[OASIS Issue Tracker] (MQTT-535) CONNACK property length should be optional

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

    [ https://issues.oasis-open.org/browse/MQTT-535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=72623#comment-72623 ] 

Andrew Banks commented on MQTT-535:
-----------------------------------

Discussed by the TC on January 31st. 2019, points raised:

1) The size of the CONNACK packet would be reduced by 1 byte in a minority of cases.

2) The CONNACK variable header requires the FLAGS and RETURN CODE bytes to be present. The packets where the property length can be omitted, eg PUBACK have no mandatory fields in the variable header.

3) In the event that a server implementation checks for the presence of a property length in CONNACK and was not updated to allow it to be absent, then it would not be able to accept connections from clients which did not insert the property length. This might have security implications.

4) Accepting the change would delay adoption of the standard by a few weeks.

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TC voted Defer:8 Implement now:0 Abstain:1ÂÂ

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> CONNACK property length should be optional
> ------------------------------------------
>
>                 Key: MQTT-535
>                 URL: https://issues.oasis-open.org/browse/MQTT-535
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: futures
>    Affects Versions: 5, CSD02
>         Environment: Public comment from Tatsuzo Osawa
> Regarding 3.2.2.3.1 (CONNACK) Property Length,
> I'd like to add "If the Remaining Length is 2 there is no Property
> Length and the value of 0 is used."
> Because, all other messages without payload has similar statement.
> Only CONNACK has not. In addition, treating the property length as
> optional helps interoperability with the former version.
>            Reporter: Ken Borgendale
>            Assignee: Ken Borgendale
>            Priority: Minor
>




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