Transport Area Working Group                                   M. Cotton
Internet-Draft                                                     ICANN
Updates: 2780, 2782, 3828, 4340,                               L. Eggert
4960 (if approved)                                                 Nokia
Intended status: BCP                                            J. Touch
Expires: November 22, 27, 2010                                       USC/ISI
                                                           M. Westerlund
                                                             S. Cheshire
                                                            May 21, 26, 2010

Internet Assigned Numbers Authority (IANA) Procedures for the Management
    of the Transport Protocol Port Number and Service Name Registry


   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 IANA's procedures by obsoleting Sections 8 and
   9.1 of the IANA allocation guidelines [RFC2780], it updates the IANA
   allocation procedures for UDP-Lite [RFC3828], DCCP [RFC4340] and SCTP
   [RFC4960], it updates the DNS SRV specification [RFC2782] to clarify
   what a service name is and how it is registered.

Status of this Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on November 22, 27, 2010.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3.  Background . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  Conventions Used in this Document  . . . . . . . . . . . . . .  7
   5.  Service Names  . . . . . . . . . . . . . . . . . . . . . . . .  8
     5.1.  Service Name Syntax  . . . . . . . . . . . . . . . . . . .  9
     5.2.  Service Name Usage in DNS SRV Records  . . . . . . . . . .  9
   6.  Port Number Ranges . . . . . . . . . . . . . . . . . . . . . . 10
     6.1.  Port Numbers and Service Names for Experimentation . . . . 11
   7.  Principles for Port Number and Service Name Registry
       Management . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     7.1.  Past Principles  . . . . . . . . . . . . . . . . . . . . . 12
     7.2.  Updated Principles . . . . . . . . . . . . . . . . . . . . 12
     7.3.  Variances for Specific Port Number Ranges  . . . . . . . . 15
   8.  IANA Procedures for Managing the Port Number and Service
       Name Registry  . . . . . . . . . . . . . . . . . . . . . . . . 16
     8.1.  Port Number and Service Name Registration  . . . . . . . . 16
     8.2.  Port Number and Service Name De-Registration . . . . . . . 19
     8.3.  Port Number and Service Name Re-Use  . . . . . . . . . . . 19
     8.4.  Port Number and Service Name Revocation  . . . . . . . . . 20
     8.5.  Port Number and Service Name Transfers . . . . . . . . . . 21
     8.6.  Maintenance Issues . . . . . . . . . . . . . . . . . . . . 21
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 21
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 22
     10.1. Service Name Consistency . . . . . . . . . . . . . . . . . 22
     10.2. Port Numbers for SCTP and DCCP Experimentation . . . . . . 24
     10.3. Updates to DCCP Registries . . . . . . . . . . . . . . . . 25
   11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26
   12. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 26
   13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
     13.1. Normative References . . . . . . . . . . . . . . . . . . . 27
     13.2. Informative References . . . . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29

1.  Introduction

   For many years, the allocation and registration of new port number
   values and service names for use with the Transmission Control
   Protocol (TCP) [RFC0793] and the User Datagram Protocol (UDP)
   [RFC0768] have 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 recognized the need for additional
   procedures beyond just assignment; notably modification, revocation,
   and release.

   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 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.

   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 the procedure by which IANA can unilaterally revoke a prior port
   number registration.  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.

   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 now also offers a method for the "early"
   assignment of port numbers and service names [RFC4020], 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 different sections of the IANA allocation
   guidelines, relating to the protocol field values in IPv4 header,
   were also updated in February 2008 [RFC5237].)  This document also
   updates the IANA allocation procedures for DCCP [RFC4340] and SCTP

   The Lightweight User Datagram Protocol (UDP-Lite) [RFC5237] shares
   the port space with UDP.  The UDP-Lite specification says: "UDP-Lite
   uses the same set of port number values assigned by the IANA for use
   by UDP".  Thus the update of UDP procedures result in an update also
   of the UDP-Lite procedures.

   This document also clarify what a service name is and how it is
   registered.  This will impact the DNS SRV specification, 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 of that 230-page document it refers.  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" is now obsolete [RFC3232] and has now been
   replaced by on-line registries [PORTREG][PROTSERVREG].  There are
   additional updates and clarifications on how DNS SRV utilize the
   Service name registry created in this document in "Clarification of
   DNS SRV Owner Names" [I-D.gudmundsson-dnsext-srv-clarify].

   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, for the purpose of uniformity it is
   expected to follow as much as possible the guidelines and practices
   around using port numbers and service names.

2.  Motivation

   Information about the registration procedures for the port registry
   has 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 [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,
   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 was introduced, the 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 [SRVREG].

   This document aggregates all 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.

   This document defines rules for registration 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 registrations from the non-IANA
   ad hoc registry [SRVREG] and from the IANA "Protocol and Service
   Names" registry [PROTSERVREG] into the IANA "Port and Service Name"
   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 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 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 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 16-bit
   port numbers in the same way as TCP and UDP (and UDP-Lite [RFC3828],
   a variant of 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 "http" (and the "www" alias) 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 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 port number registry

   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 NAT Port Mapping Protocol
   (NAT-PMP) [I-D.cheshire-nat-pmp] or Internet Gateway Device (IGD)

   Applications either use numeric 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][I-D.cheshire-dnsext-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 port number and service name for a specific
   application, and may - after successful registration - assume that no
   other application will use that port number or service name for its
   communication sessions.  Alternatively, application designers may
   also ask for only an assigned service name, if their application does
   not require a fixed port number.  The latter alternative is
   encouraged when possible, in order to conserve the more limited port
   number space.  This includes, for example, applications that use DNS
   SRV records to look up port numbers at runtime.

4.  Conventions Used in this Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

5.  Service Names

   Service names are the unique key in the Port and Service Name
   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 administrative contact for a
   particular entry.

   For each service name, there may exist zero or more associated port
   number assignments.  A port number assignment associated with a
   service name contains the transport protocol, port number and
   possibly additional data, such as a DCCP Service Code.

   There may be more than one service name associated with a particular
   transport protocol and port.  There are two valid reasons for
   allowing service name aliases:

   o  Aliases are permissible when all such service names are for the
      same service, such as with "http" and "www", which both name TCP
      port 80.  In such cases, one of the service names SHOULD be
      designated primary, for use with mechanisms such as DNS SRV
      Records [RFC2782], and the others SHOULD be designated as aliases
      of the primary service name.  This is necessary so that clients
      and servers using a service discovery mechanism use a consistent
      name by which to refer to a given service.  Otherwise, if a server
      were to advertise that it supports the "www" service, and a client
      were to seek instances of the "http" service, that client would
      fail to discover that server, defeating the purpose of having a
      service discovery mechanism.  For aliases that do not indicate a
      primary alias, a server is expected to register itself under all
      aliased service names.

   o  Aliases are also permissible when one service is an extension of
      another service, and an in-band mechanisms exists for determining
      if the extension is present or not.  One example is port 3478,
      which has the service name aliases "stun" and "turn".  TURN
      [RFC5766] is an extension to the STUN [RFC5389] service.  TURN-
      enabled clients wishing to locate TURN servers could attempt to
      discover "stun" services and then checking in-band if the server
      supports TURN, but this is 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.)

   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 MUST contain only these US-ASCII [ANSI.X3-4.1986]
   characters: letters from A to Z and a to z, digits from 0 to 9, and
   hyphens ("-", ASCII 0x2D or decimal 45).  They MUST be at least one
   character and no more than 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, which are typically written as
   all digits).

   The service name syntax MAY be used to validate a service name
   string, but MUST NOT be used for any other purpose (e.g.,
   delineation).  Any system that includes a service name inside a
   longer string is itself responsible for delineating the service name.
   Such systems MUST NOT rely on the syntax of a service name alone for
   such delineation.

   The syntax defined in ABNF [RFC5234]:

                (1*DIGIT ((HYPHEN ALNUM) / ALPHA) *([HYPHEN] ALNUM))
      ALNUM   = ALPHA / DIGIT   ; A-Z, a-z, 0-9
      HYPHEN  = %x2d            ; "-"
      ALPHA   = <See [RFC5234]>
      DIGIT   = <See [RFC5234]>

5.2.  Service Name Usage in DNS SRV Records

   The DNS SRV specification [RFC2782] requests that the Service Label
   part of the owner name of DNS SRV records includes a "Service"
   element, defined to be "the symbolic name of the desired service",
   but did not state precisely which part of the IANA database (i.e.
   STD 2 when [RFC2782] was written) serves as a registry for standard
   service names.

   This document clarifies that the Service Label MUST be a service name
   as defined herein.  The service name SHOULD be registered with IANA
   and recorded in the Service Names and Port Numbers registry
   [PORTREG].  This is needed to ensure that only a single registry of
   Service Names exists and name collisions can be avoided in the

   The details of the use of Service Names from [PORTREG] in SRV Service
   Labels are specified in [RFC2782] and the documents updating or
   replacing that specification (see the companion document
   [I-D.gudmundsson-dnsext-srv-clarify] for more information).

   The details of how applications make use of DNS SRV should be
   specified in the documentation set of the application/service.  In
   the absence of such specification, prospective clients of a given
   service should not assume the existence of SRV RRs for this service
   or, if they have indications that this will be the case (e.g., by
   configuration), must assume the unextended naming scheme from
   [RFC2782] for service discovery with DNS SRV, i.e., the Service Label
   is constructed from the Service Name registered in [PORTREG] by
   prepending a single underscore character ("_").

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 these transport
   protocols are subdivided into three ranges of numbers, and
   Section 7.3 describes the IANA procedures for each range in detail:

   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

   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

   As a data point, when this document was written, approximately 76% of
   the TCP and UDP Well Known Ports were assigned, and approximately 9%
   of the Registered Ports were assigned.  (As noted, Dynamic Ports are
   never assigned.)

6.1.  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].

   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 registers the same two port numbers and service names
   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 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, in order to continue to conserve the remaining port

   As noted earlier, only ~9% of the Registered Port space is currently
   assigned.  The current rate of assignment is approximately 400 ports/
   year, and has remained linear 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.  Note that the namespace available for
   service names is even larger, which allows for a simpler management

7.1.  Past Principles

   Before the publication of this document, the principles of port
   number and service name management followed a few mostly-undocumented
   guidelines.  They are recorded here for historical purposes, and this
   document updates them in Section 7.2.  These principles were:

   o  TCP and UDP ports were simultaneously allocated when either was

   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  Service names could not be assigned in the ports registry without
      assigning a corresponding port number at the same time

   This document clarifies and aligns 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.

7.2.  Updated Principles

   This section summarizes the basic principles by which IANA handles
   the Port and Service Name registry, and attempts to conserve the port
   number space.  This description is intended to inform applicants
   requesting service names and 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.

   IANA will begin assigning service names that do not request a
   corresponding port number allocation 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
   registrations or other situations where IANA believes expert review
   is advisable.

   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.  To help ensure
   this conservation the policy for any registration request for port
   number allocations uses the "Expert Review" policy [RFC5226].

   Conservation of the port number space is required 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:

   o  IANA will allocate only one assigned port number per service or

   o  IANA will allocate only one assigned port number for all versions
      of a service (e.g., running the service with or without a security
      mechanism, or for updated variants of a service)

   o  IANA will allocate only one assigned port number for all different
      types of device using or participating in the same service

   o  IANA will allocate port numbers only for the transport protocol(s)
      explicitly named in an registration request

   o  IANA may recover unused port numbers, via the new procedures of
      de-registration, revocation, and transfer

   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:

   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 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 not
   always reliable.  Further, previous separation of protocol variants
   based on security capabilities (e.g., HTTP on TCP port 80 vs. HTTPS
   on TCP port 443) is not recommended for new protocols, because all
   should be security-capable and capable of negotiating the use of
   security in-band.

   IANA will begin assigning port numbers for only 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 for
   only one of these transport protocols.  The new allocation procedure
   conserves resources by allocating 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 administrative contact for
   the registration MUST request IANA to convert the reservation into a
   proper 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.

   When the available pool of unassigned numbers has run out in a ports
   range, it will be necessary for IANA to consider the Reserved ports
   for assignment.  This is part of the motivation to not automatically
   assigning ports for other transport protocols than the requested
   ones.  This will allow more ports to be available for assignment at
   that point.  It also shows the importance to register the transport
   protocols that are in fact used.

   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 8 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 chose this option and register only a service name.

7.3.  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 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.  Ports in the Registered Ports range may also be
      assigned under the "IETF Review" or "IESG Approval" allocation
      procedures [RFC5226], which is how most assignments for IETF
      protocols are handled.

   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, the
      requirements for new allocations are more strict than those for
      the Registered Ports range, and will only be granted under the
      "IETF Review" or "IESG Approval" allocation procedures [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.

8.  IANA Procedures for Managing the Port Number and Service Name

   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.

8.1.  Port Number and 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 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.  The current administrative
   contact for 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 request contains some or
   all of the following information.  The combination of service name
   and transport protocol is the unique identifier of a given service:

      Service Name (REQUIRED)
      Transport Protocol(s) (REQUIRED)
      Registration Administrative Contact (REQUIRED)
      Registration Technical Contact (REQUIRED)
      Port Number (OPTIONAL)
      Service Code (only REQUIRED for DCCP)
      Description (REQUIRED)
      Reference (REQUIRED)
      Known Unauthorized Uses (OPTIONAL)
      Assignment Notes (OPTIONAL)

   o  Service Name: A desired unique service name for the service
      associated with the registration request MUST be provided, for use
      in 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 registered
      service names in the IANA registry [PORTREG].  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  Transport Protocol(s): The transport protocol(s) for which the
      allocation is requested MUST be provided.  This field is currently
      limited to one or more of TCP, UDP, SCTP, and DCCP.  This field is
      required even for services with no port number.

   o  Registration Administrative Contact: Name and email address of the
      administrative contact for the registration.  This is REQUIRED.
      The name of the administrative contact identifies the
      organization, company, or individual who is responsible for the
      registration.  For registrations done through IETF-published RFCs,
      the administrative contact will be the IESG.

   o  Registration Technical Contact: Name and email address of the
      technical contact person for the registration.  This is REQUIRED.
      For individuals, this is the same as the Registration
      Administrative Contact; for organizations, this is a point of
      contact at that organization.  Additional address information MAY
      be provided.  For registrations done through IETF-published RFCs,
      the technical contact will be the IESG.

   o  Port Number: If assignment of a port number is desired, either the
      currently Unassigned port number the requester suggests for
      allocation, or the text "ANY", MUST be provided.  If only a
      service name is to be assigned, this field MUST be empty.  If a
      specific port number is requested, IANA is encouraged to allocate
      the requested number.  If the text "ANY" is specified, IANA will
      choose a suitable number from the Registered Ports range.  Note
      that the applicant MUST NOT use the requested port prior to the
      completion of the registration.

   o  Service Code: The request MUST include a desired unique DCCP
      service code [RFC5595], if the registration request includes DCCP
      as a transport protocol, and MUST NOT include a requested DCCP
      service code otherwise.  Section 19.8 of [RFC4340] defines
      requirements and rules for allocation, updated by this document.

   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 description of (or a reference to a document
      describing) the protocol or application using this port.  The
      description must include whether the protocol uses either
      broadcast, multicast, or anycast communication.

      For registrations requesting only a Service Name or a Service Name
      and Registered Port, a statement that the protocol is proprietary
      and not publicly documented is also acceptable provided that the
      above information regarding use of broadcast, multicast, or
      anycast is given.

      For registration requests for a Registered Port, the registration
      request MUST explain why a port number in the Dynamic Ports range
      is unsuitable for the given application.

      For registration requests for a Well Known Port, the registration
      request MUST explain why a port number in the Registered Ports or
      Dynamic Ports ranges is unsuitable, and a reference to a stable
      protocol specification document MUST be provided.  For requests
      from IETF Working Groups, IANA MAY accept "Early" registration
      requests referencing a sufficiently stable Internet Draft instead
      of a published Standards-Track RFC [RFC4020].

   o  Known Unauthorized Uses: A list of uses by applications or
      organizations who are not the assignee.  This list may be
      augmented by IANA after assignment when unauthorized uses are

   o  Assignment Notes: Indications of owner/name change, or any other
      assignment process issue.  This list may be updated by IANA after
      assignment to help track changes to an assignment, e.g., de-
      registration, owner/name changes, etc.

   If the registration request is for the addition of a new transport
   protocol to an already assigned service name, IANA needs to confirm
   with the administrative contact for the existing assignment whether
   this addition is appropriate.

   If the registration request is for a service name alias (see
   Section 5), IANA needs to confirm with the administrative contact for
   the existing service name whether the registration of the alias is

   When IANA receives a registration 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 do not include a port
   number, IANA SHOULD assign the service name under a simple "First
   Come First Served" policy [RFC5226].

8.2.  Port Number and Service Name De-Registration

   The administrative contact 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.  Under this policy, it
   will appear in the registry as if it had been created through a
   service name registration request that did not include any port

   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.
   IANA will involve their IESG-appointed expert in such cases.

8.3.  Port Number and Service Name Re-Use

   If the administrative contact 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 8.2) followed by an immediate re-registration
   (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 allocation 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 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.

8.4.  Port Number and Service Name Revocation

   A port number revocation can be thought of as an IANA-initiated de-
   registration (Section 8.2), and has exactly the same effect on the

   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

8.5.  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
   a result, the IETF does 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 to grant the requested new assignment.

8.6.  Maintenance Issues

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

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 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.

   Services are expected to include support for security, either as
   default or dynamically negotiated in-band.  The use of separate port
   number or service name assignments for secure and insecure variants
   of the same service is to be avoided in order to discourage the
   deployment of insecure services.

10.  IANA Considerations

   This document obsoletes Sections 8 and 9.1 of the March 2000 IANA
   Allocation Guidelines [RFC2780].

   Upon approval of this document, IANA is requested to contact the
   maintainer of the [SRVREG] registry, in order to merge the contents
   of that private registry into the official IANA registry.  It is
   expected that the contents of [SRVREG] will at that time be replaced
   with pointers to the IANA registry and to this RFC.

   IANA is instructed to create a new service name entry in the port
   number registry [PORTREG] for any entry in the "Protocol and Service
   Names" registry [PROTSERVREG] that does not already have one

   IANA is also instructed to indicate which service name aliases in the
   existing registry are the primary aliases (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 registrations [PORTREG] meet the rules for
   legal service names stated in Section 8.1, and hence will be used

   The remaining approximately 2% of the exiting "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 unsuitable
   "Short Names", listed in the table below, the service name will be
   the Short Name with any illegal characters replaced by hyphens.  IANA
   SHALL add an entry to the registry giving the new well-formed primary
   service name for the existing service, that otherwise duplicates the
   original assignment information.  In the description field of this
   new entry giving the primary service name, IANA SHALL record that it
   assigns a well-formed service name for the previous service and
   reference the original assignment.  In the description field of the
   original assignment, IANA SHALL add 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.

   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          |

   Following the example set by the "application/whoispp-query" MIME
   Content-Type [RFC2957], the service name for "whois++" will be

10.2.  Port Numbers for SCTP and DCCP Experimentation

   Two Well Known UDP and TCP ports, 1021 and 1022, have been reserved
   for experimental use [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 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.

   | Registration Administrative Contact | IETF <>       |
   | Registration Technical Contact      | IESG <>       |
   | Service Name                        | exp1                       |
   | Port Number                         | 1021                       |
   | Transport Protocol                  | SCTP, DCCP                 |
   | Description                         | RFC3692-style Experiment 1 |
   | Reference                           | [RFCyyyy]                  |

   | Registration Administrative Contact | IETF <>       |
   | Registration Technical Contact      | IESG <>       |
   | Service Name                        | exp2                       |
   | Port Number                         | 1022                       |
   | Transport Protocol                  | SCTP, DCCP                 |
   | Description                         | RFC3692-style Experiment 2 |
   | Reference                           | [RFCyyyy]                  |

   [RFC Editor Note: Please change "yyyy" to the RFC number allocated to
   this document before publication.]

10.3.  Updates to DCCP Registries

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

10.3.1.  DCCP Service Code Registry

   Service Codes are allocated first-come-first-served 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
      seeks more than five Service Codes.

   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].

10.3.2.  DCCP Port Numbers Registry

   The DCCP ports registry is defined by Section 19.9 of the DCCP
   specification [RFC4340].  Allocations in this registry require prior
   allocation of a Service Code.  Not all Service Codes require IANA-
   registered 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 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].

   o  IANA MUST NOT allocate more than one DCCP server port to a single
      service code value.

   o  The allocation 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 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.

   The DCCP specification [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.

11.  Contributors

   Stuart Cheshire (, Alfred Hoenes (
   and Allison Mankin ( 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 [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.

13.  References

13.1.  Normative References

              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.

   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
              Specifications: ABNF", STD 68, RFC 5234, January 2008.

13.2.  Informative References

              Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", draft-cheshire-dnsext-dns-sd-06 (work in
              progress), March 2010.

              Cheshire, S., "NAT Port Mapping Protocol (NAT-PMP)",
              draft-cheshire-nat-pmp-03 (work in progress), April 2008.

              Gudmundsson, O. and A. Hoenes, "Clarification of DNS SRV
              Owner Names", draft-gudmundsson-dnsext-srv-clarify-00
              (work in progress), December 2009.

   [IGD]      UPnP Forum, "Internet Gateway Device (IGD) V 1.0",
              November 2001.

   [PORTREG]  Internet Assigned Numbers Authority (IANA), "Port Numbers

              Internet Assigned Numbers Authority (IANA), "Protocol and
              Service Names Registry",

   [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.

   [RFC1700]  Reynolds, J. and J. Postel, "Assigned Numbers", RFC 1700,
              October 1994.

   [RFC2782]  Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
              specifying the location of services (DNS SRV)", RFC 2782,
              February 2000.

   [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.

   [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.

   [RFC5389]  Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
              "Session Traversal Utilities for NAT (STUN)", RFC 5389,
              October 2008.

   [RFC5595]  Fairhurst, G., "The Datagram Congestion Control Protocol
              (DCCP) Service Codes", RFC 5595, September 2009.

   [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",

   [SYSFORM]  Internet Assigned Numbers Authority (IANA), "Application
              for System (Well Known) Port Number",

   [TRILOGY]  "Trilogy Project",

   [USRFORM]  Internet Assigned Numbers Authority (IANA), "Application
              for User (Registered) Port Number",

Authors' Addresses

   Michelle Cotton
   Internet Corporation for Assigned Names and Numbers
   4676 Admiralty Way, Suite 330
   Marina del Rey, CA  90292

   Phone: +1 310 823 9358

   Lars Eggert
   Nokia Research Center
   P.O. Box 407
   Nokia Group  00045

   Phone: +358 50 48 24461

   Joe Touch
   4676 Admiralty Way
   Marina del Rey, CA  90292

   Phone: +1 310 448 9151

   Magnus Westerlund
   Torshamsgatan 23
   Stockholm  164 80

   Phone: +46 8 719 0000
   Stuart Cheshire
   Apple Inc.
   1 Infinite Loop
   Cupertino, CA  95014

   Phone: +1 408 974 3207