IMO, change and event-based notification will be a “must have” rather than a “nice-to-have” in current
and future M2M applications and protocols. The “poll to see if there are any changes” approach can often consume more device energy/communications bandwidth than change-based.
Rick
Hi all,
Please allow me to jump in. I’m working for Intel’s Opensource Technology Center and I participated
in the development of OMA’s LWM2M (which relies on CoAP as Julien said).
I don’t think CoAP and MQTT are designed to answer the same use cases. MQTT (as I understand it)
is all about publishing events with a subscribe mechanism. CoAP is designed to be a replacement of HTTP in constrained environments. So even if CoAP features an Observe mechanism to be notified of value changes, it is not its main purpose and in this, it will
be inferior to MQTT. And as an HTTP equivalent, CoAP makes no assumption on the system topology.
At the OMA, we choose to base LWM2M protocol on CoAP because it provides the core functionnalities
of HTTP (GET, PUT, POST, DELETE commands, TLS security) in a reduced footprint. The Observe mechanism is a nice-to-have feature but not essential in the LWM2M use-case.
Regards,
David Navarro
From:
m2m-iwg-bounces@xxxxxxxxxxx [mailto:m2m-iwg-bounces@xxxxxxxxxxx]
On Behalf Of Matteo Collina
Sent: Monday, April 15, 2013 6:19 PM
To: m2m Industry Working Group
Subject: Re: [m2m-iwg] COAP
The real difference between CoAP and MQTT is in how the notification of events works:
In practice, it is the "gateway" or end-user that start observing for changes on the sensor.
In MQTT, it is the other way around, it is the sensor that publishes stuff on a broker.
However CoAP allows some true P2P communication between devices, which is not possible in a central system like MQTT.
It has a real difference, and it may be the reason because it lacks adoption.
I think deploying a central client-server system is much easier.
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