10.3 Time Services
The information in this section can help you understand your time services options as you move from NetWare to OES:
10.3.1 Overview of Time Synchronization
All servers in an eDirectory tree must have their times synchronized to ensure that updates and changes to eDirectory objects occur in the proper order.
eDirectory gets its time from the server operating system of the OES server where it is installed. It is, therefore, critical that every server in the tree has the same time.
Understanding Time Synchronization Modules
During the upgrade to OES 24.4, your eDirectory tree might contain servers running different versions of OES, NetWare 6.5 SP8, and/or previous versions of NetWare. Therefore, you must understand the differences in the time synchronization modules that each operating system uses and how these modules can interact with each other.
OES vs. NetWare 6.5
As illustrated in Figure 10-1, NetWare 6.5 can use either the Network Time Protocol (NTP) or Timesync modules for time synchronization. Both modules can communicate with OES by using NTP on port 123. However, when installing virtualized NetWare, Timesync should always be used.
OES must use the NTP daemon (xntpd).
Figure 10-1 Time Synchronization for Linux and NetWare
OES Servers Use the Network Time Protocol (NTP) to Communicate
Because OES and NetWare servers must communicate with each other for time synchronization, and because OES uses only NTP for time synchronization, it follows that both OES and NetWare must communicate time synchronization information by using NTP time packets.
However, this does not limit your options on NetWare.
Figure 10-2 illustrates that OES and NetWare 6.5 servers can freely interchange time synchronization information because NetWare 6.5 includes the following:
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A TIMESYNC NLM that both consumes and provides NTP time packets in addition to Timesync packets.
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An XNTPD NLM that can provide Timesync packets in addition to offering standard NTP functionality.
NOTE:Although NetWare includes two time synchronization modules, only one can be loaded at a time.
Figure 10-2 NTP Packet Compatibilities with All OES Time Synchronization Modules
Compatibility with Earlier Versions of NetWare
Earlier versions of NetWare (version 4.2 through version 6.0) do not include an NTP time module. Their time synchronization options are, therefore, more limited.
NetWare 5.1 and 6.0 Servers
Figure 10-3 illustrates that although NetWare 5.1 and 6.0 do not include an NTP time module, they can consume and deliver NTP time packets.
Figure 10-3 NTP Compatibility of NetWare 5.1 and 6.0
NetWare 5.0 and 4.2 Servers
Figure 10-4 illustrates that NetWare 4.2 and 5.0 servers can only consume and provide Timesync packets.
Figure 10-4 Synchronizing Time on NetWare 5.0 and 4.2 Servers
Therefore, if you have NetWare 4.2 or 5.0 servers in your eDirectory tree, and you want to install an OES server, you must have at least one NetWare 5.1 or later server to provide a “bridge” between NTP and Timesync time packets. Figure 10-5 illustrates that these earlier server versions can synchronize through a NetWare 6.5 server.
IMPORTANT:As shown in Figure 10-4, we recommend that NetWare 4.2 servers not be used as a time source.
OES Servers as Time Providers
Figure 10-5 shows how OES servers can function as time providers to other OES servers and to NetWare servers, including NetWare 4.2 and later.
Figure 10-5 OES Servers as Time Providers
OES Servers as Time Consumers
Figure 10-6 shows the time sources that OES servers can use for synchronizing server time.
IMPORTANT:Notice that NetWare 4.2 is not shown as a valid time source.
Figure 10-6 OES servers as Time Consumers
10.3.2 Planning for Time Synchronization
Use the information in this section to understand the basics of time synchronization planning.
For more detailed planning information, refer to the following resources:
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How Timesync Works
in the NW 6.5 SP8: Network Time Synchronization Administration Guide -
Network Time Protocol
in the NW 6.5 SP8: NTP Administration Guide -
NTP information on the Web
NetWork Size Determines the Level of Planning Required
The level of time synchronization planning required for your network is largely dictated by how many servers you have and where they are located, as explained in the following sections.
Time Synchronization for Trees with Fewer Than Thirty Servers
If your tree will have fewer than thirty servers, the default installation settings for time synchronization should be sufficient for all of the servers except the first server installed in the tree.
You should configure the first server in the tree to obtain time from one or more time sources that are external to the tree. (See Step 1 in Planning a Time Synchronization Hierarchy before Installing OES.)
All other servers should point to the first server in the tree for their time synchronization needs.
Time Synchronization for Trees with More Than Thirty Servers
If your tree will have more than thirty servers, you need to plan and configure your servers with time synchronization roles that match your network architecture and time synchronization strategy. Example roles might include the following:
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Servers that receive time from external time sources and send packets to other servers further down in the hierarchy
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Servers that communicate with other servers in peer-to-peer relationships to ensure that they are synchronized
Basic planning steps are summarized in Planning a Time Synchronization Hierarchy before Installing OES.
Refer to the following sources for additional help in planning time server roles:
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Configuring Timesync on Servers
in the NW 6.5 SP8: Network Time Synchronization Administration Guide -
Modes of Time Synchronization
in the NW 6.5 SP8: NTP Administration Guide -
NTP information on the Web
Time Synchronization across Geographical Boundaries
If the servers in the tree will reside at multiple geographic sites, you need to plan how to synchronize time for the entire network while minimizing network traffic. For more information, see Wide Area Configuration
in the NW 6.5 SP8: NTP Administration Guide.
Choose Timesync for Virtualized NetWare Only
When you install a virtualized NetWare 6.5 server, you should always use Timesync and configure it to communicate using NTP.
The dialog box that lets you choose between Timesync and NTP is available as an advanced option in the Time Zone panel during the NetWare installation. Choosing between Timesync and NTP is documented in Setting the Server Time Zone and Time Synchronization Method
in the NW65 SP8: Installation Guide.
Planning a Time Synchronization Hierarchy before Installing OES
The obvious goal for time synchronization is that all the network servers (and workstations, if desired) have the same time. This is best accomplished by planning a time synchronization hierarchy before installing the first OES server, then configuring each server at install time so that you form a hierarchy similar to the one outlined in Figure 10-7.
Figure 10-7 A Basic Time Synchronization Hierarchy
As you plan your hierarchy, do the following:
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Identify at least two authoritative external NTP time sources for the top positions in your hierarchy.
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If your network already has an NTP server hierarchy in place, identify the IP address of an appropriate time server. This might be internal to your network, but it should be external to the eDirectory tree and it should ultimately obtain time from a public NTP server.
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If your network doesn’t currently employ time synchronization, refer to the list of public NTP servers published on the ntp.org Web site and identify a time server you can use.
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Plan which servers will receive time from the external sources and plan to install these servers first.
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Map the position for each Linux server in your tree, including its time sources and the servers it will provide time for.
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Map the position for each NetWare server in your tree:
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Include the server’s time sources and the servers it will provide time for.
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If your network currently has only NetWare 4.2 or 5.0 servers, be sure to plan for their time synchronization needs by including at least one newer NetWare server in the tree and configuring the older servers to use the newer server as their time source. (See NetWare 5.0 and 4.2 Servers.)
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Be sure that each server in the hierarchy is configured to receive time from at least two sources.
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(Conditional) If your network spans geographic locations, plan the connections for time-related traffic on the network and especially across WANs.
For more information, see
Wide Area Configuration
in the NW 6.5 SP8: NTP Administration Guide.
For more planning information, see the following documentation:
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NW 6.5 SP8: Network Time Synchronization Administration Guide
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NTP information found on the OES server in /usr/share/doc/packages/xntp and on the Web