[Docs] [txt|pdf|html] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04 05 06

core                                                               K. Li
Internet-Draft                                           B. Greevenbosch
Intended status: Standards Track                                  R. Sun
Expires: June 19, 2015                               Huawei Technologies
                                                                 E. Dijk
                                                        Philips Research
                                                               S. Loreto
                                                                Ericsson
                                                       December 16, 2014


                    CoAP Option Extension: Patience
                 draft-li-core-coap-patience-option-06

Abstract

   CoAP is a RESTful application protocol for constrained nodes and
   networks.  This specification provides a simple extension for CoAP,
   the Patience option.  This option is used by a CoAP client to
   indicate the maximum time a client is prepared to wait for a
   response.  The CoAP server should try to return the response within
   the specified time frame.

Note

   Discussion and suggestions for improvement are requested, and should
   be sent to core@ietf.org.

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 June 19, 2015.







Li, et al.                Expires June 19, 2015                 [Page 1]


Internet-Draft            CoAP Patience Option             December 2014


Copyright Notice

   Copyright (c) 2014 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
     1.1.  Justification . . . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Patience Option Extension . . . . . . . . . . . . . . . . . .   3
     2.1.  Patience Option Definition  . . . . . . . . . . . . . . .   3
     2.2.  Using the Patience Option . . . . . . . . . . . . . . . .   3
   3.  Example . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   This specification adds a new Patience option to CoAP [RFC7252].  The
   main purpose is for the client to inform the server of the preferred
   time frame for a response.  It is used in a request to indicate the
   client patience in waiting for a response.  It then indicates "a
   response is most useful within the specified time frame".

1.1.  Justification

   It can be useful for the client to indicate that the response is
   required to be returned within a certain amount of time.  For
   example, the client could require a response within 2 seconds,
   otherwise the response is not of interest anymore.  With this
   indication of the patience for a response, the client knows how long
   it should wait for the response, and it needs to keep the state of
   the request only for the indicated time.  After this period, the
   request will be given up.  It can avoid that the server wastes



Li, et al.                Expires June 19, 2015                 [Page 2]


Internet-Draft            CoAP Patience Option             December 2014


   resources by sending a response which already exceeds the set
   patience timeout of the client.

   If the Patience option is combined with Observe option in a request,
   it indicates the maximum time an observer is prepared to wait for an
   initial notification.

1.2.  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].

2.  Patience Option Extension

2.1.  Patience Option Definition

      +-----+---+---+---+---+----------+---------+--------+---------+
      | No. | C | U | N | R | Name     | Format  | Length | Default |
      +-----+---+---+---+---+----------+---------+--------+---------+
      | 28  |   |   | x |   | Patience | integer | 1-2 B  | none    |
      +-----+---+---+---+---+----------+---------+--------+---------+

   The value of the Patience option is measured in seconds.  The range
   is from 1 second to 2^16 seconds, that is, 65535 seconds, around 18
   hours.  There is no default value for the Patience option.

   The Patience option is "elective".  It MUST NOT occur more than once.

2.2.  Using the Patience Option

   In the unicast case, this option is used by a CoAP client to indicate
   the maximum time a client is prepared to wait for a response.

   The client adds the Patience option to any request for which it is
   prepared to wait for a response.  The client sets the option to the
   maximum time that it is prepared to wait.

   The Patience option applies to both a piggy-backed response and a
   separate response.  For a separate response, the patience applies to
   the actual response, not to the ACK.  The ACK should be sent
   immediately upon receipt of the CON message.

   TBD: In case a client retransmits a request, the Patience Option
   value MAY be decreased by an amount of time equivalent to the time
   since the previous transmission attempt.  In case a client did not
   receive an ACK to a confirmable request and a time interval of at




Li, et al.                Expires June 19, 2015                 [Page 3]


Internet-Draft            CoAP Patience Option             December 2014


   least the interval indicated in the Patience Option of the request
   has passed, the client SHOULD give up the request.

   The server interprets this option as the maximum time between receipt
   of the complete request and the time that it begins sending the
   response.  The client will observe a longer time interval between
   request and response, as network transit and processing by proxies
   add delays.  If timing is critical, the client SHOULD consider the
   possible delays and choose the value for the option accordingly.

   The server MAY apply a lower value to the patience timeout based on
   local policy.  A server MAY choose to take longer to produce a
   response, at the risk that the client is no longer able to use the
   response.

   In case that the CoAP message is transmitted through a proxy, the
   Proxy MAY reduce the value of a Patience option based on a local
   policy (e.g. to consider the maximum time that an idle connection is
   kept open by a local NAT or Firewall).  A Proxy MAY add a Patience
   option if none is present.  The value in the Patience option MUST NOT
   be increased or removed.

   If the client does not receive a response within the indicated
   response time, the client SHOULD consider the request as failed.  If
   the server can't provide a response within the required time, the
   server SHOULD discard the request.

3.  Example

   This section gives a short example with a message flow that
   illustrates the use of the Patience option in a GET request.

   This example (Figure 1) shows that the client wants to get a response
   within 60 seconds.

















Li, et al.                Expires June 19, 2015                 [Page 4]


Internet-Draft            CoAP Patience Option             December 2014


     client    server
       |         |
       |         |
       +-------->|     Header: GET (T=CON, Code=1, MID=0x7d38)
       |   GET   |      Token: 0x53
       |         |   Patience: 60
       |         |   Uri-Path: "temperature"
       |         |
       |<--------+     Header: 2.05 Content (T=ACK, Code=69, MID=0x7d38)
       |   2.05  |      Token: 0x53
       |         |    Payload: "22.3 C"
       |         |



              Figure 1: Patience Option in a unicast request

4.  Security Considerations

   This presents no security considerations beyond those in section 10
   of the base CoAP specification [RFC7252].

5.  IANA Considerations

   The IANA is requested to add the following "CoAP Option Numbers"
   entry as per Section 12.2 of [RFC7252].

   +-----+---+---+---+---+----------+---------------+--------+---------+
   | No. | C | U | N | R | Name     | Format        | Length | Default |
   +-----+---+---+---+---+----------+---------------+--------+---------+
   | 28  |   |   | x |   | Patience | (ref to this  | 1-2 B  | (none)  |
   |     |   |   |   |   |          | document)     |        |         |
   +-----+---+---+---+---+----------+---------------+--------+---------+

6.  Acknowledgements

   The authors of this draft would like to thank the participants of the
   email discussion on this issue.  Thanks to Carsten Bormann, Peter
   Bigot, Barry Leiba, Linyi Tian, Gengyu Wei for the reviews and
   discussions.

7.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252, June 2014.



Li, et al.                Expires June 19, 2015                 [Page 5]


Internet-Draft            CoAP Patience Option             December 2014


Authors' Addresses

   Kepeng Li
   Huawei Technologies
   Huawei Base, Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P. R. China

   Email: likepeng@huawei.com


   Bert Greevenbosch
   Huawei Technologies
   Huawei Base, Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P. R. China

   Email: bert.greevenbosch@huawei.com


   Ruinan Sun
   Huawei Technologies
   Huawei Base, Bantian, Longgang District
   Shenzhen, Guangdong  518129
   P. R. China

   Phone: +86-755-28970171
   Email: sunruinan@huawei.com


   Esko Dijk
   Philips Research
   High Tech Campus 34
   Eindhoven
   The Netherlands

   Email: esko.dijk@philips.com


   Salvatore Loreto
   Ericsson
   Hirsalantie 11
   Jorvas 02420
   Finland

   Email: salvatore.loreto@ericsson.com





Li, et al.                Expires June 19, 2015                 [Page 6]


Html markup produced by rfcmarkup 1.127, available from https://tools.ietf.org/tools/rfcmarkup/