Topic Last Modified: 2006-06-12
WebDAV replication enables clients to synchronize data from a computer running Microsoft® Exchange Server 2007 and is the client-initiated process of:
Fetching the list of changes for a
Downloading a changed
resource from the server.
Uploading the changed
resource to the server.
WebDAV replication allows clients to work with up-to-date information directly from the server and to cache information locally so that the client can access the data if the connection to the server is lost. In addition, this mode of operation is more efficient with respect to network bandwidth because data will only have to be transmitted from the client to the server, or vice-versa, if it's different.
Every replicated resource has a resourcetag associated with it, a token generated by the server that reflects the current state of that particular resource. Every time a resource's properties or contents change, the resourcetag associated with that particular resource is updated.
The basic operation of individual collection or collection hierarchy replication is similar to that of a normal PROPFIND Method request or SEARCH Method request. The client issues a PROPFIND Method request or SEARCH Method request and includes an additional XML element tree that requests the replication semantics. The request XML body contains the client's current collblob, an opaque binary stream generated by the server that represents the current state of the client's data. In the PROPFIND Method response or SEARCH Method response, the server returns only items that the client does not have the current version of, besides information about how those items have changed.
The client then proceeds to upload changes to the server. If the client chooses to include the resourcetag of the uploaded resource in the request, the server can perform conflict detection and resolution on those changes.
The client then proceeds to download items from the server that were returned in the initial request. Again, the client optionally includes the resourcetag of the downloaded resource, and the server ensures consistency.
At any time during the entire process, the client can indicate to the server what it has successfully downloaded or uploaded and request an updated collblob.
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