LARTC - May 2001 - Anyway to adjust the bandwidth of a packet stream when it's active?

Hi:

I''m playing with TC.  I find it works fine when you predefine
a bandwidth allocation for some host or application.

But, as my testing, a FTP session is preallocated 250Kbps
bandwidth, when on one end station I''m ftping a 250MB
file, I want to reallocate/adjust the bandwidth allocated, means
give more bandwidth to the ftp client host.

I do the following:

   1. reduce the bandwidth allocated for best effort traffic from 5Mbps
to 3Mbps
        by tc
    2.  make a new allocation for ftp host

each step is done by tc with "tc add", the first works ,but the second
fails.

I want to know is it possible to do so ?

Thanks

James Shen