RFC 7605: Recommendations on Using Assigned Transport Port Numbers | RFC Editor

Skip to content Primary navigationThe RFC SeriesFor AuthorsAbout UsHomeRFC 7605 View as: Plain Text, Compact HTML Info RFC 7605: BCP 165: Recommendations on Using Assigned Transport Port NumbersIANADCCPSCTPTCPUDPAugust 2015. J. TouchBest Current PracticeSubscribe11 subscribed Add to Set Read aloud Internet Engineering Task Force (IETF) J. Touch Request for Comments: 7605 USC/ISI BCP: 165 August 2015 Category: Best Current Practice ISSN: 2070-1721 Recommendations on Using Assigned Transport Port Numbers Abstract This document provides recommendations to designers of application and service protocols on how to use the transport protocol port number space and when to request a port assignment from IANA. It provides designer guidance to requesters or users of port numbers on how to interact with IANA using the processes defined in RFC 6335; thus, this document complements (but does not update) that document. It provides guidelines for designers regarding how to interact with the IANA processes defined in RFC 6335, thus serving to complement (but not update) that document. Status of This Memo This memo documents an Internet Best Current Practice. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on BCPs is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7605. Touch Best Current Practice [Page 1] RFC 7605 Recommendations for Transport Port Use August 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction ....................................................3 2. Conventions Used in This Document ...............................3 3. History .........................................................3 4. Current Port Number Use .........................................5 5. What is a Port Number? ..........................................5 6. Conservation ....................................................7 6.1. Guiding Principles .........................................7 6.2. Firewall and NAT Considerations ............................8 7. Considerations for Requesting Port Number Assignments ...........9 7.1. Is a port number assignment necessary? .....................9 7.2. How many assigned port numbers are necessary? .............11 7.3. Picking an Assigned Port Number ...........................12 7.4. Support for Security ......................................13 7.5. Support for Future Versions ...............................14 7.6. Transport Protocols .......................................14 7.7. When to Request an Assignment .............................16 7.8. Squatting .................................................17 7.9. Other Considerations ......................................18 8. Security Considerations ........................................18 9. IANA Considerations ............................................19 10. References ....................................................19 10.1. Normative References .....................................19 10.2. Informative References ...................................20 Acknowledgments ...................................................24 Author's Address ..................................................24 Touch Best Current Practice [Page 2] RFC 7605 Recommendations for Transport Port Use August 2015 1. Introduction This document provides information and advice to application and service designers on the use of assigned transport port numbers. It provides a detailed historical background of the evolution of transport port numbers and their multiple meanings. It also provides specific recommendations to designers on how to use assigned port numbers. Note that this document provides information to potential port number applicants that complements the IANA process described in [RFC6335] (the sole document of BCP 165 before this document), but it does not change any of the port number assignment procedures described therein. Because they are thus so closely related, this document and RFC 6335 are now known together as BCP 165. This document is intended to address concerns typically raised during Expert Review (see [RFC5226]) of assigned port number applications, but it is not intended to bind those reviews. RFC 6335 also describes the interaction between port experts and port requests in IETF consensus documents. Authors of IETF consensus documents should nevertheless follow the advice in this document and can expect comment on their port requests from the port experts during IETF Last Call or at other times when review is explicitly sought. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. In this document, these words will appear with that interpretation only when in ALL CAPS. Lowercase uses of these words are not to be interpreted as carrying significance described in RFC 2119. In this document, the characters ">>" preceding an indented line(s) indicates a statement using