Posted by: kurtsh | July 14, 2006

INFO: Shared Folders… a really cool “technology” in Windows Live Messenger

Windows Live Messenger V8 ships with Shared Folders.  (Get it from
What does it do?
Shared Folders allows you to create a group of Windows Live Messenger users and collectively share a group of files.  These files are replicated to each person’s PCs enabling people to share a "virtual file share" over the Internet using Microsoft’s Peer-to-Peer (P2P) technology. 
How does it work?
Shared folders supports a replication model between 2 messenger clients – however there can be more than 2 people using a shared folder… it just means that the replication will need to take place again for each additional person sharing the folder.  This can be from ANY Messenger user’s machine that has the current files available to replicate.  
The underlying replicator technology is File Replication Services v2, which was implemented by the Windows Server R2 team, and repackaged by the Messenger team.  This is an advanced replication technology usually not found on desktops that enables byte-level differencing between sharing workstations:  In other words, if there is a 5MB Word document being shared amongst several individuals, if one person edits the large 5MB Word document, only the "changed bytes" will be transmitted to the other partners to update them, instead of sending each of them the entire 5MB file all over again.
Before you ask, NO it does not "swarm" to leverage multipoint transfers in the same way that BitTorrent does – you will see that in other technologies.  Using multipoint file transfer technology doesn’t make sense in this model because the goal of the technology is to allow people to not only continually share files but also to constantly make changes to those files.  Databases, pictures, Excel spreadsheets, etc.
Either client can contribute/modify to the shared folder.  You can put folders and large files into the shared folder.  It supports an invite model for establishing a secure sharing relationship so not just any uninvited Tom Dick or Harry can access your personal information.
When and if possible, the bit transfers will go P2P.  We recommend that people get uPNP capable routers at home.  They work great (VOIP, P2P file transfers, my slingbox for watching US TiVo from the road, etc.).
We will continue to develop and enhance shared folders so stay tuned for extensions of this technology to group/circle sharing and self-sharing.


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