Recommendations on Using Assigned Transport Port Numbers
RFC 7605
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
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