CCR - The Protocol



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CCR - The Protocol

CCR services allow a client and server to communicate information that is important in coordinating their actions. All the actions undertaken as a result of using CCR are local to the client and server processes and are separate from the CCR protocol. Thus, there is little to say about the CCR protocol itself. C-BEGIN uses a Presentation Layer service to reach a Session Layer service that establishes a synchronization point. We will look at this facility in detail later. Its significance to CCR is that it marks a place in the information exchanged between the client and the server and indicates that the client must retain this information and all that follows it until it is told it may abandon it. Thus, the atomic action is kept intact at the client until there is an indication that it has been conveyed successfully to the server. C-REFUSE, C-ROLLBACK, and C-RESTART each serve to mark the end of information retention requirement. Any of them gives permission to abandon what has been kept. C-PREPARE and C-READY use special facilities of the Presentation Layer to convey data without regard to any flow control constraints that might be in place (P-TYPED-DATA).

In summary, then, the CCR protocol is used to convey coordination information between a client and a server. It is up to the client and the server to use the information correctly. This conclude our discussion of OSI ASEs. We now turn our attention to the TCP/IP environment. The tools introduced in the next section do not have the same kind of use as the OSI ASEs, but that is because the TCP/IP protocols leave such requirements to each application to develop as needed.



boots cassel
Wed Feb 7 10:22:57 EST 1996