IANA Guidance for Managing the ULE Registry
draft-fairhurst-ipdvb-ule-iana-04

Abstract

This document proposes an update to RFC 4326 to clarify and update the allocation rules for the Unidirectional Lightweight Encapsulation (ULE) next header registry. This registry is used by ULE and Generic Stream Encapsulation (GSE) to record the codepoints of extension headers and protocols supported by these encapsulation protocols.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on June 19, 2014.

Copyright Notice

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Table of Contents

• 1. Introduction
• 2. Terminology
• 2.1. The ULE Next Header Registries
• 3. Updated IANA guidance on allocation in the ULE Next Header Registry
• 3.1. ULE Next-Header Registry
• 3.2. IANA Guidelines
• 3.3. Reservation of Next Header values
• 4. Update to registry information
• 5. Security Considerations
• 6. IANA Considerations
• 7. Acknowledgments
• 8. Revision Notes
• 9. References
• 9.1. Normative References
• 9.2. Informative References
• Author's Address

1. Introduction

The Unidirectional Lightweight Encapsulation (ULE) [RFC4326] specifies an encapsulation for links that employ the MPEG-2 Transport Stream, with support over a wide variety of physical-layer bearers [RFC4259]. The encapsulation header includes a Type field that identifies payload types and extension headers (e.g.[RFC5163]). The ULE specification requested IANA to maintain the ULE next header registries to record the allocation of the values used to derive this Type field.

The Digital Video Broadcast (DVB) Project has published an encapsulation for second-generation DVB physical layers. This specifies the Generic Stream Encapsulation [GSE]. This encapsulation shares many of the network properties of ULE and uses a common format for the Type field [RFC5163]. The ULE Next Header registries are therefore also applicable to this encapsulation.

This document updates the IANA rules and guidance defined in section 11.1 of [RFC4326] in the following way:

• The document clarifies use of the registry by GSE as well as for ULE.
• Section 3 specifies that new allocations in the ULE Next Header Registry are to be assigned by IANA using the "Expert Review" policy and provides guidance to the expert reviewer.
• Section 3.3 reserves a range of allocated values.
• Section 4 adds an explanatory note to clarify the encoding used in the registry.

2. Terminology

This document assumes familiarity with the terminology of ULE [RFC4326] and [RFC5163].

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 [RFC2119].

2.1. The ULE Next Header Registries

The Mandatory Extension Headers registry allocates decimal values in the range 0-255. These values are used to identify mandatory extension headers. The registered value corresponds to the 16-bit Type value for the mandatory extension header or the specified protocol.

The Optional Extension Headers registry allocates decimal values in the range 256-512. These values are used to identify optional extension headers. The registered value corresponds to the 16-bit Type value that would be used for an optional extension header with a length (H-LEN) of 1.

3. Updated IANA guidance on allocation in the ULE Next Header Registry

The rules for allocation were defined in section 11 of [RFC4326]. This document updates these rules by replacing these with the rules in this section:

Allocations in the ULE Next Header Registry are to be assigned by IANA using the "Expert Review" policy defined in [RFC5226]. Applications must include a reference to a specification of the next header extension in a standards document. An IETF standards-track RFC can provide such a reference. Other specifications are also permitted. The expert shall advise IANA on whether a particular specification constitutes a standards document.

3.1. ULE Next-Header Registry

This registry allocates Next-Header values within the range 0-511 (decimal). For each allocated value, it also specifies the set of allowed H-LEN values (see [RFC4326] section 5). The combination of the IANA-registered value and the H-LEN are used by ULE and GSE to derive a set of allowed 16-bit values in the decimal range 0-1535. This forms the first part of the ULE Type space (see [RFC4326] section 4.4.1).

3.2. IANA Guidelines

The following contains the IANA guidelines for management of the ULE Next-Header registry. This registry allocates decimal values 0-511 (0x0000-0x01FF, hexadecimal). IANA MUST NOT allocate values greater than 511 (decimal).

The Next-Header registry is divided into two areas:

1. 0-255 (decimal) IANA-assigned values, indicating Mandatory Extension Headers (or link-dependent Type fields). Requests for assignment in this area MUST define the value and the name associated with the Extension Header, together with the procedure for processing the Extension Header. This MUST also define the need for the Mandatory Extension and the intended use. [RFC4326] made initial assignments to this registry updated by later requests. The size of the Extension Header MUST be specified (by default the entire remaining payload).
2. 256-511 (decimal) IANA-assigned values, indicating Optional Extension Headers. Requests for assignment in this area MUST define the value and the name associated with the Extension Header, together with the procedure for processing the Extension Header. The entry MUST specify the range of allowable H-LEN values that are permitted (in the range 1-5). It MUST also define the need for the Optional Extension and the intended use. [RFC4326] made initial assignments to this registry updated by later requests.

3.3. Reservation of Next Header values

This document reserves the range decimal 144-159 (0x80-0x8F, hexadecimal). These reserved values are presently not available for general assignment, and will not be allocated until the registry is exhausted.

4. Update to registry information

This section requests IANA to record additional explanatory note in the registry:

"The Mandatory Extension Headers registry allocates values in the range 0-255 (decimal). These values are used to identify mandatory extension headers. The registered value corresponds to the 16-bit Type value for the mandatory extension header or the specified protocol.

The Optional Extension Headers registry allocates values in the range 256-511 (decimal). These values are used to identify optional extension headers. The registered value corresponds to the 16-bit Type value that would be used for an optional extension header with a header length (H-LEN) of 1."

This additional note should be placed before the current note.

5. Security Considerations

This document does not present new security considerations.

6. IANA Considerations

Section 3 specifies updated IANA allocation rules

Section 4 requests IANA to update the registry information.

7. Acknowledgments

The author acknowledges feedback from IANA, Alexander Adolf and Hans-Peter Lexow on usage of this registry.

8. Revision Notes

RFC-Editor: Please remove this section prior to publication

Draft 00

This was the first revision - it proposed the requested update.

Draft 01

This revision is thought complete and replaces the entire IANA section with the new text.

Draft 02

Section 1 includes an overview of the changes from RFC 4326, requested by Margaret Wasserman.

Draft 03

Reworded section 3.1 to calrify difference between registered value and derived Type field value, requested by Michelle Cotton.

Clarified each value as being decimal or hexadecimal.

Draft 04

No changes made, this draft was updated ready for submission to the Area Director.

9. References

9.1. Normative References

9.2. Informative References

Author's Address