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Defining a Replication Strategy
One of the more important reasons to replicate directory data is to balance the
work load of your network. When possible, you should move data to servers that
can be accessed using a reasonably fast and reliable network connection. The most
important considerations are the speed and reliability of the network connection
between your server and your directory users.
Directory entries generally average around one KB in size. Therefore, every
directory lookup adds about one KB to your network load. If your directory users
perform around ten directory lookups per day, then for every directory user you
will see an increased network load of around 10,000 bytes per day. Given a slow,
heavily loaded, or unreliable WAN, you may need to replicate your directory tree
to a local server.
You must carefully consider whether the benefit of locally available data is worth
the cost of the increased network load because of replication. For example, if you
are replicating an entire directory tree to a remote site, you are potentially adding a
large strain on your network in comparison to the traffic caused by your users'
directory lookups. This is especially true if your directory tree is changing
frequently, yet you have only a few users at the remote site performing a few
directory lookups per day.
For example, consider that your directory tree on average includes in excess of
1,000,000 entries and that it is not unusual for about ten percent of those entries to
change every day. If your average directory entry is only one KB in size, this means
you could be increasing your network load by 100 MB per day. However, if your
remote site has only a few employees, say 100, and they are performing an average
of ten directory lookups a day, then the network load caused by their directory
access is only one MB per day.
Given the difference in loads caused by replication versus that caused by normal
directory usage, you may decide that replication for network load-balancing
purposes is not desirable. On the other hand, you may find that the benefits of
locally available directory data far outweigh any considerations you may have
regarding network loads.
A good compromise between making data available to local sites without
overloading the network is to use scheduled replication. For more information on
data consistency and replication schedules, refer to "Data Consistency," on
page 99.
Example of Network Load Balancing
Suppose your enterprise has offices in two cities. Each office has specific subtrees
that they manage as follows:
Chapter 6
Designing the Replication Process
111
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