Networking

Use branch caching to ease network traffic woes between offices

Administering and managing access for remote offices gets a bit easier in Windows Server 2008 R2 and Windows 7. Branch caching can ease the bandwidth used by remote offices to access files while still allowing local authentication to the domain.

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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About

Derek Schauland has been tinkering with Windows systems since 1997. He has supported Windows NT 4, worked phone support for an ISP, and is currently the IT Manager for a manufacturing company in Wisconsin.

8 comments
Derek Schauland
Derek Schauland

Is this a feature that might lessen bandwidth usage in your environment?

andygravett
andygravett

DNS cache poisoning primarily affected external DNS servers that provided recursive look-up's, this technology is designed for internal WAN connected sites and appears to use hashing to compare already downloaded copies of files against centrally stored data for changes, much like the Citrix Branch Repeater and WANScaler systems.

andygravett
andygravett

Hi Derek, Great article, having deployed quite a few WAN optimisation solutions for clients recently, I can testify that SMB / CIFS / AD replication is a killer for low speed WAN links, though if you are serious about doing this you need to run tests over a period of a working week analysing all traffic that is using the link it may come as a shock. I am not going to product pitch but we worked closely with Microsoft on this Branch Repeater technology having been a global partner for 20 years. Regards Andy Gravett

ben@channells
ben@channells

Active Directory repliaction and Global Address some time never make it over low bandwith comm's or 3rd world countries like India or Africa with very poor telecomunications infrastructure. Next time the US or UK army go overseas and pick up there email and orders and not rely on Hotmail to send sensitive data :-)

randy_scadden
randy_scadden

It wouldn't help in my current environment but would help considerably in my previous environment. In that environment we had 9 remote locations that where on an integrated MPLS network. Each remote location had their own domain controller at each of the local sites that acted as a local file, print, wins, dns and DHCP server. We use to take and replicate using DFS and well it would just eat up a ton of bandwidth to do that. It sounds like with this technology it wouldn't necessarily eliminate DFS but it would alleviate bandwidth issues if we had people that requested a file that wasn't on the DFS share. I'm curious to see how this technology plays out.

Derek Schauland
Derek Schauland

Thanks for the feedback Andy (and others). I am waiting for a bit of feedback about possible cache poisoning, however I tend to agree with your comment about recusive DNS being partly to blame for that issue and because the caching happens at client request I am thinking that this will prevent the issue. Especially since the client needing a file checks peers in remote location before pulling a copy to cache from file server...

Derek Schauland
Derek Schauland

Hotmail for sensitive data? I had no idea... Because the caching happens when docs requested I would imagine the replication is not too bad. Doesn't wait until AD rep happens

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