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#1 2009-07-27 15:35:16

twg
Member
Registered: 2009-06-12
Posts: 18

DNS-323 disconnections

I have a problem whereby my torrents which are initiated on my desktop PC but files saved onto the DNS stop because it loses connection to the DNS.

Here's my setup:

Desktop PC - XP sp3, wired to router

WRT54GL wireless to ethernet bridge running Thibor 15c

WRT54GL ethernet bridge running Tomato

DNS-323 wired to ethernet bridge


I've tried different BT clients, same issue. I checked the routers and they are not reseting. I checked the WAN connection and it's solid. I tried changing ethernet cards in the desktop PC, seemed to help at first within the first couple of days, but now same thing. I also tried reducing the number of connections in my BT client... not sure if it's helping...

I google'd and there were some limited hits on NFS getting swamped with connections and timing out... I'm DL max 5 torrents and uploading 3... I wouldn't think this would overwhelm my DNS ???

Any thoughts ?

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#2 2009-07-27 18:51:17

fordem
Member
Registered: 2007-01-26
Posts: 1938

Re: DNS-323 disconnections

Get rid of the wireless bridge and see what happens.

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#3 2009-07-27 20:19:19

twg
Member
Registered: 2009-06-12
Posts: 18

Re: DNS-323 disconnections

i have tested it with the DNS plugged into the same router as the desktop and no issues... it's hard to replace the wireless ethernet bridge because the AP is on the 3rd floor and the ethernet bridge is 3 stories below...

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#4 2009-07-28 04:26:45

fordem
Member
Registered: 2007-01-26
Posts: 1938

Re: DNS-323 disconnections

My reason for suggesting you get rid of the wireless bridge was it was the easiest way of pinpointing the wireless as the problem.

Now that we have accomplished that task - let's see what the options to fix it are.

Why does the disconnect occur?

First a little bit of tcp/ip background - the tcp/ip suite of protocols was designed to be self healing and assuming a properly designed network infrastructure, to permit communications in the event of a nuclear blast.  It does this by detecting missing, dropped and/or corrupt packets and retransmitting them, and it does this transparently - the user is not required to take any action.

Now - here's the scenario - you have your wireless bridge and you're surfing the net and everything works great, no dropped connections - at least that you can see.  Your wireless-g bridge can handle ~25mbps (that's right, 54 mbps is only theoretical and not achievable in practise) and your cable internet connection is good for a whopping 8 mbps, and everything is hunky dory - or so you think.

In this scenario the internet connection is the bottleneck, the wireless bridge can accomodate close to 3x the throughput.  At 8 mbps, you could have a retransmit rate of over 50% and never notice - a page might take 1~2 seconds longer, but, since there are no errors, most people have no clue.

Let's now try to move data from your DNS-323 - your wireless bridge at ~25 mbps is now choked with traffic, any errors that occur cause retransmits (just as before), but you no longer have the available bandwidth to accomodate them, with high error levels even the retransmits have errors forcing retransmissions of the retransmissions, until the link collapses under the load.

Your file transfer now stops and the link heals itself.

Find a way to report the transmit & receive errors on the wireless bridge - find the causes of those errors - is it weak signal strength, is it interference from adjacent wireless networks, interference from other 2.4GHz devices - microwave ovens, cordless phones, baby monitors, game console remotes (the list is endless), and tools such as inSSIDer and NetStumbler will only show wireless networks, you need a spectrum analyser to see the rest.

I first came across this problem using an early Intel "centrino" wireless card, which, with a particular wireless access point would give mediocre performance, I replaced the access point and the problem seemed to disappear, and just as I mentioned above, surfing the web worked great - but transferring data didn't.  The problem was eventually traced to an Intel power management feature, and was fixed by a new driver, but it manifested itself as an extremely high level of receive errors (from the access point to the laptop).

One final thing - even if you can locate and fix the cause of your wireless failure - which is not an easy task, you need to bear the following in mind.  A DNS-323 over a wireless-g link will give you at best 3~4 MBytes/sec throughput - over a 100 mbps ethernet link you'll see three times that easily, and a gigabit link can deliver close to 30MBytes/sec.

It's a 0.25" diameter cable ...

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#5 2009-07-28 16:03:47

twg
Member
Registered: 2009-06-12
Posts: 18

Re: DNS-323 disconnections

I understand what you are saying... but I can transfer files manually using windows explorer from my desktop to the DNS for hours on end without and issues and at maximum transfer rates (2000-3000kb/s). My torrents download only up to about 500kb/s yet I get errors...

I too suspected the wireless link and eventually plan to wire up the house to avoid having a wireless ethernet bridge but for now this is the only option for me. I've tried a lot of things already, but I recently realized that the DNS was setup for DHCP, even though I've setup my router to assign the same IP to the DNS, I tried to set the DNS itself for static IP, this doesn't make a lot of sense because when the disconnects happen, it was during the middle of an IP lease session, ie, the IP shouldn't have been renewing... but for yuks I have been running static IP on the DNS for the past 2 days I haven't encountered any errors... <knock on wood>... will report back if the problem comes back...

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#6 2009-07-28 20:07:36

fordem
Member
Registered: 2007-01-26
Posts: 1938

Re: DNS-323 disconnections

twg wrote:

I recently realized that the DNS was setup for DHCP, even though I've setup my router to assign the same IP to the DNS, I tried to set the DNS itself for static IP, this doesn't make a lot of sense because when the disconnects happen, it was during the middle of an IP lease session, ie, the IP shouldn't have been renewing...

I'm not certain I understand this.

A couple of points - a DHCP reservation (which is where you reserve an address in the DHCP server for a particular host) is not significantly different to a normal (unreserved) DHCP lease, the only difference is that the ip address should never change.  The lease will still expire and have to be renewed, and I don't know if you know this, but the first attempt to renew the lease will occur midway through the lease duration.

I'd be surprised to see that a static address fixes the problem, but, it just may due to the fact that you are using torrents.

If I'm not mistaken an interrupted torrent transfer will automatically attempt to restart and it might be able to do this if the DNS-323 has a static address since it can look for that host and has a better chance of finding it, if the host is not attempting to renew a DHCP lease over a failed link.

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