During a recent discussion on Windows 7 there were some solid questions asked about DirectAccess and BranchCache which I did not have the answer to. So after some research here they are!


Question: What ports are used from the client to the DirectAccess Infrastructure?

Answer: (Reference from: http://en.wikipedia.org/wiki/DirectAccess)

“DirectAccess uses IPv6 to reach intranet resources. A DirectAccess client and server can use IPV6 native, 6to4, Teredo tunneling, or IP-HTTPS to send IPv6 traffic across the IPv4 Internet.

The IP-HTTPS protocol is an SSL tunnel on TCP port 443 that connects a DirectAccess client to a DirectAccess server on the edge of a target network. IPv6 subnets provisioned by the server network are tunneled over IPv4 or IPv6 to the client: IPv4 access is not provisioned with this connection.”

For additional information on protocol and port requirements see http://technet.microsoft.com/en-us/library/dd637780(WS.10).aspx.


Question: What happens when a file which has been downloaded to a branch office is in BranchCache and the content of the file is changed? Is the full file replicated across the network link or only the deltas which occurred to the file?

Answer: (This topic was discussed on: http://social.technet.microsoft.com/Forums/en/windowsserver2008r2branchoffice/thread/7da4c4bf-d6df-4410-b640-74f1188b7f58)

“BranchCache performs differential transfer of file that was changed *as long as the tail of the file is what got modified*. Changes in the ‘middle’ or ‘beginning’ of a file will lead to the file being copied in its entirety. In addition, files that are smaller than a single segment (i.e. 32 MB), any change (even at the tail of the file) will result into a different segment hash and hence BranchCache will not discover that segment in the branch, thereby triggering a complete transfer.”

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