Re: [mqtt-comment] Setting of Session Expiry Interval and Clean Start that equivalent of v3.1.1

[Richard J Coppen <COPPEN@uk.ibm.com>]

Hi Takatoshi,

Thank you for
raising this and submitting a comment to the MQTT TC.
I have raised
an issue for this in our tracking system which you can review here >
https://issues.oasis-open.org/browse/MQTT-538
<.

I will contact
the editors to review this section of the specification and will update
you once we have clarified the correct value for SessionExpiry with respect
to CleanStart=0 behavior.

Best regards


Richard

Richard Coppen CEng FBCS			IBM United Kingdom
Senior Software Engineer			Hursley Park
IBM MQ			Winchester
			SO21 2JN
Phone:	+44 (0)1962 817164		England
e-mail:	coppen@uk.ibm.com

From:
       Takatoshi
Kondo <redboltz@gmail.com>
To:
       mqtt-comment@lists.oasis-open.org
Date:
       17/03/2020
05:02
Subject:
       [EXTERNAL]
[mqtt-comment] Setting of Session Expiry Interval and Clean Start that
equivalent of v3.1.1
Sent
by:        <mqtt-comment@lists.oasis-open.org>

---

Hi,

I have a comment about the following part of MQTT Version 5.0 document:

https://docs.oasis-open.org/mqtt/mqtt/v5.0/os/mqtt-v5.0-os.html#_Toc3901048

> 3.1.2.11.2 Session Expiry Interval
>
> ...snip...
>
> Non-normative comment
>
> Setting Clean Start to 1 and a Session Expiry Interval of 0, is equivalent
to setting CleanSession to 1 in the MQTT Specification Version 3.1.1. Setting
Clean Start to 0 and no Session Expiry Interval, is equivalent to setting
CleanSession to 0 in the MQTT Specification Version 3.1.1.

I thin that "Setting Clean Start to 0 and no Session Expiry Interval,
is equivalent to setting CleanSession to 0 in the MQTT Specification
Version 3.1.1." is not correct.

Because "no Session Expiry Interval" is equivalent to set to
0.

The spec said that as follows:

> If the Session Expiry Interval is absent the value 0 is used. If it
is set to 0, or is absent, the Session ends when the Network Connection
is closed.
>
> If the Session Expiry Interval is 0xFFFFFFFF (UINT_MAX), the Session
does not expire.

So I think that the sentence

"Setting Clean Start to 0 and no Session Expiry Interval, is
equivalent to setting CleanSession to 0 in the MQTT Specification
Version 3.1.1."

should be something like as follows:

"Setting Clean Start to 0 and a Session Expiry Interval of
0xFFFFFFFF(UINT_MAX), is equivalent to setting CleanSession to 0 in
the MQTT Specification Version 3.1.1."

Am I missing something?

Thanks,
Takatoshi

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