FTP Port Download Problem

[DJSUB]

Hi M8!,

We're not using same ISP:
ex:
glori 12121 - downloading project5 - 3KB/s same day same time
glori 21 - downloading project5 - 21KB/s same day same time

Glori's port 21 is always full [ Very hard to connect ]

Why my download so slow?

We're using same ISP & line speed before, No download problem on any port, but when i tried to change my line to Cable Internet I experience this download slowdown on other port.
I already ask this to my ISP technical support, but they didn't know what to answer.
Please Help!


THANKS IN ADVANCE