Defining a Replication StrategyChapter 6 Designing the Replication Process 131• By dedicating special servers to specific tasks, such as supporting mail serveractivities.One of the more important reasons to replicate directory data is to balance theworkload of your network. When possible, you should move data to servers thatcan be accessed using a reasonably fast and reliable network connection. The mostimportant considerations are the speed and reliability of the network connectionbetween your server and your directory users.Directory entries generally average around one Kbyte in size. Therefore, everydirectory lookup adds about one Kbyte to your network load. If your directoryusers 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 aslow, heavily loaded, or unreliable WAN, you may need to replicate your directorytree to a local server.You must carefully consider whether the benefit of locally available data is worththe cost of the increased network load because of replication. If you are replicatingan entire directory tree to a remote site, for instance, you are potentially adding alarge strain on your network in comparison to the traffic caused by your users’directory lookups. This is especially true if your directory tree is changingfrequently, yet you have only a few users at the remote site performing a fewdirectory lookups per day.If your directory tree on average includes in excess of 1,000,000 entries, and it is notunusual for about ten percent of those entries to change every day, then if youraverage directory entry is only one Kbyte in size, you could increase your networkload by 100Mbyte 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, thenthe network load caused by their directory access is only one Mbyte per day.Given the difference in loads caused by replication versus that caused by normaldirectory usage, you may decide that replication for network load-balancingpurposes is not desirable. On the other hand, you may find that the benefits oflocally available directory data far outweigh any considerations you may haveregarding network loads.A good compromise between making data available to local sites and overloadingthe network is to use scheduled replication. For more information on dataconsistency and replication schedules, refer to “Data Consistency,” on page 115.Example of Network Load BalancingSuppose your enterprise has offices in New York and Los Angeles. Each office hasspecific subtrees that they manage, shown in the figure.
