[OASIS Issue Tracker] (MQTT-297) Packet Indentifier Leak on lost Subscription commands

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

    [ https://issues.oasis-open.org/browse/MQTT-297?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=65008#comment-65008 ] 

Ken Borgendale commented on MQTT-297:
-------------------------------------

I understand that this is marked post-V5 and I do not doubt that there are implementations which have this problem.  However, my point is that the MQTTv5 spec (and indeed the MQTTv3.1.1 spec) do not say that the packet identifiers for SUBSCRIBE and UNSUBSCRIBE are a part of the session state, and therefore there should be no leak across connections in a session.  If we believe that implementers got this wrong, we could explicitly state that these packet IDs are not part of the session in non-normative text.  While completing the MQTTv5 spec would seem to be the time to create such a non-normative comment. 

> Packet Indentifier Leak on lost Subscription commands
> -----------------------------------------------------
>
>                 Key: MQTT-297
>                 URL: https://issues.oasis-open.org/browse/MQTT-297
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Bug
>    Affects Versions: 3.1.1
>            Reporter: Ed Briggs
>            Priority: Minor
>
> If a SUBSCRIBE, SUBACK, UNSUBSCRIBE or UNSUBACK message is lost during transfer, the packet identifier is leaked.   The leak remains for the duration of the session, which in the case of CleanSession=0 could be indefinite, during which time additional loss of packet ids could occur.
> This cannot be fixed using the existing mechanisms, and is recorded here for future consideration (not MQTT 3.1.1. or MQTT 5.0). 



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