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CS-NoteBook
  • Introduction
  • CS144
    • concise introduction to Internet
      • 1.1 Networked Applications
      • 1.2 The 4 Layer Internet
      • 1.3 IP
      • 1.4 A Day in the Life of a Packet
      • 1.5 Principle: Packet Switching
      • 1.6 Principle:Layering
      • 1.7 Principle: Encapsulation
      • 1.8 Byte order and packet formats
      • 1.9 name and addresses:IPv4
      • 1.10 Longest Prefix Match for Link Layer
      • 1.11 Address Resolution Protocol(ARP)
      • 1.12 Summary
    • Transport Layer
      • 2.1 The TCP Service Model
      • 2.2 UDP service model
      • 2.3 ICMP(Internet Control Message Protocol 互联网报文控制协议)
      • 2.4 The End-to-End Principle
      • 2.5 Error Detection:3 schemes (Checksum,CRC and MAC)
      • 2.6 Finite State Machines(有限状态机)
      • 2.7 Flow Control
      • 2.8 Sliding window
      • 2.9 Retransmission Strategies
      • 2.10 TCP Header
      • 2.11 TCP Setup and Teardown
      • 2.12 Recap
    • Package Switching
      • 3.1 The history of Internet
      • 3.2 What is packet switching
      • [3.3 End-to-end delay and Queueing delay
      • 3.4 Playback Buffer(回放缓存区)
  • CS 61C
    • 1.4 C Memory Mangement, Usage
    • 1.5 Intro to Assembly Language, MIPS Intro
    • 1.5 extra bits operation
  • CS 61B
  • CS 61A
    • Function
    • Names
    • The Art of the Function
    • Control
    • Higher-Order Function
    • Recursive Function
    • List
    • Non-Local Assignment
    • Iterators
    • Objects
    • Data Abstraction
    • OOP
    • Inheritance
    • Representations
    • Decomposition
    • Scheme
    • Exceptions
    • Calculator
    • Interpreters
    • Declarative_Programming
    • Table
    • Aggregation
      • More_recursion
    • Databases
    • Distributed_Data
    • Tail Recursion
    • Exercises
      • lab00
      • lab01
      • hw01
      • tree Recursion example -- give Change
  • The Web DevelopMent Bootcamp
    • html5
    • css
    • bootstrap3
    • bootstrap4
    • javascript expression
    • javascript function
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  1. CS144
  2. concise introduction to Internet

1.6 Principle:Layering

Layer k+1

⬆⬇data

Layer k

⬆⬇data

Layer k - 1

layer只和上下层的layer交流，下层layer为上层提供了well-defined service，各layer可以随着时间改进而不影响其他层

  1. Layers are functional components.

    层是功能组件。

  2. Layers communicate sequentially with the layers above and below.

    层与上面和下面的层按顺序通信。

  3. Each layer provides a well-defined service to the layer above,using the services provided by layers below and its own private processing.

    每个层使用下面层提供的服务和它自己的私有处理，为上面的层提供定义良好的服务。

举例

edit

⬇Source code

compile(词法分析、解析、预处理、代码生成和优化)

⬇Object code

link(把编译文件和libraries link给起来)

⬇Executable

execute

有时必须打破 layer: 跨界优化，但是丢失了灵活性

总结

分层的原因 1. Modularity 2. Well defined service 3. Reuse 4. Separation of concerns 5. Continuous improvement

  1. 只有 Layer communication system 如 Internet 特有的 peer-to-peer communications

  2. 模块化

  3. 为上层定义良好的服务

  4. 重用

  5. 关注点分离，减少复杂度

  6. 持续改进

  7. 对等通信，我和你用的layer system是一样的。

    只有 Layer communication system 如 Internet 特有的

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Last updated 5 years ago

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