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Types of CORBA Domain Configurations
When using the multiple domains feature, you can configure two types of configurations: directly connected domains and indirectly connected domains. You, as the administrator, configure both types using the domain configuration file, DMCONFIG.
Directly Connected Domains
It is possible for every domain in an enterprise to have a gateway to every other domain it might use. Such a configuration has the advantage that a request goes directly to the target domain, with the minimum of delay. Such an "n-way" configuration is quite reasonable when the number of domains is small, but each new domain requires two new gateways. At some point, an administrator may consider a different configuration, giving up speed of delivery for ease of management of domain connections. This is when the ability to configure indirectly connected domains becomes advantageous.
Indirectly Connected Domains
An administrator should consider what the likely traffic patterns are. Domains that have only occasional interactions are candidates for gateway removal. Since there will still be interactions, it must still be possible to reach the other domain. The technique used is to route the request through an intermediate domain that does have direct access to the target domain. For example, we might have three domains, A, B, and C. Domains A and B are directly connected and Domains B and C are directly connected, but A and C are not directly connected (see Figure 3-2). For Domains A and C to communicate, they must use domain B as the intermediary. Therefore, the DMCONFIG file for Domain A must state that it is possible to connect to domain C by going through Domain B (and vice versa). That is, the connectivity is:
Domains A <-> B <-> C
Gateways GAB GBA GBC GCB
Domain A has a gateway process, GAB (the Gateway from A to B), that connects to Domain B. The Domain A DMCONFIG file states that GAB acts as a gateway to two domains, Domains B and C. The DMCONFIG file for Domain C has a similar configuration, stating that GCB is connected to B and A. The DMCONFIG file for Domain B has two gateway processes, one which connects to A (GBA) and one which connects to C (GBC). This is called an indirect connection.
Given this indirect connection, when a server in A invokes a request on an object in C, BEA Tuxedo CORBA server knows that it can send the request to gateway GAB. The BEA Tuxedo gateway does not know that its partner gateway in B cannot service the request itself, but that is acceptable. Once the request is in domain B, it is routed through GBC to C, which can service the request. Thus, the request is serviced with one extra hop.
It is even possible for the two gateways in Domain B to be a single gateway, so that there is not an extra hop within B. In effect, the same processing occurs in Domain B, but it all occurs within a single gateway process.
Indirectly Connected Domains
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Copyright © 2001 BEA Systems, Inc. All rights reserved.
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