6lo S. Chakrabarti Internet-Draft Ericsson Updates: 4944, 6282 (if approved) G. Montenegro Intended status: Standards Track Microsoft Expires: January 7, 2016 R. Droms Cisco J. Woodyatt Nest July 6, 2015 IANA Registry for 6lowpan Additional Dispatch Bytes draft-chairs-6lo-dispatch-iana-registry-00 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 bytes has not been defined in RFC6282 and RFC4944. The purpose of this document is to define the usage of ESC extension bytes. It also records the initial values for extended dispatch values and requests corresponding IANA actions. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 7, 2016. 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 Chakrabarti, et al. Expires January 7, 2016 [Page 1] Internet-Draft IANA-6lo-dispatch July 2015 (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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Usage of ESC dispatch bytes . . . . . . . . . . . . . . . . . . 3 3.1. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Example: ITU-T G.9903 ESC type usage . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Normative References . . . . . . . . . . . . . . . . . . . 6 7.2. Informative References . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 Chakrabarti, et al. Expires January 7, 2016 [Page 2] Internet-Draft IANA-6lo-dispatch July 2015 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 bytes and a co-ordination between the respective organizations and IETF/IANA are needed. The following sections describe the ITU-T specification for ESC dispatch byte code points for the record and propose the use of ESC extension bytes in the future. 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 The ESC byte [01 000000] is modified in RFC 6282[RFC6282] and [RFC4944] first introduces this dispatch header type for extension of dispatch bytes for different usage of 6lowpan applications. For example, a dispatch header type (ex: LOWPAN_HC1, MESH etc.) might need some special handling of each packet for classification. This document specifies that the first octet following the ESC byte is 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 | Ext Type | Extended Dispatch Payload +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Frame Format with ESC Byte Chakrabarti, et al. Expires January 7, 2016 [Page 3] Internet-Draft IANA-6lo-dispatch July 2015 ESC: The left most byte is the ESC dispatch type containing '0100000' Extension Type(ET): 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 extension types appear in the sequence [ESC][extension type], as opposed to the dispatch values which appear by themselves as [dispatch value] with no preceding ESC. Thus, extension types and dispatch values are orthogonal code spaces. 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. Note that section 5.1 in RFC4944 indicates that the Extension Type field may contain additional dispatch values (larger than 63). Note that the new dispatch type MUST NOT modify the behavior of existing dispatch types for the sake of interoperability. 3.1. Open Issues Legacy node behavior: When a legacy 6lowpan node receives packets with ESC bytes or nodes receiving ESC bytes it does not understand, what should be its behavior? Two alternatives: 1) discard the 6lowpan packet 2) ignore the ESC bytes. Sequence Of dispatch bytes and ESC bytes: TBD 3.2. Example: ITU-T G.9903 ESC type usage [G3-PLC] provides native mesh under functionalities. The ESC dispatch type is used with the command frames specified in figure 9-12 and Table 9-35 in [G3-PLC] . 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 2: G.9903 Frame Format with ESC Byte Chakrabarti, et al. Expires January 7, 2016 [Page 4] Internet-Draft IANA-6lo-dispatch July 2015 4. IANA Considerations This document requests IANA to register the '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 dispatch 'Extension Type' fields are: +-------+---------------------------------+---------------+ | Value | Description | Reference | +-------+---------------------------------+---------------+ | 0 | Reserved for future use | This document | | | | | | 1-31 | Used by ITU-T G.9903 command ID | ITU-T G.9903 | | | | [G3-PLC] | | 32-254| Unassigned | This document | | 255 | Reserved for future use | This document | +-------+---------------------------------+---------------+ Figure 3: 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. 7. References Chakrabarti, et al. Expires January 7, 2016 [Page 5] Internet-Draft IANA-6lo-dispatch July 2015 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC4944] Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", RFC 4944, September 2007. [RFC6282] Hui, J. and P. Thubert, "Compression Format for IPv6 Datagrams over IEEE 802.15.4-Based Networks", RFC 6282, September 2011. 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, May 2008. Authors' Addresses Samita Chakrabarti Ericsson 300 Holger Way San Jose, CA US Phone: +1 408 750 5843 Email: samita.chakrabarti@ericsson.com Gabriel Montenegro Microsoft Seattle US Email: gabriel.montenegro@microsoft.com Chakrabarti, et al. Expires January 7, 2016 [Page 6] Internet-Draft IANA-6lo-dispatch July 2015 Ralph Droms Cisco USA Email: rdroms@cisco.com James Woodyatt Nest Mountain View, CA USA Email: jhw@netstlabs.com Chakrabarti, et al. Expires January 7, 2016 [Page 7]