[OASIS Issue Tracker] (MQTT-271) Describing small device limitations, aka "the Arduino problem"

[OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org>]

    [ https://issues.oasis-open.org/browse/MQTT-271?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=60877#comment-60877 ] 

Ken Borgendale commented on MQTT-271:
-------------------------------------

I agree that transport restrictions are outside the scope of the MQTT spec, but that just indicates that restricting the size of the MQTT packet in no way means that a memory restricted client can handle it.  These same devices tend to have a very specialized TCP stack with some severe limits.

In the cases where we needed to implement this, the real limit was at the TCP layer, and the max size of an MQTT packet can be taken care of by the application which simply does not send large messages.

I do not see that any restrictions at the MQTT level help this problem.

> Describing small device limitations, aka "the Arduino problem"
> --------------------------------------------------------------
>
>                 Key: MQTT-271
>                 URL: https://issues.oasis-open.org/browse/MQTT-271
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: futures
>    Affects Versions: 3.1.1
>         Environment: Very small device implementations.
>            Reporter: Ian Craggs
>
> Small devices, like the original Arduino, may have very limited resource, like 16k of RAM, or less.  For such devices, limiting the storage used by MQTT is very important.  
> They may not even be able to process a message of 30k, for instance, at all.  If it were sent at QoS 1 or 2, it has to be read in before subsequent messages are received.  
> At the moment, it is a server admin task, or application design task, to make sure that messages bigger than a device can handle are not sent to it.



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