Alberto Ortega’s Blog

I am preparing a couple of Screencast for TechNET LATAM as part of a huge initiative of 49 Screencasts that will be launched the next month. So, I took the time to dive into some new cool Windows 7 features, this time I will share my experience with Branch Cache.

Branch Cache is a cool new feature on Windows 7 and Windows Server 2008 R2, and is now available so early adopters can take advantage of this feature right from the RC build of Windos 7 (Build 7100). The goal is to cache on branch offices workstations content downloaded from the main office to optimize the WAN link load of the branch office were it is not common to rely on high-speed links.

Highlights

• Were straight forward to deploy via GPO.
• Supported protocols are HTTP, HTTPs, streaming and SMB (Web and File server role on Windows 2008 can be configured).
• It is aimed to Intranet traffic only, for example: Documents on a file server, training videos, images in an intranet site.Works with Robocopy and standard copy, it is pretty firewall.

Branch cache supports 2 scenarios for distributed or centralized cache according to the branch office size and networks topology.

• Distributed scenario
  • The branch client access the main office to download the content, first it gets the ID of the content (which is a hash of the content itself), then it leverages WS-Discovery to broadcast a query to every other client in the branch to see if someone else has downloaded the content, if not, the 1st download begins
  • The 2nd client who needs this data from the main office will get again the hash (if the content has changed this hash will be different - in this case lets suppose it has not changed), so, with the has it uses again WS-discovery and finds that another client has already downloaded the content so the content will travel only though the branch office this time.
    
    Pasted from <http://technet.microsoft.com/en-us/library/dd755969(WS.10).aspx>

• Hosted scenario (Centralized cache)
  • Is quite the same with the difference that a dedicated branch cache server exists and every client instead of using WS-Discovery will directly search on this branch cache server, if the hash is not found the content is downloaded from the main office.
  • Then the client advertises the content to the branch cache server, so the server can get the content that might be polled from a 2nd client.
    Pasted from <http://technet.microsoft.com/en-us/library/dd755969(WS.10).aspx>

Distributed cache mode is aimed to less than 50 workstation branch offices as it has can only retrieve cached content from a single subnet. Also take into consideration that hibernated or sleeped laptops cannot server cached content to other clients.

Want to go deeper, check the following links:

Resources:

• Devrim Iyigun giving an executive overview of Branch Cache: http://edge.technet.com/Media/Branch-Cache-in-Windows-7/
• Branch Cache Technical Overview: http://technet.microsoft.com/en-us/library/dd755969(WS.10).aspx
• Branch Cache Early Adopters Guide: http://technet.microsoft.com/en-us/library/dd637762.aspx
• Server Configuration: http://technet.microsoft.com/en-us/library/dd637785(WS.10).aspx
• Client configuration: http://technet.microsoft.com/en-us/library/dd637820(WS.10).aspx