A Gateway should buffer Q0S 0 messages for ASLEEP clients

Chapter 3.19 (Sleeping clients) of WD24

During the asleep state, packets that need to be sent to the client are buffered at the server/gateway. The gateway MUST buffer application messages of quality-of-service 1 & 2.

Non-normative comment
The gateway may choose to buffer messages of all quality-of-service 0, whilst the client is sleeping and is within it's session expiry interval.

I propose to modify the above in

During the asleep state, packets that need to be sent to the client are buffered at the server/gateway. The gateway MUST buffer application messages of quality-of-service 1 & 2 & 0.

Non-normative comment
The gateway may choose to buffer messages of all quality-of-service 0, whilst the client is sleeping and is within it's session expiry interval.

With this modification the following scenario is possible:  

1. A client CONNECT to a gateway (client enrollment) with a very long session expiry interval
2. The client subscribe to a certain topic to receive pending messages as soon as it sends a publish-1 message to a certain (also different) topic
3. The client DISCONNECT with a very long session expiry interval
4. After some time the client send a PUBLISH-1 message and would like to receive (like with the PINGREQ when in ASLEEP state) all pending messages on the topic it has subscribed to, also with QoS 0 (the most efficient as they don't require any acknowledge)