Internet DRAFT - draft-ietf-6lo-dispatch-iana-registry
draft-ietf-6lo-dispatch-iana-registry
6lo S. Chakrabarti
Internet-Draft Ericsson
Updates: 4944, 6282 (if approved) G. Montenegro
Intended status: Standards Track Microsoft
Expires: October 9, 2016 R. Droms
Cisco
J. Woodyatt
Nest
April 7, 2016
IANA Registry for 6lowpan ESC Dispatch Code points
draft-ietf-6lo-dispatch-iana-registry-03
Abstract
RFC4944 defines ESC dispatch type for additional dispatch bytes in
the 6lowpan header. The value of ESC byte has been updated by
RFC6282. However, the usage of ESC extension byte has not been
defined in RFC6282 and RFC4944. The purpose of this document is to
define the ESC extension byte code points and to request
corresponding IANA actions.
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 October 9, 2016.
Copyright Notice
Copyright (c) 2016 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Usage of ESC dispatch bytes . . . . . . . . . . . . . . . . . . 3
3.1. Interaction with other RFC4944 implementations . . . . . . 4
3.2. ESC Extension Bytes Typical Sequence . . . . . . . . . . . 5
3.3. ITU-T G.9903 ESC type usage . . . . . . . . . . . . . . . 5
3.4. NALP and ESC bytes . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
[RFC4944] section 5.1 defines the dispatch header and types. The ESC
type is defined for using additional dispatch bytes in the 6lowpan
header. RFC 6282 modifies the value of the ESC dispatch type and it
is recorded in IANA registry [6LOWPAN-IANA]. However, the bytes and
usage following the ESC byte are not defined in either [RFC4944] and
[RFC6282]. However, in recent years with 6lowpan deployments, the
implementations and Standards organizations have started using the
ESC extension bytes and a co-ordination between the respective
organizations and IETF/IANA are needed.
The following sections record the ITU-T specification for ESC
dispatch byte code points as an existing known usage and propose the
definition of ESC extension bytes for future applications. The
document also requests IANA actions for the first extension byte
following the ESC byte.
2. Terminology
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].
3. Usage of ESC dispatch bytes
RFC 4944 [RFC4944] first introduces this "ESC" dispatch header type
for extension of dispatch bytes. RFC 6282 [RFC6282] subsequently
modified its value to [01 000000].
This document specifies that the first octet following the ESC byte
be used for extension type (extended dispatch values). Subsequent
octets are left unstructured for the specific use of the extension
type:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1| ESC | ESC EXT Type | Extended Dispatch Payload
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Frame Format with ESC Byte
ESC: The left-most byte is the ESC dispatch type containing '0100000'
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ESC Extension Type (EET): It is the first byte following the ESC
byte. Extension type defines the payload for the additional dispatch
bytes. The values are from 0 to 255. Value 0 and 255 are reserved
for future use. These values are assigned by IANA. The EET values
are similar to dispatch values in the 6lowpan header except they are
preceded by the ESC byte. Thus, ESC extension types and dispatch
values are using orthogonal code spaces. Though not desirable,
multiple ESC bytes MAY appear in a 6lowpan header. Section 3.1
describes how to handle unknown ESC dispatch type.
Extended Dispatch Payload(EDP): This part of frame format must be
defined by the corresponding extension type. A specification is
required to define each usage of extension type and its corresponding
Extension Payload. For the sake of interoperability, specifications
of extension bytes MUST NOT redefine the existing ESC Extension Type
codes.
Section 5.1 in RFC4944 indicates that the Extension Type field may
contain additional dispatch values larger than 63, as corrected by
[4944-ERRATA]. For the sake of interoperability, the new dispatch
type (EET) MUST NOT modify the behavior of existing dispatch types
[RFC4944].
3.1. Interaction with other RFC4944 implementations
It is expected that RFC4944 existing implementations are not capable
of processing ESC extension data bytes as defined in this document.
However, implementers have to assume that existing implementation
that attempt to process an EET unknown to them will simply drop the
packet or ignore the ESC dispatch bytes.
If an implementation following this document, during processing of
the received packet reaches the ESC byte for which it does not
understand the extension bytes (EET), it MUST drop that packet.
However, it is important to clarify that a router node SHOULD forward
a 6lowpan packet with the EET bytes as long as it does not attempt to
process any unknown ESC extension bytes.
Sequence Of dispatch bytes and ESC bytes: Multiple ESC extension
bytes may appear in a packet. The ESC bytes can appear as the first,
last or middle dispatch bytes. However, a packet will get dropped by
any node that does not understand the EET at the beginning of the
packet. The closer to the end of the packet are the EET's, the
higher chance there is that a legacy node will recognize and
successfully process some dispatch type [RFC4944] before the EET and
then ignore the EET instead of dropping the entire packet.
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3.2. ESC Extension Bytes Typical Sequence
ESC Extension bytes sequence and order with respect to 6LoWPAN Mesh
header and LoWPAN_IPHC header are described below. When LOWPAN_IPHC
dispatch type is present, ESC bytes MUST appear before the
LOWPAN_IPHC dispatch type in order to maintain backward compatibility
with RFC6282 section 3.2. The following diagrams provide examples of
ESC extension byte usages:
A LoWPAN encapsulated IPv6 Header compressed packet:
+-------+------+--------+--------+-----------------+--------+
| ESC | EET | EDP |Dispatch| LOWPAN_IPHC hdr | Payld |
+-------+------+--------+--------+-----------------+--------+
A LoWPAN_IPHC Header, Mesh header and an ESC extension byte:
+-----+-----+-----+----+------+-------+---------------+------+
|M typ| Mhdr| ESC | EET|EDP |Disptch|LOWPAN_IPHC hdr| Payld|
+-----+-----+-----+----+------+-------+---------------+------+
A Mesh header with ESC bytes
+-------+-------+-----+-----+-------+
| M Typ | M Hdr | ESC | EET |EDP |
+-------+-------+-----+-----+-------+
With Fragment header
+-------+-------+--------+------+-----+-----+-------+
| M Typ | M Hdr | F Typ | F hdr|ESC | EET | EDP |
+-------+-------+--------+------+-----+-----+-------+
ESC byte as a LowPAN encapsulation
+--------+--------+--------+
| ESC | EET | EDP |
+--------+--------+--------+
Figure 2: A 6lowpan packet with ESC Bytes
3.3. ITU-T G.9903 ESC type usage
The ESC dispatch type is used in [G3-PLC] to provide native mesh
routing and bootstrapping functionalities. The ITU-T recommendation
defines command IDs in the [G3-PLC] section 9.4.2.3 which operates
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like ESC Extension type field. The command ID values are 0x01 to
0x1F.
The frame format is defined as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 1| ESC | Command ID | Command Payload
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: G.9903 Frame Format with ESC Byte
3.4. NALP and ESC bytes
According to RFC4944 [RFC4944] section 5.1, NALP dispatch bytes are
reserved for use as a kind of escape code for identification of non-
6lowpan payloads. Since ESC bytes are part of 6lowpan dispatch types
(extended), they are orthogonal to NALP bytes.
This document clarifies that NALP dispatch codes only provide an
escape method for non-6LoWPAN payloads when they appear as the
initial byte of a LoWPAN encapsulation, and that the potential
meaning of their appearance in any other location is reserved for
future use.
4. IANA Considerations
This document requests IANA to register the 'ESC Extension Type'
values as per the policy 'Specification Required'[RFC5226] as
specified in this document which follows the same policy as in the
IANA section of [RFC4944]. For each Extension Type (except the
Reserved values) the specification MUST define corresponding Extended
Dispatch Payload frame bytes for the receiver implementation to read
the ESC bytes with interoperability.
The initial values for the 'ESC Extension Type' fields are:
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+-------+---------------------------------+---------------+
| Value | Description | Reference |
+-------+---------------------------------+---------------+
| 0 | Reserved for future use | This document |
| | | |
| 1-31 | Used by ITU-T G.9903 and G.9905 | ITU-T G.9903 &|
| | Command IDs | ITU-T G.9905 |
| | | |
| 32-254| Unassigned | This document |
| |(Reserved for future IANA | |
| | Assignment-- Spec Required) | |
| | | |
| 255 | Reserved for future use | This document |
+-------+---------------------------------+---------------+
Figure 4: Initial Values for IANA Registry
5. Security Considerations
There is no additional security threats due to the assignments of ESC
byte usage described in this document. However, this document
forbids defining any extended dispatch values or extension types that
modifies the behavior of existing Dispatch types.
6. Acknowledgements
The authors would like to thank the members of the 6lo WG members for
the comments in the mailing list. Many thanks to Carsten Bormann,
Ralph Droms, Thierry Lys, Cedric Lavenu, Pascal Thubert for their
discussions regarding resolving the bits allocation issues which led
to this document. Jonathan Hui and Robert Cregie provided extensive
reviews and guidance for interoperability. The authors acknowledges
the comments from the following people for shaping this document:
Paul Duffy, Don Sturek, Michael Richardson, Xavier Vilajosana and
Scott Mansfield.
7. References
7.1. Normative References
[4944-ERRATA]
"https://www.rfc-editor.org/errata_search.php?rfc=4944".
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
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Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<http://www.rfc-editor.org/info/rfc6282>.
7.2. Informative References
[6LOWPAN-IANA]
"https://www.iana.org/assignments/_6lowpan-parameters/
_6lowpan-parameters.xhtml".
[G3-PLC] "http://www.itu.int/rec/T-REC-G.9903-201402-I".
[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>.
Authors' Addresses
Samita Chakrabarti
Ericsson
300 Holger Way
San Jose, CA
US
Email: samita.chakrabarti@ericsson.com
Gabriel Montenegro
Microsoft
Seattle
US
Email: gabriel.montenegro@microsoft.com
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Ralph Droms
Cisco
USA
Email: rdroms@cisco.com
James Woodyatt
Nest
Mountain View, CA
USA
Email: jhw@netstlabs.com
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