[OASIS Issue Tracker] (MQTT-385) Simple clients skipping properties

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

    [ https://issues.oasis-open.org/browse/MQTT-385?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=64871#comment-64871 ] 

Ken Borgendale commented on MQTT-385:
-------------------------------------

This paragraph was added as the result of MQTT-321 and in the 12/1/2016 TC where we agreed to approve this based on accepting comments in the Jira.  If we want to revisit this you can reopen as a core issue.

Many simple clients will not do most of the checking required by this spec.  So really it is a question of whether we just declare all such clients to be non-conforming or to allow this behavior.  One classic step down from the validation requirement is to say that the client does not need to validate any data it does not use.

If the client does not use MaxQoS, MaxPacketSize, ReceiveMax, or any other such properties it is just asserting that it knows that the server it has selected does what is needed.  This is a perfectly reasonable thing for a simple client to do.  It does not matter if the client claims to be a limited function or full function client.  

> Simple clients skipping properties
> ----------------------------------
>
>                 Key: MQTT-385
>                 URL: https://issues.oasis-open.org/browse/MQTT-385
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Bug
>          Components: edits
>    Affects Versions: 5, wd10
>            Reporter: Brian Raymor
>            Priority: Minor
>             Fix For: 5
>
>
> What is the rationale for this exemption -and- how is it interoperable?
> 757 A Client MAY process the Packet without checking the Properties by skipping over the number of bytes
> 758 specified by Property Length. A Client which does not check the Properties MUST NOT make use of any
> 759 Property it has not checked. A Server MUST check all Properties in a Control Packet.
> 760
> 761 Non normative comment
> 762 This exemption for Clients is designed to allow for simple Clients that do not require the
> 763 information sent in Properties. A full function Client should check and use the information in the
> 764 Properties.



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