[OASIS Issue Tracker] (MQTT-608) Add gateway retransmssion. and clarify client retransmission

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

    [ https://issues.oasis-open.org/browse/MQTT-608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=84302#comment-84302 ] 

Davide Lenzarini commented on MQTT-608:
---------------------------------------

_"A Client MUST retransmit CONNECT, AUTH, REGISTER, PUBLISH Qos1, PUBLISH Qos2, PUBREL, SUBSCRIBE, UNSUBSCRIBE, WILLTOPICUPD, WILLMSGUPD Packets after Tretry has passed or close the Virtual Connection."_

_"A Gateway MUST retransmit WILLTOPICREQ, WILLMSGREQ, PUBLISH Qos1, PUBLISH Qos2, PUBREL Packets after Tretry has passed or close the Virtual Connection."_

[~AndrewBanks]I would propose the following changes
 * "A Client MUST retransmit CONNECT, AUTH, REGISTER, PUBLISH Qos1, PUBLISH Qos2, PUBREL, SUBSCRIBE, UNSUBSCRIBE-, WILLTOPICUPD, WILLMSGUPD- Packets *{color:#de350b}and the PROTECTION packet, if wrapping one of them,{color}* after Tretry has passed or close the Virtual Connection."

 * "A Gateway MUST retransmit -WILLTOPICREQ, WILLMSGREQ,- PUBLISH Qos1, PUBLISH Qos2, PUBREL PacketsÂ{color:#de350b}*and the PROTECTION packet, if wrapping one of them,*{color} after Tretry has passed or close the Virtual Connection."

> Add gateway retransmssion. and clarify client retransmission
> ------------------------------------------------------------
>
>                 Key: MQTT-608
>                 URL: https://issues.oasis-open.org/browse/MQTT-608
>             Project: OASIS Message Queuing Telemetry Transport (MQTT) TC
>          Issue Type: Improvement
>          Components: MQTT-SN
>            Reporter: Andrew Banks
>            Priority: Major
>
> The current specification describes the need for client retransmission in section 4.18, 
>  however there circumstances where the gateway will also need to retransmit packets.
> Â
> Discussion points.
> 1) There is little difference between sending PUBLISH Qos1 NRetry times and then stopping, and sending PUBLISH Qos 0?
> 2) Once a Qos2 PUBLISH has been sent the receiver may have stored state that it is obliged to keep until it has received PUBREL. MQTT states that 
>  in this case the sender MUST NOT apply Publication expiry if a PUBLISH packet has been sent, so that the receivers state is always deleted eventually.
>  MQTT-SN needs to do something similar , so Nretry can't apply to Qos2 messages. 
> 3) Clean start can be used by the Client to reset the protocol Session state if necessary. Session Present can be used by the Gateway 
>  to indicate that it has deleted the Session State. The client and Gateway already have a mechanism to close the Virtual Connection and restart 
>  with the Session state reset, so that NRetry would not be needed.
> 4) A retransmitted packet must be identical to the predecessor, otherwise it is ambiguous as to which version is being acknowledged. Is this OK with the Protection Envelope?



--
This message was sent by Atlassian Jira
(v8.3.3#803004)