Can't load web pages while downloading via http - still plenty of bandwidth !

[yukoncornel]

I'm having a problem where the ability to surf the web is killed whenever a small http download is in progress. As an example, if someone goes to a webpage and sees an image they like, they could right click and save it to their computer and while it's being downloaded the other users on the network will not be able to load web pages but can send e-mail, download from newsgroups, etc.

We have 10 users on a shared satellite network with 512 Kb/s down total (bits, not bytes). All users are using netlimiting software to keep the downloads to 50-100 Kb/s per connection but for some reason even the smallest http download kills the abilty of all users to surf the web. This seems to be affecting only port 80 traffic since we can still do newsgroup downloads (nntp) as well as bit torrents, p2p and I think ftp when the http downloads are running, just can't browse the web.

We had no idea initially why there were so many problems with the web usage until the last few days when we were able to isolate it to the http downloads. When the http download is stopped, web browsing is immediately restored.

Also, a few people are using download accelerators but the problem happens with the download accelerators and without.

Hardware used is a Linksys WRT54G v2.0 router running DD-WRT v23 firmware. There is also a hub thrown in there to get the additional users connected, but I don't have the information on the hub model. I've tried changing most of the settings in the router firmware, including turning Qos on and off, nothing seems to help.

Any help would be appreciated.

 

[RebateMonger]

DD-WRT firmware? I assume that's 3rd-party?

Here's what I would do, after hours. Stop when the problem is fixed:
1) Swap the Linksys router for a different router with standard firmware.
2) Disable the netlimiting software on two PCs and try doing an http download on one and see the effect on the other.

 

[yukoncornel]

Yes, it's a third party firmware quite popular with the WRT54G crowd with a great feature set.

I tried adjusting the BTU setting (1400, 1500 and auto) with no success and enabling/disabling Qos didn't help either. I'm sure the problem is in the router somewhere, I'll have my first chance to swap out the router tonight with a very standard Netgear WGR614.

 

[yukoncornel]

UPDATE:

1. We removed the hub from the network and swapped out the router with a different model this morning and the problem persisted.

2. We also took the router out of the path and connected just the hub to the modem (the modem can issue IP addresses without a router) and again the problem persisted.

So the next step is to contact the ISP and see what can be done at their end.