BranchCache extends some of the improvements made in Windows Server 2003 R2 and Windows Server 2008 by caching downloaded information from the Web and intranet sites within a branch office the first time it is requested. This is, of course, most effective when users at a remote location frequently download similar information among themselves. Since branch offices often operate on lower-speed Internet links, user productivity is improved as the day goes on since more and more files are present within the cache.

A costly upgrade to Windows 7 is required for clients to take advantage of WAN caching technology, but the good news is that a few seconds at the command line and a couple of GPOs later, you have increased the efficiency of your remote links significantly.

Essentially, BranchCache works like a big file cabinet, storing a copy of retrieved content (identified and selected by an administrator, of course) within the local branch office network. When other clients on the same network request this content, the client does a quick check to make sure its local, cached copy is equivalent to the live copy at the head office, and, if so, serves up that copy to its client colleague over the faster LAN.

Content can be web-based (HTTP) or typical files and folders (SMB), can be configured to work over SSL or IPSec-encrypted connections, and all security is maintained through an authorization process controlled by the host servers, not the "mini servers" holding the cache in the remote office.

In a demo, a document was downloaded over a 512 KB connection, taking about 30 to 45 seconds. After the cache, when another user in the same site requested that information, the transfer was nearly instantaneous. BranchCache works not only with a branch office server but also on a peer-to-peer basis among Windows 7 clients in the same location.