I was checking with a fellow sysadmin and debating whether it was better to bundle a large install, say Adobe CS5, into a single self extracting installer or leave it as a bunch of smaller files when distributing with SCCM.

My argument for bundling it into a single binary was to reduce file transfer overhead for each file where as he pointed out that a large file can be interrupted and will have to restart the entire download.

The question here becomes does SCCM handle partial downloads with BITS so that they can be interrupted or does it need to start at the beginning and does it transfer files as individual files or does it just transfer a bit stream transparently?


From Frequently Asked Questions for Software Distribution

What happens when the connection with the distribution point is unexpectedly broken? Can the client resume the download in the middle of a file?

Yes, interrupted client downloads from BITS-enabled distribution points resume at the point at which they stopped transferring, even if the client connects to a different distribution point.

Does the client use BITS or SMB by default?

It depends. If the advertisement has been set to run the program from the network, the client always uses server message block (SMB). If the advertisement has been configured to download and run locally and if the distribution point has been configured to use BITS, the client tries to use BITS but might fail over to SMB if the content cannot be accessed over BITS.

How can I tell if my Advanced Client is using BITS or SMB?

Look at the DataTransferService.log on the client. BITS downloads have a URL that starts with http://<distributionpoint>, and SMB downloads have a URL that starts with \\<distributionpoint>. For details about the BITS download, you can run bitsadmin /list /allusers /verbose | more from the command line. If the client used SMB, you can also get details in the FileBits.log on the client.


I would recommend bundling into a self-extracting installer. I suppose it would reduce file transfer overhead, but there is a bigger issue with leaving it as smaller files.

The issue is that by default, IIS on Server 2008/2008 R2 blocks downloads of files with particular extensions for security reasons. If you create a package which contains, for example, an .mdb file, and you don't explicitly disable the requestFiltering rule in your applicationHost.config file for that particular file type, your clients won't be able to download the package, and you'll spend hours trying to debug the issue.

Of course, you can go in and disable all the content filtering rules, but that increases the attack surface of your IIS server.

Here's the relevant TechNet article: http://technet.microsoft.com/en-us/library/cc431377.aspx#Config_RequestFiltering

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