Internet DRAFT - draft-castellani-core-alive
draft-castellani-core-alive
CoRE Working Group A. Castellani
Internet-Draft University of Padova
Intended status: Standards Track S. Loreto
Expires: September 30, 2012 Ericsson
March 29, 2012
CoAP Alive Message
draft-castellani-core-alive-00
Abstract
In the context of a Constrained RESTful Environment (CoRE), hosts
could frequently be energy-constrained and be turned off the vast
majority of time for energy-saving purposes.
In the case of a CoAP server, while it is offline, it is neither
available to serve requests. Clients desiring to access its
resources have no way to understand when they will find it up again.
This specification provides a simple new message that gives to a CoAP
server the ability to signal its current availability in the network.
Status of this Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 30, 2012.
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document authors. All rights reserved.
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Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Alive (ALV) Message Type . . . . . . . . . . . . . . . . . . . 3
3. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
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1. Introduction
In the context of a Constrained RESTful Environment (CoRE), hosts
could frequently be energy-constrained and be turned off the vast
majority of time for energy-saving purposes.
In the case of a CoAP server, while it is offline, it is neither
available to serve requests. Clients desiring to access its
resources have no way to understand when they will find it up again.
This specification provides a simple new message that gives to a CoAP
server the ability to signal its current availability in the network.
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. Alive (ALV) Message Type
This specification defines a new message type for the CoAP message-
layer (see Section 4.4 of [I-D.ietf-core-coap]). The type of a
message is specified by the T field of the CoAP header.
An "Alive" message (ALV) indicates that a CoAP server is up and ready
to serve requests. Alive shares T value with the Non-Confirmable
(NON) message type, but is univocally distinguishable by the fact
that it MUST be empty.
When a client receives an ALV message from a server, if it is
interested in any resource served by it, the client SHOULD try
sending a request to it since the Alive message provides an
indication of its current availability.
3. Examples
Figure 1 shows a sample use case where a server notifies its wake up
to clients using multicast.
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C1 C2 C3 S
| | | . server is sleeping
| | | .
| | | .
| | | .
| | | . server wakes up
|<--|<--|<----| ALV MID=0xfefe
| | | |
| | | | CON MID=0x1234
|------------>| GET /a
| | | |
| | | | ACK MID=0x1234
|<------------| 2.05 "A"
| | | .
| | | . server goes sleeping again
| | | .
| | | .
| | | .
Figure 1: Alive usage example
Figure 2 shows a sample application on how the Alive message can fix
the "Observer Model" problem discussed in Section 4.2.3 of
[I-D.arkko-core-sleepy-sensors].
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C1 C2 C3 P S
| | | | . server is sleeping
| | | | .
| | | | . CON MID=0x1234
| | | | . GET
| | | | . Proxy-URI: coap://S/temp
|------------>| . Observe: 0
| | | | .
|<------------| . ACK MID=0x1234
| | | | .
| | | | . (time passes..)
| | | | .
| | | | . server wakes up
| | | |<---| ALV MID=0xfefe
| | | | |
| | | | | CON MID=0xabcd
| | | | | GET /temp
| | | |--->| Observe:0
| | | | |
| | | | | ACK MID=0xabcd
| | | | | 2.05 "22.5 C"
| | | |<---| Observe: 789
| | | | .
| | | | . CON MID=0xabce
| | | | . 2.05 "22.5 C"
|<------------| . Observe: 3013
| | | | .
|------------>| . ACK MID=0xabce
| | | | .
| | | | . (time passess..)
| | | | .
| | | | . resource state changes
| | | | . NON MID=0xfeff
| | | | . 2.05 "21.5 C"
| | | |<---| Observe: 1384
| | | | .
| | | | .
| | | | . NON MID=0xabcf
| | | | . 2.05 "22.5 C"
|<------------| . Observe: 3013
...
Figure 2: Alive with Observe
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4. Acknowledgements
TBD
5. References
5.1. Normative References
[I-D.ietf-core-coap]
Shelby, Z., Hartke, K., Bormann, C., and B. Frank,
"Constrained Application Protocol (CoAP)",
draft-ietf-core-coap-09 (work in progress), March 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
5.2. Informative References
[I-D.arkko-core-sleepy-sensors]
Arkko, J., Rissanen, H., Loreto, S., Turanyi, Z., and O.
Novo, "Implementing Tiny COAP Sensors",
draft-arkko-core-sleepy-sensors-00 (work in progress),
July 2011.
Authors' Addresses
Angelo P. Castellani
University of Padova
Via Gradenigo 6/B
Padova 35131
Italy
Email: angelo@castellani.net
Salvatore Loreto
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
Email: salvatore.loreto@ericsson.com
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