Apple Network Setup manual Legacy Synchronization Algorithm

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About Network Setup

Given that legacy synchronization is slow and that legacy preferences files do not support multihoming, future system software will not support legacy synchronization.

Legacy Synchronization Algorithm

Network Setup synchronizes the database and the legacy preferences files at the following times:

■When the database is opened. Network Setup checks the modification dates of each legacy preferences file against modification dates stored in the database. If the dates are different, Network Setup assumes that some application has changed one or more legacy preferences files and imports preferences from the modified files.

■When changes are committed to the database. Network Setup determines whether the committed changes affect a legacy preferences file. If they do, Network Setup exports the database to the legacy preferences file and records the modification date of the legacy preferences file in the database.

The legacy import mechanism makes good use of the structure of the legacy preferences files. Most preferences files are resource files having the following attributes:

■A resource having a well known resource type ('cnam').

■All resources with a resource ID of a 'cnam' resource belong to that configuration. The contents of these resources are the preferences for that configuration.

■There is one fixed resource whose type is 'ccfg' and whose ID is 1 that contains the resource ID of the active configuration.

■Any resources with IDs other than those used for configurations are global preferences.

When importing a legacy preferences file, Network Setup creates an entity for each 'cnam' resource and, for each resource with the same ID as the 'cnam' resource, creates a preference in the entity whose preference type is the resource ID and whose data is the resource data. If the 'ccfg' resource indicates that the configuration is active, Network Setup places the entity in the active set.

The legacy export process is similar to the legacy import mechanism. For each network connection entity of a particular type, Network Setup creates a 'cnam' resource with a unique ID in the legacy file. Then, for each preference in the

22Legacy Issues