TURN client: send Send Request to allocated port or not?

Hi all!

I'm very new to this mailing list and TURN, and I'm not a native
English speaker, so please bear with me :)

I've read the latest draft-rosenberg-midcom-turn-07 for many times.
Now I encounter a problem:

from the draft:

"The Allocate Request MUST be sent to the same IP address and port as the Shared
Secret Request. This is because one time passwords are expected to be
host-specific." (8.3, P20)

"The Send Request MUST be sent to the same IP address and port as the Allocate
Request, and MUST be sent from the same source IP and port used to send the
Allocate request for the binding." (8.6, P22)

So, Share Secret Request/Allocate Request/Send Request are all sent to
the _same IP address and port of the TURN server_ ? Am I right?

Then, here is my problem:
 ** Why doesn't the client send the Send Request to the allocated port? **

If the client is behind a port restricted NAT, it HAS TO send
something to the allocated port before the server could relay packets
to it from that allocated port, doesn't it?

Any information would be warmly welcome!

Thanks in advance! : )