Upstream / Downstream Light |
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Why does my 'upstream' and 'downstream' light blink?
The 'upstream' and 'downstream' lights in the front panel of your cable modem (Toshiba Cable Modem) indicate traffic passing through the cable modem. The 'upstream' light will be on whenever you send data, while the 'downstream' light is on whenever you receive data.
It is not always obvious why these two lights blink. There are a few reasons for these lights to blink even if you are not 'surfing the net':
 | Your cable modem will exchange information with the Road Runner network to keep your connection open. This includes sending your RR password, and renewing your IP address through a process called 'DHCP'. |
| You may have your e-mail software setup to periodically check for new mail. |
| Do you have software like Pointcast installed that periodically downloads news? |
| ICQ or other online chat software may exchange data with a central server. |
| Lots and lots of other little helpers that will send random data over the net (time synchronization, Microsoft Explorer Channels, NetMeeting, Newsreader ...) |
On the other hand, you may also be under attack by a hacker if you see serious activity on the up and down stream side. I find 'netstat' to be a useful utility to debug these problems. Best thing about it: It comes free with Windows 95. Check the 'Windows 95 tools' section for details.
Further Reading:
| John Reinhardt's article about the Toshiba Cable Modem system. |