[OASIS Issue Tracker] Commented: (MQTT-71) Are messages order within Topic+Qos or within Qos

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    [ http://tools.oasis-open.org/issues/browse/MQTT-71?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=34366#action_34366 ] 

Raphael Cohen commented on MQTT-71:
-----------------------------------

OK, I mostly follow where you're going.

Para 2.
I agree that it just happens for QoS 1 (and implicitly QoS 0) messages.
But if you're a broker receiving a QoS2, you get the message, send an ack, get an ack back. At that point, can't the acks from the client be in a different order? And doesn't the broker need to maintain a buffer of 'pending' messages at that point, because surely it shouldn't make the message available for onward delivery until it's got the client's ack? So in this situation, is it possible for mis-ordering to occur, or have I missed something vital?




> Are messages order within Topic+Qos or within Qos
> -------------------------------------------------
>
>                 Key: MQTT-71
>                 URL: http://tools.oasis-open.org/issues/browse/MQTT-71
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: core
>            Reporter: Andrew Banks
>
> The input specification states 
> •	With an in-flight window greater than 1, message ordering can only be achieved within the QoS level.
> Should we state that 
> messages with the same Qos and Topic Name are delivered in order
> or
> messages with the same Qos regardless of Topic Name are delivered in order

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