5595]         Fairhurst, G., "The Datagram Congestion Control
                   Protocol (DCCP) Service Codes", RFC 5595,
                   September 2009.

13.2. Informative References

 [DNS-SD]          Cheshire, S. and M. Krochmal, "DNS-Based Service
                   Discovery", Work in Progress, February 2011.
 [IGD]             UPnP Forum, "Internet Gateway Device (IGD) V 1.0",
                   November 2001.
 [NAT-PMP]         Cheshire, S., "NAT Port Mapping Protocol (NAT-
                   PMP)", Work in Progress, April 2008.
 [PORTREG]         Internet Assigned Numbers Authority (IANA),
                   "Service Name and Transport Protocol Port Number
                   Registry",
                   <http://www.iana.org/assignments/port-numbers>.
 [PROTSERVREG]     Internet Assigned Numbers Authority (IANA),
                   "Protocol and Service Names Registry",
                   <http://www.iana.org/assignments/service-names>.
 [RFC0959]         Postel, J. and J. Reynolds, "File Transfer
                   Protocol", STD 9, RFC 959, October 1985.
 [RFC1078]         Lottor, M., "TCP port service Multiplexer
                   (TCPMUX)", RFC 1078, November 1988.
 [RFC1340]         Reynolds, J. and J. Postel, "Assigned Numbers",
                   RFC 1340, July 1992.
 [RFC1700]         Reynolds, J. and J. Postel, "Assigned Numbers",
                   RFC 1700, October 1994.
 [RFC2957]         Daigle, L. and P. Faltstrom, "The application/
                   whoispp-query Content-Type", RFC 2957,
                   October 2000.
 [RFC3232]         Reynolds, J., "Assigned Numbers: RFC 1700 is
                   Replaced by an On-line Database", RFC 3232,
                   January 2002.

Cotton, et al. Best Current Practice [Page 30] RFC 6335 Service Name and Port Number Procedures August 2011

 [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.
 [RFC4844]         Daigle, L. and Internet Architecture Board, "The
                   RFC Series and RFC Editor", RFC 4844, July 2007.
 [RFC5237]         Arkko, J. and S. Bradner, "IANA Allocation
                   Guidelines for the Protocol Field", BCP 37,
                   RFC 5237, February 2008.
 [RFC5389]         Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
                   "Session Traversal Utilities for NAT (STUN)",
                   RFC 5389, October 2008.
 [RFC5766]         Mahy, R., Matthews, P., and J. Rosenberg,
                   "Traversal Using Relays around NAT (TURN): Relay
                   Extensions to Session Traversal Utilities for NAT
                   (STUN)", RFC 5766, April 2010.
 [SRVREG]          "DNS SRV Service Types Registry",
                   <http://www.dns-sd.org/ServiceTypes.html>.
 [SYSFORM]         Internet Assigned Numbers Authority (IANA),
                   "Application for System (Well Known) Port Number",
                   <http://www.iana.org/>.
 [TRILOGY]         "Trilogy Project",
                   <http://www.trilogy-project.org/>.
 [USRFORM]         Internet Assigned Numbers Authority (IANA),
                   "Application for User (Registered) Port Number",
                   <http://www.iana.org/>.

Cotton, et al. Best Current Practice [Page 31] RFC 6335 Service Name and Port Number Procedures August 2011

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/
 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
 Magnus Westerlund
 Ericsson
 Farogatan 6
 Stockholm  164 80
 Sweden
 Phone: +46 8 719 0000
 EMail: magnus.westerlund@ericsson.com

Cotton, et al. Best Current Practice [Page 32] RFC 6335 Service Name and Port Number Procedures August 2011

 Stuart Cheshire
 Apple Inc.
 1 Infinite Loop
 Cupertino, CA  95014
 USA
 Phone: +1 408 974 3207
 EMail: cheshire@apple.com
 URI:   http://stuartcheshire.org/

Cotton, et al. Best Current Practice [Page 33]

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