Group Communication for the Constrained Application Protocol (CoAP)
RFC 7390
Internet Engineering Task Force (IETF) A. Rahman, Ed.
Request for Comments: 7390 InterDigital Communications, LLC
Category: Experimental E. Dijk, Ed.
ISSN: 2070-1721 Philips Research
October 2014
Group Communication for the Constrained Application Protocol (CoAP)
Abstract
The Constrained Application Protocol (CoAP) is a specialized web
transfer protocol for constrained devices and constrained networks.
It is anticipated that constrained devices will often naturally
operate in groups (e.g., in a building automation scenario, all
lights in a given room may need to be switched on/off as a group).
This specification defines how CoAP should be used in a group
communication context. An approach for using CoAP on top of IP
multicast is detailed based on existing CoAP functionality as well as
new features introduced in this specification. Also, various use
cases and corresponding protocol flows are provided to illustrate
important concepts. Finally, guidance is provided for deployment in
various network topologies.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are a candidate for any level of
Internet Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7390.
Rahman & Dijk Experimental [Page 1]
RFC 7390 Group Communication for CoAP October 2014
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Conventions and Terminology . . . . . . . . . . . . . . . 4
2. Protocol Considerations . . . . . . . . . . . . . . . . . . . 5
2.1. IP Multicast Background . . . . . . . . . . . . . . . . . 5
2.2. Group Definition and Naming . . . . . . . . . . . . . . . 6
2.3. Port and URI Configuration . . . . . . . . . . . . . . . 7
2.4. RESTful Methods . . . . . . . . . . . . . . . . . . . . . 9
2.5. Request and Response Model . . . . . . . . . . . . . . . 9
2.6. Membership Configuration . . . . . . . . . . . . . . . . 10
2.6.1. Background . . . . . . . . . . . . . . . . . . . . . 10
2.6.2. Membership Configuration RESTful Interface . . . . . 11
2.7. Request Acceptance and Response Suppression Rules . . . . 17
2.8. Congestion Control . . . . . . . . . . . . . . . . . . . 19
2.9. Proxy Operation . . . . . . . . . . . . . . . . . . . . . 20
2.10. Exceptions . . . . . . . . . . . . . . . . . . . . . . . 21
3. Use Cases and Corresponding Protocol Flows . . . . . . . . . 22
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 22
3.2. Network Configuration . . . . . . . . . . . . . . . . . . 22
3.3. Discovery of Resource Directory . . . . . . . . . . . . . 25
3.4. Lighting Control . . . . . . . . . . . . . . . . . . . . 26
3.5. Lighting Control in MLD-Enabled Network . . . . . . . . . 30
3.6. Commissioning the Network Based on Resource Directory . . 31
4. Deployment Guidelines . . . . . . . . . . . . . . . . . . . . 32
4.1. Target Network Topologies . . . . . . . . . . . . . . . . 32
4.2. Networks Using the MLD Protocol . . . . . . . . . . . . . 33
4.3. Networks Using RPL Multicast without MLD . . . . . . . . 33
4.4. Networks Using MPL Forwarding without MLD . . . . . . . . 34
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