We're currently suffering from a rather odd problem that appears to be our ADSL line...
The ADSL connection is being used to host web services (HTTPS/443). When connecting externally, small data transfers seem to work fine, however larger data transfers hang.
* Accessing Outlook Webmail, the browsing of folders and messages works fine, however as soon an attachment is attempted to be downloaded, the transfer hangs.
* Windows server (IIS) file web sharing - the directory tree can be browsed, however attempting to download a file from the system causes the transfer to hang.
Naturally, we suspected IIS, however we also have a SVN server running on Apache (different port, not a standard HTTP/HTTPS port number but still using SSL). Again, browsing the repository works fine however attempting to download a file causes the transfer to hang.
To narrow down the fault, we installed a brand new instance of Apache onto a clean laptop. Connected this laptop directly to the ADSL modem, bypassing all firewalls and network switches. Again, the access of a basic Apache page works (the "It Works!" default page), however we placed a file into the appropriate directory and attempted to download it and, again, the transfer hangs.
We replaced the ADSL modem with another (entirely different make/model) and repeated the basic test with just the laptop running Apache and, again, the transfer hung as soon as we attempted to download a file.
We have contacted our ISP (BT), and they performed a line check and everything is apparently fine.
Any ideas what the problem is likely to be and/or how we can further diagnose this problem?