Dependent Clients

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Applies To: Windows Server 2008

Dependent clients

For the purposes of this documentation, the term Message Queuing server refers to a Windows 7 or Windows Server 2008 R2 family computer that has Message Queuing installed. The term Message Queuing client can refer to either an independent client, or a dependent client. Both of these terms are used to describe Message Queuing servers that have particular Message Queuing components installed, and such computers are referred to as having independent client functionality, or dependent client functionality.

Note

Message Queuing 5.0 clients cannot be installed as dependent clients, this functionality has been deprecated. Message Queuing 5.0 independent clients running on Windows Server 2008 R2 family computers can, however, be configured as supporting servers for earlier versions of Message Queuing installed as dependent clients. This topic is provided in the Message Queuing 5.0 documentation for reference purposes for Message Queuing infrastructures that may contain a mix of Message Queuing 5.0 and earlier versions of Message Queuing.

Message Queuing servers with dependent client functionality require synchronous access to a Message Queuing server, called a supporting server, for all messaging functions. The supporting server can be any Message Queuing computer operating in domain mode with at least independent client functionality that is running on Windows Server 2008 R2, preferably in the local site, but also in a nearby site.

A dependent client relies on its supporting server to perform all messaging functions on its behalf, such as hosting queues, storing messages, sending messages, and receiving messages. If the supporting server goes offline, the dependent client will be unable to send and receive messages. By default, following installation, Message Queuing computers are not enabled to support dependent clients. For instructions on enabling a Message Queuing server to act as a supporting server, see Enable a Supporting Server for Dependent Clients. If you want to specify a Message Queuing server to act as a supporting server for a dependent client, you must also change the security configuration of the Microsoft Distributed Transaction Coordinator (DTC) on the Windows Server 2008 R2 family computer to enable network transactions. The DTC is automatically installed on each computer during Windows Server 2008 R2 family operating system installation for local transactions, and you need to enable network DTC. For instructions, see Enable Network DTC Access.

For information about how to view the list of dependent clients currently supported by a Message Queuing server, see View the Dependent Client List for a Server.

Dependent client considerations

Decide whether or not you want to deploy dependent clients in your organization. The advantages of using dependent clients are as follows:

  • Server disk space is used to store messages. When necessary, you upgrade only the server resources (such as memory and hard disk space) to improve Message Queuing performance, instead of upgrading all the client computers.

  • With fewer points of administration, you have fewer computers to back up and fewer journals and dead-letter queues to monitor.

  • Fewer resources are used if the dependent client is frequently offline and the server is not.

Dependent clients also have the following disadvantages:

  • Message Queuing 5.0 clients cannot be installed as dependent clients, this functionality has been deprecated in Message Queuing 5.0.

  • Because the Message Queuing service runs on the supporting server, encrypted messages sent to or received by dependent clients travel between the dependent client and supporting server as plaintext.

  • Queue access time is slower for a dependent client than it is for an independent client. This is because queue access is through an RPC-based connection.

  • There may be performance issues if multiple dependent clients connect to their supporting server at the same time to send or receive messages.

  • Dependent client queues are located on their supporting server, and it is not obvious which queues belong to which dependent clients.

  • When dependent client software is uninstalled, the associated queues are not automatically deleted from the supporting server.

  • Because communication from a dependent client goes through the supporting server, if the communication to the supporting server is slow or expensive (such as between two sites), all dependent client communications are also slow or expensive.

  • Dependent clients cannot run under a local user account.

  • Message Queuing features, such as HTTP transport, Message Queuing Triggers, and sending messages to multiple destinations, are not available to dependent clients. Thus, distribution lists, multiple-element format names, and multicast messaging are not supported for dependent clients.

  • Dependent clients cannot be installed on computers in workgroup mode or on 64-bit computers.