BranchCache is a new feature in Windows Server 2008
R2 and Windows 7 that is designed to optimize wide area network (WAN)
bandwidth usage by branch offices. To accomplish this, BranchCache
copies content from central office content servers and caches the
content at the branch office. Once cached, clients no longer have to
traverse a WAN connection to access content. Instead, the content is
accessed directly from within the branch office from caches on other
peer Windows 7 machines or servers running the BranchCache feature of
Windows Server 2008 R2. Therefore, BranchCache helps improve content
access times by branch office servers and clients while also reducing
the amount of traffic on a WAN link.
Note
BranchCache is only supported on Windows Server 2008 R2 and Windows 7.
Important BranchCache Concepts
When working with BranchCache, the following important concepts should be taken into consideration:
There are two
modes of operation in BranchCache: Distributed Cache mode and Hosted
Cache mode. If cached content is only being distributed using client
computers, this is called Distributed Cache mode. Hosted Cache mode,
however, is when the content cache is being hosted by a server that is
located within the branch office.
BranchCache supports the optimization of file access as well as downloads over HTTPS and IPSec.
BranchCache
protects content that is cached by encrypting it. Content can then only
be accessed by using identities, which are provided by the originating
server to authenticated clients that are members of the same domain as
the content server.
Distributed Cache Mode
Distributed Cache mode is a
peer-to-peer caching scheme that is used to cache intranet website
(communicating over HTTP or HTTPS) or file server (communicating over
the standard SMB protocol) content within a branch office without the
need of a local hosted cache server.
Server-Side Configuration
By default, BranchCache is not enabled. To enable it on a Web server or a file server, the following steps need to be performed:
1. | Web (IIS) Server— You would need to enable the BranchCache feature using Server Manager.
|
2. | File Server (SMB)—
You would need to enable the BranchCache for Remote Files role service,
which is part of the File Services role using Server Manager.
|
Additionally, for file servers, the following things need to be completed:
1. | Configure the Hash Publication for BranchCache GPO setting (Computer Configuration\Policies\Administrative Templates\Network\Lanman Server). Set this to: Allow Hash Publication Only for Shared Folders on Which BranchCache Is Enabled.
|
2. | Specify the HashStorageLimitPercent Registry value (HKLM\CurrentControlSet\Service\LanmanServer\Parameters). This is the maximum percentage of physical disk space used to store the publication hashes.
|
3. | Lastly,
tag your file shares by enabling BranchCache support for them. On the
Caching tab, select Only the Files and Programs That Users Specify Are
Available Offline. Then select Enable BranchCache, as shown in Figure 1.
|
