[OASIS Issue Tracker] (MQTT-299) Metadata: CONNECT and CONNACK Maximum Message Length

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

    [ https://issues.oasis-open.org/browse/MQTT-299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=63694#comment-63694 ] 

Ken Borgendale commented on MQTT-299:
-------------------------------------

We need to consider each of the packet types and what it would mean if they are not sent.  It would be quite ugly if the packet which cannot be returned is a SUBACK.  For CONNACK and DISCONNECT we have stated that we can limit the id/value pairs so that we never exceed the size limit assuming we put a minimum on the packet size of something like 128.  If we put enhanced diagnostics on other ACKs we will need to say the same.  The Client can control this for SUBACK and UNSUBACK by limiting the number of topics in the SUBSCRIBE or UNSUBSCRIBE.

For PUBLISH at QoS=0 just dropping the forward is commonly the best thing, but you might want to configure the Server to disconnect is such cases so that you get some diagnostics of the problem.  The suggestion will be that Packet Too Big is not a return code which should cause a retry, but that the programmer should look at the design of the application to find the problem.

> Metadata: CONNECT and CONNACK Maximum Message Length
> ----------------------------------------------------
>
>                 Key: MQTT-299
>                 URL: https://issues.oasis-open.org/browse/MQTT-299
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: New Feature
>          Components: core
>    Affects Versions: 5
>            Reporter: Brian Raymor
>            Assignee: Ed Briggs
>
> This was discussed in MQTT-276 (with notes from the F2F meetings) and has been tracked in MQTT-256 (Metadata). 
> I'm opening a separate, specific issue per Ken's comments - https://issues.oasis-open.org/browse/MQTT-256?focusedCommentId=62192&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-62192:
> "All of these would be defined in separate JIRAs, but what we should do in this JIRA is to define the mechanism used to pass these values."



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