Strange broadband problem: email fine but web pages are slow and have no pictures

Discussion in 'Broadband' started by Martin Underwood, Dec 4, 2006.

  1. I've been investigating a very weird broadband problem for a customer.
    Anyone any ideas what could have gone wrong?

    The customer has an XP Home SP2 PC, connected by Speedtouch 330 modem to
    Tiscali at 2 Mbps. He can connect 100% reliably and can send/receive email.
    But most web pages are taking several minutes to display (with a blank white
    screen until they have loaded), and when they do load, any JPG images are
    missing and replaced by placeholder rectangles. Some sites such as display partially (eg just the BBC News maroon banner) and
    then complete the loading (without pictures) a few minutes later.

    I've turned off Windows Firewall and Norton Anti-Virus. I've installed Opera
    to eliminate problems with Internet Explorer. Apart from displaying the text
    of pages (but not the photos) instantaneously, the symptom is the same with

    Doing a "View Source" during the "white screen" time, the HTML is truncated
    as if it hasn't completely transferred.

    I tried using the DOS-mode ftp to upload a variety of files (doc, pub, jpg -
    a few hundred KB) to my web server and then to download them again. All
    files go up OK and all except JPG transfer back down OK; the JPG only
    transfers about 1KB and then stops transferring without any error message.

    I can ping the sites OK. I can do a "telnet 80" and get a
    response, suggesting that port 80 traffic isn't being blocked.

    I've tested the PC on my DSL line, both using the customer's modem and my
    router, and everything works perfectly.

    I've tested my router on his line and the symptoms are as described above.

    So it looks as if the PC and its modem are working fine, and it's the line
    which is taking a long time to download HTML and is blocking JPG. Could
    Tiscali have applied some sort of traffic filtering or throttling?

    Tiscali got me to try a few simple tests like turning firewall and AV off,
    and configuring stating DNS server addresses instead of getting them from
    DHCP, and then decided that because the PC can connect to broadband and can
    access POP/SMTP, it must be a PC problem - even though I said that the PC
    works fine when connected to a different DSL line.

    Apparently it's never worked on this phone line. They had to get a new
    dedicated phone line installed a couple of months ago after the previous
    one, which is also the voice line, and which had worked perfectly up to that
    point, suddenly lost its DSL carrier one day and could not be made to work
    again. A neighbour's DSL line also failed at the same time. All that's past
    history, long before I became involved.

    Anyone got any ideas? The customer is anxious to avoid getting embroiled in
    a buck-passing demarcation dispute between Tiscali and BT.
    Martin Underwood, Dec 4, 2006
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  2. Martin Underwood

    Maneate Guest

    FWIW I suspect something on the PC/Browser, although I would not
    entirely discount gremlins in the network playing SB's.

    Any chance you can try another PC/Laptop that you know is OK on the circuit?

    At the very least this would prove/disprove the PC/Browser theory.


    Maneate, Dec 4, 2006
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  3. Martin Underwood

    Beck Guest

    Have you done a spyware check? Could be some nasties slowing him down.
    Spybot Search and Destroy is a good program for weeding out spyware.
    Beck, Dec 4, 2006
  4. Maneate wrote in message
    Even though both IE and Opera work fine on my network but fail on the

    I'd forgotten one other symptom: when I installed AdAware to check for
    spyware, it wouldn't update itself with the latest definitions on the
    customer's DSL line (it identified the presence of an update but then gave a
    "can't connect to server" error), whereas as soon as I connected it onto my
    DSL line, it worked fine. I'm not sure what protocol AdAware uses to get its
    If my laptop hadn't packed in (suspected IDE controller fault), I'd have
    tried it connected to my router on his line.
    Martin Underwood, Dec 4, 2006
  5. Beck wrote in message
    Yes, I've scanned with AdAware. Only things found were a few tracking
    cookies. Haven't checked with any other spyware programmes. There is the
    possibility that there may be a virus because the Norton expired about a
    month ago. A virus scan using the existing definitions didn't find any
    problems. The customer wanst to wait until he's got a working intenret
    connection before updating to NIS 2007 (which will need internet to get the
    latets updates).

    However if there's virus or spyware, why does it only affect his DSL
    connection and not mine?
    Martin Underwood, Dec 4, 2006
  6. Martin Underwood

    Beck Guest

    Sorry I missed the bit where you checked his PC on your line. If his PC is
    okay on your line then its a Tiscali issue.
    Beck, Dec 4, 2006
  7. Martin Underwood

    Colin Wilson Guest

    I've tested the PC on my DSL line, both using the customer's modem and my
    That pretty much rules out the computer being at fault then - could it
    be caused by congestion ?

    Does it ever improve ? (i.e. at funny times in the middle of the night
    Colin Wilson, Dec 4, 2006
  8. Martin Underwood

    Simon Guest

    This does suggest a software problem as it is hard to imagine only jpeg and
    html being affected by a problem with the line/ISP. Can you try a bigger
    range of file types? Maybe some plain text, binaries, video, different
    picture formats and see if anything else fails (I know you've tested a few,
    it would be useful to try and find another file type that fails). They may
    have something in common. Try downloading via different protocols
    -ftp/http/nntp. Are pictures still blocked over an encryted connection such
    as SSL (try hhtps or stunnel). Is it just jpeg over hhtp not jpeg over ftp?
    I was thinking there was something different about your setup that could
    allow the machine to work on your line but not the customers. The router
    would be the obvious thing, if it was blocking a virus/trojan, etc. Did you
    set it up exactly the same? Any other networking differences between the
    two setups?
    The only thing that I can see that is different is the ISP. You're posting
    from Plusnet. I think they block some ports that are commonly used by
    viruses (135, 139, 445 maybe among them, it's a while since I left
    Plusnet). If there is a virus/trojan or other malware it may only affect
    the computer if it gets internet access which could be blocked by the ISP.

    You could try a different firewall or try blocking everything except port
    80 on your router.
    It's hard to see how the line could affect only two data types unless
    Tiscali had screwed their traffic shaping set-up but I'd expect more
    complaints if they had. I think I'm starting to repeat myself so I'll stop.
    Hope I've suggested something useful.
    Simon, Dec 4, 2006
  9. Simon wrote in message
    If I get access to the PC again (if the customer calls me back) I'll give it
    a try.
    Same router, same Ethernet cable, same DSL lead, same microfilter. Identical
    router config apart from the username+password. Tried using my DSL lead and
    microfilter on customer's account to eliminate any fault there.

    Hmmm. Sounds plausible.
    Martin Underwood, Dec 4, 2006
  10. Martin Underwood

    Flyer Guest

    I had something similar a few weeks ago, some sites were loading ok, others
    wouldn't, turned out to be a dns issue, after changing dns servers,
    everything has been fine since.. Might not be relevant in this case, but
    worth a shot nonetheless ;-)

    Flyer, Dec 5, 2006
  11. Martin Underwood

    Tony Guest

    All this makes me wonder about errors on the line. The Tweak Tester at
    <> gives results that include
    retransmits - that could help to analyse end-to-end errors.
    Tony, Dec 5, 2006
  12. Have you set the IE security settings too high? You could be tripping over
    your own fences. Take the security right down and try again but do remember
    to increase the security again after testing. I appreciate this is very
    basic but it's worth mentioning just in case you've overlooked the obvious.


    Bill Ridgeway
    Computer Solutions
    Bill Ridgeway, Dec 5, 2006
  13. Tony wrote in message
    Thank you! You've just reminded me of a setting on the modem that I noted
    down but I'd forgotten about till now.

    This is a Thomson Speedtouch 330. On the ATM tabsheet of the diagnostics,
    there is a section "Cellcount" with a field "Invalid". And that has a large
    value. Does this suggest that some packets are being received corrupted and
    having to be re-transmitted? Could some packets be being lost altogether?

    I've found a diagnostic guide for the 330 and for the "Invalid" field it
    says "Indicates the number of ATM cells that are dropped because they do not
    belong to the current information flow or are incorrect." Does this suggest
    a modem fault or a line fault?
    Martin Underwood, Dec 5, 2006
  14. Martin Underwood

    Tony Guest

    What really matters is the ratio of invalid or uncorrected ATM cells to
    received ATM cells. My previous 1Mbit/s service happily worked with a
    ratio as bad as 1 in 100.
    I assume that corrupted ATM cells result in corrupted IP packets, and
    that TCP retransmits take care of them if the error rate isn't too high.
    If the error rate is too high, then I believe that TCP/IP starts to
    break down such that IP packets are indeed lost or corrupted - there
    must be some info on the Internet that shows when this starts to happen.
    Well, from that alone, I guess it could be either. However, you said
    earlier that you had tested your own router on his line, so that tends
    to rule out a modem fault. So on this evidence I bias to a line fault.
    However, I can't explain your other observations that only certain
    file-types or protocols are affected.

    Remember that your customer's Internet service contract is with his ISP,
    Tiscali. Given all your tests (especially those that tend to rule out
    the modem or PC), Tiscali ought to accept that the service is faulty.
    It's then up to them to differentiate between a fault in their own kit
    and in BT's.

    Good luck!
    Tony, Dec 5, 2006
  15. Tony wrote in message
    I agree. However judging from the highly unsatisfactory phone call that I
    had with one of their technical support people yesterday on the customer's
    behalf, I thing they are trying to wash their hands of the problem.

    Does anyone have any experience of escalating problems with Tiscali, when
    their technical support people deny that it is their problem, despite
    evidence which suggests that the problem is with the line rather than with
    the PC or modem (because both worked on my line)?
    Martin Underwood, Dec 5, 2006
  16. Martin Underwood

    Tony Guest

    Try a formal complaint?

    "you can email our dedicated Complaint Management Team
    complaints @ uk. tiscali. com"
    Tony, Dec 5, 2006
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