A synchronization structure that indicates changes to files that are to be synchronized is created. The synchronization structure is stored as a series of synchronization blocks. A first synchronization message is received from a communication device. The first synchronization message includes a next block number. A second synchronization message is sent to the communication device. The second synchronization message comprises one or more synchronization blocks that are identified based on the next block number. A third synchronization message is received from the communication device. The third synchronization message requests a number of files to be synchronized. The number of files to be synchronized are sent to the communication device.