IBM developerWorks provides three download methods: FTP, HTTP, and for large files, Download Director. In most cases, FTP is more reliable than HTTP and can reduce download time. The newest browsers provide time estimates and transfer rates for FTP downloads. In some cases, browsers can also resume an interrupted FTP download. To take advantage of these conveniences, try FTP download before using HTTP.
If you have problems downloading through a firewall using FTP, try using HTTP. Although HTTP isn't as reliable as FTP for large downloads, Internet Explorer 5.01 or later can sometimes recover an interrupted HTTP download. HTTP downloads can penetrate a firewall because they use port 80 to make data transfers. The following download behaviors and errors may indicate a firewall problem:
- The download suddenly stops near the end without completing.
- The download stops at the same point each time.
- An error 400 indicates that the proxy load failed.
- A message indicates that the file type was not found.
- A message indicates that the page has been moved.
For large downloads, Download Director offers pause and resume capability, high-speed transfer, file access through a firewall, and more. Download Director does require a Java-enabled browser, but it provides advanced features not available with other download tools. For more information, see the Download Director FAQs.