> The caller sends INVITE with Session-Expires as 1800. Min-SE expires is
> not present.
> The callee sends 200 Ok with Session-Expires as 10 seconds.
> As per RFC, if Min-SE is not present, the default is 90 seconds.
> In this error case, can the user stop the call? Pl clarify.
No, IMO it is completely legal to provide a lower-than-the-default value
here (please correct me if I'm wrong). If the given value is two low,
you still have the option to send "422 Session Timer too small".