9.3 Time Synchronization

Time synchronization is critical to maintaining the integrity of the tree.

9.3.1 About Time Synchronization in OES 2

In earlier versions of eDirectory, replica synchronization required proper time synchronization. Currently, replica synchronization uses time stamps from host servers without checking for proper time synchronization. This means that if the host servers are not time-synchronized, events can be logged out of sequence, resulting in inconsistent information about what took place and in what order.

What NTP Provides

All servers with Internet access can get time from NTP servers on the Internet. NTP synchronizes clocks to the Universal Time Coordinated (UTC) standard, which is the international time standard. The hierarchy that indicates where each server is getting its time is referred to as a stratum, with the first time provider designated as stratum 1.

A server that gets its time from a stratum 1 server is stratum 2, and so on.

The TIMESYNC NLM™ can consume and provide NTP time, but it always functions as stratum 5.

Use a Reliable, External Time Source

By default, NTP uses the server’s internal clock as its time provider, but it can be configured to use other time providers via the /etc/ntp.conf file.

NTP time can be supplied from several sources:

  • Public Time Server. For small organizations (fewer than 100 servers), synchronizing servers to accurate public NTP servers provides sufficient time synchronization. To reduce traffic, it's best to have one or two servers synchronize with a public NTP source and have those servers provide time for the remaining servers. See http://ntp.isc.org/bin/view/Servers/WebHome.

    Reference Clock. Reference clocks are devices that synchronize via a variety of technologies including long wave radio signals, GPS transmissions, or CDMA technology. These can be expensive.

    Server's Local Clock. The server's internal clock can be used as a time source, but because time can wander, this is generally not a preferred solution.

    Network NTP Time Source. This is the recommended option for larger networks. In this case, you need to set up a server as an NTP time provider and then add the IP address of the time source to the /etc/ntp.conf file for servers that will use the designated server as the time provider.

9.3.2 Planning to Upgrade Time Synchronization Services

Both the OES and the NetWare installs automate the time synchronization process where possible. For complete information about planning and implementing a time synchronization strategy and setting up time providers and consumers, see Time Services, particularly Implementing Time Synchronization in the OES 2 SP3: Planning and Implementation Guide.

Also consider the following points.

  • Designate the most reliable server in the subnet as the time provider.

  • Configure at least two time providers to set fault tolerance.

  • Configure time consumers to contact a time provider within its own local network (so they don't contact time providers across costly WANs).

  • Generally, only one server in a network should communicate with an external time provider. This reduces network traffic across geographical locations and minimizes traffic across routers and WANs.

NOTE:The time synchronization modules in Novell Open Enterprise Server (OES) have been designed to ensure that new OES 2 servers can be introduced into an existing network environment without disrupting any of the products and services that are in place.

9.3.3 Transferring Time Synchronization Services

You can use either of the two migration types offered by the Migration Tool to transfer time synchronization services from NetWare to OES 2:

To transfer time synchronization services from NetWare to OES 2, follow the instructions in Migrating Timesync/NTP from NetWare to NTP on OES 2 Linux in the OES 2 SP3: Migration Tool Administration Guide.