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Registration Procedures for Private Enterprise Numbers (PENs)
RFC 9371

Document Type RFC - Informational (March 2023)
Was draft-pti-pen-registration (individual)
Authors Amanda Baber , Paul E. Hoffman
Last updated 2023-12-12
RFC stream Internet Engineering Task Force (IETF)
IESG Responsible AD Robert Wilton
Send notices to (None)
RFC 9371

Internet Engineering Task Force (IETF)                          A. Baber
Request for Comments: 9371                                          IANA
Category: Informational                                       P. Hoffman
ISSN: 2070-1721                                                    ICANN
                                                              March 2023

     Registration Procedures for Private Enterprise Numbers (PENs)


   This document describes how Private Enterprise Numbers (PENs) are
   registered by IANA.  It shows how to request a new PEN and how to
   modify a current PEN.  It also gives a brief overview of PEN uses.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   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).  Not all documents
   approved by the IESG are candidates for any level of Internet
   Standard; see Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2023 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
   ( 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 Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
     1.1.  Uses of PENs
   2.  PEN Assignment
     2.1.  Requesting a PEN Assignment
     2.2.  Modifying an Existing Record
     2.3.  Deleting a PEN Record
   3.  PEN Registry Specifics
   4.  IANA Considerations
   5.  Security Considerations
   6.  References
     6.1.  Normative References
     6.2.  Informative References
   Authors' Addresses

1.  Introduction

   Private Enterprise Numbers (PENs) are identifiers that can be used
   anywhere that an ASN.1 object identifier (OID) [ASN1] can be used.
   Originally, PENs were developed so that organizations that needed to
   identify themselves in Simple Network Management Protocol (SNMP)
   [RFC3411] Management Information Base (MIB) configurations could do
   so easily.  PENs are also useful in any application or configuration
   language that needs OIDs to identify organizations.

   The IANA Functions Operator, referred to in this document as "IANA",
   manages and maintains the PEN registry in consultation with the IESG.
   PENs are issued from an OID prefix that was assigned to IANA.  That
   OID prefix is  Using the (now archaic) notation of
   ownership names in the OID tree, that corresponds to:

   1   3   6   1        4       1

   A PEN is an OID that begins with the PEN prefix.  Thus, the OID is a PEN.

1.1.  Uses of PENs

   Once a PEN has been assigned to an organization, individual, or other
   entity, that assignee can use the PEN by itself (possibly to
   represent the assignee) or as the root of other OIDs associated with
   the assignee.  For example, if an assignee is assigned the PEN, it might use to identify a
   protocol extension and use to identify a set
   of algorithms that it supports in a protocol.

   Neither IANA nor the IETF can control how an assignee uses its PEN.
   In fact, no one can exert such control: that is the meaning of
   "private" in "private enterprise number".  Similarly, no one can
   prevent an assignee that is not the registered owner of a PEN from
   using that PEN, or any PEN, however they want.

   A very common use of PENs is to give unique identifiers in IETF
   protocols.  SNMP MIB configuration files use PENs for identifying the
   origin of values.  Protocols that use PENs as identifiers of
   extension mechanisms include RADIUS [RFC2865], Diameter [RFC6733],
   Syslog [RFC5424], RSVP [RFC5284], and vCard [RFC6350].

2.  PEN Assignment

   PENs are assigned by IANA.  The registry is located at
   <>, and requests
   for new assignments or the modification of existing assignments can
   also be submitted at that URL.

   IANA maintains the PEN registry in accordance with the "First Come
   First Served" registration policy described in [RFC8126].  Values are
   assigned sequentially.

2.1.  Requesting a PEN Assignment

   Requests for assignment must provide the name of the assignee, the
   name of a public contact who can respond to questions about the
   assignment, and contact information that can be used to verify change
   requests.  The contact's name and email address will be included in
   the public registry.

   A prospective assignee may request multiple PENs, but obtaining one
   PEN and making internal sub-assignments is typically more
   appropriate.  (Sub-assignments should not be reported to IANA.)

   IANA may refuse to process abusive requests.

2.2.  Modifying an Existing Record

   Any of the information associated with a registered value can be
   modified, including the name of the assignee.

   Modification requests require authorization by a representative of
   the assignee.  Authorization will be validated either with
   information kept on file with IANA or with other identifying
   documentation, if necessary.

2.3.  Deleting a PEN Record

   Although such requests are rare, registrations can be deleted.  When
   a registration is deleted, all identifying information is removed
   from the registry, and the value is marked as "returned."  Returned
   values will not be made available for reassignment until all other
   unassigned values have been exhausted; as can be seen in Section 3,
   the unassigned values are unlikely to ever run out.

3.  PEN Registry Specifics

   The range for values after the PEN prefix is 0 to 2**32-1.  The
   values 0 and 4294967295 (2**32-1) are reserved.  Note that while the
   original PEN definition had no upper bound for the value after the
   PEN prefix, there is now an upper bound due to some IETF protocols
   limiting the size of that value.  For example, Diameter [RFC6733]
   limits the value to 2**32-1.

   There is a PEN number, 32473, reserved for use as an example in
   documentation.  This reservation is described in [RFC5612].

   Values in the registry that have unclear ownership are marked
   "Reserved".  These values will not be reassigned to a new company or
   individual without consulting the IESG.

4.  IANA Considerations

   Per this document, IANA has made the following changes to the PEN

   *  Values 2187, 2188, 3513, 4164, 4565, 4600, 4913, 4999, 5099, 5144,
      5201, 5683, 5777, 6260, 6619, 14827, 16739, 26975, and the range
      from 11670 to 11769, which had been missing from the registry,
      have been listed as "Reserved."  As described in [RFC8126],
      reserved values can be released by the IESG.

   *  This document has been listed in the registry's "Reference" field.

   *  "First Come First Served" has been listed as its registration

5.  Security Considerations

   Registering PENs does not introduce any significant security

   There is no cryptographic binding of a registrant in the PEN registry
   and the PEN(s) assigned to them.  Thus, the entries in the PEN
   registry cannot be used to validate the ownership of a PEN in use.
   For example, if the PEN is seen in a protocol as
   indicating the owner of some data, there is no way to securely
   correlate that use with the name and assignee of the owner listed in
   the PEN registry.

6.  References

6.1.  Normative References

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,

6.2.  Informative References

   [ASN1]     ITU-T, "Information technology - ASN.1 encoding rules:
              Specification of Basic Encoding Rules (BER), Canonical
              Encoding Rules (CER) and Distinguished Encoding Rules
              (DER)", ITU-T Recommendation X.690, February 2021,

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,

   [RFC3411]  Harrington, D., Presuhn, R., and B. Wijnen, "An
              Architecture for Describing Simple Network Management
              Protocol (SNMP) Management Frameworks", STD 62, RFC 3411,
              DOI 10.17487/RFC3411, December 2002,

   [RFC5284]  Swallow, G. and A. Farrel, "User-Defined Errors for RSVP",
              RFC 5284, DOI 10.17487/RFC5284, August 2008,

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424,
              DOI 10.17487/RFC5424, March 2009,

   [RFC5612]  Eronen, P. and D. Harrington, "Enterprise Number for
              Documentation Use", RFC 5612, DOI 10.17487/RFC5612, August
              2009, <>.

   [RFC6350]  Perreault, S., "vCard Format Specification", RFC 6350,
              DOI 10.17487/RFC6350, August 2011,

   [RFC6733]  Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
              Ed., "Diameter Base Protocol", RFC 6733,
              DOI 10.17487/RFC6733, October 2012,


   An earlier draft version of this document was authored by Pearl Liang
   and Alexey Melnikov.  Additional significant contributions have come
   from Dan Romascanu, Bert Wijnen, David Conrad, Michelle Cotton, and
   Benoit Claise.

Authors' Addresses

   Amanda Baber
   Internet Assigned Numbers Authority
   12025 Waterfront Drive
   Los Angeles,  90094
   United States of America

   Paul Hoffman
   12025 Waterfront Drive
   Los Angeles,  90094
   United States of America