[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=64937#comment-64937 ] 

Ed Briggs commented on MQTT-385:
--------------------------------

I agree that small clients may not implement or want to implement all of these properties, in particular, strings which may be larger than available memory or may lead to fragmentation of memory.  But there are several problems:

1. Ken observes that regarding MQTT-321, the TC agreed to add the ability for a client to say it did not want to receive certain properties. However, MQTT-321 was concerned with properties on ACKs (e.g. PUBACK, etc.) which provided diagnostic information, not properties sent on the CONNECT, or as part of establishing the rules for a session. I think the issues are rather different.

2a. The TC has not defined what a Small Client Is.  That would be a CORE change.

2b. The TC has not agreed to provide a  Small Client profile, and introducing it here would be a CORE change.

3.  JIRA 271  (The Arduino Problem) was closed after the April F2F meeting because the issues raised in MQTT-276 (Large Scale) contained restrictions on QoS, Message Size Limits, and Flow control,  which I believe are mandatory, and should not be ignored by a client.

I think it may be possible to handle this with non-normative language, but the first step is to agree on the approach we should take.



> 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
>            Assignee: Ken Borgendale
>            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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