Applies To: Windows Server 2008
Message routing between different sites, called intersite routing, requires connectivity between those sites. Connectivity between different sites can be defined by logical communications links, called routing links. If the message traffic between two specific sites can be configured to pass through a specific Message Queuing routing server or one of several such servers, that routing server is called a site gate. Routing links can use site gates to route messages between two sites.
If your organization has more than one site, you must create routing links to guarantee that messages can be routed between different sites. The route taken by messages between sites can be determined by the routing-link costs. All routing links are assigned a default cost of 1.
Link costs can be used to select the best intersite message route and may be based on the speed or the monetary cost of the underlying physical communication link. After you determine the number of sites in your forest, decide if you need to specify different costs for routing links. For information about how to change routing-link costs, see Change the Cost for a Routing Link.
For information about sites, see Deploying in a Domain Environment.
In a domain environment with more than one site, you must create routing links to guarantee that messages can be routed between different sites. In the absence of a routing link, Message Queuing will usually attempt to establish a direct connection with the destination computer in an unconnected site.
Each routing link is assigned a relative cost, which may reflect the speed or the monetary cost of the underlying physical communication link. The default value is 1, and costs can range from 1 to 999999. Change routing-link costs only in cases where alternative intersite routes are possible over the existing routing links and you want to enforce one route over another route using the costs of the individual links.
A site gate can belong to either or both of the sites connected by a routing link. A routing link can be configured with any number of site gates or no site gate.
Do not confuse routing links with site links. Routing links are used by Message Queuing servers to route messages between sites. Site links are used by domain controllers to replicate Active Directory Domain Services information between sites.
When a message is sent from an independent client in one site to a computer in another site, the source computer first tries to connect directly to the destination computer, and only as a second choice, delivers the message to a routing server in its site, which delivers the message to a site gate. This process continues until the message reaches the destination computer.
Intersite routing typically reduces the number of sessions created by clients. In the following figure, the routing beyond the site is transparent to the computers within the site, with the exception of the site gate. This simplifies the message route and reduces site-to-site sessions. Only the designated Message Queuing server can establish a session between different sites.