Branch caching works at the server level by creating a cache of all HTTP and SMB traffic requested by users in the branch office. This allows those users to receive faster access to files that reside on a server in the corporate office by making them locally available. The benefit is seen directly by the user because access times for files are reduced.
When files are requested, a hash value for branch cache is sent to the client from the remote location. The client can then search the LAN to find computers that contain the content requested. The requesting client will download pieces of the content and compare their value to the hash value received with the original request. If the values match, the content segments are downloaded from other PCs on the LAN. If the hash doesn’t match at any point, the download is canceled and the request is sent to the server in the original location to download the file.
If an intranet document is requested, such as http://intranet/file.pdf, the server hosting the file would send back a hash for branch caching as described above. This allows the file to be used from the local network where available, limiting the amount of bandwidth used to retrieve the file from another location.
These cached files are potentially updated every time they are requested; if a match to the original documents hash isn’t found, the original document will be downloaded along with its branch caching information. That way when another client requests the same file, the hash received will match the file downloaded earlier and allow client #2 to receive the download from the LAN.
Implementing branch cache should alleviate some of the WAN administration of shares and files needed by workers in remote offices. Allowing the server to create a cache of the documents requested will aid administrators by reducing calls to the help desk regarding the availability of documents stored within the network infrastructure and decreasing the time that can be required to access them.
Because there is no forced cache where the administrator or IT staff would need to initiate or schedule files to be sent to remote offices, the amount of IT resources needed after the initial setup of branch caching would be minimal — saving time and resources for the organization.
This feature will be available in both Windows Server 2008 R2 and Windows 7.
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