[MS-ASCMD]: ActiveSync Command Reference Protocol Specification

In order to synchronize the content of each of the folders, an initial synchronization key for each
folder MUST be obtained from the server. The client obtains the key by sending the server an initial
Sync request (section 2.2.2.19.1) with a airsync:SyncKey element (section 2.2.3.156.4) value of
zero (0) and the airsync:CollectionId element (section 2.2.3.29.5) value that identifies the folder
to be synchronized. The Sync command response (section 2.2.2.19.2) includes a new
airsync:SyncKey value, which is generated by the server for each transaction.
Figure 5: Retrieval of SyncKey value
The airsync:SyncKey issued in the initial Sync response MUST be stored by the client, and is sent
in the second Sync request. The second Sync request includes the new airsync:SyncKey element
as well as the airsync:GetChanges (section 2.2.3.72) element.
Figure 6: Retrieval of folder content
The server responds by adding all the items in the collection to the client and returning a new
airsync:SyncKey element value, which can be used in successive synchronizations. The client
deletes its copy of all objects in the collection that are being synchronized before the client performs
a full synchronization. The client can use the GetItemEstimate command (section 2.2.2.7) to
obtain an estimate of the number of items that have to be synchronized before completely
synchronizing a collection, which is useful when the client user interface displays a progress bar
while getting items from the server. In some cases, the client could have to submit a
[MS-ASCMD] — v20110315
ActiveSync Command Reference Protocol Specification
Copyright © 2011 Microsoft Corporation.
Release: Tuesday, March 15, 2011
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