Microsoft KB Archive/255708

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INFO: MSMQ Site Controller Network Traffic

Article ID: 255708

Article Last Modified on 7/2/2000


  • Microsoft Message Queue Server 1.0

This article was previously published under Q255708


Message Queuing (MSMQ) Site Controllers exchange regular information and updates by means of network messages.


At steady-state, when objects are not created, changed, or deleted, each Primary Site Controller (PSC) sends a "hello" message to each of the other PSCs, and to its own Backup Site Controllers (BSCs), every 20 minutes. Hello messages contain the latest sequence numbers of the objects owned by the sender, so that other PSCs can detect whether they have missed any replication information, and ask for recent updates again.

When a PSC requests a synchronization after determining that it missed a replication, the object is only replicated to the PSC that made the request. These hello and replication messages are express messages that are sent with a DIRECT format destination, with no storing or forwarding. This requires that all PSCs have full connectivity. For instance, you cannot have one PSC that only supports Internet Protocol (IP) and another that only supports Internet Packet Exchange (IPX).

The size of the hello message from PSC to PSC is approximately 170 bytes. The hello message from the Primary Enterprise Controller (PEC) to all other PSCs is approximately 220 bytes, because the PEC is the owner of enterprise-wide objects (sites, users) as well as its own site. The size of hello messages to BSCs, which contain the sequence numbers of all PSCs in the enterprise, is approximately (170 + (number of PSC * 50)) bytes.

When an object is created, the complete object is replicated from the owner PSC to all other PSCs, as well as to its own BSCs. When an object is changed, only the properties that changed are replicated. When an object is deleted, a fixed-length record of a few tens of bytes is sent.

When you upgrade a PEC to Microsoft Windows 2000 and MSMQ version 2.0, the MSMQ upgrade wizard installs and starts a service called "Message Queuing Replication." In a mixed MSMQ enterprise where the PEC has been upgraded, but where there are still Microsoft Windows NT 4.0 PSCs, this service allows replication of all Windows 2000 MSMQ objects to the Windows NT 4.0 PSCs, and receives replications from the Windows NT 4.0 PSCs.

NOTE: To determine the size of an object, see "Determining the Size of the Information Store" in the MSMQ 1.0 Administrator's Guide. Please note that the numbers in the Administrator's Guide refer to database disk space. On the network, the sizes are typically much smaller. For example, a user record is usually no more than 1K bytes on the network, as opposed to the 2.6K that is mentioned in the Administrator's Guide.

Additional query words: MSMQ PEC PSC BSC network traffic

Keywords: kbinfo KB255708