Nortel 250 安装指导

Nautica 250 Installation Guide

301789-A Rev.00

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Traditionally File Transfer Protocol (FTP) servers time out (or 
end) an FTP session if there is no activity after a few minutes. 
Most command line FTP clients take no steps to avoid this 
timeout. Some of the new graphical FTP clients, however, make 
frequent read (or keepalive) requests to keep the FTP sessions 
alive.

This option is fine for local network access and leased line 
Internet browsing, but it can cause your remote ISDN connection 
to stay up permanently. 

If you use such FTP clients, be aware of this problem and close 
down remote FTP connections once you have finished 
transferring files.

When you are browsing the Web, many sites use push technology. 
This feature opens a permanent channel between the Web site and 
your PC in order to update sound and graphic files continuously. 
Using a remote router, such sites will keep your ISDN connection 
open.

Other Web sites cause your browser to refresh the screen at 
regular intervals, for example, every 30 seconds. Again, this can 
cause a link to stay open.

To minimize the effect of these data streams, do not leave your PC 
unattended when you have a Web site open and close down all 
Internet connections when you have finished with them. When 
browsing the Web, be aware that ISDN calls are being made.