< draft-li-core-coap-size-option-00.txt   draft-li-core-coap-size-option-01.txt >
core K. Li core K. Li
Internet-Draft L. Tian Internet-Draft L. Tian
Intended status: Standards Track B. Leiba Intended status: Standards Track B. Leiba
Expires: September 27, 2011 Huawei Technologies Expires: November 17, 2011 Huawei Technologies
March 26, 2011 May 16, 2011
CoAP Option Extension : Size CoAP Option Extension : Size
draft-li-core-coap-size-option-00 draft-li-core-coap-size-option-01
Abstract Abstract
This document defines an extension to the Constrained Application This document defines an extension to the Constrained Application
Protocol (CoAP) to add a new option Size, which is used to indicate Protocol (CoAP) to add a new option Size, which is used to indicate
the resource size in a Put/Post request or in a Get response. the resource size in a Put/Post request or in a Get response.
Note Note
Discussion and suggestions for improvement are requested, and should Discussion and suggestions for improvement are requested, and should
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 27, 2011. This Internet-Draft will expire on November 17, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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+------+-----+-------+-----------+--------+---------------+ +------+-----+-------+-----------+--------+---------------+
2.2. Using the Size Option 2.2. Using the Size Option
The Size Option is used to indicate the size of the resource data The Size Option is used to indicate the size of the resource data
measured in bytes. measured in bytes.
It can be used in a Get response to give indication about the It can be used in a Get response to give indication about the
resource data size. resource data size.
The Get request including Size=0 is treated as a request to get the
size of the resource representation (but not the resource payload).
Also it can be used in a Post/Put request in the first Block Option Also it can be used in a Post/Put request in the first Block Option
message. message.
The Size option is not expected to be included for small resources The Size option is not expected to be included for small resources
that can easily be carried in a single MTU, but SHOULD be included that can easily be carried in a single MTU, but SHOULD be included
for resources larger than that. for resources larger than that, if the Size information is available.
In the absence of the option, the size of the resource data is In the absence of the option, the size of the resource data is
calculated after the data transmitted to the recipient, either from calculated after the data transmitted to the recipient, either from
the CoAP payload length or based on number of blocks and block size. the CoAP payload length or based on number of blocks and block size.
If the Size option is specified it MUST be accurate at that time, and If the Size option is specified it SHOULD be accurate at that time,
MUST NOT be an estimate. and SHOULD NOT be an estimate.
But due to the dynamic change of the resource data, the Size may not But due to the dynamic change of the resource data, the Size may not
be accurate. If the value of Size option is not the same as the be accurate. If the value of Size option is not the same as the
actual transmitted data, the recipient MUST take the size of the actual transmitted data, the recipient MUST take the size of the
actual transmitted data as accurate, and ignore the Size option. In actual transmitted data as accurate, and ignore the Size option. In
case that the recipient gets all the data but it is still smaller case that the recipient gets all the data but it is still smaller
than the Size, the recipient SHOULD stop the transmission. If the than the Size, the recipient SHOULD stop the transmission. If the
recipient finds out the transmitted data reaches the Size limit, and recipient finds out the transmitted data reaches the Size limit, and
there's more data left, the recipient SHOULD continue to transmit the there's more data left, the recipient SHOULD continue to transmit the
remaining data. remaining data.
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+--------+---------------+----------------+ +--------+---------------+----------------+
| Number | Name | Reference | | Number | Name | Reference |
+--------+---------------+----------------+ +--------+---------------+----------------+
| 12 | Size | Section 2 | | 12 | Size | Section 2 |
+--------+---------------+----------------+ +--------+---------------+----------------+
7. Acknowledgements 7. Acknowledgements
The authors of this draft would like to thank the participants of the The authors of this draft would like to thank the participants of the
email discussion on this issue. Thanks to Bert Greevenbosch for the email discussion on this issue. Thanks to Bert Greevenbosch, Charles
detailed reviews and discussions. Palmer and Carsten Bormann for the detailed reviews and suggestions.
8. Normative References 8. Normative References
[I-D.ietf-core-block] [I-D.ietf-core-block]
Shelby, Z. and C. Bormann, "Blockwise transfers in CoAP", Bormann, C. and Z. Shelby, "Blockwise transfers in CoAP",
draft-ietf-core-block-02 (work in progress), March 2011. draft-ietf-core-block-03 (work in progress), May 2011.
[I-D.ietf-core-coap] [I-D.ietf-core-coap]
Shelby, Z., Hartke, K., Bormann, C., and B. Frank, Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
"Constrained Application Protocol (CoAP)", "Constrained Application Protocol (CoAP)",
draft-ietf-core-coap-05 (work in progress), March 2011. draft-ietf-core-coap-06 (work in progress), May 2011.
[I-D.ietf-core-link-format] [I-D.ietf-core-link-format]
Shelby, Z., "CoRE Link Format", Shelby, Z., "CoRE Link Format",
draft-ietf-core-link-format-03 (work in progress), draft-ietf-core-link-format-04 (work in progress),
March 2011. May 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses Authors' Addresses
Kepeng Li Kepeng Li
Huawei Technologies Huawei Technologies
Huawei Base, Bantian, Longgang District Huawei Base, Bantian, Longgang District
Shenzhen, Guangdong 518129 Shenzhen, Guangdong 518129
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