IEEE 802.15.4 Information Element for the IETF
How IETF protocols carry their own data in IEEE 802.15.4 low-power radio frames.
Kivinen, T. and P. Kinney, "IEEE 802.15.4 Information Element for the IETF", RFC 8137, DOI 10.17487/RFC8137, May 2017, <https://www.rfc-editor.org/info/rfc8137>.
@misc{rfc8137,
series = {Request for Comments},
number = 8137,
howpublished = {RFC 8137},
publisher = {RFC Editor},
doi = {10.17487/RFC8137},
url = {https://www.rfc-editor.org/info/rfc8137},
author = {T. Kivinen and P. Kinney},
title = {{IEEE 802.15.4 Information Element for the IETF}},
pagetotal = 7,
year = 2017,
month = may,
} RFC text
Contents
Internet Engineering Task Force (IETF) T. Kivinen
Request for Comments: 8137 INSIDE Secure
Category: Informational P. Kinney
ISSN: 2070-1721 Kinney Consulting LLC
May 2017
IEEE 802.15.4 Information Element for the IETF
Abstract
IEEE Std 802.15.4 defines Information Elements (IEs) that can be used
to extend 802.15.4 in an interoperable manner. The IEEE 802.15
Assigned Numbers Authority (ANA) manages the registry of the
Information Elements. This document formulates a request for ANA to
allocate a number from that registry for the IETF and describes how
the IE is formatted to provide subtypes.
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 a candidate 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
http://www.rfc-editor.org/info/rfc8137.
Copyright Notice
Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Working Groups Benefiting from the IETF 802.15.4 IE . . . . . 3
4. IETF IE Subtype Format . . . . . . . . . . . . . . . . . . . 3
5. Request to Allocate an IETF IE . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Appendix A. Vendor Specific IE in IEEE 802.15.4 . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
IEEE Std 802.15.4 [IEEE802.15.4] is a standard, referred to by RFC
4944 [RFC4944] and other documents, that enables very low-cost and
low-power communications. The standard defines numerous optional
Physical Layers (PHYs) operating in many different frequency bands
with a simple and effective Medium Access Control (MAC).
IEEE Std 802.15.4 defines Information Elements (IEs) that can be used
to extend 802.15.4 in an interoperable manner. An IE provides a
flexible, extensible, and easily implementable method of
encapsulating information. The general format of an IE as defined in
Section 7.4 of IEEE Std 802.15.4-2015 [IEEE802.15.4] consists of an
identification (ID) field, a length field, and a content field.
Multiple IEs may be concatenated, and elements with unknown ID values
in a list of IEs can be skipped since their length is known. IEs
provide a flexible container for information that allows the addition
of new IE definitions in future versions of the standard in a
backwards-compatible manner.
There are two different IE types, Header IE and Payload IE. A Header
IE is part of the MAC header; it is never encrypted, but it may be
authenticated. Most of the Header IE processing is done by the MAC,
and IETF protocols should not have any direct effect on that
processing. A Payload IE is part of the MAC payload and may be
encrypted and authenticated.
IETF protocols will need to insert information in the 802.15.4
frames; the 802.15.4 standard enables that by including one or more
payload IEs in the frame that will contain the information. For this
purpose, the IETF requests a dedicated Payload IE from the IEEE
802.15 Assigned Numbers Authority (ANA) [IEEE802.15-ANA]. The
current 802.15 ANA database can be found at [IEEE802.15-ANA-DB].
The 802.15.4 operations manual [IEEE802.15-OPS] describes how a
Standards Development Organization (SDO) may request an allocation of
one IE. To make this request the SDO has to provide (i) the reason
for the request, (ii) a description of the protocol format that shows
an appropriate subtype capability, and (iii) an agreement that only
one IE number will be allocated for use by the SDO.
This document provides the information needed for the request.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in BCP 14 [RFC2119] [RFC8174] when, and only when, they
appear in all capitals, as shown here.
3. Working Groups Benefiting from the IETF 802.15.4 IE
There are several IETF working groups such as 6TiSCH, 6lo, and CoRE
that could benefit from the IETF IE. The 6TiSCH Working Group has
already expressed the need for the IE; this allocation is expected to
satisfy that need.
4. IETF IE Subtype Format
The maximum length of the Payload IE content is 2047 octets, and the
802.15.4 frame contains a list of payload IEs. A single frame can
have multiple payload IEs, terminated with the payload IE terminator,
which may then be followed by the payload.
Since the 802.15.4 standard defines a list of payload IEs along with
their structures, there is no need for this document to specify the
internal nesting structure of the IETF IE. The Payload IE format of
802.15.4 standard contains the Length field. The length of the
subtype content can be calculated from the 802.15.4 Payload IE Length
field of the IETF IE.
The format of the IETF IE is as follows:
1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subtype ID | |
+-+-+-+-+-+-+-+-+ |
~ subtype content ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IETF IE Subtype Format
o Subtype ID is the IANA-allocated number specifying the subtype of
the IETF IE. Value 0 is reserved for future extensibility, i.e.,
in case a longer subtype ID field is needed.
o Subtype content is the actual content of the Information Element,
and its length can be calculated from the Length field of the IETF
IE.
One IEEE 802.15.4 frame MAY contain multiple IETF IEs with the same
or different subtypes.
5. Request to Allocate an IETF IE
Per the IETF's request, the IEEE 802.15 Working Group has allocated
an ID (5) for a Payload IE for IETF use. The IETF understands that
this is the only ID it will be issued.
6. Security Considerations
This document creates an IANA registry for IETF IE subtype IDs (see
Section 7). The security of the protocols using the IEs MUST be
described in the documents requesting allocations from this registry.
The IEEE Std 802.15.4 [IEEE802.15.4] contains methods in which
security of the IE can be enforced when a frame is received, but this
is only per IE type. Therefore, all IETF IEs will have the same
security-level requirements regardless of the subtype ID used. This
can cause issues if different security processing would be needed and
any of those IEs would need to be processed in the MAC level. Since
all IETF protocols should operate at a higher level than the MAC
level, the higher-layer processing for these IEs SHOULD perform
separate security policy checking based on the IETF IE subtype ID in
addition to the checks done by the MAC.
7. IANA Considerations
The "IEEE Std 802.15.4 IETF IE Subtype IDs" registry has been created
as follows:
Value Subtype ID
0 Reserved
1-200 Unassigned
201-255 Experimental Use
Any change or addition to this registry requires Expert Review
[RFC5226].
Note that there are vendor-specific IEs already defined in IEEE
802.15.4 (see Appendix A); because of this, there is no need to
reserve any subtype IDs for the vendor-specific uses.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
[IEEE802.15.4]
IEEE, "IEEE Standard for Low-Rate Wireless Networks",
IEEE Standard 802.15.4,
<https://standards.ieee.org/about/get/802/802.15.html>.
[IEEE802.15-ANA]
IEEE 802.15, "IEEE 802.15 Assigned Numbers Authority",
<http://www.ieee802.org/15/ANA.html>.
[IEEE802.15-ANA-DB]
IEEE, "IEEE 802.15 ANA database",
<https://mentor.ieee.org/802.15/
documents?is_dcn=257&is_group=0000>.
[IEEE802.15-OPS]
IEEE, "IEEE 802.15 Operations Manual",
<https://mentor.ieee.org/802.15/
documents?is_dcn=235&is_group=0000>.
[RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
"Transmission of IPv6 Packets over IEEE 802.15.4
Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
<http://www.rfc-editor.org/info/rfc4944>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
Appendix A. Vendor Specific IE in IEEE 802.15.4
IEEE 802.15.4 already has several numbers for different Vendor
Specific IE types. There is one for the Vendor Specific Header IE
for Header IEs. There is one incorrectly named Vendor Specific
Nested IE for Payload IEs, and there is another one with exactly the
same name, but under the MLME Nested IE long format. All of the
Vendor Specific IEs start with a 3-octet vendor OUI to identify the
organization.
Authors' Addresses
Tero Kivinen
INSIDE Secure
Lonnrotinkatu 11
Helsinki FI-00120
Finland
Email: kivinen@iki.fi
Pat Kinney
Kinney Consulting LLC
Email: pat.kinney@kinneyconsultingllc.com
ISO Plain Language
On this page
§1Why the IETF Needs Its Own Element
IEEE Std 802.15.4 enables very low-cost and low-power communications. The standard defines numerous optional Physical Layers operating in many different frequency bands with a simple and effective Medium Access Control layer, and it defines Information Elements that can be used to extend 802.15.4 in an interoperable manner. An IE provides a flexible, extensible and easily implementable method of encapsulating information. The general format of an IE consists of an identification field, a length field and a content field. Multiple IEs may be concatenated, and elements with unknown ID values in a list can be skipped since their length is known, so IEs give a flexible container that lets new definitions be added in future versions of the standard in a backwards-compatible manner.
There are two different IE types. A Header IE is part of the MAC header; it is never encrypted, but it may be authenticated, and most of the Header IE processing is done by the MAC. A Payload IE is part of the MAC payload and may be encrypted and authenticated.
IETF protocols need to insert information into 802.15.4 frames, and the standard enables that by including one or more payload IEs in the frame. For this purpose the IETF requests a dedicated Payload IE from the IEEE 802.15 Assigned Numbers Authority, which manages the registry of Information Elements.
The 802.15 operations manual describes how a Standards Development Organization may request the allocation of one IE. To make the request the organization has to provide the reason for the request, a description of the protocol format that shows an appropriate subtype capability, and an agreement that only one IE number will be allocated for its use. This document provides the information needed for that request.
802.15.4 frames can hold extra fields, and each organisation that wants one needs a number of its own. The document asks for a single number for the IETF, along with the promise that no second number will be needed, which is what the IEEE's own process requires.
| Aspect | Header IE | Payload IE |
|---|---|---|
| Where it sits | Part of the MAC header | Part of the MAC payload |
| Encryption | Never encrypted | May be encrypted |
| Authentication | May be authenticated | May be authenticated |
| Who handles it | Mostly the MAC; IETF protocols should have no direct effect on that processing | IETF protocols, at a higher layer than the MAC |
§4The IETF Information Element Format
The maximum length of the Payload IE content is 2047 octets, and the 802.15.4 frame contains a list of payload IEs. A single frame can have multiple payload IEs, terminated with the payload IE terminator, which may then be followed by the payload.
Since the 802.15.4 standard defines the list of payload IEs along with their structures, there is no need for this document to specify the internal nesting structure of the IETF IE. The Payload IE format of the 802.15.4 standard contains the Length field, so the length of the subtype content can be calculated from the Payload IE Length field of the IETF IE.
The format of the IETF IE starts with a Subtype ID octet and is followed by the subtype content. The Subtype ID is the IANA-allocated number specifying the subtype of the IETF IE; value 0 is reserved for future extensibility, that is, in case a longer subtype ID field is needed. The subtype content is the actual content of the Information Element, and its length can be calculated from the Length field of the IETF IE. One 802.15.4 frame MAY contain multiple IETF IEs with the same or different subtypes.
The element holds a number that says which protocol the content belongs to, followed by that protocol's own bytes. The length of the content comes from the length field the 802.15.4 format already provides, so nothing extra has to be defined. A frame can carry several such elements.
- Subtype IDOne octet, allocated by IANA. The value 0 is reserved in case a longer field is ever needed.
- Subtype contentThe actual content of the element; its length comes from the Length field of the IETF IE.
- Maximum content lengthThe maximum length of the Payload IE content is 2047 octets.
- Several per frameOne 802.15.4 frame may contain multiple IETF IEs with the same or different subtypes.
§3Which Working Groups Benefit
There are several IETF working groups, such as 6TiSCH, 6lo and CoRE, that could benefit from the IETF IE. The 6TiSCH Working Group has already expressed the need for the IE, and this allocation is expected to satisfy that need.
The document is also explicit about how the element is allocated. Per the IETF's request, the IEEE 802.15 Working Group has allocated an ID, 5, for a Payload IE for IETF use, and the IETF understands that this is the only ID it will be issued.
Several IETF working groups have protocols that could ride in this element, and one of them had already asked for it. The IEEE working group gave the IETF element number 5, and that is the only number the IETF will get.
§7The Subtype ID Registry
The registry of IEEE Std 802.15.4 IETF IE Subtype IDs has been created. Value 0 is Reserved, values 1 to 200 are Unassigned, and values 201 to 255 are for Experimental Use. Any change or addition to this registry requires Expert Review.
The document notes that vendor-specific IEs are already defined in IEEE 802.15.4, and that because of this there is no need to reserve any subtype IDs for vendor-specific uses.
The numbers inside the element are allocated by IANA. The first 200 are free for real protocols, the last 55 are for experiments, and the first one is kept in reserve in case a wider field is ever needed. Changing the list needs expert review.
- 0Reserved — Held for future extensibility, in case a longer subtype ID field is needed.
- 1-200Unassigned — Available for subtypes allocated from the registry.
- 201-255Experimental Use — Set aside for experimental use of subtype IDs.
§6Security Considerations
This document creates an IANA registry for IETF IE subtype IDs, and the security of the protocols using the IEs MUST be described in the documents requesting allocations from this registry.
IEEE Std 802.15.4 contains methods in which the security of an IE can be enforced when a frame is received, but this is only per IE type. Therefore all IETF IEs have the same security-level requirements regardless of the subtype ID used. This can cause issues if different security processing would be needed and any of those IEs would need to be processed at the MAC level. Since all IETF protocols should operate at a higher level than the MAC level, the higher-layer processing for these IEs SHOULD perform separate security policy checking based on the IETF IE subtype ID in addition to the checks done by the MAC.
Each protocol that uses the element has to describe its own security, because the standard only checks the element as a whole. The layer above should therefore apply its own policy per subtype, on top of the checks the radio layer already does.