Hello everyone – my name is Vikram Ghosh, and I am Product Manager for Branch Office Solutions on the Windows Server Team. I am writing to you from, TechED EMEA here in Barcelona Spain, to describe one of my favorite new features in Windows Server 2008 R2, BranchCacheTM. (Yes, we’ve already got a trademark.) If you’re at all concerned with reducing WAN bandwidth costs keep reading, this post is for you.

Earlier during the keynote address here at TechED EMEA,  we demonstrated BranchCache using Windows Server 2008 R2 and the Windows 7 client OS. The response was wonderfully positive.  As the name suggests BranchCache helps IT administrators save on costs associated with WAN area network bandwidth by caching HTTP and SMB content at the branch office network. This not only saves on bandwidth costs, it also improves the branch end user’s experience when accessing content and shares back at corpnet. BranchCache also accelerates the delivery of encrypted content, supporting protocols like HTTPS and IPsec.

BranchCache achieves these results by locally caching frequently used content in one of two ways: Either on an existing server in the branch or among branch office clients, if no servers are present. The latter is commonly called distributed mode. To enable distributed mode, each Windows 7 client maintains a cache of the content it has retrieved, and then makes this content available to other clients when they send out requests. The content is only provided if the requestor was authorized by the server at the data center, however, so authentication and access security is maintained. As a result, this feature reduces WAN traffic, since cached data gets served locally with the additional side benefit of improving application responsiveness.

The content served to a request is always fresh, because when clients first issue an access request it always goes to the BranchCache server back at corpnet first. This serves not only authentication and access, but also lets the server send back content identifiers to the requester indicating if the file has been altered since the last time it was accessed. If those identifiers match content at the branch, then the content is served locally. If the content has changed and doesn’t match the local cache, then a new version is shipped from corpnet.  In distributed mode, these identifiers are sent out to other clients on the local branch network. If the branch has a server, also known as a hosted cache, then all cached data is stored there. We expect hosted cache to be the most popular deployment scenario for branch offices with over 10 people on-site because it reduces local network multicasts and improves cache availability. 

As mentioned previously, though BranchCache supports the HTTP and SMB protocols, it can also be used to improve response times for multimedia content–think Windows Media Player files,  Internet Explorer, or Background Intelligent Transfer service (BITS).

BranchCache builds on the bandwidth-conscious features we introduced in Windows Server 2008, including a new TCP/IP stack and SMB 2.0 (you can read more about what these feature offer here). Windows Server 2008 R2 continues our concentration on the remote experience with features including BranchCache, DirectAccess (which my colleague Oliver posted about below) and several others about which we’ll be posting in the near future.