IANA Procedures for the Transport Protocol Port Number Space
draft-ietf-tsvwg-iana-ports-00

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Abstract

This document defines the IANA procedures for registering port number values for use with the various IETF transport protocols, including TCP, UDP, DCCP, and SCTP. It provides clear procedures for the management of the port number registry, which is important for its long-term management. It updates RFC2780 by obsoleting Sections 8 and 9.1 of that RFC, and it updates the IANA allocation procedures for DCCP as defined in RFC4340.

Table of Contents

1.  Introduction
2.  Terminology
3.  Port Number Types
    3.1.  Assigned Port Numbers for Experimentation
4.  Principles for Port Number Space Management
    4.1.  Basic Principles of Port Conservation
    4.2.  Principles Specific to Individual Port Number Ranges
    4.3.  New Principles
5.  IANA Procedures for Managing the Port Number Space
    5.1.  Port Number Registration
    5.2.  Port Number De-Registration
    5.3.  Port Number Re-Use
    5.4.  Port Number Revocation
    5.5.  Port Number Transfer
    5.6.  Maintenance Issues
6.  Port Number Space Requests
    6.1.  Request Procedure
7.  Security Considerations
8.  IANA Considerations
9.  Acknowledgments
10.  References
    10.1.  Normative References
    10.2.  Informative References
Appendix A.  Updates to DCCP Registries
    A.1.  DCCP Service Code Registry
    A.2.  DCCP Port Numbers Registry
§  Authors' Addresses
§  Intellectual Property and Copyright Statements

1.  Introduction

The Transmission Control Protocol (TCP) [RFC0793] (Postel, J., “Transmission Control Protocol,” September 1981.) and the User Datagram Protocol (UDP) [RFC0768] (Postel, J., “User Datagram Protocol,” August 1980.) have enjoyed a remarkable success over the decades as the two most widely used transport protocols on the Internet. They have introduced the concept of "ports" as logical entities for Internet communication. Ports serve two purposes: first, they provide a demultiplexing identifier to differentiate transport sessions between the same pair of endpoints, and second, they also identify the application protocol and associated service to which processes bind [I‑D.touch‑tsvwg‑port‑guidelines] (Touch, J., “Guidelines for Transport Port Use,” July 2008.). Newer transport protocols, such as the Stream Control Transmission Protocol (SCTP) [RFC4960] (Stewart, R., “Stream Control Transmission Protocol,” September 2007.) and the Datagram Congestion Control Protocol (DCCP) [RFC4342] (Floyd, S., Kohler, E., and J. Padhye, “Profile for Datagram Congestion Control Protocol (DCCP) Congestion Control ID 3: TCP-Friendly Rate Control (TFRC),” March 2006.) have adopted the concept of ports for their communication sessions and use port numbers in the same way as TCP and 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" for port number 80.

Hosts running services, hosts accessing services on other hosts, and intermediate devices (such as firewalls and NATs) that restrict services need to agree on which service corresponds to a particular destination port. Although this can be a local decision between the endpoints of a connection, most Internet components use a single, shared view of this association, provided by the Internet Assigned Numbers Authority (IANA) through the port number registry [REGISTRY] (Internet Assigned Numbers Authority (IANA), “Port Numbers,” .).

Designers of applications and application-level protocols may apply to IANA for a registered port number for a specific application, and may - after successful registration - assume that no other application will use that port number for its communication sessions. It is important to note that ownership of registered port numbers remains with IANA. For many years, the allocation and registration of new port number values for use with TCP and UDP have had less than clear guidelines. Information about the registration procedures for the port namespace existed in three locations: the forms for requesting port number registrations on the IANA web site [SYSFORM] (Internet Assigned Numbers Authority (IANA), “Application for System (Well Known) Port Number,” .)[USRFORM] (Internet Assigned Numbers Authority (IANA), “Application for User (Registered) Port Number,” .), an introductory text section in the file listing the port number registrations themselves [REGISTRY] (Internet Assigned Numbers Authority (IANA), “Port Numbers,” .), and two brief sections of [RFC2780] (Bradner, S. and V. Paxson, “IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers,” March 2000.).

This document aggregates this scattered information into a single reference and at the same time clarifies the guidelines for the management of the port number space. It gives more detailed guidance to prospective requesters of ports than the existing documentation, and it streamlines the IANA procedures for the management of the port number space, so that management requests can complete in a timely manner. A key factor of this streamlining is to establish identical registration procedures for transport protocol ports, independent of a specific transport protocol. This document brings the IANA procedures for TCP and UDP in line with those already in effect for SCTP and DCCP, resulting in a single process that requesters and IANA follow for all port number requests for all transport protocols, including those not yet defined.

A second purpose of this document is to describe the principles that guide the IETF and IANA in their role as the long-term joint stewards of the port number space. TCP and UDP have been a remarkable success over the last decades. Thousands of applications and application-level protocols have registered ports 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 port number space follow principles that ensure its long-term usefulness as a shared resource. Section 4 (Principles for Port Number Space Management) discusses these principles in detail. Guidelines for users seeking port numbers, as well as a detailed history of the port number registry and alternate means for coordinating host agreement on service-to-port-number mappings, is provided in a companion document (Touch, J., “Guidelines for Transport Port Use,” July 2008.) [I‑D.touch‑tsvwg‑port‑guidelines].

In addition to detailing the IANA procedures for the initial assignment of 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-register a port number that is no longer in use, to re-use a port number allocated for one application that is no longer in use for another application, and procedure by which IANA can unilaterally revoke a prior port number registration. Section 5 (IANA Procedures for Managing the Port Number Space) discusses the specifics of these procedures.

This document also addresses two technical issues related to the ports registry that are tangential to long-term stewardship. First, it clarifies that a method for the early allocation of port numbers is available for IETF working groups, in line with [RFC4020] (Kompella, K. and A. Zinin, “Early IANA Allocation of Standards Track Code Points,” February 2005.). Second, it discusses how the use of symbolic names for assigned ports (the "keyword" field in [REGISTRY] (Internet Assigned Numbers Authority (IANA), “Port Numbers,” .)) for Service Resource Records (SRV RRs) in the Domain Name System (DNS) [RFC2782] (Gulbrandsen, A., Vixie, P., and L. Esibov, “A DNS RR for specifying the location of services (DNS SRV),” February 2000.) relates to the use of SRV RRs for applications without an assigned port.

This document updates [RFC2780] (Bradner, S. and V. Paxson, “IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers,” March 2000.) by obsoleting Sections 8 and 9.1 of that RFC. Note that [RFC5237] (Arkko, J. and S. Bradner, “IANA Allocation Guidelines for the Protocol Field,” February 2008.) updates a different subset of the IANA allocation guidelines originally given in [RFC2780] (Bradner, S. and V. Paxson, “IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers,” March 2000.) (specifically, the policies on the namespace of the IP protocol number and IPv6 next header).

2.  Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [RFC2119] (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.).

3.  Port Number Types

TCP, UDP, 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 6 (Port Number Space Requests) describes the IANA procedures for each range in detail:

• the Well Known Ports, i.e., the System Ports, from 0-1023 (assigned by IANA)
• the Registered Ports, i.e., the User Ports, from 1024-49151 (assigned by IANA)
• the Dynamic Ports, i.e., 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:

1. Assigned: Assigned port numbers are currently allocated to the service indicated in the registry.
2. Unassigned: Unassigned port numbers are currently available for assignment upon request, as per the procedures outlined in this document.
3. 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.

When this document was written, approximately 76% of the TCP and UDP Well Known Ports were assigned, as were a significant fraction of the Registered Ports. (As noted, Dynamic Ports are never assigned.)

3.1.  Assigned Port Numbers for Experimentation

Of the Registered Ports, two TCP and UDP port numbers (1021 and 1022) have been assigned for experimentation with new applications and application-layer protocols that require a port number in the Registered Ports range [RFC4727] (Fenner, B., “Experimental Values In IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers,” November 2006.). [sctp-dccp-exp] (Lars: This document should register ports 1021 and 1022 for DCCP and SCTP.)

The experimental ports 1021 and 1022 SHOULD be used for local experiments only in controlled environments, and they SHOULD NOT be used on the global Internet. Many new applications and application-layer protocols can be experimented with without requiring a port in the Registered Ports range, and port numbers in the Dynamic Ports range can be also used.

Unfortunately, it can be difficult to limit access to these ports. Users SHOULD take measures to ensure that experimental ports are connecting to the intended process. For example, users of these experimental ports might include a 64-bit nonce, once on each segment of a message-oriented channel (e.g., UDP), or once at the beginning of a byte-stream (e.g., TCP), which is used to confirm that the port is being used as intended. Such confirmation of intended use is especially important when these ports are associated with privileged (e.g., system or administrator) processes.

4.  Principles for Port Number Space Management

Management procedures for the port number space include allocation of port numbers upon request, as well as coordination of information about existing allocations. The latter includes maintaining contact and description information about assigned ports, revoking abandoned ports, and redefining port allocations when needed. Of these procedures, port number allocation is most critical, because of the limited number of remaining port numbers.

Before the publication of this document, the principles of port number space allocation followed some simple, undocumented guidelines:

• TCP and UDP ports were simultaneously allocated when either was requested
• Port numbers were the primary allocation; service names were informative only, and did not need to be unique
• Port numbers were conserved informally, and sometimes inconsistently (e.g., some services were allocated ranges of many port numbers even where not strictly necessary)
• SCTP and DCCP port number and service name spaces were managed separately from the TCP/UDP spaces

This document attempts to update these guidelines to more conservatively manage the limited remaining TCP and UDP port number spaces, recognizes the potential use of service names in the absence of corresponding port number allocations, such as in SCTP and DCCP.

The basic principle of port number registry management is to conserve the 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.

Port numbers are intended to indicate a service and enable process demultiplexing at an endpoint; uses beyond those basic requirements should be avoided [I‑D.touch‑tsvwg‑port‑guidelines] (Touch, J., “Guidelines for Transport Port Use,” July 2008.). This document also focuses on service names as a unique identifier, to increase the space available (from 4 bytes to 14), and to enable their use in the absence of corresponding port number assignments.

4.1.  Basic Principles of Port Conservation

This section summarizes the basic principles by which IANA attempts to conserve the port number space. This description is intended to inform applicants requesting port numbers. IANA decisions are not required to be bound to these principles, however; other factors may come into play, and exceptions may occur where deemed in the best interest of the Internet.

Conservation of the port number space recognizes that because this space is a limited resource, applications are expected to participate in the demultiplexing process where feasible. The port numbers are expected to encode as little information as possible that will enable an application to perform further demultiplexing by itself. In particular, there should be:

• only one port per service
• one port for all versions of a service
• the same port for different types of devices using the same service

A given service is expected to further demultiplex messages where possible. For example, applications and protocols are expected to include in-band version information, so that future versions of the application or protocol can share the same allocated port. Applications and protocols are also expected to be able to efficiently use a single allocated port, 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] (Postel, J. and J. Reynolds, “File Transfer Protocol,” October 1985.)).

These principles of port conservation are explained in [I‑D.touch‑tsvwg‑port‑guidelines] (Touch, J., “Guidelines for Transport Port Use,” July 2008.). That document explains in further detail how ports are used in various ways, notably:

• Endpoint process identifier
• Application protocol identifier
• Firewall filtering

The process and protocol identifier use suggests that anything a single process can demultiplex, or that can be encoded into a single protocol, should be. The firewall filtering use suggests that some uses that could be de-multiplexed or encoded must be separated to allow for firewall management. Note that this latter use is much less sound, because port numbers have meaning only for the two endpoints of a connection (again, as discussed in detail in [I‑D.touch‑tsvwg‑port‑guidelines] (Touch, J., “Guidelines for Transport Port Use,” July 2008.)).

4.2.  Principles Specific to Individual Port Number Ranges

It is important to note that different IANA procedures apply to different ranges of the port number registry. Section 6 (Port Number Space Requests) discusses the details of these procedures; this section outlines the rationale for these differences:

• 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.
• 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, and have a technical expert review this documentation to determine whether to grant the registration request. This documentation MUST explain why a port number in the Dynamic Ports range is unsuitable for the given application.
• Ports in the Well Known Ports range (0-1023) are also available for registration through IANA. Because the Well Known Ports range is both the smallest and the most densely allocated one, the bar for new allocations is higher than that for the Registered Ports range (1024-49551). A request for a Well Known port number MUST document why a port number in the Registered Ports or Dynamic Ports ranges is unsuitable.

4.3.  New Principles

Several new practices stem from the conservation principle that guides management of the port numbers registry, and will take effect with the approval of this document:

• IANA will allocate port numbers only to the transport protocols requested
• IANA will recover unused port numbers, via the new procedures of de-registration, revocation, and transfer

IANA will begin assigning protocol numbers only for those transport protocols explicitly included in a registration request. This ends the long-standing practice of automatically assigning a port number to an application for both TCP and a UDP, even if the request is only for one of these transport protocols. The new allocation procedure conserves resources by only allocating a port number to an application for those transport protocols (TCP, UDP, SCTP and/or DCCP) it actually uses. The port number will be marked as reserved - instead of assigned - in the port number registries of the other transport protocols. When applications start supporting the use of some of those additional transport protocols, they must request IANA to convert the reservation into an assignment. An application MUST NOT assume that it can use a port number assigned to it for use with one transport protocol with another transport protocol without another registration with IANA. The reason for this procedure is to allow allocation of reserved port numbers on the day the range has no more unassigend values. [port-reserv] (Magnus: The usage of for the above reason reserved port numbers should probably not have the same rules as the other reserved ports. Needs discussion if we should separate this properly. I think the IETF consultation part will make it difficult the day one registry runs out of unassigned ones.)

Conservation for the port numbers registry 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 5 (IANA Procedures for Managing the Port Number Space) describes these procedures, which so far were undocumented.

5.  IANA Procedures for Managing the Port Number Space

IANA supports various procedures to manage the port number space that enable ports to be registered, de-registered, reused, and revoked. This section explains these procedures, as well as other related issues.

5.1.  Port Number Registration

Registration refers to the allocation of port numbers to applicants. All such registrations are made from port numbers that are Unassigned or Reserved at the tine of the allocation. Unassigned numbers are allocated as needed, and without further explanation. Reserved numbers are assigned only after review by IANA and the IETF, and are accompanied by a statement explaining the reason a reserved number is appropriate for this action.

When a registration for one or more (but not all) transport protocols is approved, the port number for the non-requested transport protocol(s) will remain unassigned but is marked as reserved. However, IANA SHOULD NOT assign that port number to any other application or service until no port numbers remain unassigned in the request range. The current registration owner of a port number MAY register the same port number for other transport protocols when needed.

A port number registration consists of the following tuple:

Registration Contact:

Name and email address of the contact person for the registration. This is REQUIRED. Additional address information MAY be provided. For registrations done through IETF-published RFCs, one or more technical contact persons SHALL be provided. In addition, in this case the registration ownership will belong to the IETF and not the technical contact persons.

Transport Protocol:

The transport protocol(s) for which the port allocation is requested, currently limited to one or more of TCP, UDP, SCTP, and DCCP

Port Number:

The currently unassigned port number(s) the requester suggests for allocation. If specified and when possible, IANA is encouraged to allocate the suggested number. If not specified, IANA will choose a suitable number from the Registered Ports range.

Broadcast, Multicast or Anycast:

Indicates whether the protocol supports either broadcast, multicast or anycast network layer addresses.

Port Name:

The long name (description) of the port. It should avoid all but the most well known acronyms.

Service Name:

This short name for the port number, used in various service selection and discovery mechanisms, currently including TCPMUX [RFC1078] (Lottor, M., “TCP port service Multiplexer (TCPMUX),” November 1988.) and DNS SRV resource records [RFC2782] (Gulbrandsen, A., Vixie, P., and L. Esibov, “A DNS RR for specifying the location of services (DNS SRV),” February 2000.). This name is limited to 14 bytes, case-insensitive US-ASCII letters, digits, and dashes. It MUST NOT conflict with already allocated names in the service name registry [serv-nam-reg] (Lars: Add citation to the service name registry draft, when it exists).

Reference:

A reference document describing the protocol or application using this port. For registration requests for Registered Ports, this documentation MUST explain why a port number in the Dynamic Ports range is unsuitable for the given application. For registration requests for Well Known Ports, this documentation MUST explain why a port number in the Registered Ports or Dynamic Ports ranges is unsuitable.

The following rules apply to the port number registry database maintained by IANA: [database-rules] (Lars: Some of these rules below allow entries that aren't in full alignment with the procedures in this document. I assume that is, because the rules attempt to describe the state of the IANA database including all existing entries? If so, we should make that clearer.)

• Service Names MUST be unique
• Service Name MUST exist for all transport protocols
• Port Number MUST exist for TCP and UDP; it MAY exist for SCTP and DCCP
• Transport Protocol MUST exist for all entries
• Service Code MUST NOT occur for TCP, UDP or SCTP, and MUST occur for DCCP
• Port Name MUST exist for all entries
• Currently valid Registration Contact SHOULD exist for all entries; it MUST exist for all new entries
• Reference SHOULD exist for all entries

5.2.  Port Number De-Registration

The original requesters of a granted port number assignment can return the port number to IANA at any time if they no longer have a need for it. The port number will be de-registered and will be marked as reserved [res-vs-unass] (Lars: This used to say "unassigned" instead of "reserved". I suggest "reserved", so that IANA has an indication in their list that they need to be careful when re-assigning a previously de-registered port.) 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 de-registration, IANA needs to confirm that the port number is actually no longer in use.

5.3.  Port Number Re-Use

If the original requesters of a granted port number assignment no longer have a need for the registered number, but would like to re-use it for a different application, they can submit a request to IANA to do so.

Logically, port number re-use is to be thought of as a de-registration followed by an immediate re-registration 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.

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.

5.4.  Port Number Revocation

Sometimes, it will be clear that a specific port number is no longer in use and that IANA can de-register it and mark it as reserved [res-vs-unass2] (Lars: See [res-vs-unass].) But at other times, it may be unclear whether a given assigned port number is still in use somewhere in the Internet. In those cases, despite the requester's wish to de-register, IANA must consider the consequences that de-registering the port number.

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.

5.5.  Port Number Transfer

The value of port numbers is defined by their careful management as a shared Internet resource, whereas enabling transfer allows the potential for associated monetary exchanges to motivate this management. As a result, current IANA procedures do not permit port number assignments to be transferred between parties, even when they are mutually consenting. The appropriate alternate procedure is for the new party to request its own port number registration and for the previous party to release its registration via the de-registration procedure outlined above.

5.6.  Maintenance Issues

The previous procedures help IANA manage defining properties of the port name space. There are additional procedures which are administrative, and help IANA maintain non-defining information in a registration. This includes changes to the Port Name (i.e., description), and changes to contact information. These changes are coordinated by IANA in an informal manner, and may be initiated by either the registrant or by IANA, e.g., the latter when requesting an update to current contact information.

6.  Port Number Space Requests

This section describes the process for requests associated with IANA's management of the the port number space. Such requests include initial registration, de-registration, re-use, changes to the service name, as well as updates to the contact information or port name (description). Revocation is initiated by IANA.

6.1.  Request Procedure

All registration requests for a TCP, SCTP, DCCP and/or UDP ports must contain the following pieces of information:

Port number tuple:

A port number tuple, as described in Section 5.1 (Port Number Registration). The port number would typically be omitted; when provided, it indicates a preference for requesting a currently unassigned value.

Port Range:

Indicates the port range desired (i.e., Well Known Ports or Registered Ports).

Requested Action:

One of REGISTER, DEREGISTER, REUSE, SVC_NAME_CHANGE, or UPDATE_INFO (port name, registration contact).

The Well Known Ports are assigned by IANA and cover the range 0-1023. On many systems, they can only be used by system (or root) processes or by programs executed by privileged users. Registration requests for a Well Known port number MUST follow the "IETF Review" policy of [RFC5226] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” May 2008.). Registrations for a port number in this range MUST document why a port number in the Registered Ports range will not fulfill the application needs.

The Registered Ports are assigned by IANA and on most systems can be used by ordinary user processes or programs executed by ordinary users. The Registered Ports are in the range 1024-49151. Registration requests for a Registered Port number MUST follow the "Expert Review" policy of [RFC5226] (Narten, T. and H. Alvestrand, “Guidelines for Writing an IANA Considerations Section in RFCs,” May 2008.).

7.  Security Considerations

The IANA guidelines described in this document do not change the security properties of either TCP, SCTP, DCCP or UDP.

Assignment of a port number 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 the 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 registered or not.

8.  IANA Considerations

This document obsoletes Sections 8 and 9.1 of [RFC2780] (Bradner, S. and V. Paxson, “IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers,” March 2000.). Upon approval of this document, IANA is requested to adopt the procedures described herein.

IANA should take immediate actions to resolve inconsistencies raised by requirements of this document.

9.  Acknowledgments

The text in Appendix A (Updates to DCCP Registries) is based on a suggestion by Tom Phelan.

Lars Eggert is partly funded by [TRILOGY] (, “Trilogy Project,” .), a research project supported by the European Commission under its Seventh Framework Program.

10.  References

10.1. Normative References

10.2. Informative References

Editorial Comments

Appendix A.  Updates to DCCP Registries

This document updates the IANA allocation procedures for the DCCP Port Number and DCCP Service Codes Registries as defined in [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.).

A.1.  DCCP Service Code Registry

Service Codes are allocated first-come-first-served according to Section 19.8 of [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.). This document updates Section 19.8 of [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.) by extending the guidelines given there in the following ways:

• IANA MAY assign new Service Codes without seeking Expert Review using their discretion, but SHOULD seek expert review when a request seeks an appreciable number of Service Codes (e.g., more than five).
• 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] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.).

A.2.  DCCP Port Numbers Registry

The DCCP ports registry is defined by [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.) in Section 19.9. Allocations in this registry require prior allocation of a Service Code. Not all Service Codes require IANA-registered ports. This document updates Section 19.9 of [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.) by extending the guidelines given there in the following way:

• 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 IETF Action prior to allocation by IANA [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.).

Section 19.9 of [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.) requires each DCCP server port assignment to be associated with at least one Service Code value. This document updates [RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.) in the following way:

• IANA MUST NOT allocate a single Service Code value to more than one DCCP server port.
• The set of Service Code values associated with a DCCP server port should be recorded in the ports registry.
• A request for additional Service Codes to be associated with an already allocated Port Number requires Expert Review. These requests will normally be accepted when they originate from the contact associated with the port registration. In other cases, these applications will be expected to use an unallocated port, when this is available.

[RFC4340] (Kohler, E., Handley, M., and S. Floyd, “Datagram Congestion Control Protocol (DCCP),” March 2006.) 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.

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