必威体育精装版《分布式系统原理与范型第版》原书课件.ppt

DISTRIBUTED SYSTEMSPrinciples and ParadigmsSecond EditionANDREW S. TANENBAUMMAARTEN VAN STEENChapter 4Communication Layered Protocols (1) Figure 4-1. Layers, interfaces, and protocols in the OSI model. Layered Protocols (2) Figure 4-2. A typical message as it appears on the network. Middleware Protocols Figure 4-3. An adapted reference model for networked communication. Types of Communication Figure 4-4. Viewing middleware as an intermediate (distributed) service in application-level communication. Conventional Procedure Call Figure 4-5. (a) Parameter passing in a local procedure call: the stack before the call to read. (b) The stack while the called procedure is active. Client and Server Stubs Figure 4-6. Principle of RPC between a client and server program. Remote Procedure Calls (1) A remote procedure call occurs in the following steps: The client procedure calls the client stub in the normal way. The client stub builds a message and calls the local operating system. The client’s OS sends the message to the remote OS. The remote OS gives the message to the server stub. The server stub unpacks the parameters and calls the server. Continued … Remote Procedure Calls (2) A remote procedure call occurs in the following steps (continued): The server does the work and returns the result to the stub. The server stub packs it in a message and calls its local OS. The server’s OS sends the message to the client’s OS. The client’s OS gives the message to the client stub. The stub unpacks the result and returns to the client. Passing Value Parameters (1) Figure 4-7. The steps involved in a doing a remote computation through RPC. Passing Value Parameters (2) Figure 4-8. (a) The original message on the Pentium. Passing Value Parameters (3) Figure 4-8. (a) The original message on the Pentium. Passing Value Parameters (4) Figure 4-8. (c) The message after being inverted. The little numbers in boxes indicate the address of each byte. Parameter Specific