TSGL: Network Adress Translation

[Don Penlington]

System:

XP Pro SP2.

D-Link modem connected by 3Com Ethernet  XL PCI TX NIC (don't even ask me 
what all that jargon means!). ADSL1500.  Unlimited downloads.

I don't have a router, and I don't have a local network. This is a 
standalone computer.

Problem:

I have lately experienced several instances of what appears to be lost 
connections on long downloads or occasionally when trying to connect to web 
pages. I'm not aware of any recent additions which might have caused this.

It also happens after about 30-60 minutes of intensive browsing. Suddenly 
the browser (Maxthon/IE6) Sometimes I have to walk away for 1/2 hour, then 
everything's fine again.

Azureus Bittorrent tells me that I most likely have a "NAT" ("Network 
Address Translation") problem. Most (all?) their suggested fixes seem to 
relate to routers or LAN's, of which I have neither.

Bittorrent and other download speeds are about normal---except for these 
apparent interruptions to the connection.  Modem lights remain flashing as 
if it is still downloading (probably trying to seek reconnection).

Device Manager shows that in the Ethernet card/Device Properties/Advanced:

    1. 802.1p support is enabled.
    2. Flow control is disabled.
    3. Network Address is marked "not present".

Should I change any of these settings? Presumably item 3 only applies where 
there is a local network of computers.

Last week I was unable to access a paysite file, I kept getting "file in 
use" error messages. After extensive investigation and various suggestions 
re browser security settings (enabling ActiveX etc), they could not solve 
the problem and decided that it must be some setting unique to this computer.

I've a feeling these might be 2 aspects of the same problem.

I've run antispyware scans with Spybot, AdAware, A-Squared, and a-v scan 
with AVG. Apart from the few usual
non-critical fleas, the system comes up clean.

I've also done a "repair" on the connection icon (flushing DNS cache etc), 
and several times reset the modem by powering off for 60 seconds. No 
difference.

Does anyone have any suggestions what might be causing these dropouts?  Of 
course, I can't entirely rule out overloads at the ISP, but I've been with 
the same major ISP for several years, and have always found them completely 
reliable.

Don Penlington


 From the Beach at Surfers Paradise in sunny Queensland.
Computer tutorials, local scenery,  and other things at my website:
http://users.tpg.com.au/deepend/index1.html