Timing is
everything, especially on NetWare servers
Without precise time synchronization, many network services will prove to be
unreliable—or worse, they might fail. Here's how you can synchronize time
properly on your NetWare network.
Novell has developed a very reliable time synchronization scheme
that requires all NetWare 4 or 5 servers to participate and be configured as
time servers. When the server loads, TIMESYNC.NLM is loaded to manage time
synchronization. TIMESYNC.CFG is used to store time synchronization settings.
However, you can temporarily change these settings by issuing SET commands at
the system console.
You can configure a NetWare server to be a single reference, reference, primary,
or secondary time server.
Single reference servers
The first server installed into the tree will automatically become a single
reference time server. The single reference server always believes that its time
is correct, and it always believes that its time is synchronized with network
time. The only other type of time server that can coexist with a single
reference server is a secondary server.
Reference time servers?
A reference time server is normally configured on networks containing more than
30 servers, and it's important because it becomes the central time provider on
the network. Further, it provides the time to primary and secondary servers.
A reference server cannot coexist with single reference servers or with other
reference servers on the same LAN. While it is possible to have more than one
reference server on a network, they should always be present at different sites
in a WAN setting.
Primary time servers
Primary time servers are used to provide time to secondary servers and clients.
To calculate the time they provide, primary servers poll the reference server
and other primary servers for their time. A weighted average is calculated to
determine the "correct" network time. If the calculated time is more
than two seconds different from network time, the primary server changes its
time 50 percent each polling cycle until its time is synchronized with network
time.
Secondary time servers
Secondary time servers provide time to secondary servers and clients. They
receive their time from single reference, reference, primary, or other secondary
servers. Secondary servers believe that the time they receive is always correct.
Time servers communicate using either a configured list or the service
advertising protocol (SAP). SAP is the default method of communication for time
servers. However, SAP is considered a chatty protocol that can cause bottlenecks
on slow WAN connections.
Configured list use
If you have a network that contains more than 30 servers or has slow WAN
connections, you should use a configured list. The TIMESYNC.CFG file will
contain the source from which the server will receive the time.
You can implement both configurations (configured list and SAP) for fault
tolerance. However, remember that SAP can generate heavy network traffic.
As mentioned earlier, default NetWare settings dictate that the first server
installed in the tree will be a single reference server, and all subsequent
servers become secondary servers. These servers will use SAP to communicate
network time to one another. No additional configuration is required as long as
the network contains fewer than 30 servers, doesn't have any slow WAN
connections, and all of the servers use IPX. The default settings in NetWare
will do everything for you. It doesn't get any easier than that, does it?
What happens when your single reference time server
goes down?
If the single reference time server should fail, one of the secondary servers
can temporarily take its place. You can perform the operation by entering the
following command at the system console: SET TIMESYNC TYPE = SINGLE. Just don't
forget to change the temporary single reference server back to a secondary
server shortly before bringing the real single reference server back up. To do
this, enter the following command at the system console: SET TIMESYNC TYPE =
SECONDARY.
Unless you have a large network or slow WAN links, or you want to use IP, the
default NetWare settings should be sufficient. The single reference server will
happily provide time to the other secondary servers using SAP, and you can spend
time doing something more interesting, like configuring that Quake server for
play after 5:00 P.M.
