Planning server-to-server connections

Servers must connect to each other to exchange data, for example to replicate databases and exchange mail. You can create connections between servers across a local area network (LAN) or wide area network (WAN), by using a pass-through server (a server that acts as an intermediary server between a client and its destination), or over the Internet. Create a Server Connection document whenever you need to establish any new or additional server connections. You can modify this document when necessary.

For a calling server to connect to a given destination server, it requires information about how and when to contact the destination server. The information about how to contact the destination server includes the network to use to reach the target server, and, depending on the type of network, the network addresses and other information needed to make the connection.

When a server needs to connect to a destination server on the same IBM® Notes® Named Network, the information needed to make the connection is readily available and the connection occurs automatically, without any administrative intervention. However, when two servers do not share a common network, the calling server must be able to obtain this information by some other method. In an IBM Domino® network, administrators create connections documents in the Domino Directory to store information about how to connect to a destination server.

In addition to providing the network information required to contact a destination server, Connection documents can also specify when to contact the destination server. Depending on the type of communications required, a calling server may attempt to establish contact with the remote server immediately, or only at scheduled intervals. For example, a server looking up a name on, or performing cluster replication with a given destination server requires immediate access to a remote server.

On the other hand, to perform tasks such as routing mail or replicating databases, a calling server may require only periodic access to the destination server. When setting up a Connection document for a task that doesn't require immediate access, you can specify when the calling server attempts to make the connection. Network information in a Connection document is used to create the connection to the specified destination server, whether or not the connection is related to a task defined in the schedule part. In other words, a calling server can use the network information in a Connection document to contact a specified destination server when contacting that server for reasons other than mail routing or replication.

Connections between servers -- your connection topology should enable servers to exchange information reliably and efficiently, maximizing the capacity of the physical network, while minimizing connection-related costs.

When creating Connection documents for scheduled operations or to enable contact with a destination server, keep the following factors in mind:

• The physical network to which the servers belong -- Are servers in the same, or different IBM Lotus Notes® named networks?
• Function of the server -- What is the primary role of the server? For example, is it an application server, Web server, or Directory server? Does the server provide pass-through or dialup access to connect remote or disparate networks?
• Tasks running on the server -- Does the server require Connection documents for both replication and mail routing?
• Access requirements -- Does the server need to be reached as a pass-through destination?
• Access requirements -- Does the server need to be reached over a modem connection or as a pass-through destination?
• Does the planned connection topology make the best use of the available network infrastructure? It the server hardware adequate to support its role in replication or routing? For example, if a server is to be used as a replication hub, does it have a fast processor, sufficient memory, and enough disk space? Does the server require multiple NICs? Is there enough bandwidth between servers to support the anticipated traffic?
• Keep the number of Connection documents and the number of "hops" -- that is, the number of between the connecting and destination servers -- to a minimum.
• The Domino domain location of the servers -- Are servers in the same domain, adjacent domains, non-adjacent domains?

The number of Connection documents that you create for a server depends on whether the server is running the replication task and/or the mail task. When you configure a server, the Server document, by default, enables mail routing. When you create a Connection document, replication is enabled. Depending on how you use the server -- that is, whether you store mail files and/or application databases on it -- you must create a minimum of one or two Connection documents.

Servers can also use information gathered from an External Domain Network Information (EDNI) document to make a connection. As an administrator, you configure this document to look up names and addresses of servers in another domain, so that users and servers do not require Connection documents to connect to servers in that domain.