CoAP Multicast

Document Type Expired Internet-Draft (individual)
Last updated 2018-04-19 (latest revision 2017-09-13)
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Multicast is a preferred approach to send a single message to multiple recipients but it is typically lossy. CoAP is the choice of messaging for IoT. If using multicast to transmit CoAP messages there is a risk they get lost and a further risk that sequences of messages get disrupted and leave the system in an unknown or unpleasant state. In the device world we might want to guarantee that a whole sequence of commands arrives at the device. For example a sequence to Open, Report, Do some action, and Close. It is better that all of these messages arrive or all of them do not arrive rather than have some of them arrive and to not know which ones failed. CoAP messages tend to be small due to constrained resources on the recipient devices. Existing frame sizes though are relatively large so it is possible to pack these frames with several smaller CoAP messages and send them as a group. CoAP Multicast proposes the simplest way to do this. It is a device independent method and adds no need for encryption channels.


Roger Lucas (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)