XEP-0124 / BOSH: Omit ACK in response

I'm reading the XEP-0124 / BOSH specification and do not understand the following sentence in chapter 9.1 Request Acknowledgements:

The only exception is that, after its session creation response, the connection manager SHOULD NOT include an 'ack' attribute in any response if the value would be the 'rid' of the request being responded to.

In my words: I should not send an ACK if the respond is dedicated for the last and only request (in connection manager's queue).

But: There is a client with it's own state machine. Maybe the client already send a second 开发者_Python百科request -- where the first one is not replied -- and expect to get two answers. In this case the client except a ACK with RID of the "older" request and the connection manager have to set ACK.

Conclusion: The connection mananager MUST set ACK as long multiple requests are allowed.

I'm not sure, but is this text paragraph dedicated only for the use case where no further request is send by the client but the session creation phase is finished successfully and the connection manager have to send "ping" messages to the client due to "wait" timeouts ?

---

So, as I read it:

If the highest RID (in sequence) that you have received is 11 (you might have received 14 after that, but it is out of sequence since 12 & 13 are missing), and you are responding on:

1. The same request, then you should not (it is recommended that you do not, but if you have a good reason to, then you may) send an 'ack' attribute.

2. An earlier held request (say RID 10) then you should set 'ack' to 11 since that is the highest in-sequence RID that you have received so far.

It's okay if the client sent multiple requests and the server doesn't yet know about them. This is because there is a chance that when the client sent 11, the server has no held connections and it will respond back on the same connection. In that case, there are 2 requests sent out (11 & 12), but the response for each one acks that same request since the server always has something to send back immediately.