Time Source Server Functions

The Single Reference, Primary, and Reference time servers are all time source servers. That is, they provide time to the network. Secondary servers do not provide a time to other servers; they only receive a time from a time source server. (They do, however, provide time to client workstations.)

Time source servers use one of two methods to find each other: SAP or custom configuration.

SAP (Service Advertising Protocol)

By default, Primary, Reference, and Single Reference time servers use SAP to announce their presence on the network.

Primary and Reference time servers use the SAP information to determine which other servers to poll in order to determine the network time.

Secondary time servers use the SAP information to choose a time server to follow.

An advantage of the SAP method is that it allows for quick installation without regard to the network layout. It also allows automatic reconfiguration if operating modes are changed or if new servers are added to the network.




	CAUTION: The SAP method might generate additional network traffic. The SAP method might also be disruptive in large network environments where "test" servers come and go, especially if the test server is configured as a time source (Single Reference, Reference, or Primary time server).

Custom Configuration

Custom configuration of your time servers might give you more control over time synchronization, but it requires more planning to synchronize servers efficiently.

An advantage of custom configuration is that you maintain complete control of the time synchronization environment.Also, custom configuration might help eliminate nonessential network SAP traffic, as well as errors associated with accidental reconfiguration.

To customize your time servers, you can use either System Administration Manager (SAM) or the nwcm command line utility to set the following parameters:

Time Sources. Lists the specific time source servers that a server should contact.
Configured Sources. Specifies that a server should not listen for SAP information from other time source servers.
Service Advertising. Disables time source SAP information from being broadcast to the network.
Directory Tree Mode. Indicates the server should ignore time sources advertising via SAP if the advertising does not originate on the server's Directory tree. This parameter has no effect if the Configured Sources parameter is turned on.

For detailed information on setting these parameters with SAM, see "Managing Network Time Synchronization" in Supervising the Network. For information on nwcm, see "nwcm" in Utilities Reference.




	CAUTION: The custom configuration does require additional time for planning and configuration. It also makes it more difficult to install or remove Primary, Reference, or Single Reference time servers on the network. You must manually change the approved server list maintained on servers that depended on a removed server.

Time Source Server Functions

Technical documentation

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SAP (Service Advertising Protocol)

Custom Configuration