Paul Kyzivat wrote:
> I'm not sure about INFO, but overlap is allowed for NOTIFY. Furthermore, 
> messages belonging to different usages of the same dialog can overlap - 
> e.g. UPDATE and NOTIFY. (Assuming you have multiple usages in the dialog.)

I think UPDATE can never overlap, because there can only be one 
outstanding offer/answer, cmiiw.

Good point about CSeq below.

-benny


> *BUT* overlapping has the potential to get you into trouble except in a 
> few specific cases. The problem is that if the messages get reordered 
> before delivery, then when the second one arrives it will be seen as 
> having a CSeq that is too small, and so will fail. In some limited cases 
> this may be ok. In particular, if you have an event package where each 
> new NOTIFY supercedes the prior one, then all may be well. In all other 
> cases it will be a problem.
> 
> So in practice it may really be necessary to serialize most messages in 
> a dialog.
> 
>       Paul

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