MSMQ calculates inter-site routing based on the cost of each site link. Site-link costs are defined using relative numbers between zero and 999,999. It is up to the administrator to define the relative cost of routing between sites. An administrator typically balances cost with delay (the speed of one link versus another).
You set site-link costs when you install new sites. If you have only two sites, choose any value above zero. If you have three or more sites, and the cost of routing between sites is more or less equal, use the same value for each site link. However, if you have three or more sites and if the cost of routing between sites is not equal, use site-link costs to define the difference in the routing costs. For example, suppose you have two sites called A and B in one city connected by a high-speed link, and one site called C, which is overseas and connected to site B by a low-speed link. Define the site-link cost between A and B as 1, and between B and C as 2.
A site-link cost of zero indicates that the two sites are not connected.
For more information on defining site links, see "MSMQ Routing" later in this chapter; "Installing a PSC" in Chapter 2, "Installing MSMQ"; and MSMQ Explorer Help.