[OASIS Issue Tracker] Commented: (MQTT-15) Should the CONNECT packet Protocol Name and Protocol Version fields be changed?

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    [ http://tools.oasis-open.org/issues/browse/MQTT-15?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=33516#action_33516 ] 

Raphael Cohen commented on MQTT-15:
-----------------------------------

Some observations:-

- Whilst it's nice to have this string use the same generic encoding, simple deep packet inspectors (eg firewalls) will want the offset of this version string to be constant, and the size to be constant

- It may be worth considering that the size and offset should remain constant even between major versions

- I'd suggest we end the differentiation in the spec between the letters and the number - and just make the whole thing a 'version token'. After all, any inspector is simply going to do a 'string switch' or hash map like dispatch. That's not to say that the value could be 'MQTT311' or whatever, just that there's no separation (ie it's opaque).


> Should the CONNECT packet Protocol Name and Protocol Version fields be changed?
> -------------------------------------------------------------------------------
>
>                 Key: MQTT-15
>                 URL: http://tools.oasis-open.org/issues/browse/MQTT-15
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: core
>            Reporter: Allan Stockdill-Mander 
>
> The draft specification states that the Bytes 1 to 9 of the variable header section of the CONNECT packet are currently a spec encoded string (2 prefix bytes indicating the string length followed by the string data) containing the letters 'MQIsdp' followed by the number 3. Changing these fields would be an easy way to differentiate between old and OASIS spec compliant clients.
> Reasons for wanting to differentiate between clients include using discrimination of access to MQTT servers and understanding/implementing behavioural differences.

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