Interrupt generated by device driver asynchronous io

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Interrupt generated by device driver Asynchronous I/O operation completes Signal received from OS Event may stop before reaching Layer N if it can be handled by some intermediate layer Multiple events at Layer J may be combined into a single higher-level event which is sent to Layer J+1 Client Layer N Layer N-1 Layer 2 Layer 1
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Implementation Determine the number of layers (i.e., abstraction levels) Name the layers and assign responsibilities to them Define the interface for each layer Error handling strategy Part of a layer's interface is the set of errors it might return The errors returned by a layer should match its level of abstraction Errors received from the layer below should be mapped into higher-level errors that are appropriate for the layer above Low-level errors should not be allowed to "leak out" and become visible to high-level layers
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Relaxed Layers Layer J can call directly into any layer below it, not just Layer J-1 Pros More flexible and efficient than strict layers Easier to build than strict layers Cons Less understandable and maintainable than strict layers
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Known Uses: Typical layered application architecture Hardware Operating System Data Storage/Retrieval Networking GUI Toolkit Utilities Application Logic User Interface
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Known Uses: Web applications Browser Web Server Application Server Database Server
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  • Fall '08
  • Woodfield,S
  • virtual machine, Web server, Internet Protocol Suite, Layer j

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