FTP uploads intermittently fails on NTL Broadband
 

Re: FTP uploads intermittently fails on NTL Broadband
 

I've now been able to run a tcpdump on both the server and the client.

I can see the packets leaving my firewall but never arriving at the server until about 2 minutes later! The conclusion is that the FTP packets are being held up somewhere on the way. Given that access via ZEN adsl is fine, I can only conclude that ntlworld are delaying these packets somewhere on the way.

Running the login on a different client shows the packets working fine, ariving at the server and then being sent back and arriving at the client. So it seems to be sensitive to the NATed client ie the return port address.

Please help with any ideas !

Re: FTP uploads intermittently fails on NTL Broadband
 

None to offer, ntl don't delay / throttle any ports, only process that happens is complete blocking of known worm ports as detailed earlier.

Where in the country are you? When did this issue start?

Re: FTP uploads intermittently fails on NTL Broadband
 

Yep - same problem here.

In belfast, 700kbps connection, Linksys W54G router, BladeFTP client.

Trying to upload a 150meg file, just stops transfer after a few percent...

What's going on here do you think?

Not exactly sure what you mean here, do you mean when you login via your zen adsl account?

Might be worth trying to switch to "passive" mode ftp transfer - will give it a go myself this weekend. AFAIK passive just means it doesn't rely on return packets for confirmation of data transfer at the client side. Useful for when you're ftp'ing from behind a firewall.

Re: FTP uploads intermittently fails on NTL Broadband
 

tcpdump only shows the user data that is sent or received: it does not show the protocol traffic on the wire, and the TCP recoveries and retransmissions in the event of failure.

A possible explanation of your observed "delay" is that there was no delay in NTL at all, but that a TCP packet was lost on the way from your FTP client to the remote server, or the TCP ACKs from the far end never made it back to your FTP client, so your FTP client sat there timing out and retransmitting the TCP packet until eventually it got through. An ethernet sniffer on the wire between your NAT router and the cable modem would reveal all.

A possible cause of packet loss might lie within your own network if, for instance, you have an ethernet duplex mismatch on any link. The best duplex setting depends on what model of cable modem you have.

Other causes are known to be Pace digital TV set top boxes (if that is what your cable modem is), if they are pushed anywhere near the upstream rate cap (as FTP uploads tend to do). You might get better upstream throughput by rate-limiting your aggregate upstream demand to be about 80% to 85% of the nominal upstream rate cap for your cable account. Then the STB will never get stressed anywhere near the upstream rate cap.

Re: FTP uploads intermittently fails on NTL Broadband
 

Yey, Robin. Welcome back!

:D

Re: FTP uploads intermittently fails on NTL Broadband
 

I'll fill in some of the blanks...

1) The modem is a Surfboard 3100 ethernet modem going into a smoothwall based firewall.

2) Currently using passive FTP. May try using active FTP to see if that helps (I'll open up the ports from just the server in question).

3) Problem has only occurred in the last few (5 maybe) weeks.

4) Pinging the server always works with good <35ms delays.

5) I accept the point made about tcpdump.

6) The zen adsl test is done by setting the gateway address to the other end of a VPN to a different office, causing the traffic to go via a ipsec tunnel between the two. From our Bristol office that traffic then goes off to our colocated webserver.

The bottom line is that strangeness is going on. Most strange is that when one client stops working for 30mins or so the opther will all still work, until they fail.

It sounds like some router somewhwre is throwing a wobbly and waiting to time out and reset itself.......

Ho hum... Lets see if active ftp makes any diference.

Re: FTP uploads intermittently fails on NTL Broadband
 

Does the problem occur without the router/smoothwall box in the equation?

You really need to eliminate those 1st.

Re: FTP uploads intermittently fails on NTL Broadband
 

In which case, you should manually configure the smoothwall WAN interface to be fixed at 10Mbps half-duplex, as the 3100 is incapable of supporting auto-negotiation correctly.

Re: FTP uploads intermittently fails on NTL Broadband
 

I will try the half-duplex/10 MBps idea...

An excellent set of replies - thanks guys.....

I will also report back when/if I get anywhere as that way the thread will be usefull when people search on it in the future.

<EDIT>ethtool reports that 10/half is already set for the eth1 smoothwall i/f.

Also if this was causing the problems it would happen for all FTP sites and all intensive traffic.

I can download things like XP-SP2 quite happily.

Back to the passive/active ftp idea </EDIT>

Re: FTP uploads intermittently fails on NTL Broadband
 

Seems to rule out the speed/duplex issue?

Re: FTP uploads intermittently fails on NTL Broadband
 

Tried 10/100 stuff.

1) Set to auto (original setting) - problem still occurs
2) Set to 10/half - problem occurs

I'll try FTP set to active and see if that helps....

Although the fact that other clients work when one won't makes me think that it is a NAT issue. Either:

A) the smoothwall router (although why would it suddenly start doing this ?), plus I would think the problem would still occur when going to different FTP sites...

B) The NTL network is going funny..... Hmmmmm surely not ?

Is anyone else getting this and have thay found a solution as it is really starting to irritate me....

Just tried the passive/active thing - Problems still there...

I've also just tried changing the IP address of a non-working client (test out the NAT theory....) and it still doesnt work !

ARRRGGGHHHHHHH :mad:

Re: FTP uploads intermittently fails on NTL Broadband
 

I had the idea of trying NTL's own ftp server as if there is any transparent ftp proxing that is causing a problem then it may not appy here....

Upload the same set of files 10 times and no problems what-so-ever...

So that would tend to prove that:

a) It is not a problem with my network/firewall/cable modem.

b) It is a problem with NTL

c) It is a problem with the server I'm trying to upload to.

"c)" is kind of eliminated by the fact that the remote host still responds fine to requests by other clients....

So is there anything I can do about "b)" ?

Can I bypass and FTP proy that NTL may be running or route my info via a different route ?

Re: FTP uploads intermittently fails on NTL Broadband
 

NTL don't proxy FTP. If it's only one of your LAN PCs affected, then you need to study the setup of that one PC carefully. If it is a Windows system, run HijackThis on it to see if there are any unexpected components present.

Re: FTP uploads intermittently fails on NTL Broadband
 

I had a similar problem last night it took over an hour to get a couple of pictures uploaded. the problem dissapeared as it suddenly arrived without anything being altered. I put it down to perhaps a UBR having a wobbler.

Re: FTP uploads intermittently fails on NTL Broadband
 

Thanks for posting Kits....

The problem has been ongoing for probably the last 6 to 8 weeks.

Today I tried an FTP session to the same server from a friends ADSL account (using my firewall and a client) and as expected the process was flawless.

As far as I am concerned this means that the fault *has* to be with NTL's network.

Does anyone have any idea how I can talk to someone at NTL (number or name) who will be able to help me diagnose this ?

Re: FTP uploads intermittently fails on NTL Broadband
 

Has there been any further developments on this? I'm Manchester and I can no longer FTP to any of my (non-NTL) sites. The hosting company has confirmed that FTP trafic from other sources is reaching them, but not from me. HTTP, email etc all working fine.

Re: FTP uploads intermittently fails on NTL Broadband
 

No, no further developments.....

But the more people that have the problem, the less likely the fault lies anywhere else than with NTL.....

Perhaps one of teh NTL bods that frequent these forums will add something to the questions I've posted above.

I've contacted NTL, but no-one there can really follow the discussions. To be fair I imagine that 99% of related to user misconfiguration and setup mistakes.

Can someone from NTL help here ?

To be honest I'm getting ready to get a freeview box and a BT line with ADSL....

ADSL/Freeview here I come....
 

I've been trying to get the issues raised in the following thread sorted for the last month.....

NTL tech support refuse to admit there is a problem. "Citing well if one PC is working, it can't be us....."

The tests outlined in the thread imply heavily that it is nothing to do with my network.

Thread:
http://www.cableforum.co.uk/board/sh...ad.php?t=20226

If I don't get this sorted by xmas, INTL are going to lose a TV, Phone and cable modem customer.

:mad:

Re: FTP uploads intermittently fails on NTL Broadband
 

Where are these boxes you are having problems with located (give us some examples). There are still some routing issues on the internet in general (some of my us servers again lost sight of some uk ip ranges this morning).

Re: ADSL/Freeview here I come....
 

There is nothing in that thread to indicate an ntl problem, so I'm not surprised they refuse to admit it.

Re: ADSL/Freeview here I come....
 

You also didn't answer the question of whether the problem occured with out the Smoothwall router.

The best thing you can do is remove all your network stuff, & connect the modem direct to the PC & see if the problem re-occurs. If it doesn't at least you know the issue lies on your side, & if it does you know it's ntl's side.

You need to eliminate your own hardware/software before you start blaming ntl IMO. :)

[Edit]-I'm going to merge these 2 threads soon as we don't need 2 on the same subject.

Re: FTP uploads intermittently fails on NTL Broadband
 

Thanks for answering...

But way back at the beginning I explained that the problem was not restricted to simply one PC..

I'll fill in some of the blanks...

1) The modem is a Surfboard 3100 ethernet modem going into a smoothwall based firewall.

2) Currently using passive FTP. May try using active FTP to see if that helps (I'll open up the ports from just the server in question).

3) Problem has only occurred in the last few (5 maybe) weeks.

4) Pinging the server always works with good <35ms delays.

5) I tried an FTP session to the same server from a friends ADSL account (using my firewall and my client) and as expected the process was flawless.

6) I have tried both linux and Windows clients, the symptoms are the same for both.

7) FTP to upload.ntlworld.com works fine - always. Even on a machine that is suffering a problem with getting to the server in question.

8) When the problem occurs FTP packets start to take up to 2 minutes to arrive at the server - all packets from any client not suffering the problem arrive within 30ms or so.

The bottom line is that strangeness is going on. Most strange is that when one client stops working for 30mins or so the others will all still work, until they fail and then behave as explained.

It sounds like some router somewhere is throwing a wobbly and waiting to time out and reset itself.......

Re: ADSL/Freeview here I come....
 

Thanks for posting Paul:

I would say that a combination of:

points 3 & 7 above imply that it is not my network, 5 especially implies that it is an NTL thing with FTP sites outside their network.

However, I have spent hours working on this.... If you think my conclusions are false, please say so and outline your reasoning as to where you think the problem lies....

Cheers

Re: [Merged] FTP uploads intermittently fail
 

so have you connected one of your pc's direct to your cable modem and tried the ftp from there?

Re: ADSL/Freeview here I come....
 

Neil, thanks, point 5 above implies that my own hard/software seems to be OK.

When connected to ADSL, the whole process works fine. Whenever I am trying to debug something like this I always try to change one thing at a time...

Changing *just* the broadband connection and finding that the problem goes away really does imply that something to do with the broadband is the issue here.

I must admit intermittend problems like this are infuriating as they are so much harder to track down...

Re: ADSL/Freeview here I come....
 

unless you do as Neil suggests you will never actually find out if it is your setup or ntl. As you can probably appreciate it is a process of elimination.

it is unlikey you will discover your solution to this problem unless you catually follow the advice of the (very knowledgable) forum members

Re: [Merged] FTP uploads intermittently fail
 

Ok Ok Ok !!! ;)

I'll make an image of one of the clients and expose it unfiltered to the sesspit out there that is the internet...

Lets see what the XP2 firewall thinks of it all !

At least I can put the image back afterwards !

I'll let you know how I get on...

I know that I may have sounded short, but this problem has been infuriating for the last 6 weeks now - please rest assured that I *do* appreciate everyones help.

Cheers,

Re: [Merged] FTP uploads intermittently fail
 

Ok,

Tried the following setup:

Motorola Surfboard 3100 modem connected directly to:

a) A linux laptop
b) a winXP-SP2 desktop

Trying each in turn, both had the same problem....

"connection timed out" when trying to FTP to the remote server. After about 30 minutes the laptop was able to reconnect, after 30 minutes the desktop was still unable to reconnect.

Both were still able to FTP to upload.ntlworld.com.

During this period the server was running fine (I accessed it from another office using VNC to run a FTP client from a PC at the other office).

Rebooting both the cable modem and the client did not make the problem go away.

Please can someone come up with some ideas.....

The only conclusion I can reach is that for some reason after some 2 years of perfect service, the NTL network has been changed or is casuing these problems.

Anybody ?

Re: [Merged] FTP uploads intermittently fail
 

I have just tried throttling the upload bandwidth.

Whilst uploading to upload.ntlworld.com ping times went from:

21/151/315 (no throttling) to 20/40/82 (with throttling)

I'm now going to try uploading to see if that has helped....